Purdue SIGBots Wiki works to provide VEX Robotics competitors at all skill levels with a wealth of community-driven knowledge that has been developed over a rich history of BLRS competition and work within the community. We also envision a place for students to share what they have learned, and host a location for learning to begin, and grow.

How are we achieving this goal?

With this Wiki, we seek to centralize the wealth of information between generations of robotics students in one location. Many of these articles have been passed down in the Purdue SIGBots internal documents and have been updated for public usage.

By making this project open-sourced, we can help expand this knowledge base with diverse viewpoints and sources. For more information on how you can help, check out our contributing guidelines page.

The VEX community is one that is better together, we believe that the increased sharing of knowledge that is accessible to every team will bring about better robots and, most importantly, better engineers.

Thank you,

• The SIGBots Wiki Development Team

Get ready for High Stakes!

Getting started with VEX Robotics?

Here on the Purdue SIGBots Wiki, you will find a place to grow your robotics knowledge. Whether you need to start a club with our Team Financials article, or you want to learn some more about programming with our Odometry article, there is more to learn here.

The wiki was created to host the knowledge of the VEX community with resources for competitors at all levels. It started with years of SIGBots documentation but has expanded with many open-source contributors, and new articles always being added. The wiki will stay up to date with new knowledge and continue to strengthen the articles already published.

If you are interested in contributing to the wiki feel free to open a pull request on the wiki's repo. Simply click edit on GitHub on any of the pages to see where in the repo that specific page is. We also allow contributions by PDF and Word Documents, so check it out under contributing guidelines.

If you would like to discuss or bring up an issue with the wiki without fixing it yourself, feel free to open up an issue on the aforementioned wiki repo.

As always if you have any questions or concerns feel free to contact us at: sig.robotics.purdue@gmail.com. Please CC your coach in the email to help us assist you more effectively.

This work is licensed under a Creative Commons Attribution-ShareAlike 2.0 Generic License.

PDF or Word Document Submissions

The Purdue SIGBots Wiki provides access for contributors without the ability to create markdown documents with this google form. Please note that this does not guarantee that your article will be accepted, and we may make revisions to the original article for different reasons. All contributing guidelines still apply. All content submitted through this form will be considered SIGBots Wiki property, but we will try to attribute teams for their work.

Direct Link: https://forms.gle/La5r4CVCzxH2wnb67

Github Markdown Submissions

The Purdue SIGBots Wiki uses Github integration for contributing, moderation, and general version control. It uses Github markdown for formatted text in our articles, and a guide for this can be found here. More on using Github for version control here.

If you are looking to contribute and don't know where to start, a good place to look is the projects and issues section on our github page!

Making Modifications (Advanced):

To make a modification to an article or create a new article, submit a pull request (PR) on our github page which can be found here.

Submitting your Pull Request will allow the SIGBots Wiki Development team to review and process any changes proposed.

Please include:

• Why your proposed changes should be made.

• What changes are being proposed.

• Include you or your team on the bottom of the page in the list of contributors (make a new section on your new page if you created a new page).

  • There's good examples of this under each page.

Terminology Guidelines:

• Try to avoid slang in general and region specific terms for mechanisms.

  • Example: "Goliath Intakes" as a nickname for roller intakes.

• If a term is widely used, but has an unprofessional connotation please refrain from using it.

  • Example: "Pooper" being used to describe ball extraction mechanisms.

• If a term is appropriate. widely used, and you'd like to use it in your article, please clearly define it as a substitute for the professional/exact term you are referring to.

• Always feel free to ask in your pull request if a term is suitable or not.

Mentioning Specific Teams and Outside Sources

Mentioning outside sources and other specific teams and their robots are allowed to be mentioned on the wiki, as long as their usage is relevant, respectful, and consensual.

If this is done, please include the source itself with a description and proper embedding for images, videos, and other forms of media.

This guide is designed to walk contributors through the process of embedding CADs on our Wiki articles. This guide can be generally applied for all HTML, CSS, and JS embeddables but is tailor made for CAD.

1. Upload your CAD to Fusion 360, and Share the Embedded HTML Code

First, upload your CAD file to Fusion 360, and follow this guide below to retrieve the embedded code to share your CAD.

The code to copy should be located here.

2. Paste the Code in a CodePen Project

Sign up for CodePen, and paste the code under the "HTML" section. Once the code is in the project, you should see a preview of the CAD. Your project is already public, and what you need to copy now is the URL in your browser tab.

If this wasn't cleaer enough, this is what we mean:

3. Paste the link URL from your browser into these locations:

If using the in-browser editor, paste the URL of the CodePen project into the project, and make a press enter to auto-embed.

If using github markdown directly, check this raw file to see how the CAD below was embedded.

If you are making a contribution in another format (Google Docs or PDF), please complete steps 1 and 2 and include the URL on your submission in the appropriate location so we can embed it for you when processing your document.

Sample CAD Embed:

Note that the CAD takes a bit to load, and the ratio for the viewing window is suboptimal. If others have different solutions please let us know at sig.robotics.purdue@gmail.com.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

• 319K (319K Kodiak)

2024 - VURC Over Under

Opening Ceremonies VURC, V5RC (MS), and JROTC Opening Ceremonies

Innovate Division Qualification Matches (Day 1) Qualification Matches (Day 2) Qualification, Playoffs, & Awards

Spirit Division Qualification Matches (Day 1) Qualification Matches (Day 2) Qualification, Playoffs, & Awards

Closing Ceremonies & Finals VURC, V5RC (MS), and JROTC Closing Ceremonies and Finals

2023 - VRC Spin Up

Opening Ceremonies VEX U, VRC Middle School, and JROTC Opening Ceremonies

Design Division Qualification Matches Qualification, Playoffs, & Awards

Research Division Qualification Matches Qualification, Playoffs, & Awards

Closing Ceremonies & Finals VEX U, VRC Middle School, and JROTC Closing Ceremonies and Finals

2022 - VRC Tipping Point

Opening Ceremonies VEX U, VRC Middle School, and JROTC Opening Ceremonies

Science Division Practice & Qualification Matches Matches, Playoffs & Awards

Technology Division Practice & Qualification Matches Matches, Playoffs & Awards

Closing Ceremonies & Finals VEX U, VRC Middle School, and JROTC Closing Ceremonies and Finals

2019 - VRC Turning Point

Opening Ceremonies VRC Parade of Nations

Divisions Design Division Innovate Division

Skills Finals VRC Skills Final

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2018 - VRC In The Zone

Opening Ceremonies VRC Parade of Nations

Divisions Innovate Division Design Division

Skills Finals VRC Skills Finals

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2017 - VRC Starstruck

Opening Ceremonies VRC Parade of Nations

Divisions Innovate Division Design Division

Skills Finals VRC Skills Finals

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2016 - VRC Nothing But Net

Opening Ceremonies VRC Opening Ceremonies

Divisions Research Division Design Division

Skills Finals VRC Skills Finals

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2015 - VRC Skyrise

Opening Ceremonies VRC Opening Ceremonies

Divisions VEX U

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2014 - VRC Toss Up

Opening Ceremonies VRC Opening Ceremonies

Divisions VEX U

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2013 - VRC Sack Attack

Opening Ceremonies VRC Opening Ceremonies

Divisions College

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2024 - VIQRC Full Volume

Opening Ceremonies VIQRC Opening Ceremonies

Design Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Innovate Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Opportunity Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Research Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Spirit Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Closing Ceremonies & Finals VIQRC Closing Ceremonies and Finals

2023 - VIQC Slapshot

Opening Ceremonies VIQC MS Opening Ceremonies

Arts Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards Design Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards

Engineering Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards

Innovate Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards

Math Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards

Opportunity Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards

Research Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards

Science Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards

Spirit Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards

Technology Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards

Closing Ceremonies & Finals VIQC MS Closing Ceremonies and Finals

2022 - VIQC Pitching In

Opening Ceremonies VIQC MS Opening Ceremonies

Math Division Practice & Qualification Matches Matches, Playoffs & Awards

Technology Division Practice & Qualification Matches Matches, Playoffs & Awards

Science Division Practice & Qualification Matches Matches, Playoffs & Awards

Engineering Division Practice & Qualification Matches Matches, Playoffs & Awards

Arts Division Practice & Qualification Matches Matches, Playoffs & Awards

Innovate Division Practice & Qualification Matches Matches, Playoffs & Awards

Spirit Division Practice & Qualification Matches Matches, Playoffs & Awards

Design Division Practice & Qualification Matches Matches, Playoffs & Awards

Research Division Practice & Qualification Matches Matches, Playoffs & Awards

Opportunity Division Practice & Qualification Matches Matches, Playoffs & Awards

Closing Ceremonies & Finals VIQC MS Finals and Closing Ceremonies

2019 - VIQC Next Level

Opening Ceremonies VEX IQ Parade of Nations

Divisions Science Division Technology Division Engineering Division Math Division Arts Division

Closing Ceremonies & Finals ​VEX IQ Finals and Closing Ceremonies​

2018 - VIQC Ringmaster

Opening Ceremonies VEX IQ Parade of Nations

Divisions Science Division Technology Division Engineering Division Math Division Arts Division

Closing Ceremonies & Finals VEX IQ Finals and Closing Ceremonies

2017 - VIQC Crossover

Opening Ceremonies VEX IQ Parade of Nations

Divisions Science Division Technology Division Engineering Division Math Division

Closing Ceremonies & Finals VEX IQ Finals and Closing Ceremonies

2016 - VIQC Bank Shot

Divisions Science Division Technology Division Engineering Division Math Division

2015 - VIQC Highrise

Divisions VIQC Middle School

2014 - VIQC Add It Up

Divisions VEX IQ Challenge

2013 - VIQC Rings-N-Things

Divisions VEX IQ Challenge

2024 - V5RC Over Under

Opening Ceremonies V5RC (HS) Opening Ceremonies

Science Division Practice & Qualification Matches Qualification Matches

Technology Division Practice & Qualification Matches Qualification Matches

Engineering Division Practice & Qualification Matches Qualification Matches

Arts Division Practice & Qualification Matches Qualification Matches

Math Division Practice & Qualification Matches Qualification Matches

Design Division Practice & Qualification Matches Qualification Matches

Research Division Practice & Qualification Matches Qualification Matches

Innovate Division Practice & Qualification Matches Qualification Matches

Spirit Division Practice & Qualification Matches Qualification Matches

Opportunity Division Practice & Qualification Matches Qualification Matches

Closing Ceremonies & Finals Finals, Closing Ceremonies, VRC Game Unveil

2023 - VRC Spin Up

Opening Ceremonies VRC HS Opening Ceremonies

Arts Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Design Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Engineering Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Innovate Division Practice & Qualification Matches (Part 1) Practice & Qualification Matches (Part 2) Qualification, Playoffs, & Awards

Math Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Opportunity Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Research Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Science Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Spirit Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Technology Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Closing Ceremonies & Finals VRC HS Closing Ceremonies and Finals

2022 - VRC Tipping Point

Opening Ceremonies VRC HS Opening Ceremonies

Math Division Practice & Qualification Matches Matches, Playoffs & Awards

Technology Division Practice & Qualification Matches Matches, Playoffs & Awards

Science Division Practice & Qualification Matches Matches, Playoffs & Awards

Engineering Division Practice & Qualification Matches Matches, Playoffs & Awards

Arts Division Practice & Qualification Matches Matches, Playoffs & Awards

Innovate Division Practice & Qualification Matches Matches, Playoffs & Awards

Spirit Division Practice & Qualification Matches Matches, Playoffs & Awards

Design Division Practice & Qualification Matches Matches, Playoffs & Awards

Research Division Practice & Qualification Matches Matches, Playoffs & Awards

Opportunity Division Practice & Qualification Matches Matches, Playoffs & Awards

Closing Ceremonies & Finals VRC HS Finals and Closing Ceremonies

2019 - VRC Turning Point

Opening Ceremonies VRC Parade of Nations

Divisions Science Division Technology Division Arts Division Math Division Engineering Division Research Division

