FRC 48: Transmission Issue

Technical Technical Discussion
1

This past Friday was our 24(+) hour Build-a-thon before our pre-ship event on Saturday. During our overnight build session we finally mounted and ran chain to our modified AM Shifters only to find out that they don’t shift on the fly. It will shift from high to low with little chatter but when we pull out from low to high it tugs, stops, moves slowly to the point where the dog grinds horribly on the teeth on the low gear and then slams into high gear.

over the length of almost a whole day another build student and I racked our brains trying to find a solution…we have yet to come up with one. this is where you the CD community come in We would like you help.

We have already done or checked these things:

It is designed to AM shifters spacing on everything…Gears ,spacer width and servo position.

Cleared Dog of lubricant.

Changed Servo.

Switched around what motor was powering it to see if speed/torque were a problem.

Changed out shifting cluster.

2

It’s probably your servo still. The amount of force that must be applied by the servo is great, and the servo simply doesn’t have enough torque to shift the transmissions well with the gear ratio that you are using.

3

What happens when you shift when the motor speed is really low? From what you posted, I’m taking that the dog is sticky on the hex shaft and/or the servo isnt strong enough to shift. As the servos generally ARE strong enough to shift, you should probably take apart the dog/pin/hex assembly and file the corners of the dog and the slot for the pin that goes through the dog.

From my experience with dog shifters (Ive made 3 different designs), shift resistance has ALWAYS been due to friction in the dog assembly, never had anything to do with the gear speed, torque, etc. Just take the thing apart and file it and it should be fine. The servo should be plenty strong.