Timing Belt Reduction


A plain ribbed belt won’t have the “grip” to drive this kind of setup, it will almost definelty slip, a bit more trial and error pacificmeister and you’ll get it working.

You could try flanged cogs it’ll help with keeping the belt aligned


Hi, Chris_wilson, I finally see on the forum an impeller from high quality aluminum. It’s clear from the photos that you have almost everything to produce a quality jet propulsion. Only some components that are not too stressed can be printed from cheap material on a 3D printer.


Dear Nathan,
This would only happen if something rigid caught the prop. In the case of friction of the propeller in the water this type of belt will not slip but protect the motor and consequently the damage.
In practice this already happens with some heavy work tools with this type of belt.


Well it would have “sliding off” protection, but this type looks like it needs to have a tensioner. :confused: I am not sure is there a room for 1. With no teeth to hold the power, i wouldnt trust it much. But i am far from belt expert!


Thanks @Ivan. I don’t have experience with these belts and pulleys. What do the pulleys for these belts look like and do these work without a 3rd tensioner wheel? No room for a 3rd wheel. But for tension I can update the model to create any type of belt tension and with the 2 parts design I can lever a belt to any tension during assembly without problems. FYI, I am using these pulleys right now:


It’s a pleasure to try to help,
This type of pulley is very efficient and ensures that the belt stays on the rails. A tensioner is not required. Just make the mechanism with the correct distance between the pulleys.
Another important point is that any simple winch is capable of producing this type of pulley with the exact diameter you need, because all the work of the mill is circular and in the same direction.
If possible for you, I suggest that you go to an electric tool store and ask to see up close an electric planer that works with this type of pulley and pulley. This can greatly help you to see the operation and feel the necessary tension of the belt with your own hands.


https://www.ebay.com/itm/2-Pcs-Power-Tool-Planer-Cutter-Head-Pulley-for-Makita-1900-Electric-Planers/282827749303?epid=932360055&hash=item41d9d8f7b7:g:t- hello guys xab9nE


But this type of belt needs quite high tension to transfer torque without slipping. This high tension gives a lot of radial load to the bearings.

Why you use belt anyway? Why not gears, efficency would be better.

If you use belt, check for HTD (high torque drive) belt type. I think a HTD 5 with 15-20mm belt width should be able to handle the torque.



Thanks for the details @Ivan, I will consider it. Let’s see Joan the next belt holds up.

@Toto44 thanks. I thought about gears but wasn’t sure what types and how the speed ratings are. I also didn’t like the idea of grinding noisy gears (as in the planetary gears), the belts run pretty quiet, probably even quieter with the belt Ivan suggests. But can you recommend gears? I was trying to find the HTD5 belts/pulleys in that size without luck, I am using them on the skateboard.


Check here they have it all and where i buy most my stuff



In case you want to try gears, I would recommend a steel gear on the motorshaft, and a nylon gear on the propshaft.
Here you can get what is necessary:


I think Module 1,5 can handle the forces…


Hi Toto44,

I would never do a nylon pulley for a belt that will work at great rpm. The nylon simply melts!
Aluminum or brass are easy to work on the cutter and withstand high temperatures.

You can even make circular holes in the part to decrease the weight and possibly the temperature caused by the friction with the belt.


In reference to the nylon gear, I believe @Toto44 is talking about using spur gears (no pulleys involved). Utilizing a steel gear with a nylon gear will reduce noise and friction in the system over using two steel gears.


Dear nmcma,
Even for spur gears, high rotation on nylon does not work. Any inaccuracy of fit will cause friction / heat / melting of the material.


If you’ve done it then you know better than I do. I haven’t, I’m basing this on intuition.


Hello Ivan,
Small steel pinion and big nylon gearwheel works best. I am flying model helicopter and a design and built them. With a 14:112 gear reduction these electrical helicopter can Transfer up to 12Kw peak power and around 3Kw continious. Nothing is melting.


Indeed great idea to checkout 600, 700 type helicopter reduction gear. Such this:

GARTT 700 Main Gear Fits Align Trex 700 RC Helicopter
http://s.aliexpress.com/6VjiIr6r?fromSns=Copy to Clipboard

2PCS GARTT 700 Drive Gear For Align Trex 700 RC Helicopter
http://s.aliexpress.com/qMzYjMBr?fromSns=Copy to Clipboard


Thats great info. Is your heli gearbox enclosed? I was just wondering of temperature buildup in enclosed box rather than air cooled since there is motor temp buildup too. I dont think it would melt but do plastic/nylon gears get softer?
I remeber older ebike reductions with nylon gears, no problems other than faster wear but far from short lifetime, wasnt an issue.
In my humble (o)pinion :wink: foils would use/need a lot more torque/load than heli’s, or am i wrong? There is a lot more weight and friction.


E skate builders use 3d printed gears or Nylon and steel and even steel on steel gears. All with great success rates. Some run with grease some not. Extreme high torque on starting up and slowing down. And there is no problems with them.
No problems with heat. Water is much better cooler than air so would help a lot with gears.

Rather than the gearing being offset to the side. Some E skate builders are running internal gear against the outer gear. This would help make a slimline build for E foil with less drag than an offset.
Some photos below
Top photo is offset gearing
Whilst bottom is internal gearing



Hi Pacificmeister,

why are your pla parts not waterproof? I’ve seen that my pla parts they leak water for many days after i wash them, but my printer was not working fine. Are you printing your PLA parts 100% fill or other filling settings?
I love the idea of getting rid of Gearbox… It would lower the overall price of those buildings. Keep up the excellent work.


Hi Totto44,
They are different systems and forces. But if you really believe that nylon works just test. Certainly a long life will not have.