Tank Drive

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.

Sample Tank Drive by Xenon27 on the VEX Forum

Pros of Wheel Choices

4 Omni Wheels	6 Omni Wheels	4 Omni Wheels, 2 Traction Wheels
Space efficient	High forwards traction	High forwards traction
High maneuverability	Reduces compression due to each wheel	High horizontal traction
	Can add traction wheels later if desired	Reduces compression due to each wheel

Cons of Wheel Choices

4 Omni Wheels	6 Omni Wheels	4 Omni Wheels, 2 Traction Wheels
Low forwards traction	Low traction from side	Low maneuverability
Low horrizontal traction	Medium maneuverability
Does not allow for later traction addition

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.

8059A TP Bling Drive

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.

169 Calvary 2019 using a traction wheel around a sprocket

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.