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How many flanges are required on drive train pulleys?

Hey guys, I’m trying to figure out how to fix this issue that I am having with the DIY ES kit. The belt is rubbing against the tire and causing this swirl effect, it fairly deep and it feels like ridges. I don’t know how to stop it. The option is allow the belt to fall off the other direction or rub against the wheel. I was supplied with a 9mm belt and the small pulley is 15mm wide.

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More accurately I guess I’m asking if this “Wheel plate” that comes with the Enertion kits resolve the issue I have?

@Gatwod - The issue can be fixed by adjusting the motor pulley either inward to the motor mount or outside more.

You’ll notice when the wheels turn either front or back that the pulley belts will move.

Ideally, the way to fix it would be to use a 9mm width pulley instead of the 15mm belt pulley.

If you want I can send you a 12T 9mm width pulley. I have more coming but not available yet.

The motor pulley seems to be too big and is causing slack for the belt to travel in part hitting the wheel and dragging it.

I think you could flip the motor pulley and you should be fine.

@torqueboards I’ve tried flipping the motor pulley and find that there isn’t anything keeping the belt from coming off completely. It’s like finding a lesser of two evils. If you have a 9mm wide motor pulley then I’d be more than happy to take it off your hands. My first belt only lasted 10 miles :frowning:

Ahhh… That’s bad… Haven’t heard/seen that yet.

But send me an email and I’ll send you the 12T 9mm width belt which should fix the problem.

The newer 36T pulleys which I’m having made now… I included a flange on it to space out a bit from the wheel itself which should help a lot even though this issue isn’t that common.

I can send you a new 36T once they arrive.


I can’t argue with that costumer service! Thanks a ton brotha!

Found myself a temporary fix! A few nicely fitting O-rings are keeping the belt right where I need it! I put about 6 miles in today and everything looks pretty good :slight_smile:


I was hoping somebody would put a flange on their wheel pulleys. While this issue might not be too terribly common, I have two sets of wheels with belt marks on them as well.

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Somebody did…and still does. I know him too! He’s pretty cool :blush:

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@Gatwod nice fix! I would love to see flanged wheel pulleys become the standard.

I have always flanged my pulleys too.

@treenutter @lowGuido Upcoming drive wheels will include a flange :smile: I’ve been thinking about that too.

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thats awesome! Great idea!

Regarding a flange on the wheel pulley, YES generally the more flanges the better.

But technically speaking it is not needed, with such short center distances the suggested minimum is two flanges total, they can be located on just one pulley or you can have a flange on each pulley but diagonally opposing each other.

If you do have just two flanges and on just one pulley you need to make sure the pulley tooth width & belt width tolerance is fairly tight because the belts will always want to travel one direction due to the twisted strands of fiberglass inside the belt. Timing belts have strings of twisted fiber glass in them to stop them stretching and give them strength.

If anyone would like to read the 90+ page technical journal on belts & pulleys check it out:

Here is a quote from page 39

Because of a slight side thrust of synchronous belts in motion, at least one pulley in the
drive must be flanged. When the center distance between the shafts is 8 or more times
the diameter of the smaller pulley, or when the drive is operating on vertical shafts, both
pulleys should be flanged.

FOR EXAMPLE: The enertion motor mount center distance is approx 70mm, the smallest pulley (13T) diameter is about 19.5mm diameter. The center distance is less than 8 times (it is just 3.6 times) the diameter of the smallest pulley. So technically two flanges is sufficient.

I doubt anyone has a motor mount with 8 times center distance on an esk8

The other reason I chose not to flange the wheel pulley is because of manufacturing restraints. The flange needs to be pressed onto the pulley. This requires special tools… increases cost, etc.

Anyway, I personally don’t think you need a wheel pulley flange, you just need to make sure you have a motor pulley width that is the correct size for the belt.

Or as @Gatwod has ingeniously shown just use rubber o-rings!

No that is not what it does, it simply aligns the heads of the bolts neatly on the outside of the wheel.

while technically speaking flanges aren’t necessary, They are nice to have.

especially with a skateboard. we put skateboards through things where systems like pulleys and bearings are not designed to operate. dirt, rocks, water, and who knows what else get introduced to our wheels and belts that can effect the precision of our machines. its always good to over engineer.

I mostly agree, but no point over engineering & increasing cost if it doesn’t give a measurable improvement. it’s a fine balance.

In terms of flanges on a wheel pulley, it’s not going to be a huge cost increase, maybe just a few dollars per pulley, but the stamp press machines that they use to press the flange onto the pulley are not very accurate so you can get flanges pressed on that are slightly off-center giving an annoying wobble.

I suppose making a mold & molding the pulley with aluminium is a good option.

but there are also some other negatives for not doing it.

  1. Width, each flange adds about 1.2mm, so if you have a wheel pulley with two flanges and on a dual rear drive board you lose an extra 2.4mm of space. This is an issue if you use 5060 type motors because they won’t fit anymore. With 6355 motors there is more room but not much.
  2. Belt installation, if you have two flanges on the wheel pulley and two on the motor pulley it makes it much harder to install the belt. the belt can slip-onto the pulley.

Flanges would be great! BTW nice fix gatwod. Would love to see your final build look.