6 CIMs and 4 MiniCIMs - Will they stay?

[DampRobot]

Let me just say this: 6-CIM drivetrains can break the main 120 amp breaker if they are stalled. With a 6-CIM drive, you're essentially giving good defenders a way literally shut your robot down.

As for continuing to have insane amounts of power like we did this year? I sure hope it continues, but I certainly wouldn't take this much raw power for granted. It obviously depends on the game, but I'd bet on 4 CIMs and 2 Mini-CIMs for next year.

[Mark Sheridan]

Originally Posted by DampRobot

Let me just say this: 6-CIM drivetrains can break the main 120 amp breaker if they are stalled. With a 6-CIM drive, you're essentially giving good defenders a way literally shut your robot down.

As for continuing to have insane amounts of power like we did this year? I sure hope it continues, but I certainly wouldn't take this much raw power for granted. It obviously depends on the game, but I'd bet on 4 CIMs and 2 Mini-CIMs for next year.

Well you still have to get your gear ratio and traction correct. Having extra motors gives you a few more variables to play with.

Originally Posted by DampRobot

Let me just say this: 6-CIM drivetrains can break the main 120 amp breaker if they are stalled. With a 6-CIM drive, you're essentially giving good defenders a way literally shut your robot down.

As for continuing to have insane amounts of power like we did this year? I sure hope it continues, but I certainly wouldn't take this much raw power for granted. It obviously depends on the game, but I'd bet on 4 CIMs and 2 Mini-CIMs for next year.

I know a few teams who made a single-speed 6-CIM drivetrain and never had any problems that I've seen (one that comes directly to mind is 973).

[F22Rapture]

Originally Posted by DampRobot

Let me just say this: 6-CIM drivetrains can break the main 120 amp breaker if they are stalled. With a 6-CIM drive, you're essentially giving good defenders a way literally shut your robot down.

So can 2 CIMs, or 4 CIMs. As long as you don't gear too high for the amount of torque you have available (which will increase with the number of CIMs), your drivetrain should stay traction-limited and never stall.

[cgmv123]

I only see the extra motors staying if the available power increases (bigger battery/main breaker).

[Tom Line]

Originally Posted by cgmv123

I only see the extra motors staying if the available power increases (bigger battery/main breaker).

I disagree.

This is one of those things that teams need to be aware of and design around, as part of the design challenge. I think it's much more real-world to actually have some imposed design constraints rather than having FIRST provide us a system that can be plugged together and won't fail (like Lego League). Even FTC needs to be careful about motor loads.

[cbale2000]

Originally Posted by DampRobot

...6-CIM drivetrains can break the main 120 amp breaker if they are stalled...

Does anyone know of an instance where this has EVER happened on a FIRST robot?

[DampRobot]

Originally Posted by cbale2000

Does anyone know of an instance where this has EVER happened on a FIRST robot?

Yes. 766 shut down 971 in this way at a match at SVR, and we won the match because of it. I have also heard anecdotal evidence of 254 having similar problems.

Originally Posted by DampRobot

Yes. 766 shut down 971 in this way at a match at SVR, and we won the match because of it. I have also heard anecdotal evidence of 254 having similar problems.

Maybe someone from 971 can answer this, but what gear were they in (and what speed)? Do you have video of the match?

[DampRobot]

Originally Posted by Andrew Lawrence

Maybe someone from 971 can answer this, but what gear were they in (and what speed)? Do you have video of the match?

I believe its on TBA. It might have been match 50.

[MichaelBick]

Remember 971 also has 2" wide wheels which give them a ton more traction. I have a hard time believing that they are not traction limited in low gear, but is it possible that in high gear they blow faster because of this?

[Nuttyman54]

Originally Posted by Andrew Lawrence

Maybe someone from 971 can answer this, but what gear were they in (and what speed)? Do you have video of the match?

We had this issue a few times this year. We are traction limited in low gear, but not in high gear. The instances where this happened occurred when our driver failed to shift down soon enough. Because of the 2 extra CIMS, the breaker blew much quicker than our driver was used to reacting to shift down. If we do a 6 CIM drive next year, there will likely be some mechanical and/or programming solution to prevent this from happening.

[Mark Sheridan]

Originally Posted by DampRobot

Yes. 766 shut down 971 in this way at a match at SVR, and we won the match because of it. I have also heard anecdotal evidence of 254 having similar problems.

I should know 766 drivetrain since 3309 is running their drivetrain. We are running pretty much the same gear reduction as 254 except with just 4 motors. however we would be more likely to trip the breakers. A big difference was we chose not to groove the colson wheels knowing our gear ratios in both gears were too high to permit that. If we ran 254's wheels, we would have breaker issues big time. We managed our traction and were safe to prevent breaker trips. 3309 tested this ourselves by doing a simulate push test, the wheels always spun in low gear, we could never trip the breaker.

We gotta credit 766's old mentor Scott Baron for teaching us this back in 2005.

[Mark Sheridan]

Originally Posted by cbale2000

Does anyone know of an instance where this has EVER happened on a FIRST robot?

Yeah i did this in 2003. Long wheel base 4 wheel drive with 2 inch wide wheels w/ conveyor tread on them. It was two CIMs and 2 drill motors. Couldn't turn and would pop the breaker from the stall. Would up changing to low traction wheels.

[Pratik Kunapuli]

Originally Posted by cbale2000

Does anyone know of an instance where this has EVER happened on a FIRST robot?

Yes. We had 6 CIM's for our drive train, and in our first event of the year (Hatboro Horsham), we got into a few pushing matches and popped our main breaker more than twice. When all of our CIM's stalled, they pulled about 780-800 amps for more than a few seconds, which is definitely enough to trip the main breaker.