Here are .STL’s (updated Jan 23, 2022) files for those interested. Just added a Big Segmented gear. The materials and settings are just a suggestion, but they seem to be working very well. Has large overhangs, support material required.
Attempting to build a one size fits most geared motor drive unit that will hopefully reduce the custom farm shop fabrication to a minimum.
I started with @Math Fiat gears altered with a buffer wheel, and found that zip ties are sufficient to self center and hold the ring gear on tri spoke steering wheels. The zip ties must choke behind the spoke smaller than the diameter of the spoke. using two ties really concretes them in place. Care must be taken that the fat ends are not in a position that can touch the drive motor.
Herringbone gears are great because the thrust load is cancelled out so they ride centered and keep centered.
The large gear is printed out of PETG which is very hard. The gear is printed so the teeth are solid in the hopes of never taking it off. 3.6mm wall thickness, 2mm top and bottom, 60% infill. Takes 310g of material and 1.5 days of print time.
The smaller gear is TPU, when printed thick TPU is hard like a hockey puck, but still rubbery. Since it is softer it should be sacrificial and save the larger gear from damage. 2.8 mm wall thickness for solid teeth and 2mm top and bottom 80% infill. Uses 40g of material and takes 5 hours to print.
Added bonus of TPU is during fitment, if too much spring tension is applied the gears will squak. Once they are fully bedded and quiet, tension is proper. In open cab lots of dirt will make the gears noisy. But dirt accumulation seems to be prevented by spraying them with dry silicone lubricant. It does not take much force to keep the gears engaged, the PETG does not try decouple the TPU.
Version one was very chunky and took over two days to print
Version two dropped a bunch of mass, and print time without compromising strength,
Here are the V3 gear and V1 quick attach .STL (updated Sept 24, 2021) files for those interested. The materials and settings are just a suggestion, but they seem to be working very well. Has large overhangs, support material required.
Those wondering the benefits of gears vs wheel tire, the main advantage of gears is zero slippage and wonderful repeatability making tuning with them more precise. Also Having the full use of the steering wheel at all times, especially with the cytron freewheel modification.