Author Topic: Need help with pulley system/shaft fitting  (Read 1113 times)

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Offline clubirdTopic starter

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Need help with pulley system/shaft fitting
« on: August 14, 2013, 12:14:40 PM »
I am trying to use a stepper motor to control the turning of a knob.  The stepper motor has a 5mm smooth, rounded shaft. The knob is around 15mm and has a texturized aluminum surface. 

I can't figure out how to drive the knob or how to find the parts to do so. I have two basic ideas:

1) use a flexible coupling device with one 1/4 inch bore and one 5/8 inch bore.
 -issues: How to fit the inch bores to the metric shafts? Also, it will be difficult to get the near-perfect alignment that the coupling requires (assuming it allows less than 2 degrees  misalignment)

2) use a timing-pulley system
-issues: I have searched all over for 2 pulleys that will fit the shafts but I can't seem to find any, and when I do get close, I can't figure out how to secure them to the shafts. (I can only seem to find bushings that require a key-way)
-I'm having a hard time finding metric-sized bores, and when I do, there are very few pulleys that are offered in both 5mm and 15mm bore sizes.

Any suggestions welcome but please keep in mind that I have limited access to machines for creating key-ways,widening bores, etc

Offline jwatte

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Re: Need help with pulley system/shaft fitting
« Reply #1 on: August 14, 2013, 06:29:52 PM »
I was going to say "cut a keyway in the shaft" but if that's not possible, then a metal file and a basic vise will let you file a D-shape onto the shaft, which will be enough to screw various collars/couplings into it.

Another option is to use a simple friction contact; something like a rubber or plastic wheel on the stepper, and mount it with pressure against the existing knob. Depending on how durable it needs to be, a rubber band used as pulley could even work :-)


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