Anyone using the 42mm gearbox should carefully read the (now three page) recommendations for use thread (
http://www.chiefdelphi.com/forums/sh...=53010&page=1), in which several people including myself have been evaluating the problem and offering suggestions ranging from software to heat treatment.
The CAD files may be proprietary, but nobody can stop you from measuring the thing. I can save you the effort:
Thickness: 4mm (precision-ground 5/32" stock works well)
OD: 25mm
Shaft Diameter: 10mm
Shaft Flats: 8mm
Pin Hole Radius: 9mm, 4 places, evenly spaced
Pin Size: 3mm, maybe undersized 3mm. Doesn't matter much, use a #32 drill for a workable press fit.
Also, as I have posted in the recommendations thread, I would be willing to rough cut a (small) batch of the 42mm plates on a waterjet THIS WEEK if there is interest. So far only one person has replied yes. They would be O1 tool steel, similar to the stock plates,
NOT hardened and
NOT finish-machined (the pin holes would still need to be reamed and the double-D would have to be filed to take out the taper from the waterjet).
They can be hardened and tempered to a C40. I can provide a procedure for that if you have a local shop that can do it. I did this for our 56mm plates and they have not deformed or fractured. We also used a non-hardened (annealed) plate in our 256:1 42mm gearbox for over a week with only minimal deformation, so they can be used for cheap spares if you don't beat them up. (Until hardened, the tool steel is actually slightly softer than the stock plates.) For what it's worth, our arm is not counterweighted and we have no gas spring. The only thing protecting the gearbox is a 7.2:1 reduction. And thus far I have yet to see anything even close to failure of either the stock plate or our new soft plates.
BaneBots had to take care of the larger problem, the 56mm gearboxes, so I'm not surprised they didn't get around to the 42mm non-kit stuff. But it seems like there are only a limited number of teams still using them and if that's the case, I can produce a small quantity of rough cut 42mm spares (in about an hour). If there is interest, please let me know as soon as possible. I would just ask for payment to cover my materials/machining (waterjet is cheap...$5 per part maybe)/shipping costs.