Skills Finals VRC Skills Finals

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2018 - VRC In The Zone

Opening Ceremonies VRC Parade of Nations

Divisions Science Division Technology Division Arts Division Math Division Engineering Division Research Division

Skills Finals VRC Skills Finals

Division Round Robin / Playoffs VRC HS Round Robin

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2017 - VRC Starstruck

Opening Ceremonies VRC Parade of Nations

Divisions Science Division Technology Division Arts Division Math Division Engineering Division Research Division

Skills Finals VRC Skills Finals

Division Round Robin / Playoffs VRC HS Round Robin

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2016 - VRC Nothing But Net

Opening Ceremonies VRC Opening Ceremonies

Divisions Science Division Technology Division Arts Division Math Division Engineering Division

Skills Finals VRC Skills Finals

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2015 - VRC Skyrise

Opening Ceremonies VRC Opening Ceremonies

Divisions Science Division Technology Division Arts Division Math Division Engineering Division

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2014 - VRC Toss Up

Opening Ceremonies VRC Opening Ceremonies

Divisions Science Division Technology Division Arts Division Math Division Engineering Division

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2013 - VRC Sack Attack

Opening Ceremonies VRC Opening Ceremonies

Divisions Science Division Technology Division Arts Division Math Division Engineering Division

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2024 - V5RC Over Under

Opening Ceremonies VURC, V5RC MS, and JROTC Opening Ceremonies

Arts Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Design Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Engineering Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Math Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Science Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Technology Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Closing Ceremonies & Finals VURC, V5RC MS, and JROTC Closing Ceremonies and Finals

2023 - VRC Spin Up

Opening Ceremonies VEX U, VRC Middle School, and JROTC Opening Ceremonies

Arts Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Engineering Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Math Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Opportunity Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Science Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Technology Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Closing Ceremonies & Finals VEX U, VRC Middle School, and JROTC Closing Ceremonies and Finals

2022 - VRC Tipping Point

Opening Ceremonies VEX U, VRC Middle School, and JROTC Opening Ceremonies

Engineering Division Practice & Qualification Matches Matches, Playoffs & Awards

Arts Division Practice & Qualification Matches Matches, Playoffs & Awards

Innovate Division Practice & Qualification Matches Matches, Playoffs & Awards

Spirit Division Practice & Qualification Matches Matches, Playoffs & Awards

Design Division Practice & Qualification Matches Matches, Playoffs & Awards

Research Division Practice & Qualification Matches Matches, Playoffs & Awards

Opportunity Division Practice & Qualification Matches Matches, Playoffs & Awards

Closing Ceremonies & Finals VEX U, VRC Middle School, and JROTC Closing Ceremonies and Finals

2019 - VRC Turning Point

Parade of Nations VRC Parade of Nations

Divisions Opportunity Division Spirit Division

Skills Finals VRC Skills Final

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2018 - VRC In The Zone

Opening Ceremonies VRC Parade of Nations

Divisions Opportunity Division Spirit Division

Skills Finals VRC Skills Finals

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2017 - VRC Starstruck

Opening Ceremonies VRC Parade of Nations

Divisions Opportunity Division Spirit Division

Skills Finals VRC Skills Finals

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2016 - VRC Nothing But Net

Opening Ceremonies VRC Opening Ceremonies

Divisions Opportunity Division Spirit Division

Skills Finals VRC Skills Finals

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2015 - VRC Skyrise

Opening Ceremonies VRC Opening Ceremonies

Divisions Opportunity Division Spirit Division

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2014 - VRC Toss Up

Opening Ceremonies VRC Opening Ceremonies

Divisions Opportunity Division Spirit Division

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2013 - VRC Sack Attack

Opening Ceremonies VRC Opening Ceremonies

Divisions Opportunity Division Spirit Division

Closing Ceremonies & Finals VRC Finals and Closing Ceremonies

2024 - V5RC Over Under

Opening Ceremonies VURC, V5RC MS, and JROTC Opening Ceremonies

Research Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Opportunity Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Closing Ceremonies & Finals VURC, V5RC MS, and JROTC Closing Ceremonies and Finals

2023 - VRC Spin Up

Opening Ceremonies VEX U, VRC Middle School, and JROTC Opening Ceremonies

Innovate Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Spirit Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Closing Ceremonies & Finals VEX U, VRC Middle School, and JROTC Closing Ceremonies and Finals

2022 - VRC Tipping Point

Opening Ceremonies VEX U, VRC Middle School, and JROTC Opening Ceremonies

Math Division Practice & Qualification Matches Matches, Playoffs & Awards

Closing Ceremonies & Finals VEX U, VRC Middle School, and JROTC Closing Ceremonies and Finals

Introduction

Pneumatics are a system of components that use compressed air to create motion. In most cases, this is linear motion from cylinders (sometimes called pistons) but this motion can be used in many different ways. In your life, think about pumps for athletic balls, nail guns, and shocks on bikes. There are 3 subsystems to pneumatics in Vex. There is Air Storage, Air Control, and Pneumatic Cylinders.

Air Storage is where the pressurized air is held in a robot. For Vex, this is done in aluminum reservoirs. In most seasons, a team can have 2 of these on their robots and they are pressurized to a maximum of 100 psi (Pounds per Square Inch). The 2 main considerations in storage are the volume and the pressure of the air. The volume changes how many times that you can fire the cylinders and the pressure changes how strongly the cylinders fire.

Air Control defines when and how actions are taken with pneumatics such as cylinders. In pneumatics, this is done with either Finger Valves or solenoids. A Finger Valve is a manual 'on and off' switch for cylinders and pneumatics. Solenoids are used for actuation as they plug into the V5 brain and control the flow of air through the system (and can be programmed). This is the main way that teams will interact with pneumatics on the robot through programming (see Pros guide for more). The Pressure Regulator is used to control the pressure released from the reservoir to the solenoids. Placed near the reservoir in the system, the pressure can be increased or decreased as needed.

Pneumatic cylinders are the third subsystem of pneumatics and are where the motion comes from. In Vex, there are both single, and double-acting cylinders. Single-acting cylinders are powered outwards and then released with no force in the other direction. Double-acting cylinders on the other hand are powered in both directions with the same amount of force. The two do have different types of solenoids though.

Components

Pneumatics consist of seven major components:

• Tubing

  • Physical carrier for the pressurized air.

• Reservoir

  • Storage for the pressurized air.

• Pressure Regulators

  • Valve to regulate the pressure of air in the system.

• Finger Valve/Flow Switch

  • Simple on/off switch for airflow.

• Solenoids

  • Control components that turn electrical signals into commands for pressurizing the system. Connected to both V5 Brain(requires drivers) and Pneumatic tubing for control.

• Cylinders

  • Linearly actuating component

• Reservoir Valve

  • Used for attaching tubing to reservoir

• Solenoid Valve

  • Used for attaching tubing to solenoids

• Cylinder Valve

  • Used for attaching tubing to Cylinder

Above is an ideal system. At the bottom of the reservoir is the bike pump fitting to refill and pressurize the reservoir. The top is the valve for tubing where a pressure regulator could also be installed. Following the tubing is a T-fitting which is used to move air around the system and robot. Following the fitting are the solenoids (with 2 more valves on each) and the drivers (the wires extending out) followed finally by the solenoids.

GOATS Non Vex Pneumatics Order Form

Programming

To program pneumatics, they act as a generalized digital output that can be controlled with whatever ADI API is provided on your respective programming languages. Learn more here

Contributors to this Article

• MTBR (Michigan Task-Based Robotics)

• Max Johnson (BLRS)

• Andrew (GOATS/977Z)

2024 - VIQRC Full Volume

Opening Ceremonies VIQRC Opening Ceremonies

Arts Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Engineering Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Math Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Science Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Technology Division Practice & Qualification Matches Qualification Matches (Day 1) Qualification Matches (Day 2)

Closing Ceremonies & Finals VIQRC Closing Ceremonies and Finals

2023 - VIQC Slapshot

Opening Ceremonies VIQC ES Opening Ceremonies

Technology Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Science Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Design Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Spirit Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Research Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Innovate Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Opportunity Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Arts Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Math Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Engineering Division Practice & Qualification Matches Qualification, Playoffs, & Awards

Closing Ceremonies & Finals VIQC ES Closing Ceremonies and Finals

2022 - VIQC Pitching In

Opening Ceremonies VIQC ES Opening Ceremonies

Math Division Practice & Qualification Matches Matches, Playoffs & Awards

Technology Division Practice & Qualification Matches Matches, Playoffs, & Awards

Science Division Practice & Qualification Matches Matches, Playoffs & Awards

Engineering Division Practice & Qualification Matches Matches, Playoffs & Awards

Arts Division Practice & Qualification Matches Matches, Playoffs & Awards

Innovate Division Practice & Qualification Matches Matches, Playoffs & Awards

Spirit Division Practice & Qualification Matches Matches, Playoffs & Awards

Design Division Practice & Qualification Matches Matches, Playoffs & Awards

Research Division Practice & Qualification Matches Matches, Playoffs & Awards

Closing Ceremonies & Finals VIQC ES Finals and Closing Ceremonies

2019 - VIQC Next Level

Opening Ceremonies VIQC Parade of Nations

Divisions Apollo Division Cassini Division Hubble Division Chandra Division Viking Division

Closing Ceremonies & Finals ​VEX IQ Finals and Closing Ceremonies

2018 - VIQC Ringmaster

Opening Ceremonies VEX IQ Parade of Nations

Divisions Apollo Division Cassini Division Hubble Division Chandra Division Viking Division

Closing Ceremonies & Finals VEX IQ Finals and Closing Ceremonies

2017 - VIQC Crossover

Opening Ceremonies VEX IQ Parade of Nations

Divisions Science Division Technology Division Engineering Division Math Division

Closing Ceremonies & Finals VEX IQ Finals and Closing Ceremonies

2016 - VIQC Bank Shot

Divisions Science Division Technology Division Engineering Division Math Division

2015 - VIQC Highrise

Divisions VIQC Elementary School

2014 - VIQC Add It Up

Divisions VEX IQ Challenge

2013 - VIQC Rings-N-Things

Divisions VEX IQ Challenge

In materials science, stress refers to the internal forces that exist within a material as a result of external loads or forces acting on it. Stress in metals can be caused by a variety of factors, including temperature changes, mechanical loads, and corrosion.

There are five types of stress that can occur in metals: shear stress, bending stress, torsion stress, tensile stress, and compressive stress. In Vex robotics, the most common types are Bending, Torsion, and Compression/Tension (opposites).

The strength of a metal is determined by its ability to withstand stress without failing. When a metal is subjected to stress, it will either deform elastically (temporarily) or plastically (permanently). If the stress is high enough, the metal will eventually break, which is known as yielding or failure.

Stress can also affect the physical and mechanical properties of metals, such as their ductility, malleability, and toughness. For example, a metal that is subjected to high tensile stress may become more brittle and less able to withstand further stress.

Managing stress in metals is important in order to ensure their structural integrity and prevent failure. This can be done through various methods, such as using stress-relieving techniques, applying appropriate protective coatings, and designing structures to distribute stress evenly. In Vex, stress can be managed by assuring that loads are properly distributed and pieces are properly braced.

Bending

Bending is the most common type of stress in the robotics design process. Bending comes from a force being applied perpendicular to the length of an object. Commonly, a piece of metal that is used in a lift will have forces that cause bending.

Torsion

Torsion is very common in underdeveloped robots. Torsion is caused by force applied tangent to an object's axis, commonly called twisting. Oftentimes, this is seen along long pieces of metal that might be sparsely supported or an axle in high torque situations with little support.

