Converting a 25:1 gearbox to 75:1 reduction with 3d printed parts

I've been thinking for a while I would like to try a 50:1 or 75:1 gearbox instead of the 25:1 I am currently using for traction loss. It just seems a bit sluggish getting up to speed and changing direction even though top speed doesn't need to be too fast. I haven't however been able to find a replacement that has the hole through the shaft like the current one.

I decided to try and convert the existing one to a 75:1 reduction using 3D printed parts, here's what I came up with. It's an addittional 3:1 reduction that fits between the motor and existing 25:1 gearbox.



For comparison the output shaft speed of the original motor with 25:1 reduction...



And the output shaft speed with the additional 3:1 reduction stage (3D printed parts)...



It is somewhat noisier however I had forgotten to add any lubricant to the gears at this time so I need to pull it apart and do that to see if it makes much difference.

Here is how it all fit together...



I estimate the total cost around AU $5 to $10 depending on how cheap you get the bearings and bolts. All up it used about 20m of 3d printer filament at $27.50 a Kg which works out to be under $1.50 for those parts.



I have yet to fit it to my traction loss. Requires a bit of dismantling of rig so will do that on the weekend.

I have no idea how it will wear or last or if it will now be too slow for traction loss so all that testing is still ahead, but so far it seems good and I think it should be fast enough and provide a more snappy response due to less load on the motor.

STL files in attached .zip

Thanks, I'll do an update video when it's fitted to the sim.

Congratulations !
This gives really want to s'équiper printer 3D

Fécilitations !
Cela donne vraiement envie de s'équiper d'imprimante 3D

Yeah that's a really smart design @RufusDufus.

Great idea Noorbeast; Done

Incredible! I wish you it will last long

Thank you for sharing.

Looks great! Are those the Canadian ebay motors?

those are the Motion Dynamincs it looks like from the sticker. Basically identical tho.

@RufusDufus How have these stood the test of time so far ?

Hi @Nick Moxley, they are still working OK but they haven't had much use since installation unfortunately - I've been side tracked on other things and not used the motion sim much the last few months. Just realised I never posted a video either.

You are also correct about the motors - they are motiondynamics 25:1 motors.

Thanks for the upload, printed mine using makerbot replicator 2x.

I'm glad someone has found a use for it. Let us know how it works.

Yes Alexey please do report how you get on with it. Rufus, any chance of working out the gearing ratio for a 50:1 swap ? I really wouldn't need the torque of the 75 setup. Thanks

Very impressive, think i'll save this in my 'just in case' folder.

My pins ended up being a tad noisy (rattling up and down) because they were probably a tad short, so instead of stuffing around and re making the pins I cut some teflon discs to cover the metal surfaces and reduce that metal on metal contact.




I also used teflon grease on the gears with no effect on noise reduction in the gearbox, I am thinking my prints aren't as accurate as they could be and the larger gear is rattling around. Would be good the be able to bolt that gear into position rather than being a floating gear.



I've ordered some PETG and will try out a print with that material.

EDIT: atcually, looking at your videos again rufus you may want to try the same plastic spacer fix.

Yes I need to find some time to revisit this and see if the noise can be reduced.
It will be interesting to see if the PETG works better - I used ABS.
I found that it was quieter under load. Also the sides of the gear spurs were rubbing at times so I sanded them a bit and it made some improvement. It could also be tolerances, I did some initial calculations but never really tested how closely the printed parts matched so maybe increasing/decreasing the size of the gear parts a very small amount may help.

Hi Nick, working out gear ratios is easy enough but the way I designed it would pretty much mean a start from scratch to make the change - maybe in a while but currently trying to complete some other projects.

Thanks Rufus,