pic: Planetary Wheel - Exploded View 4

Final exploded view, shows planetary gearset, flanged wheel, shafts and second mounting plate.


This is a novel, unique, creative design. From what I can tell no one in FIRST has done anything like this. You are “blazing a trail” here, with this design. Since this is new and no one has any experience with it, much development is needed. In order to make something like this work, you are going to need to get much imput, make various prototypes, and then expect to re-do things.

At this point, you have drawn a good concept. It does need some improvement, mainly in the area of wheel stability.

I am mostly worried about the wheel being able to withstand a side load. Currently, if a side load was put on the wheel at the location of the tread, the ring gear would slip off of the 4 planets. Gears would jam, metal would break, and general chaos would follow (well, not really).

I suggest this: Make something that will enable the wheel to be robust without involving the ring gear. Imagine removing the ring gear and having the wheel spin on the central shaft, around a bearing. If the wheel had a 1" wide (or bigger) hub with two sealed ball bearings on either side, then it would start to withstand the side load a wheel will see in a FIRST application.

Actually, you don’t even need a custom wheel to do this. You could mount your ring gear on the side of a regular wheel (skyway), much like teams do when they mount a sprocket to a wheel. The ring gear just needs to be spaced out to the near side (the same side as the motors) of the wheel.

Good job, Matt. You should be a “gearmonkey” instead of a “codemonkey”.

Andy B.

I like it! It has potential for reducing weight and keeping CG low, etc.
Andy, what if you changed the bearing plate, increased the surface area of the inside diameter of the hub and added a second plate on the outside so that you could use radial needle bearings on both sides of the wheel? That would take some pretty good side loads. The weight of the robot would be distributed to the bearings on the planetary set, right?

Matt, Nice design man.
I was kinda thinking of doing something like that, except with shifting and the good 'ol 222 ball shifting.
I have some paint files of it, because I don’t know how to use CAD :o .
From what I can see on your design, much weight would be saved if you could make the wheel smaller, keep the innards the same but get rid of the spokes, if the wheel size is crucial in desired the desired ratio, change it some where where else. IMHO smaller is better, this is a design to save weight so try to look in all areas. In the on design I drew up, the “wheel” is nothing more than an internal gear with edges to mount brackets for mecanum rollers. Think outside of the box and go for featherweight. Good luck man.

Can someone go over (in simple terms, no fancy symbols) what the equations for reduction are for planetaries of fixed planet and planetaries of fixed ring? Thanks.

And here

Hope these help.