1kw rc car brushless motor for e-bike.

[userperson1748]

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[flat tire]

You will need an extremely large rear sprocket, probably around the size of the rear wheel itself to gear that motor down to be usable in a bike. That motor will turn 15K RPM with only 24V. You are looking at more like 50:1 reduction to get ~35mph.

Also if the bike is full suspension, you will not be able to run a belt without complicated tensioner or it will slip as the center-center sprocket distances change thru the rear travel.

 

[userperson1748]

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[flat tire]

Attaching as a friction drive automatically gives you a gigantic reduction gear ratio, but as you noted without the hassle of a belt.

If you're just looking to get rolling, try it. It should work ok. But be warned, you will probably love the concept of a motorized bike and are heading for a slippery slope that ends in really powerful, expensive bikes!

Since your bike doesn't have rear suspension it will suck offroad, negating most of the advantage of a mid drive. Consider one of the many cheap rear 1000W direct drive hub motor kits on ebay, amazon, etc. Those will get you moving easily, smoothly and quietly.

 

[userperson1748]

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[spinningmagnets]

Here's a build that used an RC motor, and it may be useful to consider...

https://www.electricbike.com/3d-printed-rc-drive/

 

[amberwolf]

Attaching as a friction drive automatically gives you a gigantic reduction gear ratio,

No, it doesn't.

It's not intuitive, but using a motor to drive a tire does not change the speed/torque of the motor at all. It is exactly as if you were driving the motor on the ground surface.

 

[flat tire]

Attaching as a friction drive automatically gives you a gigantic reduction gear ratio,

No, it doesn't.

It's not intuitive, but using a motor to drive a tire does not change the speed/torque of the motor at all. It is exactly as if you were driving the motor on the ground surface.

Well, duh, an idler (the wheel) doesn't change the ability of the motor's case to tractor to ground but that's not what we're comparing it to. What I meant was one rev of motor to one rev of wheel. Like if you connected it to the wheel with a single stage chain and sprockets like the op originally suggested. Compared to that or any other reasonable ratio doable with sprockets a friction drive is a good reduction. Especially if he uses a small transfer roller than the case itself.

 

[userperson1748]

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[amberwolf]

Ok, I guess you'll have to build it and see what I mean. I just wanted you to be clear on how it works, so you don't end up with the wrong gearing and have to rebuild things.

 

[userperson1748]

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[amberwolf]

I have a question for you though, you say "don't end up with the wrong gearing", how accurate does the gearing have to be, what target speed do I built the gearing for?(I can make to motor thicker or add a gear if needed to adjust target gear ratio and speed)

If you are willing to do some reading, and playing wiht systems in a simulator to get an idea of what different "gearing" (wheel size with a hubmotor, etc) will do, you can go to http://ebikes.ca/simulator, and read the whole page and setup various systems in there, and change just the wheel size, then change the slope, and see how the wheel size affects one particular system (vs the same with a different wheel size); you can A/B them and visually see the differences in power/torque/heat/etc.

How "accurate" it has to be depends on how quickly your motor will overheat with the wrong gearing for a specific circumstance, and how often you run into those circumstances. The less power you need to use thru it, and the less you push it to the max, the less of a worry it is, in general, for the same size motor/controller/battery system. (meaning, if it's a 500w system and you never really use more than 250w and it's geared for that circumstance, then if you run into a situation needing 500w it'll be fine...if you run into one needing 1000w it probably can't do it...one needing 600w will bog it down and begin overheating it, etc etc. )

Also, I have a question for all other peoples: Why do e-bikes always have high voltages? Why are there no 24v 1500w e-bike kits/motors? Does higher voltage allow for lower speed motors or something?

There's a lot of reasons; if you want the details you can look up the various threads about Voltage vs Current (sometimes stated as Speed vs Torque).

But basically, the higher the voltage, the lower the current, for the same power. Low voltage means high current, which means bigger wires tat are harder to fit thru axles and the like, higher current fuses, FETs, and other parts, and it is also significantly harder on the batteries, unless you make them a lot more parallel cells to compensate. (though a 24v battery of the same Wh as a 48v would be twice as many Ah anyway, and thus, if built of the same parts, be capable fo twice the current output).

As a rule of thumb, it can be cheaper for ebikes and stuff like this to go higher voltage / lower current up to a certain voltage--at that point, FETs for the controller (and BMS, etc) start to get more expensive, or you end up swithcing to other devices (like IGBTs) and once it costs more, companies will shy away from that (since their goal is to make money).

Also, because 48v (13s) systems (not jsut ebikes, but other electrical and battery and motor industry stuff) are already common,, more devices, parts, etc., are made to work on and/or use this voltage, so those parts are cheaper due to higher quantities being available. The same is true of any other voltage system that's come along...while it's popular, more stuff is made for it; what makes it popular is multifold, but cost of teh bits to make them is a pretty highly ranked factor.

 

[ScooterMan101]

timl132

Make your life much easier and your e-bike faster by just buying a Kepler Friction Drive. It has all the things you want , RC motor, simple friction drive, low voltage pack so you can make or buy a very cheep battery.

Kepler has spend hundreds or even thousands of hours on perfecting his drive, just buy what he has and the motor and other items from the proper places , he will tell you where and what to buy besides his mounting kit.

https://endless-sphere.com/forums/viewtopic.php?f=31&t=86961