motor clutches

[Bryce Paputa]

We would like to put a small friction activated clutch on one of our banebots gear boxes so we can run it into a hard stop without burning up the motor or destroying the gear box, does anybody know of where we could get one?

[MrForbes]

mcmaster-carr search for torque limiting couplings

Or...if you're programmers are good, use a limit switch.

[Ether]

What do you mean by friction activated clutch?

[Bryce Paputa]

That's probably not the correct term, one that limits the torque transmitted through it.

Originally Posted by MrForbes

mcmaster-carr search for torque limiting couplings

Or...if you're programmers are good, use a limit switch.

Our previous design used limit switches, but they are very close (~1-2 inches) from the axis of rotation, so the slight differences of when they are pressed could become noticeable differences in angle. We measure the angle by using an encoder that was zeroed at the lower limit switch, so these small differences apply to every shot we make. We're planning on just running the shooter into the hard stop, until the encoder reads a speed of 0, and using this as our reference point as it should always be the same. The mcmaster carr ones look good, except that weakest one slips at 25 in-lbs, which is quite a bit too much (more than the motor & gearbox can produce at stall current). We also don't really want a flexible one, and the rigid ones only go down to 72, which is almost 5 times the torque of the motor.

[MrForbes]

also look into using the clutch on a cordless drill....they usually have an adjustable setting for tightening screws.

[AlexH]

you could hack the gearbox out of a cheap cordless drill like a harbor freight 900rpm with 3/8" chuck or the ollies brand equivalent


they accept 550 size motors and the output shaft thread is 3/8-24


i wrote an instructable on the process of hacking the gearbox a while ago

http://www.instructables.com/id/Hack...rs-for-/#intro

hope it helps...

[roystur44]

I'm surprised that VexPro doesn't have a small magnetic/slip clutch attachment for the VersaPlanetary Gearbox. Hint hint cough cough.

Building robots would be so much easier.

This is what you need.

http://www.mcmaster.com/#torque-clutches/=lx8mgg

Bryce,

I've made one from a delrin spacer. I parted the shaft into two pieces Reamed one end of the spacer to the shaft diameter and .002 over the shaft on the other end. I also cut a oring groove on the outside of the spacer with the bigger hole. I band sawed the spacer across the diameter and used a small oring over the outside to create the tension. I pressed one the spacer to the one shaft and inserted the shaft into the spacer. It worked pretty good.

We later changed out the mechanical spacer clutch and used a Jag in current sensing mode to make a software clutch.