Does anyone know what a reasonable range is for the angular free play of the output shaft of a Banebots P60 256:1 gearbox?
I’ve got one here that has 15 degrees free play, and I’m wondering if that is a sign of damage and/or impending failure.
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Sounds like where the dog features engage between shaft and first planetary set are rounding off. That’s what ours did (along with the tube turning and rolling the pins off the flats) and then the whole feature twisted off. I think the 35 ft lb max limit on those is pushing it, and you need to consider shock loads beyond that limit if it can happen in your design.
Remove gearbox, disassemble, take pictures, post pictures.
There’s plenty of time… :yikes:
Uh uh…Fed Ex will be picking ours up by 2:30…it was crated at 9:30 this morning and I am NOT taking it out no matter how much the children beg and sit on the crate! 
In ours there was no free play when new. I would suspect the Double-D shaped end of the shaft is rounding out in the plate (I am correct in saying these are driven like that right?). It may yield until some point and then not go any further. If you have that much free play though, I’d suspect it would keep opening up. Hard to say.
It will continue to open up. If you are using it for an arm, it is likely being overloaded, especially if quickly reversing direction. We have doubled up these transmissions on the arm shoulder, and have eperienced similar results, but not failure. TIG welding the shaft to the output plate by an experenced welder has been done in the past.
I ran into a similar failure mode with my P60 256:1. I think it resulted from applying a large amount of torque on the output shaft (trying to backdrive an arm) while the friction inside the gearbox caused the shaft to not rotate, thus causing the little pins to sheer the ringgear.
If you’re in a pinch to repair it, I believe you can weld the ringgear on. I fortunately had a spare on hand, so I didn’t need to use the one that was repaired yet, so I won’t be able to testify as to whether or not it is more robust than the original.
why do these always seem to fail? we have a dewalt drill gearbox with exactly the same output method and it supports 400 ft lbs, has anyone considered making a new axle out of harden-able steel?
Does DeWalt make a 256:1 gear ratio with 400ft-lbs output capability for the same price, size, and weight as a Banebots?
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The standard dewalt gear-ratio is about 47:1. And 400 ft-lbs… well…::rtm::
But I understand your question was fairly rhetorical ether…