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Unread 03-08-2016, 23:00
Tcrump47 Tcrump47 is offline
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Re: Custom Gearboxes

Quote:
Originally Posted by Max Boord View Post
Just about any aluminum plate or thick polycarb will do. This year 4592 did them out of 5052 H32 which is far from ideal but even with heavy pocketing worked well as the ratio we wanted was higher than anything available commercially. If you have access to waterjet making the plates should be easy. I prefer 1/4 inch plates as it lets you take advantage of the full .25 inch bore of an R8 Bearing (.5 ID 1.125 OD) Do you guys have access to a lathe? making custom gearbox spacers are nice but ones from McMaster work too. We used plastic ones at the start and switched to aluminum for the 2nd version of our gearboxes even though the plastic ones would probably have worked fine. for spacers PVC works well enough although delrin ones from vexpro are nice as they do not require sanding to an exact length. for bolts i recommend 10-32s as they can be used to hold the gearbox together and also be used to hold the cims to the gearbox. You can make clearance holes on the front plate ant tap the rear plate so the whole gearbox dosnt fall apart before it is installed although I generally find using long screws to attach motors through the front plate to be good enough retention.

When it comes to designing custom gearboxes, try to use a mounting pattern that is identical to a COTS gearbox for your first few. That way in the worst case you can drop in an off the shelf replacement should your custom gearbox fail. For gear spacing use normal pitch diameters +.003 to account for manufacturing slop and wear and tear on the plates. make sure to include 1 or 2 spots where you can change ratios if the final speed is undesirable. Pinions are a common place for this adjustment but changing spur gears is also an option, although this will more than likely require disassembly of the whole gearbox as opposed to just removing the motors. For shafts its nice to be able to do snap rings and bearing rounds as the combination can be used with a round bearing to retain the shaft when the outer plate is removed as well as opening up the back hole for a sensor.
Thanks, and we do have access to a lathe.
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