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DriveBase

The Tank Drive

The tank drive is just a Drive that has a motor on the left side and a motor on the right side. If both motors turn at equal speeds the drive goes straight. If the Left side goes faster than the right, the drive will turn towards the right. To turn left the right motor turns faster than the left motor.

Fusion 360 design

Each side can have one motor or several motors. On each side all motors turn at the same speed.

tank Drive VEX robotics

Here is the drive base that we will be building. it is a 2 motor tank drive , one motor on each side.  The motors directly drive a single traction wheel. The second set of wheels are omnidirectional wheels that allow the wheels to roll sideways, this make the drive very easy to make fast turns. It also makes it a little hard to learn to drive well.

vexrobotics parts

These are the parts we will need to build this tank drive.

Before we build it is a good idea to test the electronics. We would not want to spend a lot of time building and only later find a faulty motor or wire.  Whenever you add a motor or sensor to your robot you should test it first.

Our test is to just plug everything in and check the devices menu.  All devices should show on the screen and show a solid red light at their connector.

When the radio and remote are connected there should be red lights blinking on the radio.

The included drive code can be run to test that the remote can control the motors. 

single screw bearing

On one end we have a single screw bearing. The axle goes through the round plastic hole at the third hole of the c-channel. 

screw axle

On the other end is a screw that is configured to be a dead axle.  it is said to be dead since it does not turn, rather the wheel spins freely on it.

wheels

The wheels are mounted with the correct amount of spacer to make it fit between the 2 chassis rails, but not too tight, that would make for high friction.

For the omni wheel it will be better to use 2 of the same size spacers. So 2 units on each side.

lock nut

On the dead axle the wheel and spacers are stacked then finished with a nylok nut to hold the wheel tight but allow it to spin freely. A technique for this is to tighten until the wheel can not spin then loosen up just enough to allow the wheel to spin freely.

chassis rail

After placing the second chassis rail on the dead axle we tighten down a star keps nut.  This make the dead axle part of the drive base structure, as the 3rd point defining the plane of the chassis rails.

Now we have two identical sides that we will connect by cross structures

A c-channel top and bottom complete the structure.  Here we use full length c-channels making the drive 17.5 inches wide. The drive can be made with shorter c-channels as well.

Time to mount the brain and battery clips. Here are the parts needed.

Clips mount like this.

The brain mounts with 2 screws. it is important to not use screws more than 1/4 inch long.

With the brain mounted all that remains is to wire it up.

Wiring up the Robot

We will be using the included drive code for the first tests so there is a specific way to wire the motors. We will use port 1 for the left side motor and port 10 for the right side motor. The radio will be plugged into port 21 on the side of the brain.  The battery is plugged in with a 4 wire power cable to the side of the brain.