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Unread 17-04-2007, 15:21
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Re: 56mm Banebot problems @ Championship

I know this may not be the best thread to post this in, but the information is quite appropriate for this thread.
During the Davis regional, we burned up two CIMs and damaged two 56mm trannies. Ultimately we figured out the root cause and made a modification to our bot to stop the problem from re-occurring a third time.
During build season, we determined that adding the outboard drive shaft support bearing would be a really good idea. After receiving the bearings, we fabricated to mounts and put them on our bot. We didn't notice until the second time we replaced a motor and tranny that when the support bracket was assembled to the bot that it didn't actually support the end of the shaft (long story that doesn't need to be spelled out here). Needless to say, the student who installed it the first time said, "oh, I was going to fix that later, but forgot." That aside, without the support, the output shaft was being pulled off axis.
Inside the trannies, the output shaft has a short extension that protrudes into the center of the final sun gear. The clearance of this fit are quite small. Once the shaft is pulled off axis, the little extension rubs against the inside of the sun gear. No amount of lubrication is sufficient to dissipate the friction this causes. The resulting heat and binding caused the sun gear to seize onto the output shaft. As you might imagine, really bad things happen when the final stage of a planetary gear system becomes fused together.

So, how do you fix this problem?

Bore out the sun gear to allow plenty of clearance. Make sure the end of the output shaft is properly supported!!!

Once these two steps were completed, we had no further problems with our drive train.

BTW, this happened with a hardened carrier plate as well as with the original plate.
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CalGames 2009 Autonomous Champion Award winner
Sacramento 2010 Creativity in Design winner, Sacramento 2010 Quarter finalist
2011 Sacramento Finalist, 2011 Madtown Engineering Inspiration Award.
2012 Sacramento Semi-Finals, 2012 Sacramento Innovation in Control Award, 2012 SVR Judges Award.
2012 CalGames Autonomous Challenge Award winner ($$$).
2014 2X Rockwell Automation: Innovation in Control Award (CVR and SAC). Curie Division Gracious Professionalism Award.
2014 Capital City Classic Winner AND Runner Up. Madtown Throwdown: Runner up.
2015 Innovation in Control Award, Sacramento.
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