Turning the swerve module


I’m doing some motor calculations to figure out the torque I need to rotate the bottom part of the swerve module I’m designing, here is my math
160 lbs for robot weight with battery and bumpers
160lbs/4 modules = 40 lbs per module
the colson wheels have a CoF of 1 (this is from the vex website). Times 2 wheels per module is 80 Lbs.
at a distance of 1.5" each wheel should create 120 Lb-In of torque.

If we convert to nm we get about 13.5. I was planning on using a BAG motor and was hoping to have it on a 20 Amp breaker, and also only use one gearbox stage. With this criteria I can achieve a 80:1 gear ratio for the bag. Even at 20 Amps, this only gets 12nm of torque.

I was wondering how other teams handle this problem. The bag can handle it at 20-30 Amps, but then the system uses all our 40-30 amp breakers, I could use a 2 stage gearbox, but this adds considerable cost to the design. Also, I’m not exactly sure about my physics, so if you have any suggestions, or corrections to the physics, I would be grateful for your expertise.

After further thought, I was thinking I could pull it off if I used the banebots wheels. However, I don’t know the CoF for these wheels and don’t know where to find this info.

The PDP has 16 slots, 8 of which are 40 A and 8 of which can be 20 or 30 A. So all 8 of the smaller slots can be 30A, allowing you to run the steering motors on the smaller slots. We run a 550 motor with an about 63:1 gear ratio turning one colson wheel and it is at a pretty solid turn rate. A BAG motor has a lower RPM than a 550 so the gear ratio will be slightly different but it should be able to be done with 2 overall stages such as the one you have right now with 80:1. I’ll see if I can re run the math with our swerve modules and see if theres any difference in how you are calculating it.

1 Like

We’re running colson wheels, although each module only has one wheel and it is almost centered, on a bag with about an 80:1. In the past we’ve run from 100:1 to 50:1, and we’ve found 80:1 is about a sweet spot.

Thanks for the clarification. I haven’t dealt a lot with the electronics, not my forte. But if the small PDP slots can do 30 I should be fine.