Compression / Tension

These two are opposite forces where a force is being applied through an axis of an object either pushing (compression) or pulling (tension). In robotics, this is often times seen at connections between pieces through screws, standoffs, or spacers that become inconsistent over time.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

RPM, or revolutions per minute, is a measure of the rotational speed of an object. It is defined as the number of complete revolutions an object makes around its axis of rotation in one minute. RPM is often used to describe the speed of mechanical systems, such as motors, gears, and shafts.

The relationship between RPM, torque, and the speed of a shaft is complex and depends on several factors, including the size and shape of the shaft, the type and amount of load being applied, and the efficiency of the system.

In general, the torque required to rotate a shaft increases with the speed of the shaft. This is because the faster an object rotates, the more force is required to overcome the centrifugal forces acting on it. As a result, shafts operating at high speeds typically require higher torque to maintain their rotational motion.

Conversely, the speed of a shaft is directly proportional to the torque applied to it, assuming the load and efficiency of the system remain constant. This means that increasing the torque applied to a shaft will result in an increase in its speed, and decreasing the torque will result in a decrease in its speed.

The RPM and torque of a shaft are important factors to consider in the design and operation of mechanical systems. Engineers must carefully balance these variables to ensure that the system operates efficiently and safely and that the shaft is able to withstand the forces acting on it.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

A Gear Ratio is defined as the ratio of the rotational speeds of the first and final gears in a train of gears or of any two meshing gears. Essentially, the ratio of the input speed to the output speed of a geared set of shafts. These can be decided to choose a ratio of Speed (large gear driving small gear) or Torque (small gear driving large gear).

Gear ratios are often simplified fractions of the number of teeth on each gear. This is because (at least in Vex) gears have a proportional number of teeth to their diameter which defines the difference in output speed. From the above image, there is a 12 tooth gear, driving a 36 tooth gear which would constitute a 3:1 ratio.

The benefit of gear ratios is the ability to choose speed vs torque in a system. These have an inverse relationship however where a faster output will have lower torque. With the above example, the output shaft has 3x the torque, but also 1/3 the speed.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

The center of mass (COM) or center of gravity (COG) of a robot is the mean location of all the mass of a robot.

Measuring COM Position

• Model the robot in CAD, and use a "measure"-type tool.]

• Lift the robot by the chassis using 2 fingers. When the robot balances on your fingers, the XY location of the COM will lie in the line formed by your 2 fingers.

• Hang the robot, and observe how the robot tilts to settle.

Vertical COM Position (Z)

When a robot brakes, the friction between the wheels and the floor rapidly decelerates the robot (velocity is in the opposite direction of acceleration in this case). This creates a torque around the center of mass of the robot, jerking the back of the robot up. In many cases, the rear wheels lose grip with floor as well.

To mitigate jerking ...

• lower the height of the COM off the ground

  • use lighter materials in the upper sections of the robot (ex. 1x1 L channels on arms, plastic screws / nuts)

  • use heavier materials in the lower sections of the robot

• decrease the max acceleration available to the driver

• implement motion profiling and other motor control techniques

Horizontal COM Position (XY)

Turning

The turning center of the robot is less predictable if the COM (in the horizontal plane) is far from the midpoint of all the wheels. Keeping the COM centered side-to-side and front-to-back ensures more stable and predictable turning.

Hanging

The end effector used during a hang is typically implemented with a joint. If the horizontal COM is offset from the point where the robot hangs, the robot will tilt until the COM aligns directly beneath the hanging point.

Control

To control the position of the COM in the XY plane ...

• place towers optimally after building the chassis

• add/remove weight selectively around the robot

Torque, also known as moment of force, is a measure of the rotational force applied to an object. It is defined as the product of the force applied to an object and the distance from the object's axis of rotation to the point where the force is applied. Torque is a vector quantity, meaning it has both magnitude and direction.

Torque is often represented by the symbol "τ" (tau) and is calculated by the following equation

where:

• τ (tau) is the torque, measured in newton meters (N·m)

• F is the force applied to the object, measured in newtons (N)

• d is the distance from the axis of rotation to the point where the force is applied, measured in meters (m)

Torque is an important concept in mechanics, as it is used to measure the ability of an object to rotate around an axis. It is a fundamental principle in the operation of machines, such as motors, gears, and levers, which use torque to transmit power and motion.

In robotics, the most common way that torque is important is anything relating to motors. In a drive train, torque is needed to accelerate quickly, hold a top speed, and be able to push opponents on the field. In a lift, more torque allows the ability to lift heavier loads, lift items faster, and maintain speeds during lifting. For a flywheel, torque allows for higher speed, less loss of speed between shots, and easier tuning of speeds.

In summary, torque is a measure of rotational force that is essential in the design and operation of machines and structures. It is used to calculate the ability of an object to rotate, transmit power, and withstand external forces.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

The most commonly used type of metal in VEX, C-Channels provide a stable, secure grounding for a majority of subsystems that can be used. The “C” shape contains two corners, which give the C-Channel a strong, sturdy form, making it ideal for structural use and bracing. There are three variations of C-Channel, in terms of their width:

2 Hole Width

This variety is the most used of the three, as the relatively small form factor makes it ideal for conserving space and weight.

3 Hole Width

A balance between the smaller 2-hole and larger 5-hole widths, the 3-hole width c-channels are great for saving space and weight, while giving slightly more room for mounting subsystems to the chassis.

5 Hole Width

The largest of the three widths, 5 hole width maximizes space for mounting, while taking up considerably more space and weight. Ideal for making your bot heavier, and less susceptible to defense as a result.

U-Channel

A variation of the C-Channel, the U-Channel has an extra hole on the bracket portion of the stock, giving it a more “U” shaped appearance. This stock is great for bracing different towers and other supports, as the “U” shape can envelope the towers, adding additional space for box-bolts, making the towers more secure.

Angle Bar

Forming the shape of an “L,” these stocks of metal have either 1 or 2 holes on each end of the L, forming a 1x1 or 2x2 angle bar. Both are mainly used for support, rather than as a main piece of structure.

1x1 Bars

1x1 angle bars are mainly used for cross bracing, in the form of triangle or X bracing.

2x2 Bars

2x2 angle bars can be used to brace to parallel towers, while providing additional mounting space in the up or down direction.

Teams Contributed to this Article:

Types

There are three types of retainers sold by VEX Robotics which come in both hex nut and standoff retaining forms.

1-Post Retainer

4-Post Retainer

1-Post Retainer With Bearing Flat

Use Cases

Both hex nut retainers and standoff retainers alike have significant use cases thanks to their fastener captivity ability. Generally, these retainers can serve as a gateway to saving weight on a robot because they make previously obscure fasteners more viable by allowing them to stay captive. For this reason, nuts that would struggle to stay threaded onto a screw when faced with vibration, such as a basic steel hex nut, could be used liberally with the help of a retainer. Some helpful use cases for using a retainer could include:

• Attaching a hex nut/standoff retainer with bearing flat on a rotating mechanism to reduce friction while saving weight.

  • Unlike a normal bearing flat, which requires two screws and two nuts to attach to a robot, a retainer with bearing flat only needs one screw and one nut.

  • Since a retainer with bearing flat is mounted off-center (the bearing hole is on the side), attention to detail is required to ensure that the retainer properly aligns itself and is flush with the metal.

• Utilizing 1-post hex nut retainers to make the following fasteners impervious to vibrations and therefore viable:

  • Steel 8-32 hex nut

  • Nylon 8-32 hex nut

  • Aluminum 8-32 hex nut

• Utilizing 1-post standoff retainers to make the following fasteners impervious to vibrations and therefore viable:

  • Narrow 8-32 hex nut

  • 4-40 hex nut

• Using a 1-post hex nut/standoff retainer's protruding square peg to eliminate slop between two pieces of metal while also potentially saving weight in the process.

  • Rather than using two shoulder screws to fasten the two surfaces together, only one is needed since the retainer's square peg will inherently eliminate slop.

• Using a 4-post hex nut retainer to save weight (by only requiring one pair of fasteners instead of two) and eliminate slop at an attachment point of two perpendicular C-channels.

  • This should only be done in low-stress situations. If done in a scenario where the perpendicular C-channels are likely to become deformed, the structural integrity of the 4-post hex nut retainer is ambiguous.

Teams Contributed to this Article:

Bearing Flats

The most frequently used type of bearing among competition teams, Bearing Flats are most often used on joints to ensure the axle spins smoothly without jamming against a flat face.

Pillow Block Bearings

While not quite as commonly used as Bearing Flats, Pillow Block Bearings achieve a similar function for a different use-case.

While standard Bearing Flats are mounted the the main structural component parallel to the axle of the rotation, Pillow Block Bearings are mounted in a perpendicular fashion. For example, Pillow Block Bearings would be mounted on the top of bottom of a c-channel flange, whereas a standard Bearing Flat would be mounted within the two flanges. Using a Pillow Block Bearing can help either raise or lower the main chassis structure from the ground, either raising or lowering overall ground clearance.

High-Strength Varieties

Both Bearing Flats and Pillow Block Bearings are available in high-strength varieties. These high-strength bearings have a much larger center bore, in order to accommodate high-strength axles.

The high-strength Bearing Flats and Pillow Block Bearings do not differ in overall functionality from their standard variants, the only difference is their ability to accommodate a larger axle. These parts can be useful for high-stress environments when designing a robot, such as in high-torque gear ratios.

Ball Bearings

Ball Bearings are an incredibly versatile option for ensuring low-friction under stress in moving parts.

While taking up more space than a standard Bearing Flat, Ball Bearings do offer unique advantages, such as consistently low friction under heavy load. Because of this, Ball Bearings are incredibly useful for high-speed mechanisms such as Flywheels, where having consistent rotation and low friction are essential.

Gussets

There are many different varieties of Gusset available to use in the VEX Robotics Competition, which can be broken down into two overall categories: Angle Gussets and Coupler Gussets.

Angle Gussets

While there are a variety of different Angle Gussets available, they are all similar in that their purpose is to mount structural components at various angles and elevations.

Coupler Gussets

C-Channel Coupler Gusset

Angle Coupler Gusset

Though less popular than other available gussets, Angle Coupler Gussets are still an effective way to connect or reinforce structural components.

Brackets

Brackets are a relatively uncommon part used in the VEX Robotics Competition, marketed mostly towards containing various gearboxes that can be constructed using VRC-legal gears.

Metal Material

While being a seemingly insignificant factor, choice in metal material can have a drastic impact on a robot's performance. There are two types of metal used in VEX products:

Characteristics

On the Robot

Due to its lighter weight, aluminum should be used in subsystems that need to be kept as light as possible, such as lifts and game piece manipulators.

Steel is commonly used in areas where weight is less of a concern, or when a subsystem needs to be made heavier. In the event of a drive ratio favoring torque, a robot can be made heavier to help prevent being pushed by other robots.

As a general rule, however, aluminum should be used in the vast majority of places. Having a heavier robot, unless designed to be so, can be detrimental, and using aluminum instead of steel helps to drastically reduce the weight of a robot or subsystem.

Washer Material

Similar to the material of metal used, different types of washers can have drastic effects on the performance of a subsystem.

Using plastic washers between two pieces of metal or metal and plastic helps to drastically reduce friction, and provides for a much more smooth rotation. In cases of plastic on plastic contact, metal washers provide the same benefits.

Traction wheels, mostly only referred to plainly as "wheels" by VEX, are the simplest wheel type offered in the VEX Robotics Competition, only having one degree of freedom (forward and backward). They are made up of two simple parts: an acetal frame and a tire that fits around said frame, typically made of rubber or a material similar to rubber. They are typically used in the center of drivetrains to restrict unwanted sideways movement (such as from defense).

