I am trying to turn a wheelchair electric and want to use a VESC to do so. However, I was wondering if an outrunner brushless motor with a belt to a larger gear would be effective and could move the wheelchair with a person if I had two of them. I am looking at a motor like this: https://www.amazon.com/vanpro-Brushless-Outrunner-Motor-Electric/dp/B07FNHQ3JK/ref=sr_1_2_sspa?keywords=brushless+scooter+motor&qid=1561407288&s=gateway&sr=8-2-spons&psc=1

and a VESC like this: https://www.amazon.com/HGLRC-FLIPSKY-SK8-ESC-Electric-Skateboard-EScooter/dp/B07GFB55NV/ref=sr_1_1?keywords=vesc&qid=1561408198&s=gateway&sr=8-1

Please feel free to suggest other solutions if this does not seem reasonable as I am still new to electrical and mechanical engineering.

Thanks, Maanit

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    \$\begingroup\$ Your question is likely to be closed as too broad and you are requiring your readers to follow two links just to understand your question. I haven't checked but I can guess that because they are Amazon links there won't be a proper datasheet for either so detailed specifications will be missing. Our recommendation is, "No datasheet? No sale!". \$\endgroup\$ – Transistor Jun 24 '19 at 20:54
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    \$\begingroup\$ I'm voting to close this question as off-topic because this is a question about the properties of a device that can only be answered with information from the datasheet of the device, but no datasheet is available, due to OP's purchasing decisions. \$\endgroup\$ – Marcus Müller Jun 24 '19 at 21:20

I was wondering if an outrunner brushless motor with a belt to a larger gear would be effective

No, a single gearing would not be sufficient. You'd really need either multiple levels of gear reduction, a worm gear drive, or a different type of motor.

The motor you're looking at is specified with a nominal speed of 6000 RPM.

Most wheelchairs have wheels with a diameter of 24 inches (61 cm). To move at a reasonably fast speed of 5 mph (8 kph, 2.2 m/s), the wheels would need to rotate at ~70 RPM. (This is probably too fast for a wheelchair, but setting a lower top speed would make the analysis come out even worse.)

For a 6000 RPM motor to drive a wheel at 70 RPM, you'd need a gear ratio of roughly 85:1 -- e.g. if the large gear were the same size as the wheelchair's wheel, the small gear would be about a quarter of an inch (~7 mm) across. This is smaller than the drive shaft of the motor -- it's not clear that a gear (or pulley) this small would even be mechanically sound, let alone that it could transmit enough torque to drive a wheelchair.

Note that what I haven't analyzed here is whether this motor can even provide enough torque to move a wheelchair. This is because there are no torque specifications available for the motor you're looking at.

  • \$\begingroup\$ 24 kilometers per hour? Holy moly! It must be no more than 2.4 kilometers per hour or you can't control the damn thing. (In wheelchair sports, they use a model specifically designed for higher speeds up to roughly 10 kilometers per hour. Faster at your own risk.) \$\endgroup\$ – Janka Jun 24 '19 at 21:37
  • \$\begingroup\$ @Janka Make sure to augment the handling and suspension when you increase your wheelchair nominal speed to 24km/h so you can make it around corners. \$\endgroup\$ – DKNguyen Jun 24 '19 at 21:51
  • \$\begingroup\$ @Janka LOL, fair point -- I suppose this is a wheelchair, not an electric scooter. I've dropped the target speed to 5 mph, which shrinks the drive gear to a clearly unreasonable diameter of 7mm. \$\endgroup\$ – duskwuff -inactive- Jun 24 '19 at 21:55
  • \$\begingroup\$ The most important part you need for any kind of motorized wheelchair are rear wheels. At least as "training wheels". Skipping those is a recipe for disaster. \$\endgroup\$ – Janka Jun 24 '19 at 22:16
  • \$\begingroup\$ A diameter of 24 inches? That seems smaller than most wheelchairs I've seen, though perhaps power wheelchairs use smaller wheels. \$\endgroup\$ – Hearth Jun 24 '19 at 23:38

The published specifications seem to be:

Brushless Outrunner Motor Power N5065 270KV 1450W for DIY Electric Skate Board Bicycle Scooter

1.Max Efficiency Current: 80A

2.Motor Dimensions: Φ50 x 65mm

3.Shaft Diameter: Φ8mm The shaft length: 20mm

4.Rotational Speed: 270 (kv) 6000RPM/V

5.Electric Skate Board Vehicles Remote Control Toys Manned bicycle

1450 W / 80 A = 18.1 V

270 X 18.1 = 4890 RPM

Torque = 1450 X 9.549 / 4890 = 2.83 Nm

The maximum efficiency point may or may not be the rating for continuous operation. It appears that the motor has sufficient power to drive a wheelchair including an allowance for substantial losses in an appropriate speed reduction gear. A 1450 W motor will likely need to dissipate 150 to 200 watts of losses. To dissipate that power and avoid overheating the motor is likely needs the air flow generated by a propellor.

The motor is called an out-runner, but the picture of the motor mounted on a skateboard seems to show an in-runner. The details also show a shaft.

Overhung Load

A shaft that drives a pulley to sprocket is subjected to a radial force called overhang load. I doubt that an 8 mm shaft and bearing are going to be able to withstand for long, much if any overhung load at 4890 RPM. I suspect that finding an appropriate speed reduction system to drive a wheelchair will be very difficult. Even the motorized skateboard pictured on the Amazon page is suspect. The motor shaft and bearings do not look to be as substantial as the wheel bearings.


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