we’re using some very small 1/4" face 32 pitch gears for our shifting tranny… the dog is extremely small too (1" diameter) with 1/4" prongs sticking out… do you think these will hold up or will they get messed up etc… anyone have problems using these tiny tiny parts
In general, if you are using these 1/4" face gears on the low torque, high rpm portion of your gearbox, it is OK. Gear stress calculations can be done, but if the torque is low, then stress is low. If you put these gears on the lower rpm, higher torque area, I would suggest a wider face width to be safe.
As for a 1" diameter dog shifter with 1/4" prongs sticking out, it is difficult to say. The width and the length of the prong are also important. If your prong’s cross section has good area, then you should be ok. From what I recall, the dogs I have been using have about a 0.07 in^2 area, and they work fine. They also only stick out about 0.14".
Keep in mind that the stress on the gears and dogs that is most critical is the shock load from reversing. This load will be a combination from driver input and impacts on the robot. If you place the shifter in the high rpm, low torque section than you may have some shearing of the pins during shift on the fly.
Reliability is key, testing will prove your design. I suggest building now and test before the season starts. This will allow you to make changes before you need to build your new gearboxes. In 2003 we built our first dual speed in August and tested during the off-season. Several changes were implemented based on driver feedback for our 2004 design.
What material are they? I would recommend against aluminum or brass at all. Something like stainless or hardened steel will be alright in the applications listed above. I would not recommend doing the actual shifting with these gears. Keep them very near the motors in your drivetrain and they should be okay.