Is it possible to put your pulleys too close together?

I’m using a 12t motor pulley to a 60t drive pulley. Is there a minimum distance I should keep between them? The trucks I’m mounting everything to have little room for mounting stuctures, so I’m building a cantilevered 2020 extrusion frame. The closer I can keep the motors to the axle the better, but I don’t want to sacrifice good belt grippage.

I just feel like the closer the small pulley is, the less angle the belt will come in on, therefore less teeth grabbing. Is this correct thinking? pulley%20detialtoptooclose


You’re correct, you can fix that issue by adding an idler though. It’ll press the belt inward, and the teeth will have more contact on the pullies.

Yeah, that’s a good idea. I’ll just do that. Thanks!

Is there an optimum angle for the belt to be coming in at? Or a tangent reference?

No, just do it far enough that you have more teeth in contact, w/o running into the pulleys. You can make it adjustable by using one of those extrusions, and just sliding the Idler up and down the extrusion to tighten the belt.

Thread locker is also gonna be important w/ using bolted aluminum extrusions.

Yeah I plan on adding the motor mount to horizontal extrusion and then I can add the idler to a vertical piece. Good call! I do have some thread lock handy, that’s a good tip too. Thanks @MrHappy

No problem, you can PM me if you need anything else

The minimum adviseble is 15 teeth for pulley. 12T is to low and you will get belt slipage. In order to grab more teeth (thus more torque) is to add Idlers. But minimum, use 15T pulley.

Thanks @pixelsilva. Yeah, i was thinking simllarly. Just worried about the size of the drive pulley at 75t I guess I can do some tests and see if i can make 15/75 work.

I’ll give you my experience, and it kinda throws logic out of the door.

I am using a 55T wheel pulley with a 20T motor pulley wedged literally right up to the wheel pulley to where they are just not touching… With zero belt skipping no matter how hard I brake or accelerate… It’s amazing. I’ve ran the same 55T wheel pulley with 16T motor pulley, same results- no skipping.

When I use the 20T motor pulley with 32 or 36T wheel pulleys, with or without idlers, no matter the tension, just further away, I always have varying amounts of belt skipping. Same with 16T.

I think having less free unmeshed belt between pullies makes a huge difference.

So, in my experience, I’d keep your pulleys as close together as possible and you might be fine… Even with a 12t motor pulley. Just to be safe, I’d design in some adjustability and ability to add in an idler in case you do get skipping.

Cool. Yeah I’m trying to keep this thing as modular and “slide-y” as possible to allow for all possible configurations and modifications down the line.

Your way is definitely a way to try. and if it doesn’t work…just try somethign else. This is the fun part, right? :slight_smile:

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I thought I read a 6 Tooth min. gear mesh of the pinion gear for best results

6 tooth minimum of actual full contact teeth (milage may vary depending on belt pitch and width)

16 is for the overall pulley. You can go as small as you want, so long as you get the full 6 teeth meshing then you should be fine.

As others said, 12T is too low, the radius the belt has to bend is too small

I say from experience, used 12/36 for a while and the belts would last at most 150km

Also, if you are going to use a idler don’t make it too small or the same problem happens

Nice cad works

I’m building 12/72t right now and decided to run idlerz. Also running 20mm wide belts to prevent skipping