tapping CIM axles?

[mrnoble]

for direct drive. good idea or bad? why? any ideas on how best to accomplish? thanks!

[dellagd]

What does this accomplish exactly that a keyed shaft and hub or coupling can not?

[wilsonmw04]

if you don't have those things, tapping the shaft works well. We have used all three methods in the past.

[Ether]

Originally Posted by wilsonmw04

if you don't have those things, tapping the shaft works well. We have used all three methods in the past.

I wonder if this would work:

Put the CIM in the freezer for 10 minutes, drill a hole in the piece you want to connect the CIM shaft to, heat that piece nice and hot, and shrink fit it over the CIM shaft.

[mrnoble]

We're using keyed hubs mounted to skateboard wheels, and would like the wheels to stay on the axle, so are tapping it to place a washer over the top. Just did one and it worked very well. Thanks!

[wilsonmw04]

Originally Posted by Ether

I wonder if this would work:

Put the CIM in the freezer for 10 minutes, drill a hole in the piece you want to connect the CIM shaft to, heat that piece nice and hot, and shrink fit it over the CIM shaft.

Hmmm, Interesting idea. I might have to try that sometime.

[JamesCH95]

Originally Posted by Ether

I wonder if this would work:

Put the CIM in the freezer for 10 minutes, drill a hole in the piece you want to connect the CIM shaft to, heat that piece nice and hot, and shrink fit it over the CIM shaft.

It's potentially easier to heat up the part you're installing on the CIM with a torch. Raising the temperature by 300-600 degrees with heat will get a bigger dimensional change than cooling by 100 deg.

When this sort of thing is done IRL (bearing races, for example) one part is usually put in an oven and heated to 300-500F and the other part is put in an alcohol bath with dry ice at -109F.

As for actually retaining something on a CIM shaft, check out the normal pinion retainer rings available from AndyMark and/or VEXPro. They may seem a little flimsy, but do a pretty great job holding on.

[Ether]

Originally Posted by JamesCH95

It's potentially easier to heat up the part you're installing on the CIM with a torch. Raising the temperature by 300-600 degrees with heat will get a bigger dimensional change than cooling by 100 deg.

did you miss this part?

Originally Posted by Ether

heat that piece nice and hot

[JamesCH95]

Originally Posted by Ether

did you miss this part?

Yes, yes I did, clearly.

[thedude019]

it works just fine my team did it while prototyping. it took a while but it works just be sure not to tighten the screw to much as it can rub and not work as well but keep it tight enough so the wheel doesnt wobble or it will vibrate to much and well in prototyping lets just say i hurt my finger

[Ether]

Originally Posted by thedude019

it works just fine

Please, what does the pronoun "it" refer to?

Your post is linked to this one:

http://www.chiefdelphi.com/forums/sh...39&postcount=9

[pmangels17]

Silly question, but is it legal to do this? I know FIRST has very specific rules on modifying motors.

[mrnoble]

Yes, I think it is legal to tap the axle to mount a screw. It does not change the performance or safety of the motor, which are FIRST's concerns.

[Al Skierkiewicz]

R33
The integral mechanical and electrical system of any motor may not be modified. Motors, servos, and electric solenoids used on the ROBOT shall not be modified in any way, except as follows:
A. The mounting brackets and/or output shaft/interface may be modified to facilitate the physical connection of the motor to the ROBOT and actuated part.

However, the bearings on a CIM don't like side loads at all. They are only bronze sleeve bearings.
Also, are you drilling and tapping across the shaft or down the center of the shaft?

[mrnoble]

Down the center.