🔩 1:7 belt drive for mountainboard with badass torque

[Marsl187]

Hey guys,

sinde a longer time I’m looking for a silent, cheap and torquey solution for my second mountainboard. So is designed a gear drive in a similar shape as this belt drive. I used existing parts from Mädler to keep the cost low but relealized later that the gear may not hold (cheap machining steel). These have been helicals. So I upgraded the construction to hardened gears. These were straight cut and a lot wider. As I like a silent drive I came up with this one here (which is not realley wider than the second gear drive version) which I will finally build now

As 190 kV is kinda the standard for esk8 motors nowadays you need a high gearing for a mountainboard because the topspeed would be useless high and you’re not using the full torque potential. Higher kV motors also have a lower resistance, so you can push more amps through it, which means even more torque.

The most common gearing in mountainboards is 1:5. With 190 kV this is not enough in my opinion. So I used the concept of multiple gearing, which gives me a gearing of 1:7 for this belt drive system.

Features:

• High gearing (1:7)
• Very good clearence
• Completely sealed
• Silent operation (hopefully )
• Low maintenance
• Pulleys are secured with a keyway
• Seperate cover for easy adjustable belt tension
• Positioning angle is adjustable
• No need to machine the truck

The clearance is similar to a 1:4 gear drive or a 64T belt drive without cover. Especially the high gearing drives from Trampa (belt drive and spur gear drive) have a very low clearance.

Materials:

• Stainless steel (plates, Superstar adapter, shaft, bolts, bearings)
• 7075 aluminium (rods, spacer)
• plastic, 3D printed (wheel pulley, pulley adapter, wall between plates)

The drive is designed to fit Trampa Infinity and Vertigo trucks. Other trucks would be easy adaptable (just need to change the truck adapter). I just designed the hub adapter for Trampa Superstar hubs, here others would be quite easy adjustable aswell.

The drive is relatively heavy because I will use lasercutting for the plates (cheap), therefore the material will be stainless steel and no light 7075 aluminium. I maybe upgrade that later.

I think such a drive system is perfect for high kV motors in combination with a mountainboard (never enough torque ). Especially when you switch to 9" tires you loose a lot of torque. This is where this design really comes into play. The gearing is easily changeable to even higher ratios. 1:8,5 needs just a slight increase in size of the whole drive.

Here are some more renderings. Some small things might change for the final version.
Sorry for beeing lazy and not adding the second side and the most bolts

I ordered the most parts with a rather long shipping time. Next week I will finish the construction and will order the laser cut parts. Hopefully end of march I can start with some test

Let me know what you think of this project!

[Venom121212]

As someone who is going from a 10s battery, 8" wheels, and a 15:72 gearting with 200kv motors to 12s, 9" wheels, and the same motors…

I’m very interested.

[WavRX]

Pretty cool, can’t wait for some test numbers.

[brown5tick]

I love the idea of that sexy kink but, considering the unit’s thickness, it’s probably gonna bite the deck… unless you orient it the other way, in which case, you’ll have a lot of vulnerable overhang. Is it possible to check that cos it would be awesome to keep its kinkiness.

[rusins]

Why aren’t there just larger wheel pulleys for the larger wheels?

[Jamie42]

There are. But the diameter increases with the pulley.

[Venom121212]

What dis guy said. To keep the same tooth profile and spacing to match the belt, a 90 tooth htd 5m pulley would likely be bigger than the wheel itself.

[Chricious]

TBH I don’t see a usecase for this. Since we have motors with 4kW-6kW and 130kv-170kv you have more than enough torque with 15T/72T.

[moon]

Low kv motors overheat easier

72/15 is only 4.8 ratio

Some guys need 6:1. Here he wants 7:1

[Venom121212]

Gearing down is more efficient

[Chricious]

I’m testing at the moment 15T/72T 170kv on 9" at 12kW. Torque is the very last I’m missing. But maybe with lower power output some rider could want more torque.

[janpom]

How much more? Got any numbers? Genuinely asking.

[Chricious]

@moon

Some guys need 6:1. Here he wants 7:1

At what kV and kW? Maybe with 10" 6:1 would make sense or if you have under 8kW or 190kV+.

But like I said, that’s just my opinion.

[Agressivstreetlamp]

No numberst though Its one of many things I would love to do a research and write up on.
The best arguement I’ve heard is the general case of “mo Amps , mo Losses”
THough Im sure its more complicated than just that

[WavRX]

Gearing down is more efficient in terms of power consumption, in exchange of lower top speed.

[Chricious]

But just during acceleration, not at constant speed. But yes in most AT situations that’s right.

[sesat]

Let me ask, for the same battery and wheels, is the 200kv motor mated to a 1:3.5 gearbox less efficient than a 100kv motor mated to a 1:7 gearbox?

One has more losses in the copper winding, one has more losses from a more complicated gearbox…

Edit: I had the kv’s mixed up

[janpom]

All I can say is I didn’t notice a significant difference in consumption when switching from 1:3 geared 190kv motors to 72kv direct drive and that’s one hell of a difference in gearing. So I’m thinking that maybe the difference is actually negligible and nothing to worry about?

[ducktaperules]

@Marsl187 this looks great. im just curious, why mount the motor so far out? if you have a 2 stage reduction you get a lot more flexibility for the motor to wheel distance, so why have the motor so far from the axle?

@Chricious

I’m testing . . . at 12kW.

Not this again, do you really need someone to explain how power works one more time?

@WavRX

Gearing down is more efficient in terms of power consumption, in exchange of lower top speed.

Higher KV motors are more efficient so a larger reduction allows the motor to be higer KV whilst giving the same speed at the wheel.

@sesat

is the 200kv motor mated to a 1:3.5 gearbox less efficient than a 100kv motor mated to a 1:7 gearbox?

Think your mixed up here, 200kv motor is twice as fast as 100kv, and 1:3.5 give less reduction than 1:7 so output is faster. 200kv motor with 1:3.5 gearbox is 4 times as fast as a 100kv motor with 1:7 gearbox so not a far comparison to discus efficiency.

@Venom121212

Low kv motors have less windings but thicker windings. High kv has more windings of thinner copper.

also seems to be mixed up.

A low Kv motor has more winds of thinner wire. A high Kv motor has fewer winds of thicker wire. the thicker wire means lower resistance and therefore less heat generated and less copper losses.