motor gear pitches

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Posted by Raul.

Engineer on team #111, Wildstang, from Rolling Meadows & Wheeling HS and Motorola.

Posted on 6/10/99 6:49 AM MST


In Reply to: 16 Tooth 32 pitch... as I recall... posted by Joe Johnson on 6/9/99 9:12 PM MST:



I had a lot of experience with this little pinion this year because we created our own transmission for that motor. Here is what I learned:

First of all, it obviously has 16 teeth. What is not obvious is that it is a metric 'M0.7' pitch diameter. I found this out first the hard way and then by finally getting a print of that little gear from Bosch (this was not easy and took quite a while).

At first I also used a standard 32 pitch gear and found that it did not mate correctly. Then, I tried a M0.8 metric gear which was not easy to find. It was even worse. Now, I did not even know that there was such a thing as a M0.7 pitch. All this time I did not have the print telling me the proper size. So, I went back to the 32 pitch and used an off-the-shelf brass gear from Small Parts. Using brass was important to allow the teeth to wear in and not harm the pinion on the motor. One good thing about the pinion is that it is hardened and is very durable.

Anyway, by the time I got the print and realized it was M0.7 I had run out of time and did not want to change our design (redo the gear centers on the mounting plates) because it seemed to be running OK.

Some advise if you use mate a 32 pitch gear: Run it for a while under no load to wear it in. We blew out one gear because we ran it under load in practice without wearing them in. Ever since we wore them in properly, we never broke teeth on those brass gears. It will make a lot of noise at first and will eventually smooth out. And of course, be sure to use plenty of grease.
I’m not sure I agree with Joe about allowing a little extra clearance. In fact, we moved the center .010' closer than required by standard 32 pitch gears. The standard clearance seemed too sloppy.

In the future, I would try to get the M0.7 gears. I think, Stock Drive Products (516-328-3300) has them

Good luck

Raul