window motor spec sheet confusion

[kiracofe8]

Originally Posted by andy

I'm designing the final stage of the articulation of our arm and we have choosen to use the window motor

<http://www2.usfirst.org/2004comp/Specs/Nippon-Denso_Window_Motor_specs.doc>

However, where the sheet mentions the specs for the output gear, they list 12-14 as the diamatral pitch. Why are there two pitches??? Which one should we use when we order gears to mesh with that gear? Have any teams used one/or the other with any success? Are we allowed to remove the output plate and press on our own gear?

Thank you in advance!

Good luck this year!
-Andy

This one confused me for a few minutes too, until I happened to come across a little paragraph in Machinery's Handbook. The drawings label these as "Stub tooth gears". There is an old standard for stub tooth gears called the "Fellows Stub Tooth" design which uses two pitches. The first is used for determining the pitch diameter, and the second is used for determining the addendum and dedendum. The result is that you have a 12 pitch gear, but the teeth are only as high as they would be for a 14 pitch gear. We have not tried it yet, but what we are planning on doing is using a standard 12 DP gear, but increasing the center distance a little as needed. I saw this idea posted awhile ago (like maybe years ago) by somebody (Joe J. I think). The gear was slightly different back then (different number of teeth?) but it was the same stub tooth, so I think it still applies. Do a search on "Window motor gear" and I think you'll turn it up...

As far as removing the plate and pressing on a new one, I'm pretty sure that that is explicity disallowed by rule R62.