Gearbox DIY (4,5:1)


I am Andreas and I want to build an efoil with the slingshot windsurf foil fwind 1 (we have one).
For the first tests, the windsurf foilboard slingshot dialer 130l will be used, then it is planed to switch to a DIY board with integrated electronic box etc.
The propulsion system will be near the one of pacificmeister.

So I decided to make the gearbox by myself, it is planed with a ratio of 4,5:1.

The gears and the aluminium is ordered, the work in the CAD done,
so the production of the prototype will be started soon.

Best Regards


The pinions on a test plate and the printed pinion to the prop.
If it is not stable enough, i turn the steel pinion to the correct diameter and screw it on a milled holder.

Best Regards Andreas


That looks awesome. Why did you use plastic planets? Is it expected to be a wear part?

I think that the plastic pinions should be good enough, they have modul 1, that means big teeths an there are used three ones around to share the load. Most load is on the center pinion, it is steel. The gearbox is not used daily as a machine, so the wear should be acceptable.
It is finished so far, but I will need some more time to build the rest around before making water tests.

I beg to excuse my bad english.


Do you have a video of it in operation?

No, first, I must buy a controller.

Any update on this build? I’m defiantly interested in the idea of building my own gearbox

Yes, it is completed and runs very smooth.

The first test, still outside of the water and only with 6S. (planed to use 12S)


Any chance you’d be willing post your cad files?

Sure, there are no secrets.
I load them up when tests with 12S in the water are done and all is okay.


Very cool. It is nice to see complete builds here with details. You could print little caps for those screws to make them more aerodynamic.

That’s a good idea,
there could be used countersunk-head skrews , too.
I dont’ know if it’s really an aerodynamic problem at the relative low speed, the hydrofoil will do but nevertheless, it looks better.

The first water test with 12S is done.
At max speed, the current was about 26 Amp.

First water test propulsion system


Does the central pinion absolutely need to be in metal ? Or do you think that a 3D printed one could hold ?

Thank you.

I think it won’t be stable enough, not even when build in PA 6, what is much more stable than PLA etc.
The one problem is the load on the very few teeth, the other is the fixation on the motor.

But there is no need to build it by yourself, it is cheap and available with the correct diameter inside.

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Thank you @2d-foiler

Wow. Would love to see the STEP files and the adress where to purchase that “sungear” central pinion :slight_smile:

What about the heat vs printed plastic ? I had the feeling that those things may get hot…

hello could you send me the stl files by mail?

Thanks & Greetings

the step and stl files and a list of material will be posted here in the forum, give me a few days. :slight_smile:
All the gears are from, the order numbers will be added to the list of material.

If the printed gear gets too hot, there is a plan B.
The metal internal gear shown in post 2 will be combined with a base made from PA 6 or POM to a composite solution. In this case, the metal gear has to be turned down outside and there have to be drilled some holes for the connection with the base.

Best Regards

P.S. It’s a little difficult for me to do this in english, please excuse me and correct if I’m wrong.


Started into designing my own. 4 days into tweaks and test prints and its actually seeming achievable.

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