Motor and Gears: Try, Try, Try, and Try Again
We had to go through several iterations before we came up with a design for the motor and gears that worked. At first, we only used one motor, one of the new motors with internal gears.
Professor Anderson was kind enough to point out that one motor for both wheels would not allow TTM to turn. Putting a second motor on complicated the situation a great deal – our space on the frame for the motors and gears was limited.
The first 2-motor iteration placed one motor at each end of the “engine” section of the frame with the wheels in between. The gear tracks from each motor extended inwards toward the center where the wheel axel was. The track consisted of an 8-spoke gear on the motor, with a 24-spoke directly beneath it, which was attached to a 8-spoke, which in turn connected to a 40-spoke on the final axel with the wheel. Unfortunately, this iteration did not have enough torque to propel the weight of the box and two tennis balls we had temporarily placed on top of TTM.
At first we thought changing the caster in front to two free wheels would quickly solve the problem. However, it did not and simply made turning TTM more of a hassle. We put the caster back on and changed the motors from the old ones to the new ones that have gears within them. Luckily, Professor Berg gave us some advice on gearing at this point, suggesting that we put one of the 8-spoke and 24-spoke gears in our gear track on the same axel in order to increase the torque. We had to redo the entire layout of the motor and gears to affect these modifications. The 2 motors were moved to the very back of TTM where they sat side by side. On each motor we attached an 8-spoke gear, under which was a 24-spoke with an 8-spoke attached on the same axel. The 40-spoke gear and wheel was flush with the last-mentioned 8-spoke. This design proved effective – although at first the wheel axels were not on the same rung; but we changed that quickly enough. TTM could finally move.