Variations

Although all anti-static wheels perform identically, the original wheels and traction wheels all have very different functionality.

Anti-Static Wheels

Anti-static wheels have a high amount of traction and, unlike their predecessors, have a uniform width and tire shape. Although they are wider than the original wheels, this is actually an advantage rather than a detriment since the larger tire surface area increases the odds that the wheel will make contact with the field tiles, allowing the tire's traction to have a larger effect on the wheel's overall performance. Additionally, the width for all three sizes only comes out to be 1 inch, a compact wheel in comparison to the various wheels VEX Robotics has manufactured.

Conveniently, the hubs of the wheels come with many mounting holes which allows the user to fasten gears or other relevant motion objects onto the hub.

These wheels have tires with special properties that prevent the accumulation of static, which decrease the odds of damage to electronics due to electrostatic discharge. For this reason, the tire material feels slightly different from the original tires which are made entirely of rubber.

Original Wheels

2.75" wheels feature a small hub and a green, filleted tire. Although the traction of the rubber on the wheel's tire is excellent, the fillet of the tire causes massive loss of traction due to there being a very small point where the tire actually contacts the tile. The fillet of the tire can actually be useful in use cases other than a drivetrain, though, such as spinning a roller from a wide angle in the 2022-23 VRC game Spin Up, for example.

3.25" traction wheels have the most unique structure of the original wheel variations, boasting mounting holes on its hub akin to the ones seen on the anti-static wheels and having a unique tire shape which features bumps protruding from its circumference. In its base state, the 3.25" traction wheel has been widely avoided because of its "bumpy" tire shape. Due to the topography of the tire being variable, it loses out on potential traction it could have gained by having the receding parts of the tire contacting the field tiles. However, legally modified 3.25" traction wheels used to be considered viable in Tipping Point before the release of 3.25" anti-static wheels. Using a belt sander, teams such as 99999V would sand away the bumps on the tire, making the tire's circumference constant. With this new wheel, teams would use it as a hub for a 3" flex wheel tire (a flex wheel which has all of its spokes cut out).

4" traction wheels have the unique property of having interchangeable tires, being the only wheel where this is an intended feature. There are two possible tires: the base tire and the high traction tire. The base tire lacks traction almost entirely and takes up a strange pattern of triangle and lines in an attempt to mimic car tire tread. The high traction tire has significantly more traction, but suffers from the same issue as the 2.75" wheel, in which the filleted tire causes the contact area of the tire to be very small.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

This section covers the difference between various High Strength and Low Strength components in VEX. While the two variations do function as the same part, there are often different use-cases, as well as extra considerations that need to be taken into account.

Metal Shafts

Outside of screw joints, metal shafts are the main way of transferring energy in VEX, by use of sprockets or gears mounted to the shaft.

Low Strength Shafts

Low strength shafts are the much more commonly used variant of shaft. the main reason for this being that low strength shafts fit through standard bearings and metal without any alterations.

This variant of shaft is much more flexible and likely to be bent in high torque situations, and should often be checked and replaced if needed as such.

High Strength Shafts

High strength shafts, while useful, are not used in nearly as many places as low strength shafts. The main reason for this being that high strength shafts do not fit through the standard holes in metal, meaning that larger holes will have to be manually drilled out.

High strength shafts, as the name implies, are much more durable than low strength shafts, being able to be used in much higher torque situations as such. For instance, high strength shafts are ideal for linking both sides of a lift through a common shaft.

Gears and Sprockets

Sprockets

As high and low strength sprockets have different size teeth, the different size sprockets cannot be linked to one another, as each requires different size chain.

In the vast majority of cases, high strength sprockets and chain should be used over low strength. The main reason for this being that you want to make chain as unlikely to snap off as possible, and using high strength chain further decreases those odds.

Gears

Unlike with sprockets, the teeth on high and low strength gears are the same size, and can therefore be used in conjunction with one another.

Dissimilar to sprockets, there is not so much a clear cut boundary of when to use high and low strength gears. In higher torque situations, using high strength gears is advisable, as the extra thickness reduces the odds of the gear snapping. In lower torque areas, or in places where space is a concern, using low strength gears may be a better option.

Due to the popular use of gears in a drivetrain, it is worthwhile to note that low and high strength gears can be alternated in the gear chain. This is a good balance between the risk of gears snapping in an all low strength gear drive and the bulkiness of an all high strength gear drive.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

• 94999E (Yokai Robotics)

Mecanum wheels are advanced wheels used widely in the scope of robotics and often in compeitive robotics due to their ability to introduce fully omnidirectional movement onto a drivetrain. These wheels take advantage of angled rollers which restrict their degrees of freedom onto one axis, allowing them to move freely diagonally. When spun in a uniform direction, the mecanum wheel functions as a typical wheel and propels a drivetrain forwards. However, when spun in conflicting directions with the wheel adjacent from it (in terms of a four wheel drivetrain), the robot begins to strafe thanks to its angled rollers.

Variations

In VRC, there are only two legal sizes of mecanum wheels: 2 inch and 4 inch. Each size has two variations which are crucial to the functionality of the drivetrain: a left and a right variant. The difference between those two variants is that the rollers angle themselves inherently differently.

The proper placement of these wheels based on their variants is described in the article "VEX Drivetrains"; this placement holds true for any mecanum wheel, regardless of its size.

Traits and Performance

While these wheels theoretically allow a robot to strafe in all directions, the mecanum wheels manufactured by VEX Robotics are riddled with a number of tradeoffs that can make them difficult to use effectively. However, they can be elegant when paired with the right builder, programmer, and/or driver.

Generally speaking, mecanum wheels inherently suffer from a few tradeoffs that can be mitigated through a smart design, but never eliminated completely. For example, because of inevitable frictional losses from the rollers, a realistic mecanum wheel drivetrain cannot strafe as fast as it can move forward. For a similar reason, mecanum wheels require a lot of torque to power in tandem with each other since they must move in conflicting directions in order to strafe, making it very difficult to strafe with them at any linear velocity above 3.29 m/s (300 RPM on 4 inch wheels). Additionally, these wheels are burdened by any shift in center of gravity, meaning that if the center of gravity is not close enough to the center of the robot, the wheels will simply fail to strafe and will cause the drivetrain to turn instead.

2 Inch Wheels

First manufactured as a part of the VEXpro line and then made legal for use in VRC in 2021, the 2 inch mecanum wheels appear to be a compact solution to the complexities of holonomic movement. They measure 1.5 inches (around 38 mm) in width, and of course boast a very small diameter. Unlike most other wheels used on drivetrains, this size of mecanum wheel in particular utilizes a hexagonal bore, meaning it is necessary to use a VersaHex to convert the bore into a square bore.

The functionality of the 2 inch mecanum wheel has been an enigma that competitors have been desperate to understand further. Although mechanically rated to be suitable for a VEXU drivetrain (therefore also making it compatible with a VRC robot), it has been observed that these wheels actually have trouble supporting the weight of the robot. This is because the architecture of the wheel's frame gives a near-zero amount of clearance between the frame and the rubber roller, causing the frame to actually sink into foam tiles if the robot is too heavy. For this reason, it has mostly been limited to usage on intakes. If used on the drivetrain of a moderately heavy robot, the robot will struggle to strafe as the angled rollers will be unable to make sufficient contact with the tiles.

Multiple plausible solutions to the wheel's clearance issue have been proposed, although it is unclear how effective each solution actually is because there has been limited testing of this wheel in drivetrain usage.

The first obvious solution that has been attempted is to shave down the area of the frame near where the pin connects to the roller, thus artificially increasing the clearance between the tile and the wheel's frame. This would allow the wheel to be more "tolerant" of sinking into the tiles under the robot's weight. One potential issue that could arise from this is the chance that shaving down the frame too far may lead to a detrimental decrease in structural integrity near the pins of the roller, which may cause the wheel to disintegrate altogether if used in a high-stress situation.

The second suggested solution is to use eight wheels instead of only four on the drivetrain, thus spreading out the weight of the robot amongst more wheels which would lead each wheel to sink into the foam tiles less. This comes with two major tradeoffs, though: it is expensive to purchase four extra wheels to do this, and it also requires much more space since there is not only more wheels but also the necessity to introduce an additional gear train to ensure each wheel moves in the proper direction.

The final solution is to simply make the robot lighter, but this is incredibly difficult considering that the weight threshold of the 2 inch mecanum wheels appears to be relatively low; through testing done by BLRS3, it seems to not be possible to have a drivetrain of four 2 inch mecanum wheels that strafes properly if the robot weighs anywhere above 13 pounds, and even going below that still may not ensure optimal performance.

4 Inch Wheels

Manufactured since 2011 as a part of the then-named "VEX EDR" line, 4 inch mecanum wheels are a reliable but somewhat bulky option to use in creating a holonomic drivetrain. These wheels measure in at around 2.5 inches in width, and, deceptively, their diameter actually happens to be 4.125 inches, not 4 inches.

Although not afflicted by the same clearance issue as the 2 inch mecanum wheels, the roller profile of the 4 inch wheels cause a couple of issues.

First of all, the rollers are arranged in a dual-sided cantilevered setup, which causes immense amount of friction for the rollers. This limits how quickly the mecanum wheel can strafe, making it such that the strafing speed is somewhere around 80% of the forward speed from frictional losses alone. These frictional losses are of course subtly seen on the 2 inch wheels, although its not clear how close or far they are in magnitude to the 4 inch wheels' losses due to a lack of data.

Second of all, each roller utilizes a conical sort of shape, more specifically that of a cone's frustum. This minimizes the wheel's traction because the wheel covers less surface area, giving it more of a chance to slip because the force of friction is acting on a smaller area. Other, more effective mecanum wheels appear to utilize cylindrical rollers instead.

Teams Contributed to this Article:

• BLRS, BLRS3 (Purdue SIGBots)

Gears and sprockets are both used to transfer motion from a powered to an unpowered object, with the difference between the two being how they carry that motion.

Gears

Gears transfer motion by meshing with each other, turning other gears in a sequence/ratio. They are ideal for covering shorter distances, or larger distances with a long gear sequence. It should be noted, however, that the more gears are added to a sequence, the more friction and energy loss incur, reducing the overall effectiveness.

In addition to carrying motion in a 1:1 ratio, gears can be used to amplify and detract from the speed and torque generated by the motor. For more information on ratios, click here. Gears are produced in the following varieties, differentiated by the number of teeth on each gear:

In addition to the different sizes of gear, gears are also produced in both low and high strength thickness grades. Both high strength and low strength gears can mesh with one another.

Sprockets

Sprockets transfer motion by using chain to link multiple sprockets together, as individual sprockets themselves should not be physically meshed together. They are ideal for covering longer distances with minimal moving parts, or in scenarios where gears cannot be properly spaced. Although sprockets and chain are more flexible than gears, chain carries the inherent risk of snapping while in use, rendering the driven component motionless.

Similar to gears, sprockets can also function in a ratio. For more information on ratios, click here. Sprockets are produced in the following varieties, again being differentiated by the number of teeth:

As described in the chart, sprockets are produced in a both high and low strength varieties. Unlike gears, however, low and high strength sprockets are linked with different size chains, making it impossible to mess high and low strength sprockets.

Chain Tensioners

The use of chain tensioners provides additional stability to large chain routes on a robot, reducing the likelihood of chain snapping during competition.

Chain tensioners are often created by use of a screw joint, with the exception of using free-spinning spacers instead of metal to rotate on the screw. As such, no bearing is necessary, as the screw will be stationary on the metal, and spacers require no bearings.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

• 94999E (Yokai Robotics)

Plate Metal

As barebones as it gets, Plate Metal is a 5x15 or 5x25 hole plate consisting of the standard square VEX bores every 0.5 inches (12.7mm).

