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Old Mar 07, 2006, 05:58 PM
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sheerLuck's Avatar
Novato, CA USA
Joined Jan 2002
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GWS servo gear replacement

Just thought I'd share my experience, in case it will help someone else. When I initially did a search, the references all gave me the impression that replacing servo gears is a no-brainer, like changing batteries in a flashlight. Well... almost.

1. Some sources of GWS servo gear sets :

http://www.allerc.com/index.php?cPath=40
http://www.aircraft-world.com/shopexd.asp?id=766

2. Only info I could find which included pictures of the gear train (in case you accidentally scatter the gears, as I did...).

http://www.noeticdesign.com/robotics...cobb_hack.html

3. There were 2 tricky parts to the operation:

a. Once you have the case apart, the top gear is press-fit onto the potentiometer shaft. The only way I could see to get the top gear off was to tug and twist. This worked, but the reference above suggests prying gently between it and its' neighbor gear (on the same shaft). Replacing the top gear was simpler - I just pushed & it went on. It's probably desirable to insure that it's not pressed so far as to cause any binding.

b. When I tried the servo without the top gear, it had varying reactions, but at the end the servo was just running like a geared motor - there was no response to transmitter commands. I thought I had killed the servo until I thought about that potentiometer thing again. It turns out that, with the servo running, you can grab the potentiometer shaft with long nose pliers, and twist it one way or the other until the servo gears stop spinning. At this point, disconnect things, add the top gear and you're good to go. To hold the case together, I used some shrink wrap which is 1 1/8" when flat, but tape would probably word about as well. I might add that perhaps trying the servo without the top gear is a bad idea...

I suppose everyone but me knew that the top gear was secured to a potentiometer shaft - and everyone but me knows what the heck a potentiometer is and what it does. Well, just in case there is anyone else out there as uninformed as me - now you know a little more about servos. If anyone who actually knows what they're doing would care to add their knowledge, please jump in.

Larry
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Old Mar 07, 2006, 08:35 PM
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ivanc's Avatar
United States, TX, Round Rock
Joined Dec 2004
9,344 Posts
My LHS - HobbyTown USA could get me replacement gears for the Park HPX. They were extremely slow but at the end ordered them for me.

Ivan
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