The most accessible and cheapest gearbox

Hello! I found a very affordable gearbox and built an e-foil on it.

This gearbox is designed for installing a motor from a gas trimmer on a bicycle.
I used it with a SSS 56104 motor (500 kV) and a 7 1/4 x 5 inch propeller.

I used 3D printed supports to mount the motor and gearbox onto the fuselage.
To connect the motor shaft to the gearbox shaft, I used a coupling that was machined to order. To connect the output shaft of the gearbox with the propeller, an adapter was machined according to my order.
I assembled a 12s lithium-ion battery from flat soft cells and used VESC 75200.
The assembly turned out to be quite powerful.
I made the hydrofoil and stabilizer from plywood and laminated it with fiberglass and epoxy resin.
Unfortunately, the summer was cold at first and my build took a long time, leaving me little time to properly master riding. I’ve only been on the water about 10 times. Only the last time I managed to ride a little while standing on the board. Before this I trained lying down and on my knees.
I don’t know English well and I use machine translation, so please excuse me.

I spent a lot of time trying to find the 3D printing parameters to create waterproof parts. However, over time, water still penetrated into the gearbox and motor. The gearbox did not have a gasket between the two halves of the housing. But there are seals on the shafts. I watched a video of this gearbox and they used to have a gasket in them. But then, apparently, they decided to reduce the cost of production. I tried to make a gasket myself, but it didn’t work out and I had to use silicone sealant.
It also looks like my bearings are a little worn out. The gearbox has some play on the shafts. Overall I don’t think my design was very successful, but I had a good experience. I believe that beginners can use a similar design. It’s probably not suitable for salt water, but in fresh water my motor and gearbox did not suffer any noticeable internal damage.

I’m currently working on improving my design. I’m going to use a different gearbox - now it will be a planetary gearbox from a car starter, this idea was proposed several years ago by a member of this forum ArtemkaMax. I also want to try to make my own motor with a direct drive. I want to try using a stator from an asynchronous motor for this. I don’t know yet whether I will succeed or not.
I thank the creators and participants of this forum, especially the living legend Pacificmeister and my compatriot Anatoly (thread “Build from Moscow!”).


Very nice and it works ! Do you have a link to the gearbox ? An idea about the gear ratio ?
The gearbox setup must generate a lot of drag. It would be more efficient with a 3D printed fairing since you have access to a 3D printer.

I ordered from a store within my country, but I found it for you on Aliexpress, here is the first link I came across:

Gear ratio is about 4.5:1.

Yes, the gearbox has a rough shape and large dimensions. It would be nice to make fairings, but I spent too much time trying to figure out the print modes, as well as making my own remote control. That’s why I didn’t have time to make the fairings.

This gearbox has helical gears. I find them to be quite durable. Perhaps the gearbox can last a long time if it is equipped with a gasket and good bearings.

If anyone is going to repeat my experience, I want to give one piece of advice: be sure to use thread locker or locking nuts in all screw connections. I almost lost the gearbox. I noticed that all the screws had come loose except one. And yet I lost the propeller. Then I printed the propeller on a 3D printer. I made it with splines in the hub, and no longer used an adapter, but mounted it directly onto the output shaft of the gearbox. But it seemed to me that with the printed prop the thrust decreased a little.


I designed a planetary gearbox for the 65162 motor with 65 mm diameter.

Ratio 2,87 to 1

The spurgear works fine since 15 hours and the angled gear ( 20 degrees) needs some improvement as it failed after 1 hour

Also tested with 75165 motor and 14 NM of torque

All parts 3 D printed

Prop 3 D printed 215 mm dia and pitch 3D printed

Thrust is so much more powerful

Ich will publish final design when ready

Cost with all Bearings, Screws and Print Material approx 50 Euro, however if the bearings should be saltwater proof you need stainless steel and you will reach easily 100 Euro.

The gear runs wet in water that it is cooled …


Why are you making gearboxes for these motors? These motors were specially designed for direct drive of the propeller. Are you claiming to get more thrust? Wouldn’t it be better to develop optimal propellers for these motors? I’m afraid that the plastic printed gears won’t last very long.