Given the lack of flanges on either end of the plate, Plate Metal tends to be flexible along the longer flat face. As such, it is not advisable to use plate metal for any use-cases that require rigidity in that direction - Plate Metal is considerably stronger along the thin edge faces. One of the more common uses for Plate Metal is to cut and form it into custom-shaped pieces, rather than cutting plastic to achieve the same result. Using Plate Metal for this functionality keeps the standard VEX bore spacing, as well as introducing more rigidity compared to VRC-legal plastics.

Plate Metal can be found at vexrobotics.com.

Flat Bars

Similar to Plate Metal, Flat Bars are flat surfaces consisting of the standard VEX square bores, appearing in a 1x25 hole variety.

While not as apt for making custom pieces as Plate Metal, Flat Bars are still effective as a source of mounting parts that require little rigidity over longer distances. Use-cases that require stronger connections, such as bracing important subsystems on a robot, should be left to stronger components such as C-Channels or Standoffs.

Flat Bars can be found at vexrobotics.com.

Items Needed

• Electric Stove (DO NOT USE GAS)

Instructions

1. Clean parts thoroughly with dish soap to remove dirt or oils.

2. Add roughly 3 parts water along with 1 part dye and 1 part acetone to a stainless-steel bowl. Have enough liquid to cover the desired parts. (Additional water, acetone, and dye will be needed to have more on hand)

3. Place the bowl on the stove over Medium/Low heat until the mixture reaches 160°F.

4. Add desired parts to mixture slowly and carefully. Beware of splashing as mixture should be coming to a low boil.

5. Monitor mixture's temperature and volume. The goal is to keep the mixture between 160°F and 190°F with all parts consistently submerged. Stir occasionally and add more water, acetone, and dye as needed to keep volume consistent. When adding acetone, always pre mix with water.

6. After 10-15 minutes (when parts are dyed to satisfaction), let bowl cool and rinse parts thoroughly until water runs clear.

Additional Notes / Recommendations

• The best color to aim for is black. Anything lighter is difficult to produce with green parts especially. Colors such as purple and orange are possible with basic color combinations however will take more practice and tuning to get right.

• When working with smaller parts such as nylon spacers, stir more often as the dye tends to settle and parts may come out cloudy or inconsistent.

• Dyeing of wheel rollers (omni / mecanum) is possible but tend to wear out over time. Assure that no residue is left behind in testing as damage to field or game elements can be cause for disqualification from a tournament.

• If a part is heated too high or for too long, it can alter the physical attributes of the part which would render the part illegal for use in VRC and IQ competition.

Teams Contributed to this Article:

Non-functional 3D printed license plates, are permitted. This includes any supporting structures whose sole purpose is to hold, mount, or display an official license plate.

Teams Contributed to this Article:

Painting

Some helpful notes

• Apply several light coats with time to dry between. Use at minimum 3 coats while avoiding heavy coats that would fill holes in metal or distort dimensions.

• Use high quality, trusted spray paint designed for metal. The paint will chip as a result of use and match play. It is better to put in effort up front to assure the metal lasts longer.

• A final clear coat is recommended

Anodizing

Anodizing metal is not an easy or cheap process but does lead to a better result than painting which is why it is chosen by some teams. Most schools do not have the ability to anodize in house so some commonly used vendors have been compiled.

Teams Contributed to this Article:

Omnidirectional wheels are a commonly used wheel type within the VEX Robotics Competition that make use of many cylindrical rollers to ensure that the wheel itself has more degrees of freedom.

Unlike a typical wheel which only has one degree of freedom in the forward/backwards direction, the omnidirectional wheel has an additional degree of freedom with sideways movement. Some benefits to this additional degree of freedom include being able to make fluid turns and the potential for holonomic drivetrains to be created. However, this behavior also means that a robot utilizing only omnidirectional wheels on its drivetrain is much more prone to defense from adjacent robots. Teams have historically used omnidirectional wheels in tandem with traction wheels at the robot's center of turning in order to mitigate the effects of defense.

Variations

There are six variations of the omnidirectional wheel that are legal for use in VRC. The wheels come in three sizes, and also have two functional variants: original or anti-static.

Anti-static wheels were developed in order to try and mitigate the amount of static built up from the wheels rubbing against the field, therefore decreasing the odds of damage to electronics due to electrostatic discharge. These wheels also happen to be thinner than the original wheels for all sizes and have smaller rollers.

Unique Traits

In the case of the 4 inch omnidirectional wheel, the anti-static version is genuinely 4.00 inches in diameter as compared to the 4.125 inch diameter of its original counterpart. This makes it compatible geometrically with other wheels, like a 4 inch flex wheel or a 4 inch traction wheel.

The original 3.25 inch omnidirectional wheels have been less favored by the VRC community because they are the only set of wheels which utilize plastic rollers rather than rubber rollers. This leads to an immense loss of traction, making it less reliable when facing off against defense or in the instance of a platform needing to be climbed, like in Turning Point and especially Tipping Point. However, these wheels do have their advantages. They are the thinnest of the original trio of omnidirectional wheels, coming in at the same width as the anti-static wheels, and it is also possible that the plastic rollers may bring less frictional losses when used on a holonomic drivetrain like an X-drive.

Usage

Omnidirectional wheels have been commonplace on VRC drivetrains since their creation. They are especially useful when creating X-drives or "Kiwi" (three wheel holonomic) drives because of their ability to expand the amount of degrees of freedom the drivetrain has. When the wheels are arranged diagonally, the robot is still able to move smoothly because as it moves in any direction, the wheel's rollers spin along with the wheel, accounting for the movement in both the sideways and forwards direction.

2.75" omnidirectional wheels can make great tracker wheels for odometry purposes due to their small diameter. In fact, 2.75" omnidirectional wheels used to only be used for odometry, until more recent seasons in which teams have begun to get more creative with their drivetrain gear ratios.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

• Matthew 1727B (REX)

Flex Wheels, formally known as "Straight Flex Wheels" are compressible cylinders with spokes made of a blend of rubber silicone. The compressible nature of the Flex Wheels makes them versatile for many use cases, such as intakes, flywheels, and drivetrains. Additionally, because their composition includes rubber, their coefficient of friction is higher leading to a significant amount of traction.

Flex Wheels are an unusual exception to other motion components: they do not utilize the typical square insert, but instead utilize a hex bore which is typically filled using a VersaHex as well as a VersaHub if it is necessary depending on the size of the Flex Wheel.

Sizes of Flex Wheels

For VRC, Flex Wheels come in four sizes.

There is also a Flex Wheel with a 5 inch outer diameter, although this is not legal for VRC.

Hardness of Flex Wheels

Each Flex Wheel has a given durometer reading, which measured how difficult it is to compress the wheel. There are three variants:

• 30A

  • Light grey in color

  • Easiest to compress

• 45A

  • Grey in color

  • Compresses moderately

• 60A

  • Black in color

  • Incredibly difficult to compress

For flywheels and drivetrain traction wheels, 60A Flex Wheels are typically ideal. However, for intakes, 30A Flex Wheels might be more ideal. 45A Flex Wheels do not have many use cases, however they could hold some merit for use on 1.625" Flex Wheels.

Attaching Flex Wheels to Axles

Because Flex Wheels utilize a hexagonal bore rather than a square bore, it means that you have to utilize unique methods to attach them to axles compared to any other motion component.

Using "Versa" Adapters

There are two types of adapters relevant to Flex Wheels: VersaHexes and VersaHubs. These two adapters are the most common method of attaching Flex Wheels to square axles. However, while VersaHubs and VersaHexes are reliable, they also may not be available always due to their consistent high demand.

VersaHex Adapters

The VersaHex Adapter is the primary adapter used for any Flex Wheel with an outer diameter smaller than 3 inches. The adapter is slightly larger than the hexagonal bore in the Flex Wheel, meaning the wheel has to be stretched a bit to allow the adapter to fit. This is easy to use on small wheels with durometer readings of 30A or 45A, but it may make it difficult for the adapter to fit on a very hard wheel like a 60A wheel.

VersaHex Adapters are also necessary to convert a VersaHub Adapter's hexagonal bore into a square bore.

VersaHub Adapters

The VersaHub Adapter is the primary adapter used for any Flex Wheel with an outer diameter of 3 inches or larger. It also is used in tandem with a VersaHex Adapter as its secondary adapter. Large Flex Wheels have large, circular holes in the center of them. The purpose of the VersaHub Adapter is to convert the large circular bore into a hexagonal bore, which then allows for the VersaHex Adapter to convert the hexagonal bore into a square bore. Unlike the VersaHex Adapter, the VersaHub Adapter is not as much of a friction fit, in the sense that it does not need to stretch the circular hole in order to fit. This makes it easy to fit a VersaHub Adapter into a hard wheel, such as a 60A 3 inch Flex Wheel, whereas it would be difficult to fit a VersaHex Adapter into a 60A 2 inch Flex Wheel.

"Press Fit" Custom Adapters

It is possible to use common VEX components rather than VersaHexes and VersaHubs to create a square bore within a Flex Wheel. Typically, you would use a circular component that has an area for a high strength shaft insert (such as a square insert) to be placed inside of it. You would then fit the circular component into the Flex Wheel by stretching the wheel's circular bore with the component to create a friction fit.

Press Fitting a Gear/Sprocket

One way to create a custom adapter would be to fit gears into the center of a Flex Wheel. For 3 inch and 4 inch wheels, a 36T High Strength Gear should suffice as a friction fit, although it should be noted that it would be incredibly difficult to fit it into a Flex Wheel with a hardness of 60A since a 36T High Strength Gear stretches the circular bore considerably.

For smaller Flex Wheels, a 12T Pinion is perfect as a friction fit in the hexagonal bore of the Flex Wheel. Additionally, this method does not stretch the bore as much as a 36T High Strength Gear would stretch the circular bore, so it may be possible to use this method with a small Flex Wheel that has a hardness of 60A.

Hardware-Based Custom Adapters

Various hardware components can be used to create custom adapters. These usually don't deform the Flex Wheel as much unlike a press fitted custom adapter, making them easily compatible with wheels that have a 60A durometer reading.

Some useful components that could be used when creating a custom adapter include:

• Lock Bars

• Steel/Aluminum Plates

• Polycarbonate when used in tandem with a laser cutter or CNC mill

Cutting Flex Wheels

3" and 4" Flex Wheels are manufactured with a 1" thickness, much too high for many use cases. Because Flex Wheels are made of silicone, they are very difficult to cut, so guides are often used to ensure a precise division and increase safety. 3D printed cutting guides for all Flex Wheel sizes can be found here: https://github.com/owen169/Flex-Wheel-Guides.

If you don't have access to a 3D printer, try making your own guides.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

The double reverse four bar (also referred to as DR4B or RD4B) lift is one of the more complicated lift designs used in VEX Robotics competitions. The lift is comprised of two iterations of a four bar lift. One iteration is mounted in the same manner as for a standard four bar lift. The second iteration is mounted at the end of the first iteration at the location where the intake or object manipulation mechanisms would normally be positioned. The second four bar lift faces the opposite direction as the first iteration. This allows the overall lift to rise almost completely vertically as opposed to a single four bar lift that rises forward and up simultaneously. This can be an advantage or disadvantage depending on the desired task.

Double reverse four bar lifts keep the weight of a load centered over the base of the robot instead of lifting it up in front of the robot. To be more specific, the center of gravity of the robot goes slightly backwards before going forwards when lifting a load up. This helps prevent the robot from tipping over. The double reverse four bar lift has a significant height advantage over a four bar lift without the lifting the load in front of the robot. The double reverse four bar lift design is much more complex than a four bar lift or a six bar lift and thus is more difficult and time consuming to build. Double reverse four bar lifts must be carefully constructed, coded, and maintained to ensure optimal functionality. They are more prone to breaking parts and motors than other lift designs.

