An Unplanned Motor/Wheel assembly Test Stand

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BVH   100 W

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An Unplanned Motor/Wheel assembly Test Stand

Post by BVH » Mar 12 2018 11:03pm

I have a Fatte-Bike SGT. Mingo in the pipeline for sometime in May. It'll be their first bike delivered in an XL frame size - about 21.6". It comes with a Bafang 750 Watt Nominal geared motor. I want something in the neighborhood of 1500 Watts nominal with peaks to 2000 Watts. I found a Direct Drive 1500 Watts Nominal RiSunMotor laced into a 26" x 4" Blue Anodized wheel with 175mm Drop Out spacing online. I wanted a way to test it out before leaving feedback and was thinking about how to secure it for a test run since I don't have a bike with 175mm dropouts. My wife happened to be donating her 2003 Raleigh beach cruiser which has been in a bike trainer stand for years. I suddenly saw my motor testing stand. I machined a few countersink points to insert into the stands' pinch bolts and which fit into the ends of the motor axle. Then I found a 36" long piece of 3/4" thick by 2.5" wide aluminum bar I had laying around and machined a .384" wide groove in the end of it to create an almost press-fit over the axle flat to act as an Anti-Torque arm.

Hooked up a Lyen sensorless controller to my Prodeco 51V pack and a spare throttle and away she went. Turns exactly 700 RPM full throttle, unloaded according to my optical tach.

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footloose   10 kW

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Re: An Unplanned Motor/Wheel assembly Test Stand

Post by footloose » Mar 13 2018 9:26am

"I suddenly saw my motor testing stand."

Nice! Trainer stand becomes test stand, with addition of simple torque arm. It's a great feeling when you discover that a solution to a problem is already available right there in your own house or shop... just maybe with a different label on it currently.

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Dauntless   100 GW

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Re: An Unplanned Motor/Wheel assembly Test Stand

Post by Dauntless » Mar 13 2018 10:35pm

Wait a minute, what's this 'Optical tach?' Looks like a fascinating setup if we learn how it really works. What are you supposing the peak rpm will be under load, don't forget
Any sufficiently advanced technology is INDISTINGUISHABLE FROM MAGIC!
- Arthur C. Clarke

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amberwolf   100 GW

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Re: An Unplanned Motor/Wheel assembly Test Stand

Post by amberwolf » Mar 14 2018 3:57am

Dauntless wrote:
Mar 13 2018 10:35pm
what's this 'Optical tach?'
it's sitting next to his controller; the thing that looks like these
https://www.amazon.com/Digital-Photo-La ... B001N4QY66

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BVH   100 W

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Re: An Unplanned Motor/Wheel assembly Test Stand

Post by BVH » Mar 14 2018 8:29am

The optical tachs have been around for decades. They come with some strips of reflective tape. Cut a quarter inch of tape, stick it on the side of the rim and point the tach at it. If I had a non-Fat Tire wheel on there, I could even make use of the black variable load device that is currently swung down out of the way. It is not calibrated so there's no way to measure H.P. as with a Dynomometer. But there are trainer stands that come with more sophisticated units that measure Watts so it is possible to make yourself a Dyno to load and measure Watts (H.P.) Eventually, I'll clean up the torque arm to make it shorter and bolt to the trainer stand and one for each side.

My Prodeco cruiser turns 510 RPM unloaded and does about 28-29MPH. I don't know if I can speculate linearly but if so then 700 RPM should equal 39 MPH. But I somehow don't think that will happen.

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Re: An Unplanned Motor/Wheel assembly Test Stand

Post by fechter » Mar 14 2018 9:43am

If you wanted to load the motor without using a tire, you could place some really strong magnets on a bracket so they are about 2mm away from the rim. This will generate eddy currents in the rim and create some drag. The resistance would be a function of speed and the magnet spacing. You could vary the resistance by moving the magnets further away.
"One test is worth a thousand opinions"

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BVH   100 W

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Re: An Unplanned Motor/Wheel assembly Test Stand

Post by BVH » Mar 14 2018 2:49pm

Doing some more playing around with my Motor test stand. I needed to figure out how to get the Phaserunner Regen working. Had some help from Grin and wanted to have the bike so that I could run the motor many times to fine tune my Phaserunner settings. The stand worked perfectly. Allowed me to spin up the motor to full speed and then apply the ebrake switch to ensure regen is working. I didn't shoot that process but shot beforehand playing around with the variable load device on the test stand. It is not the best load device and is very load and lots of rattles and noises.


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