The drivetrain was a quite interesting process. We had a lot of trouble in the beginning because we had to decide which wheels to use, how many to use, and what the shape of the base would be. We originally decided to make the base a square shape with four omni wheels. Since we were looking for a shape that would provide the design of the robot with the most surface area per side of the base, we decided a square would not be the best choice.
We then decided to use either a pyramid or a triangle shaped base with three wheels. In order to strafe using the omni wheels, we had to use more that 120W of power. Since the robot would not have that big a battery, and sideways movement was not an integral factor, we opted not go with the omni wheels. Designing the base was quite difficult considering we didn’t have a good way to mount the wheels to it.
In our next prototype, we laser cut a pyramid shaped base out of plywood to use for the robot. We used this shape because it gave more room in the base for wires, computers, servos, etc. Eventually, we found that it would be easier to construct the body of the robot if the base was a pentagon that was shaped like a house.
Since we wanted the robot to be manuverable, we decided to use three wheels. The two in the front were motorized and the one in the back was a caster. Since the front wheels needed to be strong enough to move the entire robot, we used motors that are used to roll up car windows. For the back wheels. we used laser-cut circles made of plywood.