My obsession with idler pulleys

I love this subject but I haven’t had time to dive into it yet. Just a quick drive by question for you with some experience, Is there a good rule of thumb or placement guidelines yet? have you guys come to a standard of where it exactly needs to be for best results?

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As close to the motor pulley as possible IMO. The idea is extra guidance without extra stress

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Ive just copied what cars manufacturers seem to do, pulley on the slack side. Id not worry too much about it. Just use at least one pulley, and bare in mind the more the belt is deflected and warped the lower its life expectancy. So go for as large of a pulley as you can and use as little deflection as needed.

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Keep in mind that needs to be slack side during most stress, which is during hard braking. So, the slack side when you are braking, not accelerating!

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dang, ok, that fixed me, had that wrong, lol thanks and makes perfect sense, like duh…

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I do more accelerating and cruising than breaking,

Have you been using this setup much yet? It appears as the idler-bolts are on the motor? How is it holding?

When the motor drives the wheel (accelerating): the little motor-pulley generates the belt tension, pulling the wheel into rotation. In this situation, there is very little chance of the belt skipping.

When the wheel drives the motor(braking): the wheel pulley acts against the resistive Force of the motor by pulling the belt around the little motor pulley at a highly increased likelihood to allow the belt to skip.

Ergo, whether the majority of usage of a belt driven mechanical system is used for acceleration or deceleration does not matter. A belt is more likely to skip around the smaller pulley when it is the larger pulley generating the force.

So even if you spend 90% of your time riding downhill, using the motor as a braking Force, the most ideal location of a single idler pulley is going to be on the braking side of the belt drive.

It’s why @Nowind and @lowGuido @JuniorPotato93 and myself do it this way!!

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It doesn’t matter. If the belt skips, it’s going to happen during braking. And I hope you don’t do any breaking! Wear a helmet just in case :stuck_out_tongue:

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Lol 10 char

I have not used the double pulley on the reverse motor mounts yet. I have a single pulley on the regular TB motor mounts and it works great.

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Using a pulley on both sides will allow super loose belts so you have great free wheel.

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For sure! I nearly stripped the m4 motor holes on one of the motors, so I just use one.

I get some pms from time to time about links for parts. Figured it’s easiest to leave it here, not sure if I have already

M4-0.7*24mm or whatever size bolt that you can Dremel off the end so that it doesn’t sink to deep and short the phase wires. Socket head is necessary so you don’t need a speed ring as the head is the size of the inner race of the bearings https://www.amazon.com/dp/B01DIVTWYW/ref=cm_sw_r_cp_apa_7ZLqAb1SDVD0X

M4*8mm 6.5mmOD steel threaded spacer. This is necessary for the other side to sandwich 3 bearings, this is also the size of the inner race of the bearings so that speed rings aren’t needed https://www.amazon.com/dp/B00PKLKUX6/ref=cm_sw_r_cp_apa_2YLqAb08V3XP0

4135mm bearings - high speed bearings with a double buna seal to keep dirt out. Don’t use metal shielded. https://www.amazon.com/dp/B071L5FKBL/ref=cm_sw_r_cp_apa_AQLqAbHJZYY0M

Make sure to wash the bearings when you get them, and replace the grease with a high speed oil like Bronson or OUST. Grease will create heat and these bearings will be spinning in the range of 1-18krpm depending on speed. These bearings are half the size of the 16T motor pulleys, so it’s effectively 2:1. 190kv motor on 12s is about 9krpm at the top which is almost 18krpm on the bearing. Service your wheel and idlers every 150-250miles(15-25 charges depending on your range). Cover your idlers to prevent large debris from binding between idlers and motor pulleys.

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Hopping on the Idler train! Figured I post a pic as I was able to fit an in an idler with a 72t pulley and pneumatic wheels. It can be done! I am loving the idler btw.

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Looks great. Did you have belt skips during braking prior to the idler pulley added?

@E1Allen Oh yeah definately. I wasn’t using this exact setup before, I added the idler pulley when I switched to pneumatics, but when I switched my belt wrap on the motor pulley would have gotten worse (had I not added the idler), so I can only imagine that the skipping would have gotten worse.

That setup looks stressful for the belt, because of the sharp bend. I would make sure to run that belt SUPER loose to avoid premature failure.

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I think running it loose is kind-of the point. Also, belts are cheap :stuck_out_tongue_winking_eye:

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Awesome contribution @PatRocks & @JuniorPotato93! I’ve been trying to resolve some skipping that I’ve been experiencing at the lower end of rpms/acceleration curve. I’m now having to be very cautious when accelerating as I’ve skipped and been thrown off my board. I also have the same experience as you when braking. Even after taking everything apart and make sure the pulley was centered and the tension was as hard as possible, I still had the same challenges. This is a wicked solution. Appreciate the time and testing that you’ve done! Now, to give it a try!

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