Pros and Cons Analysis

Weight Classes of Double Reverse Four Bars

Depending on whether or not the lift needs speed, height, or torque the core design of the lift changes.

Lifts that are designed for height are usually more heavy because they have longer arm lengths and have a series of bracing and supports so that the lift and reach its maximum height efficiently keeping the lift very stable and lifting straight up and down without leaning to the right or left.

Lifts that are designed of speed are significantly lighter than height based DR4Bs so that they have less inertial mass. Things that have less inertial mass are more susceptible to changes in velocity allowing the lift to move up and down very quickly and with significantly reduced recoil.

In reality the lift should designed be somewhere in the middle of tall and fast because a short and slow lift is useless. That's why there is 4 main weight classes of DR4B designs:

• Heavyweight

• All Round

• Lightweight

• Featherweight

These terms are fairly arbitrary and are just to group together similar designs. Rather than exact definitions it is better to think of these weight classes as a spectrum and as the lift can take design aspects of each weight class to better fit what it needs.

Heavyweight

This weight class is typically only found in VEXU because of size and motor restrictions. But nonetheless highlights important design considerations to make an all rounded lift more sturdy and stable. It should also be noted that its ability to be used as a 24" robot as a relatively wide lift allows for more cross bracing between the two sides of the lift (as shown in the "Big Chungus" pictures), or potentially another subsystem if the team plans accordingly.

Characteristics:

• Powered from bottom and middle

• Heavy Top Manipulator

• Boxed C Channels

• Very Tall

• Lots of C Channel bracing

• Lots of rubber bands to counteract the weight of lift and manipulator

• Strong drive train to be able to move around lift as well as the game objects without getting tired

All Round

An extremely reliable lift with 2 motors that is both quick and tall is easy to do the with the power of V5 motors. This type of lift is going to fit the needs of most applications.

Characteristics:

• 2 V5 Motors

• Powering motors are in the middle

• Found with decent amount of cross bracing

• Typically done with Double Reverse Four-Six Bars to increase height.

• Recommended to use 2 V5 Motors

• Powered in the middle

• structurally made almost entirely of 2 wide channels

Lightweight

The lightweight weight class is a good option for motor count efficiency or lighter game elements (Example: Cones in In The Zone and Caps in Turning Point).

Characteristics

• Potentially could be powered with 1 V5 Motor

• Stand off bracing

• Can typically be found with half-cut C-channels to reduce weight.

• Typically done with Double Reverse Four-Six Bars to increase height.

• Lighter weight intakes to reduce strain on lift itself

Featherweight

This design of double reverse 4 bar is a very niche weight class and strips down the "Double Reverse" design to its bare minimum to create a very space efficient lift. These designs typically have another actuating device or lift on the end of the lift and can be used

• Similarly to the lightweight class, these have smaller intakes for reduced strain on the lift.

• Lift towers are mounted very close together.

• Instead of having two sides, the upper portion of the lift in this class normally consists only of one centralized section (as shown in picture above).

• Mounting intakes on this lift is typically harder due to the lack of two mounting points on two sides of a normal DR4B.

The "Double Reverse" Design

One thing that may be important to note is that the "Double Reverse 4 Bar" design is just an umbrella term for the "Double Reverse" design as a whole. The "Double Reverse" design is not rigid that requires have 2 four bars. The only requirement for a lift to be a "Double Reverse" design is to have one lift with another mechanically connected lift on top of it. This is important because the main idea of the "Double Reverse" design is to combine the heights of 2 bar lifts. Combine the knowledge of other bar lifts and linkages to be able to design the perfect lift for the job.

The following lifts are not "DR4Bs" and use different techniques to make the lift taller.

Consensus

These can be regarded as difficult, but they are much more stable, compact, and easy to maintain than other lifts that reach similar heights. This type of lift has been incredibly popular for both the Skyrise and ITZ seasons, and for good reason.

The six bar lift is a derivative of the four bar lift. It utilizes the same geometry of four parallel bars, but in two stages. This split into two stages allows the lift to maintain a lower profile on the robot and condense into a smaller space, allowing for a larger lift to fit within the build limits.

It is typically recommended that only the top bar on the static end be driven by the motors, as there will be increased friction on the bottom arm as compared to the top. This can be alleviated by utilizing a PID control on the arm to ensure that one motor does not provide more force than the other on a given side, stressing the lift components and motors. As with every lift, using screw joints is highly encouraged to reduce friction, decrease slop, and increase strength.

Pros and Cons Analysis

Because the lifting length is longer on a six bar than a four bar, more torque is required in order to lift the arm to its full height. The weight and length of the six bar lift also creates additional friction on the joint of the lift and the motors powering it. This can lead to more issues than would be encountered with a four bar lift such as burnt out motors or broken parts. The added length of the lift arm can create a greater tendency for the robot to tip forward when lifting or moving. Heavier loads will increase this chance of tipping. Despite these issues, the six bar lift is a very common lift system as well because it is relatively easy to build and maintain when compared to scissor lifts and reverse six bar lifts. Like the four bar lift, the six bar lift keeps the lifted end at the same angle throughout a lift or decent.

Resources

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

• MTBR (University of Michigan Task Based Robotics)

Two Bar

Description

Compared to other lifts found on robots, the two bar is one of the easiest and lightest lifts to build. Usually consisting of 4 c-channels (2 used for the tower and 2 for the lift), the two bars are usually used when a robot would like a lift, but one that does not take a lot of space. One of the main downsides and features of a two bar is that the orientation at the end of the lift stays constant despite lift angle. In addition, compared to other lifts, the two bar cannot carry as much weight compared to other lifts. Some examples of the usage of the two bar lift can be found in the game Tower Takeover as shown above.

Pros and Cons Analysis

Best Practices

• Make sure the c-channel is secured on the axle of the motor

• Make sure the axle is secure in the motor.

• If possible, use a gear ratio with a screw joint to reduce slop and increase torque of the motor.

Chain Bar

Description

With a similar appearance to a 2-bar, the chainbar has the compactivity of a 2-bar but with the capability to keep its mounting orientation constant throughout its movement.

This is done by adding a fixed orientation sprocket at the base of the lift bar, and then adding a free-turning one at the end of the lift bar with both being constrained by chain. If an intake or mechanism is mounted on the sprocket(s) at the end of the lift, the mechanism will maintain the same orientation throughout the lift's movement.

Pros and Cons Analysis

Best Practices

• Best practices for 2-Bar also applicable here

• Make sure chain is tight, avoid using mechanical tensioners as seen in picture above if possible to increase mechanical efficiency.

• Try to keep the mounted intake or subsystem light, to reduce load on chain.

Elevator/Cascade Lift

Example: NorCal 2021 Robot (View in .5x or full screen):

Example: Jpearman Prototype

Description

A cascade or elevator lift is a lift that provides an immense amount of height, while taking not a lot of space. It utilizes c-channels, sprockets, and chain to connect each bar together. These bars run parallel to the structural frame of the lift, which is connected to the chassis of the robot. Issues that are prevalent among cascade lifts is the lack of support found on the lift, as when fully extended, the linear characteristic of the cascade lift could cause issues in preventing the lift from failing. In addition, the difficulty in tuning and repairing cascade lifts due to its compactness makes it difficult for quick repairs or adjustments when failures do occur.

Pros and Cons Analysis

Best Practices

• Reduce friction between the c-channels

• Make sure the chain used is tight

• Try to reduce weight of structural c-channels by using thinner c-channels or aluminum without degrading structural stability.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

The scissor lift is named because of its overlapping metal bars that open and close similarly to scissors. Scissors lifts are comprised of two sets of overlapping bars, one on each side, that are able to freely rotate in respect to one another. The lift can be as simple as two crossed bars on either side of the lift, but it can also contain many repeated iterations, stacked vertically, of the first one and be able to extend to many feet off of the ground. The upward motion is created by motors located at the base of the lift that move one edge (either the front or the back) while the other edge remains stationary but is allowed to rotate. Moving the two edges closer together will extend the lift upwards and moving them apart will lower it.

One of the biggest advantages of a well-designed scissor lift is the fact that the weight of the load will always remain over the base of the robot and thus help the robot to remain upright. With lift systems like the four and six bar lifts, the load will be moved up in front of the base which can cause the robot to fall forward. Another advantage of the scissor lift is its collapsible nature. A scissor lift can often compress to almost completely flat which allows for the robot to fit within size restrictions or pass under overhead obstacles, such as those that appeared in the Toss Up competition. One of the issues with scissors lifts is the precise calibration that they demand. Both the left and right sides of the lift must move up and down in almost perfect unison. If the two sides are not aligned properly, the lift may start to bend to one side or another. This could cause a loss of game object due to a non-horizontal containment field or cause the robot to tip over due to a center of gravity that is no longer above the base of the robot. In order to prevent this, the lift must be carefully constructed, constantly inspected, and the code should take advantage of many sensors to ensure that the motors controlling the lift are working at the same speed and power.

Pros and Cons Analysis

Good Practices and Optimizations

Below is a video from 53999f showing scissor lift optimization. Although not built in an ideal way, it does a great job in showing the potential optimizations that can help improve the scissor lift.

As shown in the video above, cross bracing and other bracing is used to help further stabilize the lift. This is crucial given the height of the lift, so both sway and other movements do not effect the lift's functionality.

Joint vs Slide vs Gear Base

Since the scissor lifts have terrible friction when built with VEX linear sliders, some teams have found an alternative in this by building their base with a gear mechanism. This reduces the friction and increases mechanical efficiency when built properly.

Below are some examples, all credits belong to their respective teams.

This building technique is something that is often overlooked as the stigma behind scissor lifts (hence the controversy) is the reason most teams do not even take this design into consideration. However, by using gearing rather than linear sliders the largest downside of using a scissor lift can be overcome.

Consensus

Scissor lifts are generally harder to build than Double Reverse Four Bars. However, its advantages over the DR4B should not be overlooked. Most notably, its the much higher maximum size, its relatively stable platform, and its potentially large platform size for mounting other subsystems. When deciding which lift to build, teams should consider what the right tool for the right job is as well as if their members realisitcally have enough skill for certain lifts, as scissor lift construction has a very high skill ceiling.

Screws

In the scope of the VEX Robotics Competition, the typical screw will be steel and will have an #8-32 thread size and can have a length anywhere from 0.25 inches to 2.5 inches. However, in VEXU, limits on the thread size, material, and length are lifted.

Of more importance to the user of a screw is the drive style and its specialty features.

Drive Styles

Star/Torx Drive

Star Drive, otherwise known by its trade name as "Torx" Drive, is the most common drive style in VEX. It offers the advantage of being generally more resistant to stripping than its hexagonal predecessor, but has the tradeoff of being difficult to purchase at a hardware store. Convenient sources of these types of screws include the VEX Robotics website, Robosource, and McMaster-Carr.

Hex Drive

Hex Drive was widely used in previous seasons of VRC, but has since been mostly eclipsed by Star Drive screws. Hex Drive is now largely unpopular due to the fact that it is notorious for stripping easily. Additionally, similar to the Star Drive style, it is difficult to find commercially. Potential sources of these types of screws include the VEX Robotics website and McMaster-Carr.

Phillips Head

Phillips Head screws are not screws that are commonly associated with VEX Robotics, but they can be utilized conveniently due to the fact that they are incredibly easy to purchase. Normally, most hardware stores will sell their #8-32 screws with a Phillips Head style. Additionally, those hardware stores will almost certainly sell tools that are compatible with these screws. You can purchase these screws at a hardware store such as Ace Hardware, Lowes or Home Depot.

Specialty Features

Most screws will be normal screws that have no additional benefit. However, there are three particular types of screws that can perform special tasks.

