pic: GBX-114 swerve with PTO

[asid61]

Originally Posted by Ty Tremblay

Have you done the calculations to estimate current draw on this? 1678 had to take extra steps to reduce the chance of popping their main breaker. Same goes with 254 and many other teams. The only reason 6-CIM drivetrains are even possible is because we know the breaker can hold more than 40A for longer than the spec sheet says.

You're adding 230W of power AND reducing torque. It's not a matter of acceleration, it's a matter of keeping your robot powered while you accelerate.

This will blow the breaker in a pushing match due to the massive power behind it. However, as with any high-geared 6+ cim drive, there must be good autoshifting code to prevent disasters. IIRC 1678 had a main breaker blow in the finals at SVR due to their autoshifting code having problems.

With swerve drives, if we get into a pushing match, we have three
options:
1. Translate away. Good for offensive tactics, especially with this blistering speed.
2. Push back. Useful only against lightweight robots or if we are stuck somehow. Or to slow other's robots down.
3. Cross the wheels. If the wheels are in an X-formation, then we can't be pushed unless they lift us (cue opponent's breaker blowing). Esentially, the driver has a trigger to lock the wheels, and when the opponent tries to go another direction our driver releases the trigger and moves. This is an extremely effective defense (in theory) as long as our driver can move to block them when they try to get past. I'm confident our speed is high enough for this.

The purpose of low gear is to allow for precise positioning and very short drives. That's why it's geared so high here.

The 40a breakers are on each motor. The main breaker is 120a, which is usually the problem.

Originally Posted by Nemo

I don't think the math will work out on those speeds when you take into account the voltage drop that happens when you run all twelve motors on at the same time.

Thank you for the input. I hadn't considered that. However, this only supports slightly more power than 6 cims, so it might not be that bad.

Originally Posted by 75vs1885

Looks sweet, but I am concerned about the turning gears, they're so close to the ground that if anything bounced up, it could potentially break or chip a gear tooth.

There is around 0.25" clearance to the ground. Not much we can do about that, but at least they're vex gears so they're easy to replace. Many swerve drives use gears so close to the ground, and I haven't heard of so many problems.

EDIT: One of our mentors mentioned that a bigger problem would be the current spike killing us on startup. Some things we have to solve with software; this kind of drive won't be used for at least a year (2016 game) so we have plenty of time to do tests.