Chief Delphi - pic: Planetary wheel (cutaway)

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pic: Planetary wheel (cutaway)

Re: pic: Planetary wheel (cutaway)

2007 will be a year of robot design innovation.:)

Go ahead and make a wheel hub that goes right over the bearings and retained with ring clips on each shaft. This way you can remove the planetary gearing if something goes wrong and still use the wheel, or vice versa.

Re: pic: Planetary wheel (cutaway)

Quote:

Originally Posted by 11Ed71 (Post 546587)

Cutaway view of an idea I had that I fleshed out into a design. It will probably never get built, but here's the first revision of the design. All parts are stock parts available from McMaster or SDPSI or are easily machinable on a CNC mill. Opinions are welcome, but if all you're going to say is that it won't work, I don't need to hear that.
Side loads may be an issue, but since the whole thing is riding on roller bearings, I don't think it will be.
Completed, the module runs directly off a CIM, and is bolted to a frame member on both sides (this mounting plate isn't visible here to make the gearing visible), with the wheel part (everything seen here) spinning at a 16:128 reduction. (Stationary planets, driven ring as output/wheel surface.) The wheel surface would be sheet metal with some kind of rubber tread.

How are you supporting the outer ring with respect to the planet gears and planet carrier? If your outer ring can wobble about the central axis, you're probably going to encounter a lot of uneven tooth wear. You definitely can't rely upon the tooth mesh to support the weight of the robot.

Also, is the 16 tooth gear hardened steel? Because it probably ought to be. (What's the SDP/SI part number?)

Re: pic: Planetary wheel (cutaway)

Quote:

Originally Posted by Tristan Lall (Post 546589)

Out of curiosity, where does the planet carrier come from?

Re: pic: Planetary wheel (cutaway)

Quote:

Originally Posted by Tristan Lall (Post 546589)

Materials aren't final, but I believe it was hardened steel.

As for the ring, you'll see there is a ring gear and a circular aluminum ring (2 actually, but only one visible), which is bolted to the ring gear. The aluminum rings are riding on bearings on the planet shafts(those 3 cylinders), which take all of the load of the weight of the robot.

Quote:

Originally Posted by M. Krass (Post 546591)

Out of curiosity, where does the planet carrier come from?

Everything but the gears and bearings would be custom-machined.

Again, odds are this will never be built, I just wanted to see the public reaction. Even if this design does see the light of day, it won't be on MORT '07. (Not my department, I'm end effectors.)

Re: pic: Planetary wheel (cutaway)

Thats crazy ed, post a picture of the whole assembly with the mounting plate.
How much do you estimate it weighs?

looks intense

Re: pic: Planetary wheel (cutaway)

I posted a new picture here.
Inventor says the weight is around 1.9 pounds (plus CIM and mounting hardware.) I don't trust that number because I haven't double-checked my materials and because it's an inherently rough estimate, but I expect the final to weight in under three pounds, which compares pretty well to the kit gearbox if I remember correctly.