Shoulder Screws

Shoulder screws are screws which are not threaded near the head. Usually, this lack of thread, referred to as the "shoulder", has a length that spans no more than 1/8 of an inch. The benefit of using a shoulder screw is that the shoulder is larger than the diameter of the threading. This means that, when passed through the hole of a C-channel or angle, the screw will always be nearly perfectly centered in the hole. This is excellent for any structural purpose, and should especially be utilized when constructing drivetrains to ensure that the drivetrain is "square" and aligned properly. Shoulder screws can be purchased in the Hex Drive variant from the VEX Robotics website or in the Star Drive variant from Robosource.

Locking Screws

Locking screws are normal #8-32 screws that have thread locker brushed onto the ends of the screw's threading. They bring the added benefit of making the screw resistant to vibration, meaning that the screw cannot loosen unless a screwdriver interacts with it. They can be purchased from the VEX Robotics website with thread locker already brushed onto them, or they can be made by brushing any commercial thread locker, such as Loctite, onto an #8-32 screw.

Thumbscrews

While not particularly useful, VEX's thumbscrews offer a simplistic way to tighten screws. The method of tightening these screws is as the name suggests: they can be tightened by hand using the knurled head. One benefit that competitors have found within the thumbscrew is the fact that it is made of plastic compared to the typical stainless steel. This would make it a lightweight alternative to using any other screw. They can only be purchased from the VEX Robotics website.

Types of Nuts

Standard Hex Nuts

These nuts are the least used in VRC, as they have no teeth to keep them tight without heavy maintenance, nor rubber to maintain their position on the screw.

Keps Nuts

The most common type of nut used in VEX, these nuts have teeth on the inner portion of the nut (the end that contacts the attached surface), which keeps the nut solidly in place without much maintenance.

Able to be used most everywhere without problems.

Nylock Nuts

Nylock Nuts, or Nylocks, these nuts have a rubber ring on the top portion of the nut (that faces away from the attached surface), which keeps it in place on the screw. Able to be used in the same places as Keps Nuts, but generally should not be, as Keps Nuts are easier and more efficient to use.

Most commonly used in Screw Joints, as it is not advisable to tighten the outer nut on a screw joint all the way (this would stop whatever is on the joint from moving). Using a Nylock for this purpose allows the nut to retain its place on the screw, without needing to be tightened as far as it can go.

Standoffs

Standoffs are a fairly common part with a wide variety of use-cases in the VEX Robotics Competition.

Comprised of a long, threaded interior formed into a hexagonal shape, standoffs are often used to space pieces of structure over long dimensions, as screws can be threaded into either end of the cylinder. Due to their versatile dimensions, standoffs are often used in bracing components of a robot, and are sometimes used as main structural components themselves.

In the VEX Robotics Competition rules, there is a maximum length of 2.5 inches (63.5mm) for any commercially available standoff. Common sources of standoffs include the VEX Robotics website, RoboSource, and McMaster-Carr.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)

The four bar lift is one of the most used lifts in VEX Robotics competitions due to its relative simplicity and ease of building. The four bar lift is constructed using two sets of parallel bars that move up and down in unison. Two sets of vertical bars line both the front and back of the linkage, so that the lift can be attached to a robot base parallel to to object interaction mechanisms being attached.

One advantage of the four bar lift is how the lifted end will always remain parallel to the static mounting point through the entire duration of a lift or decent, with the exception of non-parallel mounting as mentioned previously. This helps prevent game objects from falling out of the object interaction mechanisms due the lift being inclined or declined. The simplicity of the design also makes four bar lifts very reliable and low-maintenance. Once one is constructed and set up, very little else is necessary to be done and the lift should continue to function without issues. The low number of moving parts allows little to go wrong during operation, and thus sensors and fail-safes are often not necessary.

Because four bar lifts are simple in nature, the linkage does not provide much height advantage. The maximum height of a four bar lift is determined by the length of bar used, which is constrained by the size limitations of the robot itself. While not common, four bar lifts may result in a center of gravity that does not remain over the base of the robot when faced with a heavy load. However, due to the size limitations, this is not often a problem.

Pros and Cons Analysis

Using Rubber Bands

Besides pressure from the pneumatic reservoir and electricity from the battery, elastic energy from rubber bands is a great way to augment the functions of a robot. Depending on the placement of the rubber band joints, you can achieve different amounts of friction and lift force on both the up and down stroke of a 4-bar lift.

As a general rule of thumb, if the rubber bands ...

1. decrease in length as the linkage moves, they provide force in support of that movement

2. increase in length as the linkage moves, they provide force against that movement

3. do not change in length by a significant amount, they are either

   1. providing no force

   2. internally resolving the forces as friction or heat and resisting any change in movement.

When the robot lifts an object, the rubber bands should decrease in length with the upstroke and increase in length with the downstroke. When the robot must lift itself (ex. grabbing onto a post and lowering the lift), the rubber bands should increase in length with the upstroke and decrease in length with the downstroke.

Simulation

Twisting

Possible Solutions

1. different rubber band pivot positions

2. screw joint bracing

5. double-sided banding

Non-parallel Four-Bar

Additional Uses

In addition to the widely used use-case of a vertical lift, four bar linkages can be used for many other applications. For instance, a four bar linkage can be rotated 90 degrees, to move with horizontal motion, rather than vertical. This can be used in many different scenarios such as subsystem deploy and passive mechanisms.

These are the four most common types of Vex Drivetrains:

• Tank Drive

• Mecanum Drive

• X-Drive

• H-Drive

Contributing Teams to this Article:

To control any type of flywheel, you have a few options. You can either max out the voltage/velocity, but if you would not like the maximum force of your motor, it is highly recommended to use a PID controller to keep the speed of your flywheel consistent. Without a PID controller, your flywheel will be in a loop of over and undershooting the speed, causing inaccurate results.

Single Flywheel

A single flywheel is by far the most common flywheel used in Vex because of its consistency and accuracy. Single flywheels use a single wheel spinning at high RPMs with a back plate (most commonly Lexan or ABS). The back plate is formed around the wheel and tuned for the right amount of compression (varies based on the object being fired) and cut to the desired launch angle of the object. The biggest benefits of single flywheels over double flywheels are their consistency, reduced use of motors, and distance because of greater backspin. They're consistent because of their back spin with the plate, and only tuning of one motor.

Single flywheels were the dominant design of Nothing But Net. Below is a picture of 1104M in the world finals with a single flywheel (3/6 finals teams in NBN were 1104 with essentially the same robot).

Single flywheels were also common in Turning Point where the main goal was precision and power. Robots like 169A chose flywheels because they are very consistent, and allowed for quick double shots (especially later in the season). 169A’s robot is shown below.

This robot used many mechanics similar to what 1104 did in NBN. The biggest innovation of this robot was the addition of an angle-changing hood. This hood allowed for the robot to shoot 2 flags(of different heights) very quickly and very accurately.

Double Flywheel

A Double flywheel is similar to a single flywheel but instead of a backboard has another rotating wheel. These wheels are often placed horizontally next to each other (but have also been done vertically). They are much more advanced and allow for more tuning, most commonly changing the speed of a wheel to adjust the projectile’s path. When vertical, the wheels can have different speeds that allow for more/less backspin to make the object fly at different distances. Double flywheels are larger, and heavier, but most importantly need more compression because of the reduced contact time with the ball. This means that they take longer to spin up and put more strain on the motor. Double flywheels generally consume two motors, but can also be configured to only use one motor with a clever gearing scheme. In a one motor configuration, a seperate gear train is required to make sure the wheels are spinning in opposite directions.

Below is VCAT Robotic’s nothing-but-net early season 15” VexU robot. It is one of the better-known double flywheels. They did however change the design soon after this to use a single flywheel.

Release Adjusters

Release adjusters deflect the game objects after it exits the flyhweel. They were commanly called angle shifters in Turning Point and bloopers or deflectors in Spin Up.

Examples

Refinement / Optimization

Before spending too much time on refinement, make sure the build quality of the flywheel is satisfactory. A well-built flywheel with no refinement should still be relatively consistent (even if it performs poorly). Because flywheels rotate at such high angular velocities, faults in build quality and programming will be significantly more apparent as they attempt to approach their top speed. Ensure that the structure of the flywheel is properly aligned, bearings are fully seated, and no shafts are bent to establish an efficient flywheel mechanism.

General Optimization Design Process

1. Test and quantify the metrics of the flywheel.

2. Change a parameter.

3. Remeasure metrics.

4. Analyze results.

5. Repeat.

Design Metrics: variables that can be measured in testing

Design Parameters: variables that control the operation of the robot

Examples of Flywheel Data Collection

Vibration

Flywheel balancing is a process that evenly distributes the mass of the wheel to prevent vibration or wobbling during operation. Balancing typically involves adjusting the weight distribution of the flywheel by adding or removing material, or by using counterweights, to achieve equilibrium and minimize vibrations.

1. Spin the flywheel at a constant input voltage or constant input rpm.

2. Measure the vibration through the following options. More useful metrics like flywheel speed and power usage can also be measured here.

   1. Use a mobile phone app. Tape the phone to the robot (near as possible to the flywheel) if necessary.

      1. As of 4/21/2024, Vibrometer, Sonic Tools ("VIB Scope"), or PhysicsToolbox ("Linear Accelerometer") on iOS can serve this purpose.

   2. Use the VEX Inertial Sensor. Save the accelerometer data to a csv file / SD card.

   3. Try feeling the vibration with a finger near the flywheel (be safe).

3. Quantify the vibration by analyzing accelerometer data.

   1. Estimate the amplitude of the vibration waveform.

      1. Vibrometer gives an "Average" reading in the app.
   2. Frequency analysis can also be done through a Fourier or wavelet transform. Shifts in frequency often correlate with shifts in flywheel speed. This depends on the resonant frequencies of the robot.

4. Add or move a counterweight on the flywheel.

5. Repeat from step 1 until the the vibration is sufficiently low, flywheel speed is high enough, or power usage is lower, etc.

Example Testing

Below are 3 sample tests of many to show the effect of weight distribution on a flywheel (81P Spin Up)(2/18/23).

Teams Contributed to this Article:

• 81P VEXMEN: Pandemic

Bracing

Bracing is the act of securing a lift with bars at the base of the lift, between different lift bars, and other places where there may be a need for structural support. Many teams iteratively find some of these areas as they test their design. This article further discusses the two most common types of bracing seen in good lift designs.

Bracing is the most crucial aspect of designing a stable (and fast) lift. It may seem counter-intuitive, but adding weight for a better braced lift can often improve its speed. 2017-18's game ITZ and 2014-15's Skyrise caused a lot of the research into this topic.

X-bracing

X bracing is the most common strategy used in bracing a lift. Structurally, it has strong tension, but not much else. As a result, it works well with 1 hole wide c-channel on the middle of a DR4b, for instance, but using c-channels won't give you much improvement. It also will not prevent twisting, which the main problem plaguing most VEX lifts.

Be sure not to use this strategy with 1x metal, as it will likely have little noticeable impact.

5-by bracing

Bracing with horizontal 5 hole wide C-Channels (often doubled up) was a common and very effective technique used by New Zealand teams in 2017-18's ITZ to brace the bottom section of DR4Bs. This is the most effective way to prevent the lift from twisting, and while the doubled 5-by is very heavy, the additional stability causes the lift's joints to be more efficient and the lift to be faster. To make this approach more effective, use shoulder screws to keep holes aligned better.

Joints

Linear punchers are one of the simplest, yet most effective ball-launching mechanisms. The name of the mechanism comes from its linear actuation and the forceful impact on the ball that sends it flying.

