Wenzani | MBS Core 16| MBS Matrix Trucks | 10sXp | rest is still unknown

Okay, after some… relatively more than just some reading and a bit of doodling I got to a point where I have parameters. I’m designing for range not speed. IMG_9774 Batteries: will be LiPo 10s(depending on cash)p. Motor: 225KV (will see what I can find but this is based on the theories of Vedder who wrote and did some awesome stuff on this forum) Motor Mount: Got some CAD and drawings of the MBS trucks and Rockstar hubs still busy with designing but this is least of the problems. Drive Train: Now this is where it gets interesting… I have chosen a belt drive system. I initially desired and designed for a maximum speed of 45km/h, which requires a gear ratio of 1:7.2. but with a 5m or 3m belt the slave wheel will be too big, resulting in poor ground clearance or to be totally unpractical. The hub of the Rockstars has an outside diameter of 105mm I do not want to exceed this by more than 10mm on the radius. So gear ratio is now 6.5 with GT3 belt, thus pulleys 20T:130T. Also Dont want to go smaller on the drive pulley to extend belt life, max speed is now around 50km/h.

Tomorrow I’ll see what type of belt I can source in South Africa as so far I cannot find a GT belt but have sort off found a local supplier who can supply me with a HTD 3M belt which looks okay. Would have liked to use a 5M belt the pulleys seem to be too big for the board or I’ll have to change the gear ratio.

What do you guys think? Does this make sense other ideas maybe?

Ok… after some more reading and pondering. My max speed is too high thus I figured the other solution is reducing the KV value of the motor. There is no use in sourcing a motor for an application that will never run at its optimum thus I got these 2 motor options Turnigy Aerodrive SK3 - 6364-213KV and Turnigy Aerodrive SK3 - 6364-190KV the one gives 51km/h and the other 45km/h (that is all theoretical now). I chose the drive train ratio to be 1:6. I want as much torque possible and not exceed the wheel hub diameter too far, with 19T:114T the PCD of the drive pulley is only 2mm higher than the wheel hub, I can live with that. A gear ratio of 1:6.5 is nice but the drive pulley becomes too big. Hopefulley tomorrow I’ll be able to chat with a local belt supplier and maybe generate some CAD renders of the motor mount.

Does anyone have an idea on how to have a drivetrain ratio of 6 and not exceeding Ø110 PCD on the drive pulley using 5M teeth pitch.

Why you don’t want to go lower in kV. There are nice 150kV motors out there which will fit your needs.

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You can get htd5m belts here

They not as good as continental belts but for me they worked well.

I think they sell other formats too.

I wouldn’t go with 3m belts thou

Hi Andy, I guess I can go lower in KV. Though there are lots of information on ideal motor RPM and most “literature” I read so far points out that the efficiency is best at around 8000 RPM. If I go lower in KV keeping 50km/h as max speed the drive train ratio will be 4.3… I feel that is a bit low and it will compromise torque…? Correct?

Honestly I never went so deep to look into the optimal rpm with a specific kV. I would say my favorite sweet spot is 170kV With a 15/72 gearing you would be around 48km/h with 8“ or better to say 180mm wheels. That gives you still a ok clearance and very good torque. But your average loaded rpm is just at 6700.

If you want to go the high kV, high gearing way, than there is probably no way around a gear drive. Like this from @Nowind with 1:6.25 gearing ratio


Thanks Andy87, I just ran this…Is this accurate compared to real figures? image

You get a bit more information on this calculator https://calc.3dservisas.eu/?Pc8xD8IgFATg_8JsDBQo6oqmk4bExO7KUBNJSToa_7vvDuv2vdfjKG91j5M6qNezzmojw0UGuw3iJV7FxpJJ6KiIgNaawxGT8c3IdG3PTiOs6OgBJH07VxO2HZVWscp6Esue_Bc9Jn6nTqKdJm847uASf02Fvx24SzPsSLyg3V8i1wjncQHZlofz-po8jMLABG7ba_X5Ag==

I would measured my wheel diameter and my 8“ wheels not 200mm, more like 180, so top speed will be less for sure.

Why you want to go so high teeth with the motor pulley?

Small correction to that post. I still had 12s in the calculator. So your rpm would be lower with 10s, sorry for that.

20T is what the belt manufacturer sugests for better belt life. That was actually part of my belt question… is the higher T-number on the motor gear really making a difference say if one would use 17T?

For htd5m most people on mtb use 14-16th max. people use up to 18-20 th on street boards for the motor pulley. Sure the more teeth have contact the better is the transmission, but for this you could also use idler which will guide your belt between both pulleys a bit down and with it more teeth have contact and you can run the belts more lose too. So less stress on them.

Yeah… I was thinking about putting an idler in as well, ok, I guess 16T will be the minimum then.Geees… that is a small pulley. Would a 20mm belt with be a good choice?

I never used but just bought some 20mm belts not long ago too. I would say it’s the same here, the wider the belt the more surface is involved and the better the power transfer. If you can, sure go with wider belts. I wanted to use even 25mm belts but couldn’t find a motor pulley which would fit without that I need to rework it.

Think this is better… Between 12s and 10s it is easier to change.


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This is the plan so far. 150KV, 15T:71T with idler and belt is 5GT.



The mounts look pretty :ok_hand:

Looks good to me

image How is this motor? It looks a bit on the low torque side judging on its Watt rating and diameter… image

Where’s the shaft? O.o

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