As my season is over (the teams I help out) I started my “off season” project. It maybe crazy but then I am an old retired crazy dude lol
What I am attempting is to make a ball drive using 6 in balls instead of tires and arrange it in an X drive or Kiwi Drive. First attempt is going to be Kiwi as I never done one
So first you need some hubs
3d Printed of course - I selected PETG and I stepped a couple of times on it (295lb) So looks like it might be strong enough
They are glued together and use some #6 sheet metal screws to keep them close together while drying. As glue I use gorilla glue which works fine on PETG (and HIPS and ABS etc)
There are 2 TPU partial spheres that are glued to the hub (the tool boxes and bolt box is to keep things in place while it dries. Next to it the polar capse that will glued and put in place with #6 deep recessed sheet metal screws. (at least 1/2 in . At the thickest spot the polar caps are about 18mm at the thinnest the tire is about 5.6mm
pics off a prototype to cage the ball there will be a bottom part that will allow at least 2 in ground clearance max to clear obstacles potentially more . The bearing ball assy are from furniture movers and rated at 120 lb each
parts of an omni wheel and holders amongst others The omni also includes the double helical ring gear of a planetary at its center and some bearings/races to take the load of the gears.
The rollers have teeth to give them a chance with a little wiggle here and there to catch and line up with the holes on the tire which also double as a profile. The hole are small enough to provide enough torque and big enough to appear almost flat to the furniture mover balls. The rollers will be mounted in 2 sections of 6 each offset similar to the 6 in omni from andymark and will have brass bushings and steel shafts and brass eylets to protect the TPU rubber from lateral forces and cut down on rolling resistance as you only have brass on brass and brass on steel contact (5mm rods)
The sun gear which is the input of the planetary will be a bevel setup that takes a cim/neo (8mm keyed ) shaft input.
Those are the planetary holders and the holders for the bearings that function as wheels
Here is the bevel side one with the 6806 bearing inserted that will hold one end of the sun on the outside the sun also has a 688 bearing for the 8mm(or 5/16) shaft/bolt used as an axle. The bolts used for mounting are m5 machine screws the heads are counter sunk and the nuts are captive to allow a tight package. The bevel will also have a 688 gear on the 8mm center axle (most likely a 5/16 bolt as that is 7.937p mm and the bearings slide on really nice on that most 8mm shafts need some work with some sandpaper to get the bearing on. The bearings used in the planets and the ones used as wheels to take the loads off the planets are 625. The gears in the planetare have 1.3mm modulus are 20mm wide and are double helical - herring bone and should give a smooth performance and are strong enough. The helical angle is 20 deg and the pressure angle 14.5 and of course involute with a .5mm fillet as a crown.
Is it going to work - IDK I will also have to make a frame that I probably will make a composite (3dp base with Fiberglass wrap. and some 12 in square aluminum tubing.
This is a candidate - probably will do it with trusses but the shape will be about that. This particular design will have 119.5 in circumference figuring on 1/8 in fiberglass (3-4 layers of 10 oz cloth on the outside. ) Which with the 3/4 in plywood from the bumpers flush against it should be strong enough.
Well its crazy but it beets watching netflix - at least in my book.