[Oblarg]

Re: main breaker trips, our team had a lot of experience with this over the past season with an aggressively-geared 6-CIM SS drive. Way more than we would have liked. Here's a rough outline of what we discovered:

Six stalled CIMs will pull around 40 amps/CIM from a fully-charged FRC battery. Note that this is significantly lower than the rated stall current of a CIM - this is because as you draw more current, the effective voltage of your battery drops. The standard FRC main breaker, from our testing, could sustain this for anywhere from 10-30 seconds. The effects are "quasi-cumulative," in that since the breaker is triggered by heat buildup, and heat dissipates over time, you regain some of that time when you remove the current draw, but in our experience, not very much over the time scales involved in an FRC match.

Six slipping CIMs on our robot (120lbs w/ bumpers, drive geared 6.11:1) pulled around 30 amps/CIM and could be sustained almost indefinitely without breaker trip over the course of an FRC match. Our robot in this configuration was just on the very edge of being able to slip the wheels, so this was essentially the "worst-case" scenario for wheel-slipping, and other configurations would likely draw less.

What can be discerned from this is that as long as you can be absolutely sure that you will not stall your drive motors while pushing, you should not have breaker problems with a 6CIM drive. Unfortunately, figuring out precisely what gearing gives you that certainty is nontrivial, as it depends critically on several subtle factors (how much current your robot is drawing apart from the drive, how long the wires leading to your drive motors are, how fresh you expect your battery to be in-match, among others). You could try to calculate this beforehand (the math is not hard), but I'd recommend simply erring on the side of caution and picking a relatively slow low-gear (no faster than 7FPS*). Do that, and you should have no worries about breaker trouble.

Your fast gear can be however fast your drivers feel comfortable with. Just make sure you do not get into a pushing match while in your fast gear, or you can (and will) trip the breaker.

* How I arrived at that number: Our robot was just able to slip the wheels at 14fps gearing while weighing 120lbs. Our wheel COF was 1.1. For a "worst-case" scenario, assume a 150lb robot with a 1.5 wheel COF. Both factors scale linearly with required torque, so our gearing would have to be 14FPS * (120/150) * (1.1/1.5) = ~8 FPS. Reducing this to 7 FPS gives you a bit of overhead for not-quite-charged batteries/other stuff pulling current/whathaveyou. You could probably claw back a bit by having better (read: shorter and/or fatter) wiring than what we had, or by having exceptional drive efficiency (though, subjectively, I thought ours was pretty good on the robot in question).