A couple of things to note about the design:

• The shooting is powered by rubber bands (not shown, but connected from the standoff on the back of the rack c-channel to the front of the assembly)

• The puncher is drawn as the rack and pinion set moves the rack away from the ball, and then when the shaved section of the pinion gear reaches the rack, the rack is released and shoots forward

• The rack shown in the photo is stopped from exiting the assembly by the horizontal bolts with black spacers.

Applications

Linear punchers are used most commonly when needing to launch an object (normally a ball), a far distance. In the past, they were used in Turning Point (2018-19) and in Nothing But Net (2015-16) where teams needed to launch balls (relatively small) across the field. In the case of Turning Point, they were often used because they could be used in different points on the field with angle-changing mechanisms.

Construction

There is no single best method for creating a puncher. Different game objects require different mechanisms, but there are a number of best practices.

• Use a short linear slide length. Longer slides have more power but suffer from high friction. Shorter lengths have less friction, and higher consistency, and will increase the lifespan of the rubber bands.

• Make sure the rubber bands are parallel with the linear slide. If the rubber bands pull the slide up or down, it will add friction and reduce exit velocity of the ball significantly.

• The slide should have a loose fit in the slide trucks. This can be achieved by filing the slide trucks down. The extra slop is negligible on performance, and the reduction in friction is massive.

• Utilize some form of lubrication to reduce friction even further. Common choices for lubricants are white lithium grease or graphite

Modifications

Pros and Cons Analysis

Teams Contributed to this Article:

When using pneumatics, there are many things to keep in mind for optimal performance. These range from the design process to actually in operation.

Design

• Leave spacing for Solenoids.

  • The solenoids which control the pistons are small, but make sure that you leave ample space around the connectors for tubing so the connectors fit well.

• Do not design tight corners for Tubing.

  • There is a high risk that your connections will be ripped out if you run the tubing around sharp corners, tubing and solenoids can both get damaged. There is also a chance that the tubes could be kinked and stop or limit airflow

• Consider weight distribution of Reservoirs

  • The reservoirs may be aluminum but are still fairly large and heavy. It is beneficial to keep these low and centered on your robot. It is also important to keep room for these components as they do take up a lot of space.

Construction

During robot construction, there are not many helpful tips, but these should always be followed.

• Always overuse Tubing.

  • There is never a downside to using too much pneumatic tubing. Using too little can lead to connections being damaged and tubes being stretched. Having slack in tubing lines is important to ensure consistent operation.

• Know your pivot points.

  • The majority of applications for pneumatics have linear motion being converted to some rotational motion. Make sure to solidify whichever point you have that pivots.

• Distribute the Loads.

  • Be certain to even out the force on each side of the pneumatic cylinder. If only one side is loaded, there is a high chance the pneumatics will not function as intended.

• Never work on pressurized pneumatics.

  • For safety, never work on pneumatics that has pressure, use the regulator and flow switch to depressurize or isolate workable components before doing any maintenance.

• Use Teflon tape.

  • Teflon tape is used to seal anywhere that there is a thread in the system. For all valves, Teflon tape helps to reduce the risk of leaks. If your system has leaks, the best place to look is at valves.

Operation

For ideal operation, follow these tips.

• Optimize the airflow into Tanks.

  • The pneumatics kits come with a regulator. Experiment with the amount of airflow through the regulator so that your pneumatics have just enough force to complete your intended action. This will mean the cylinders can actuate more times per full pressurization.

• Pressurize tanks at every opportunity.

  • The legal pressure is set at 100psi, which is quite low for most applications. Due to this, the constant re-pressurization of tanks must be a priority.

A catapult is a launching mechanism that utilizes rotational movement in order to fire objects. This is achieved by rotating an arm where an object placed at the end will gain momentum in the desired direction, and abruptly stopping the arm so that the object will continue its trajectory through the air. In VEX, catapults are often chosen because of their versatility, as they are able to easily launch any object regardless of shape or size, as well as being able to launch multiple objects simultaneously. Catapults have made several appearances throughout previous games, such as the 2013-2014 game Toss Up and the 2018-2019 game Turning Point.

Elastic Catapult

Catapults powered by elastics (rubber bands, surgical tubing, etc.) are the most versatile and widely used method of applying force. There are many reasons why this is a popular design choice, however there are some drawbacks.

One of the benefits listed above was the ability to power an elastic catapult through a variety of ways, which are discussed below.

Slip Gears

Slip gears are one of the ways where the rotational force of a motor is utilized to draw back and fire an elastic catapult. A slip gear is a gear that has several consecutive teeth shaven off, so that another gear driven by the slip gear will "slip" when it rotates to the section of the slip gear that has no teeth. Slip gears are often used in tandem with ratchets, to reduce the load on motors. These components are also commonly used in linear punchers.

For elastic catapults, the arm of the catapult is attached to a gear that is being driven by a slip gear. When the slip gear is rotated so that the shaven teeth are not engaging with the gear of the catapult, the catapult arm is able to rotate freely, allowing the built up tension from the elastics to rotate the catapult in the opposite direction.

Below is a video demonstrating how slip gears are used on catapults:

Gear Ratios

The more elastic force applied on a catapult, the more torque the motor will need to provide in order to draw back the catapult. To accomplish this, gear ratios can be used to increase the output torque of the motor. For most catapults, a simple gear ratio of 1:5 or 1:7 can be used with 100 rpm motors. However, compound gear ratios can be used to fine-tune the output torque of your motor, so that you can power your catapult more efficiently.

Additional Methods

Beyond slip gears, there are many other innovative ways to power a catapult which can be used to achieve the same effect:

Nautilus Gears/Cams

A nautilus gear/cams utilizes the changing outer radius to draw back the catapult, and fire when the radius drops off, as seen in this video:

Connecting Rods

This method of powering allows for a fast rate of fire, without the need of using slip gears:

Pneumatic Catapults

Pneumatics can also be used in a catapult to launch objects, as the quick actuation in tandem with a lever arm can be used to send objects flying through the air. As with elastic catapults, there are many pros and cons to this type of catapult:

Pneumatic catapults were extremely popular in the 2013-2014 game Toss Up, where teams would use pneumatics to launch the large, inflatable balls, as seen in this reveal video:

Optimization

Tuning a catapult to launch an object a specific distance can be tricky, so having the proper understanding of how certain factors can affect your shot can make a big difference in your catapult. There are three main aspects of a catapult that contribute to the arc of your object:

Rotational speed

The rotational speed of your catapult arm is the most obvious component of a catapult. The faster your arm swings, the faster your object will travel through the air. In VEX, the main contributor to the rotational speed is the amount of force that is being applied to your arm, whether it be rubber bands or pneumatic pressure. Increasing this will result in an increase in both the horizontal and vertical direction of your arc, and a decrease will do the opposite.

Length of arm

The distance between the object and the point of rotation, or the catapult arm, is very closely related to the rotational speed, and has similar effects. If an arm has a constant angular speed, then an object placed farther away from the center will have a faster linear than an object placed closer to the center. Because of this, catapults with longer arms will be able to launch objects further, and vice versa

Launch angle

Tuning the launch angle of a catapult will allow you fine tune the trajectory of your ball. The vertical height and horizontal distance of your trajectory will have opposite responses to a change in the launch angle. For example, if you change the launch angle to increase the vertical height of your object, then the horizontal distance will decrease, and the same is true for the other way around. Below you can see a diagram of how different launch angles result in different heights and distances. In VEX, the launch angle of a catapult can be changed by implementing or changing the hard-stop of the catapult. The hard-stop is what prevents a catapult from rotating past a certain angle, so changing this angle will change the launch angle.

Possible Movement Vectors

Advantages / Disadvantages

The Mecanum Drive is just as simple to build as the Tank Drive, but has the ability to drive sideways. It uses VEX mecanum wheels in order to drive, turn, and strafe.

The Mecanum Drive is compact and simple to construct as compared to other holonomic drives, but it can be difficult to push from the side and its strafing movement is slower than forward driving. The VEX mecanum wheels' limited roller sets (7) can result in a clunky driving experience, which may hinder programming autonomous functions using integrated motor encoders.

The Mecanum Drive was utilized by 7K's Tower Takeover Robot. Mecanum wheels are especially effective in games like Tower Takeover which involve rows of game elements or aligning with the field perimeter.

Tank drives are a very popular type of drivetrain used in the VEX Robotics Competition. These drives consist of two separately controlled sides of parallel wheels, which allows for precise control of the robot. This allows for greater maneuverability and control over the robot's movement, which can be important in competitions where speed and agility are key factors. Additionally, tank drives are relatively easy to build and can be modified and adjusted to suit a variety of different competition scenarios.

Pros of Wheel Choices

Cons of Wheel Choices

Advantages and Disadvantages: The Tank Drive is very simple to build and consistently performs well. Many former world champions have used the Tank Drive for its simplicity. However, it suffers both from being able to be pushed sideways and from an inability to strafe.

One solution to the problem of being pushed from the side utilizes locked omni wheels and is sometimes referred to as the "Bling Drive":

The reasoning behind and process of making locked omni wheels is explained in this video by the Rolling Robots. Twenty-four 0.5" screws can be used to make one locked omni wheel. The locked omni wheels should be placed in the center of the robot (more or less in line with the robot's center of gravity) to optimize turning. In addition, only two locked omnis should be used per robot, as more will create difficulty turning and possibly damage the wheels.

This type of drive was utilized by 240P's Early Season Turning Point Robot and by 8059's Turning Point Robot(s). The locked omni drive was common in Vex Turning Point because of the defensive nature of the game.

An alternative to locked omni wheels which is becoming more prevalent is wrapping a Vex traction tire around a 30-tooth sprocket as shown in 7700R's Tower Takeover Robot Explanation. This diameter of this assembly is very close to the diameter of a 4" Vex omni wheel, making it a viable alternative for those who don't wish to lock their omni wheels.

This video does a great job show casing some of the best practices when building a drivetrain.

Core Components

Bearing Blocks

When installed, the bearing flats are mounted directly onto the VEX V5 structure and provide a stable and secure platform for the shaft to rotate. The shaft is inserted through the center of the bearing flats and is held in place by the flats, which prevent the shaft from shifting or moving out of position.They are used to drastically reduce friction when shafts and screws are used.

Stand Offs

Using standoffs in the design of a VEX drive base provides several advantages, most notably increased rigidity. A drive base that is not rigid enough will have a lot of wobble, causing the robot to move around unpredictably and making it difficult to control. Standoffs can help prevent this by providing a solid, immovable structure that prevents the base from flexing and shaking during movement.

C-Channels

C-channels come in various lengths and widths that can be easily cut and modified to suit the specific needs of the robot's design. They can be used to create a variety of structures, and act as the basic building block for drivetrains.

One of the main advantages of using C-channels in the design of a VEX drive base is their ability to provide additional support and stability to the structure. The C-channel's U-shape allows it to distribute force evenly across its length, helping to prevent any bending or warping of the metal plates.

Holonomic drives have become a popular choice for VEX Robotics teams due to their enhanced maneuverability and flexibility in movement. These drives allow for precise and agile movement in all directions, providing a distinct advantage in VEX Robotics competitions where accuracy, and agility are crucial. Holonomic drives in VEX Robotics can be further categorized into mecanum drives and omni drives, each with its own unique strengths and limitations. As the demand for advanced robotics technology increases in VEX Robotics competitions, holonomic drives are becoming increasingly popular among teams seeking to gain a competitive edge.

X Drives

The X-Drive is a bit more complex to build than either the Tank or Mecanum Drives, but it allows for greater maneuverability than the Mecanum Drive.

The X-Drive is the most maneuverable and efficient Vex holonomic drivetrain and, unlike the Mecanum Drive, its forward speed is equal to its sideways speed. However, the wheel assemblies take up quite a bit of room on a robot, leaving less space for mechanisms.