pic: Planetary...Wheel?

[Jizvonius]

Hey nice design. One way to reduce the range of loading on the gears would be to find a way to support the wheel on it's own bearing. It may have to be a needle roller bearing with a large inner diameter to keep the design compact but it should work out with a bit more structure. That way the wheel loads go to the bearing and the gears don't have large time varying loads that will occur even without impact with the present design.

Also, you can get away with using fewer gears now that the loads don't have to be distributed that much. That should save a little on weight.

[sanddrag]

If this turns out to be more trouble than it's worth (which I'm not saying it necessarily is) there is always the option of making a traditional fixed ring planetary, and having the output of that be your wheel axle. You'd have to take some precautions so that wheel impact doesn't happen or if it happens that it doesn't affect the gears. It would end up being a little bit long to space out the bearings (probably an inch of spacing between them will do), but you could have the wheel double back over the gearbox sort of like the MER rovers. You could have a deep dish wheel so the gearbox goes inside of it a bit.

I'm even thinking maybe a Chiaphua/Dewalt directly driving a wheel by modifying the output shaft and end of gearbox to give better support for holding a wheel. The only thing is though you wouldn't want to go any larger than about a 5" wheel straight on a Dewalt, but at least I think that is enough to clear it so the gearbox can go inside the wheel a little bit.

The thing with making planetaries is that I haven't been able to find a source of wide face internal gears. The largest I've found is 5/16 and it is brass.

[Jizvonius]

I think the internal gear idea can work if the pitch diameter is large enough. Then it wouldnt require nearly as much force on the gear teeth as it would be applied far from the center of rotation. This thread actually made me resurrect an old idea that can possibly make a very compact drive module. The gears(except the internal gear), brackets and shafts are missing from the inventor drawing, but the spacing has been worked out in 2D. The model so far should give you an idea of what I'm working towards though. The gear ratio ends up being about 15:1. The weight looks like it will end up being about 8 lbs and the size is about 8"x6"x6". The design obviously needs more thought, but I figured that I'd put it out there.

I have many variations of this design that move components around for different purposes. This one is to minimize the amount of gearing and space for the motor-gearbox-wheel system.

Jevawn

BTW i did this last night at around 4:30am so any resulting crappyness of the model can be attributed to that.