3D printed Inner Gear Drive | Trampa Holypro | VESC 6 | Overion 130kv | GT2B + Arduino

Hey people!

As you might remember from the other forum, i’ve been working on a 3d printed inner gear drive for my trampa mountainboard.

Why? idk man, i just wanted to see where the limits of fdm printing are and how far i can push it.

This is basically the second edition of the drive. The first edition didn’t work out because i could never get the motor mounts aligned and stiff enough. I used it last year and it kinda worked, but it was far from perfect. Back then i used Taulman Alloy 910 for mounts and gear and, while it’s a great filament, it’s too soft for a mtb drivetrain.

So the basic idea is this and i think it’s pretty straight forward:

While those test prints are made from PLA i already printed the actual gears out of Polymaker PC Max and rode them a few times.

The other major upgrade is the design of the motor mount. It’s much thicker than the original one and has steel rods a support which solves all the stiffness issues. I know i stole this idea from someone on the forum, but i totally forgot who that was :sweat_smile:
The motor mount also doubles as a spacer for the wheel.

This how it looks when it’s mounted. The green covers are testprints as well and do not fit perfectly yet.

The rest of the board is nothing special. I use a 3d printed case for the VESCs and a modified GT2B remote (the mad munkey mod) with a arduino on the receiver. The arduino is connected to a VESC and shows me voltage, amp hours and distance for quick telemetry since that’s what i had laying around.

I’m having a few issues with the control and the sensor connections at the moment, but the project is coming along nicely. I probably rode 50 kilometers on the new drivetrain right now and it works really really well. Much better aligned and sturdier than the previous version.


Very nice, have you had any issues with the gear teeth breaking or deforming? I know PC is hard but against PLA I’m surprised they take the load

do you expect any melting issues?
Some ebike gears made with POM/delrin melt after a certain RPM for extended periods

@ShutterShock i’ve never had gear deforming issues, also not with Alloy 910 filament. I’m printing with 100% infill and i’m honestly not really worried about it.

@murdomeek no, not really. Polymaker claims that this PC can withstand 110°C and i’m not exactly running high RPM with a top speed of ~33km/h. One of the PLA mounts melted a little bit last time because it was hot outside, but i want to print them again out of PC anyways.

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you could consider PLA+ too I think it is a little more resilient, I am gonna use it to print some AT hubs for the ali express tires I got

Very cool!
Simple and to the point.


Hy joe
Would it be possible to share your print settings gor the pc max

Great build!!!

PLA+ would work too, but PC Max isn’t actually as hard to print as you might think. I’ll use my PC Max up go from there i guess.

@Sharky I’m using 265°C on the Nozzle, 90°C on the Bed, and i don’t know what my retraction is. The Cetus 3d Printer i’m using is a bit restrictive in that sense. I’d start with the standard PLA retraction settings though, as both materials should behave similar when their melting point is reached.


This looks a lot like this design, https://www.thingiverse.com/thing:2901312

I really like this idea, as a matter of fact very much similar to what i was planning on doing next. Only i was planning on making helical gears instead of spur gears.

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Hm interesting. I suppose it depends on the capabilities of your printer too. I think mine only goes to 250 on the hotend

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I think metal on the motor spur gear and nylon on the wheel gear was the preferred materials for gear drives. How does your material compare to nylon?

Im making a nylon inner gear drive for a friend of mine very similar to the one of joe
We will try to improve the strength of the nylon printed wheel gear through this steel ring glued to it with epoxy or kb weld

So ill reduce the outer diameter of the wheel
gear and slip the steel ring over it


That looks really cool, i also like the hub adapter. I think i’ll try to incorporate something like this down the line.

@Alpacaslapper i haven’t had a pure nylon gear, but the Alloy 910 filament i used before was a Nylon/Polycarbonate Blend and the whole gear was way more bendy than the PC gear. The teeth were pretty much the same though.

@Davewesh additive manufacturing and helical gears are a perfect match, but i’m not sure wether you can actually achieve that level of accuracy with 3d printed motor mounts to get them to mesh perfectly.

With the teeth inside you’ll definitely need the reenforcement, but the think where the strength is needed is the teeth themselves, especially under heavy brake, they will grind down if too soft.

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We will try it and find out :sweat_smile:
Ill let you know

Prototypes are looking real good
Some minor changes need to be made then the nylon prints can start


Nice how are you sealing between the wheel gear ring and the motor mount body?

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That looks awesome, how did you print it? It doesn’t look like there were any supports.

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Its just the prototype for the test fitting made out of pla
The final version will be printed next week out of taulman 910 nylon

Oh there are supports but they get off real easy in case of the pla
Lets see how the nylon supports will behave but i thibk there will be some smoothing needed

I started this whole project because of you joe cause i saw tht it worked for you
This drive is for a colleage of mine and i make obe for streetboards fo myself


Dont know right now
Theres another ring on the inside tht schould stop stones ftom getting into the gear
If this doesnt work ill go for a big v seal ring i think