An Unplanned Motor/Wheel assembly Test Stand

BVH

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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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"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.
 
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
 
Dauntless said:
what's this 'Optical tach?'
it's sitting next to his controller; the thing that looks like these
https://www.amazon.com/Digital-Photo-Laser-Tachometer-Contact/dp/B001N4QY66
 
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.
 
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.
 
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.

[youtube]De-btxIJPwE[/youtube]
 
Our Triad EV Assn along with the Light EV Assn are doing some ebike testing on test tracks in Western NC. At times we would like to have a "standardized" test and after seeing the Motor/Wheel Test Stand in the posts here, we started looking around for something like that which would:
  • Provide a repeatable test for an ebike giving a defined "profile" of resistance to the driving wheel AND
  • provide a test stand we could use at demos to have people try out an ebike on a test stand, and not be bored to tears!

We found two bike stands that are a bit pricier than basic trainers we have used in the past; at $400-$500 they are inexpensive enough to consider starting with:
  • Saris M2 Smart Trainer; Saris support is interested in helping us out, but none of us have an M2 Smart Trainer
  • Kinetic T6100 which one of our members already owns, no special advice from Kinetic support, but forums seem useful

If we can work up some profiles to mimic the current actual test rides that people take on our courses, we could have some virtual testing in a lab area. It appears we can use the Zwift or Rouvy apps with either and have a "virtual" ride with a video monitor and speakers. But are there any sedate, low key rides in either of these apps for use with these trainers and novice ebike riders as opposed to non-ebike training?

Has anyone done this before for testing/demo rather than training? Any hints/tips on doing so? It wold be great to figure out how to have "virtual test rides" where a few people at each place can go on virtual rides and share experiences on ebikes riding on these smart exercise stands!

Saris M2 Smart Trainer
M2_8150.jpg


Kinetic T6100 Smart Trainer
IMG_WEB_17-810x540.jpg


People on a virtual ride using either Smart Trainer
11c92bb7b85e6006fbaed73d6d8d0e6195c78b72_zwift-com_section3_ipad_ny.jpg
 
Yes, several people have privately mentioned you need "road" tires for the Kinetic or Saris trainers, rather than trail/knobby tires.

Also, neither training stand has any calibrated power output meter.
 
Maybe fab up something like this.. It's a 2 motor rim drive friction setup as a ebike conversion,so you could use the motors for load and metering without needing a tire. His flip away from the wheel when turned off, but you wouldn't need anything fancy like that, just some width adjustment.

images (16).jpeg
b13bd32b-3f62-457c-a0ac-48425b388a39.jpg
 
Dauntless said:
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

Re the tach, its not set up to give full time reading like to a dashboard... You have to pick up the unit and aim it at the rotating part, push a button and it shoots a laser out. It's used a quick diagnostic, usually like in a car engine or something but not meant for full time monitoring.
 
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