Is this a safe gearbox?

[tpaul18]

I am trying to find a gearbox that will be able to make the robot go about 20 ft/s. Is this gearbox (3 CIM Ball Shifter) safe to use without blowing a sim motor? http://www.chiefdelphi.com/forums/at...d=14528178 69

[wyrzykowskij1]

It's safe, but at 22 ft/s there is definitely a much higher possibility of popping your breaker with that configuration.

[Kevin Sevcik]

Originally Posted by tpaul18

I am trying to find a gearbox that will be able to make the robot go about 20 ft/s. Is this gearbox (3 CIM Ball Shifter) safe to use without blowing a sim motor? http://www.chiefdelphi.com/forums/at...d=14528178 69

That is a good gearbox, but you do NOT want your robot to go 20 ft/s. You really, really won't be happy with the results. 20 ft/s is far too fast to control easily. You'll find yourself constantly shifting into low gear to do pretty much anything. You should really aim for a top speed of no more than 14 ft/s.

[Munchskull]

*CIM motor

[CalTran]

Originally Posted by tpaul18

I am trying to find a gearbox that will be able to make the robot go about 20 ft/s. Is this gearbox (3 CIM Ball Shifter) safe to use without blowing a sim motor? http://www.chiefdelphi.com/forums/at...d=14528178 69

Particularly with the defenses trisecting the field, there's no point in bothering with 20fps, given that you will almost never have a stretch of field to even approach that speed. Go with what Sevcik says, aim for 14fps, possibly even lower and take advantage of being able to push people around.

[RoboChair]

Originally Posted by Kevin Sevcik

That is a good gearbox, but you do NOT want your robot to go 20 ft/s. You really, really won't be happy with the results. 20 ft/s is far too fast to control easily. You'll find yourself constantly shifting into low gear to do pretty much anything. You should really aim for a top speed of no more than 14 ft/s.

I would like to point out that 20 fps is the geared speed, actual speed will be lower. I would guess about 17fps actual. Our 2014 robot was geared to 22fps and we got an actual top speed(on an open field) of about 18-19fps and our driver was more than able to handle it. It just required practice and coding to minimize the control challenges for the operator.

You want your robot to be fast, but you are unlikely to reach top speed on the field with that gearing. I'd aim for closer to 18fps theoretical top speed. You still have the brown out issue to deal with however.

EDIT: I have never seen a CIM motor straight up die. Lose max power by some percentage, yes, but never have I seen a team fry one(heard a couple stories though where egregious operator error was at fault). Also I only have good things to say about the 3 CIM ball shifter gearboxes.

[asid61]

Originally Posted by Kevin Sevcik

That is a good gearbox, but you do NOT want your robot to go 20 ft/s. You really, really won't be happy with the results. 20 ft/s is far too fast to control easily. You'll find yourself constantly shifting into low gear to do pretty much anything. You should really aim for a top speed of no more than 14 ft/s.

I know we went for 15fps in 2014 and it was quite easy to control. Last year we geared for 15fps and did ok as well, although we did end up running a software speed cap for when we held stacks.
With sufficient driver practice you can go up quite high. I would just worry about brownouts from drawing too much current.