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Unread 16-01-2013, 17:32
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Oldbikerider Oldbikerider is offline
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Re: tapping CIM axles?

Whilst not addressing the exact question of the OP, I'll add here that heat shrinking a pulley/hub/gear to a motor shaft will work, but it is tricky.

The heat from the hub will soak back into the motor shaft which can damage the rotor, and will certainly bleed oil from the front motor bearing if it is sintered bronze.

Also, heat shrinking is a one-shot process, you need to get it just right first time. If you don't get the hub fully seated down to the correct position before it starts to grip on the shaft, you then have to bash or press the hub into place which will risk bending the shaft. If it won't budge, you'll have to turn the hub off the pulley on a lathe, which is now difficult to do because you have the front motor end cap sandwiched in there, making steadying the shaft all but impossible.

I can warn anyone attempting to heat shrink a hub or gear on this way that when it grips and the hub starts to loose heat to the shaft and the shaft starts to warm up, the whole assembly locks up real quick.

A much easier way to do this job is to use a retaining compound such as Loctite 680. I have assembled thousands of gears on motor shafts with 680 and never had a failure. It will fill gaps up to a few thousandths of an inch IIRC. 680 works very well on "reactive" metals such as steel, but will still grip with aluminum.

Graham.
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