Electric Razor

NO NO not that

That’s more like it.

Let me start off by saying that this project was inspired entirely by the work of Charles Guan, and I take no credit for the original idea of putting an in-hub brushless motor on the back of a razor scooter. I should say that my design, while inspired by, is not a carbon copy of Charles Guan’s design, and that I have made a few key changes.

Now that that’s out of the way, let’s get started with the design. The goal of the projects is to design and build an in-hub brushless motor that can be mounted in place of the rear wheel of a razor scooter (the A3 model to be specific), and the associated electronics and support system to power it. An in-hub motor is essentially a motor where the stator, which in a regular DC motor would be the armature, is held stationary, and a permanent magnet laden rotor is allowed to rotate around the stationary stator, doubling as the wheel. In order to get the alternating magnetic field that is required to produce motion, you need to feed the stator windings with an alternating current, 3 phase current to be specific. This requires a specialized type of motor controller which converts the DC current that is supplied by the battery and switches it to produce the 3 phase current that is required to power the motor.

So the plan is to build an in-hub brushless motor using Neodymium magnets and a really nice 18 pole stator from goBrushless. The motor will be mounted in place of the rear wheel. Since it will be a bit wider than the stock wheel, some extensions will be added to the rear of the platform which will allow the wheel to move freely.

Doesn't PhotoWorks do a nice job

The motor will be powered by 2 4400mah 4s lithium-polymer batteries connected in series to give me about 30v total. This will be controlled by a 70A brushless ESC built for RC airplanes. Since it does not use sensors or EMF-feedback it cannot start the motor from a standstill, and so the scooter will have to be “kick started.” Plans are in the works to build an EMF-sensing brushless ESC, but it will take a while.

That is pretty much it. The RC ESC will need a pwm signal which will be produced by a simple 555 timer chip circuit, which will be controlled by a simple potentiometer attached to a simple throttle mounted to the handles.

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2 Responses to “Electric Razor”

  1. Shane Says:

    Yay new blog to follow!

    Awesome! How many magnet poles are you planning?

    Also, I’ll put in a major plug for sensored control. As nice as the plane ESCs are, instant torque from a standstill is also nice. Check out the Maxon DEC 50/5, which Charles and I think might be easily hackable to higher currents (spec’d 10A). If you Google it I think Charles’ site is above Maxon…

    Another one to check out is Jed’s electric long board build:
    http://mitrocketscience.blogspot.com/search/label/ELB
    He’s also using the 18T GoBrushless stators.

    -S

  2. honickmonster Says:

    I am planning on 20 magnet poles as per the is site http://powercroco.de/navigation.html.

    About starting the motors from a standstill, I plan to start out with the airplane ESC’s to get things going, and then to build a zero-RPM starting, sensorless ESC using EMF feedback using the ML4425. It seems to be kind of an old chip, but it should do the job.


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