There are a pair of DC servo motors, each driving a short (3") 037 (3/8") .2" pitch timing belt from the 2nd level down to the first, 23:15 ratio for a 1.33 speed increase. The motors are mounted on opposite ends
On the first level are three short axles on each side of the 'bot, connected on 8" centers by the same timing belts, and 20 tooth pulleys. There are belt tensioners (4) between each pair of pulleys pressing down on the top of the belt. (I do remember hearing that the tensioner pulleys should be on the driven side of the pulley, so one pair is on the wrong side).
The belt system appears to run fine in straight runs, grass, concrete, etc., even when moving quite fast. The problem arises when the 'bot starts to make a turn (more torque required). I start hearing loud “popping” sounds, which I take to be the belt(s) jumping teeth.
I can’t determine which belt(s) is jumping. Since I first observed (heard) the problem, I’ve strengthened up the bearing supports between the axles, made a better tensioning nut for the belt tensioners (idlers), and increased the tension on the upper drive belts as well. Specs say 3-4 oz at 3/64" deflection on the belts, although I don’t have a way to accurately measure it. The belts “sing” when they run, like they are being “plucked”, so I think they’re pretty tight.
The angle of the upper motor belt is about 50 degrees, and I haven’t yet figured out a way to add a tensioner to it.
I’ve been reading and admiring your build for days now! Really amazing! Did you end up figuring out your drivetrain issues?
I’m contemplating a similar build, but using six motors (small ones). What diameter shaft did you use to mount your pulleys? I assume that this must fit into the driveshaft/axle from Traxxas?
Your last post mentions that you used DC servo motors; what made you choose those?
Sorry for all the questions; this is all just so fascinating
