Thread: What is your favorite method for attaching gears to shafts?
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Unread 24-06-2002, 04:00
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I agree with Dr Joe, but there are other ways
Posted by ChrisH at 04/30/2001 5:20 PM EST


Engineer on team #330, Beach 'Bots, from Hope Chapel Academy and NASA JPL, J & F Machine, Raytheon, et al.


In Reply to: What is your favorite method for attaching gears to shafts?
Posted by bill whitley on 04/30/2001 3:51 PM EST:



Bill,

It's very hard to beat a "double D" shaft. While you don't necessarily need a press fit, you do have to have some retention method. If you don't know what a double D is look at the end of a van door motor output shaft. The problem is that you either need to use a milling machine, EDM or a broach for the hole, depending on the exact shape. Our machine shop had a custom broach made for the van door shaft end a couple of years ago.

It's not too hard to make a square shaft out of a round one, but a square hole is harder. If you can make a square hole (see above methods), a square hole on a square shaft will work fairly well.

We like to use flanged fittings on shafts like Dr Joe said too. This is a very good approach if you're not quite sure on the gear ratio. Changes are quick and relatively painless if you have the gears ready.

Key ways and keys of various sorts also work well if designed properly. However they can be difficult to add to a motor in the field, so be sure to have spares with keyways pre-installed. If you want to check these out look for a good mechanical design book. "Machine Design" by Shigley has a pretty extensive discussion on keys and keyways.

BTW I regard "pins" as a four letter word in this context. They're almost as bad as set screws and we all know what set screws do.

Chris Husmann, PE
Team 330 the Beach'Bots



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