Best way to cool CIM motors?

[theCADguy]

Originally Posted by rainbowbear998

It seems that having a worm or planetary gearbox is the best option to stop the motors heating up at the moment. I have one question though - will they perform ok with a few kilos of weight on them?

We designed part of our lifter gearbox with VEXPro versaplanetary gearboxes. However, I would check your load requirement against this document before purchasing one:

http://content.vexrobotics.com/vexpr...s-20150106.pdf

Watch out if you are planning on using a very low reduction with a CIM or a MiniCIM

[asid61]

Originally Posted by theCADguy

We designed part of our lifter gearbox with VEXPro versaplanetary gearboxes. However, I would check your load requirement against this document before purchasing one:

http://content.vexrobotics.com/vexpr...s-20150106.pdf

Watch out if you are planning on using a very low reduction with a CIM or a MiniCIM

Only if you plan on using all of that load. We have a pretty fast elevator (1-2ft/sec) and we haven't run into load problems yet in the versaplanetary.

[John Retkowski]

Depending on how much you want to lift you may need a stronger motor. We can reliably lift five totes without a can. If one wanted to lift heavier weights, adjustments would probably have to be made. As for performance. We did have a problem with the motor breaking. But we found that it was caused by our top limit switch malfunctioning. This caused the winch to constantly stall against the top of our elevator, which ruined the motor. Other than that the assembly has performed spectacularly.

[MrRoboSteve]

You could also make a winch:

[rainbowbear998]

Originally Posted by MrRoboSteve

You could also make a winch:

Attachment 18662

I love that idea! How hard was that to manufacture? How reliable is it?

[Tim Lehmann4967]

Last year we cooled our CIM motors and Compressor with server rack blowers. They were considered legal, and worked amazingly well. You can put the KOP heatsinks on them for further cooling.

[MrRoboSteve]

Originally Posted by rainbowbear998

I love that idea! How hard was that to manufacture? How reliable is it?

It's built from:

AM-0145 Toughbox
AM-0396 long hex output shaft, cut down a bit
2 - AM-0069a 500 Hex hub, modded with set screws. One hub is also modded with teeth
2" of aluminum tube - 1.75" OD
Mini Cim
HS-422 servo
#10 threaded rod
3/4" x 1/2" aluminum bar as spacer for dog (has F <-> B in photo)
3/4" x .125" aluminum bar for dog
.090 servo support plate (sits between bar and the gearbox, holds the servo in position)
small qty of .090 polycarbonate to make dog actuator for servo
2 longer bolts (I think they're 1/4x20) for fastening spacer bar and plate to gearbox
#10 machine screw with washer for pivot. The spacer is tapped to accept the screw and there's one washer on the other side.
spring (random hardware store spring)
smaller machine screws (#6?) to fasten servo to servo support plate

It's probably 3-4 hours of work all together.

One key to longevity is to keep the dog from riding on the modded hex hub when the winch is operating. When we operate the winch in the lowering mode, we slightly raise it first before actuating the servo, so that the dog does not bind.

The only concern we have is that the winch is supported on only one side. We're bringing another gearbox plate and necessary hardware to make a support for the other side if that turns out to be a problem.

[Ether]

Originally Posted by Dale(294engr]

144 / ~.1ohm 14.4 watts

1440 watts.

[Ozuru]

Not too long ago there was a thread talking about dry ice and its legality. Maybe that might work well

[ay2b]

Keep them cool by not running them. It may sound a bit snarky, but in this case it sounds like you're basically spending a lot of time with the motors stalled (i.e. putting power into the motor, but getting no motion out). That's a good way to both heat up your motors and run down your battery fast.

I'd suggest looking for alternate solutions to the gearbox. Many worm-gear drives are not back-driveable. You may instead be able to add some sort of break system. Look for solutions that allow you to hold the totes off the ground without running motors to do so. Many teams use window, van door, or snow blower motors to drive winches. They aren't as fast or as powerful as CIMs, but they also aren't back-driveable (thanks to the attached wormdrive gearbox).

[Sperkowsky]

I recommend liquid nitrogen.

[rainbowbear998]

Originally Posted by Sperkowsky

I recommend liquid nitrogen.

Oh god... Please no.

Thanks to MrForbes for clarifying that rule.

Back to my surgical tubing idea!

[rich2202]

Did you check the jumpers on your motor controllers? There is a jumper that lets the CIM freewheel (coast) or brake. Make sure you have the Motor Controllers in Brake mode. That will apply some counterforce, without having to power the motor. On our robot, brake mode is enough to keep the totes from dropping.

[JamesCH95]

Two CIMs should not be heating up during a match unless they are being very over-worked. Gear your mechanism more effectively to solve your real problem, don't address the symptom of over-heating motors.

Our 'totem' can support between 2 and 8 totes, plus the tote-grabbing bars, with a single stalled RS550 motor with no ill effects after two district events and lots of practice. We are using a 64:1 reduction with a 0.88in diameter spool to wind up cable.

[Ether]

Originally Posted by JamesCH95

Gear your mechanism more effectively to solve your real problem, don't address the symptom of over-heating motors

@OP: If you're willing, please tell us about your gearing. How many motor turns does it take to raise the boxes 1 foot?