Quote:
Originally Posted by Rauhul Varma
Is it really that common in FRC to add 2-3 thou? (I honestly don't know) For every gearbox I've designed I've only added half a thou and haven't had any problems with wear.
I do see the problems with the actually trimming the OD, depending on the team's machining expertise and capabilities it could be quite difficult to do. correctly
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Adding three thou is a psuedo-standard in FRC. It's a good rule of thumb for custom gearboxes. It's also one way to artificially shift your tolerance band.
Quote:
Originally Posted by T^2
I think this practice is also becoming slightly less common because of the prevalence of VEXPro gears. Their hex is oversize, while the shafts are undersize; this leads to slop. Adding .003 to c-c can lead to very noticeable backlash.
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Yeah... We had a 6(!) stage arm transmission this year and we had over seven degrees of slop in our original arm. We added the three thou but all of the loose hexes added way up. All of the shock loading of the arm flopping around in the straight up position led to multiple gear failures.
So yeah, I think we're going to .001 next year. I've heard people run zero backlash with Vex gears with no problems, but I'd like a little bit more space for grease in there, and this avoids having to break in gearboxes for any extended period of time. (The kids made me promise I wouldn't push for a geared arm again too)