I was even surprised that your plastic gear lasts 15 hours. This is great.
I have a planetary gearbox made of steel. But I don’t know yet how to secure the sun gear to the motor shaft. Because my sun gear has splines, and the motor has a D-shaft. I also thought about printing a gear, but decided that it would not work for even a few minutes under load. Now you have given me some hope. I guess I’ll try. True, my motor speed is about 4 times higher than yours, but yours has much more torque.
What kind of plastic did you print the gears from?

I guess I understood your idea. Motor can produce more power at higher RPM. With the help of a gearbox you reduce the RPM, and now you can use a large propeller, which is more efficient.

Good morning

the explanation why to do this is the following:

To get maximum thrust at given speed of the board the optimum prop has max diameter and min volume flow at this speed.

Same as designing a prop for a plane to get best performance in aviation.

Thrust is a function of volume speed of the fluid and the energy needed is a function of volume speed squared.

Thats why jet drives are a bad idea for efoils and not so efficient

I needed 1,4 KW to foil now I need less than 1 KW

All parts are special PLA.

The spur gears have no wear so far

The prop is very strong as it has a bigger thickness of the profile due to its diameter

Disadvantage is the hearable noise of the gears . Spur gears are hearable for others the helical gears are almost not noticeable

Hope this helps


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Good morning.
Thank you.
It’s amazing that you were able to create a printed gearbox.
What if you use a smaller motor? Is it possible to make a two-stage gearbox? Since 1 kW is enough for you, you can take a much smaller motor and much cheaper. However, it is difficult to find a waterproof one.
Did you measure the torque on the motor shaft or on the output shaft of the gearbox? Or do you use motor specifications or calculated data?
I’m currently working on building my own motor and looking for a way to measure torque.

What limits the maximum diameter of the propeller and the maximum pitch?
Where can I read this information?
I did my assembly without a scientific approach, based on the experience of the participants in this forum.

This is a very clever design. Great for DIY on a budget.

There are so many factors that can skew a comparison like this. Is it with everything except the prop and gearbox the same (foil, board, weight, pitch, speed etc)?
Which was the prop that you tried in direct drive?

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I have ordered the metr equipment bit not yet installed.

The data I got with the VX3 remote and I agree that its a little bit vague

Just what I had at that time

In my case bigger would have contacted the fuselage

My assumptions to do that are the following:

The motor runs best and most powerful at approx 2/3 of idle speed so approx 5500 UpM

The ratio with a 3D printed design with max planers was approx 3

There is a prop generator on the internet where you can rype your values and it proposes you a design

This is how I came across wirh my concept


Direct drive also works fine I just had fun and was super amazed that it can be printed.

I thought the geards would explode by the first turns

Here are some pictures of my powerplant.

Motor after use. It looks like only the front cover screws are a little rusty. The motor works, I didn’t disassemble it.

The front motor support, which also serves as a transition from the motor housing to the gearbox housing. Rubber ring installed.

Rear motor mount. There are power cables running through her leg. The wires go into the fuselage, then into the mast. The fuselage is made of rectangular aluminum tube. I didn’t have to make any extra holes in the mast. Rubber ring installed.

Gearbox from the inside.

Gearbox and 3d printed prop.

Gearbox on the motor side with a coupling screwed onto the shaft for connection to the motor shaft. Instead of a clutch there was a clutch cup for connection to the trimmer motor. I put this cup away.

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I had a plastic prop from China that I cut to 5 1/2 diameter

Theoretically it should be not a good design but I spent on day in the pool measuring theust via power etc.

This was the best and better than 2 cnc props I specifically bought for efoils


If you design a specific motor gear prop unit you must determine what you want.

Max speed, max efficiency, best performance at given speed etc

Its like the gears from a car. First gear is good power to start but low speed , 5 th maybe too weak to start

I designed for 25 kmh speed and best efficiency as I dont like to fall down at 40 kmh

I reach max 35 kmh with this setup its just more efficient than my old direct drive

Thank you for the flowers :wink:

I am on vacation now but found these two more pictures