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I want to build an eBike for myself. I've read a lot on the subject of converting Bikes to eBikes and I think the best approach would be to build a so called friction drive, wherein a small RC BLDC motor (so called outrunner motor like this) directly turns the real wheel by friction with tyre.

Problem is, RC BLDC motors need ESC (Electronic Speed Controller) to run and as RC BLDC motors are built for applications like RC Drones, Boats, Cars etc. their ESCs burn out (probably due to high amp draw by small motors under high load) and high amp rated ESCs are costly. They burn out too, I've read. There's also open sources VESC, which is equally costly, and I can't build it.

  1. So I came across this cheap "sinewave" BLDC motor controller, which claims to control Brushless "Sensored" Motor. My question is, can I use this controller instead of ESC to run RC motor linked above? If not, why not? I understand that RC motor I'm talking about seems to be 2 kW and the controller is going to provide just 250 W power to the motor, but that wouldn't hurt the motor, right? This controller is best option because it is specifically made for eBikes and has many other features/sensors for eBike purpose. Also supports Cheap Lead Acid batteries.

  2. If above controller isn't advisable, my Plan B is using this ESC, which is cheap but unbranded. Problem with burning ESC is high amp draw when eBike tries to pick up speed from stand-still only using motor. Can I use this ESC safely with the same RC motor referred above if I use the motor only when bike is already in motion?

  3. Plan C is to use this RC Motor/Controller combination (which seems made for each other, instead of matching an ESC with a Motor sourced from different places) and run it carefully (only while eBike is in motion) like Plan B. It's rated at just 820 W, which seems plenty for an eBike.

Overall purpose is to make my bicycle electric assisted by spending as little money as I can. US$ 100 Motor and US$ 100 ESC, plus Battery cost are too much. Also, as you can see, I'm looking for a plug and play approach, don't have much know-how to modify electronics myself.

If you think above setups aren't good thinking on my part, do suggest other affordable ways. Hub-drives are even more costlier, so friction drive seems best option to me. It's simple and elegant.

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  • \$\begingroup\$ 250 W is plenty for a push/e-bike. Where are you getting 250 kW (1/4 MW!) from? \$\endgroup\$ – Transistor Apr 6 '18 at 22:38
  • \$\begingroup\$ It's 250W, not 250 KW. Typo. Apologies. \$\endgroup\$ – Milind Patel Apr 7 '18 at 4:54
  • \$\begingroup\$ You need to edit your question then to fix the typo. \$\endgroup\$ – Transistor Apr 7 '18 at 7:21
  • \$\begingroup\$ there is a motor controller called the VESC which is really popular among electric skateboard enthusiasts; you should check it out. It's open source too! \$\endgroup\$ – hatsunearu Apr 7 '18 at 13:19
  • \$\begingroup\$ Yes, VESC is mentioned in my question too, but they are as costly as ESCs. Around US$ 100. \$\endgroup\$ – Milind Patel Apr 7 '18 at 14:29
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Not one to discourage you, but you will find that a plane motor has no requirement for sustained operation at full power, or in fact for operation for more than a few hours total.

While they have huge powers, it is momentary, with forced air cooling, without road-grit and water, without side thrust on bearings, with poor efficiency, without long life.

The most cost effective, and actually lasting, will be a small hub motor, probably on your front wheel.

If you do want to hack something, better to start with a small DC brushed motor - the control circuits are trivial, and you can find something at the car wreckers.

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  • \$\begingroup\$ DIY Hub Motors are much complicated to build, friction drive is much easier IMO, but will look into it. I understand the limitations of RC motors (or other set-ups), but I don't fully understand the electronics to decide if a particular set-up will even work or if it does, can it be safely run without frying the costly parts. I guess there will always remain that risk in any DIY projects. \$\endgroup\$ – Milind Patel Apr 7 '18 at 5:11
  • \$\begingroup\$ Not suggesting diy the hub. Your motor +esc hardly seems like a bargain compatred to DC motors here: aliexpress.com/store/… \$\endgroup\$ – Henry Crun Apr 7 '18 at 5:35
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Answering my own question for anyone who comes across the same question.

Answer is, Yes. The cheap Chinese motor controller can be used to control small RC motors. In fact, these controllers are purpose-built for this application, despite there being no substantial literature regarding this except this long old instructable.

In summary, some variants of those RC motor controllers like the one linked in the question can control sensored and sensorless motors, and their price ranges spread from US$ 10 to 50. There are videos on you tube wherein such controllers have been "tested" by EV enthusiasts. There's scarce information about such controllers on "Endless Sphear Forum" which was my initial source of research. These controllers seem to be derived from so called "6 mosfet" controllers which were developped/used by DIY enthusiasts to control RC motors and most probably ESCs too run on same technique, but my knowledge in this area is almost non-existent.

So if someone comes to this question seeking a simple yes-know answer that if so called "brushless motor controllers" will drive the brushless RC motor, the answer is YES.

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