Build a Simple Dynamometer using Hub motor

[Kingfish]

Greetings –

I am making plans to make plans to build a custom motor over the winter.

However, I also need a reliable way to measure the output of this motor against a known quantity. I have been running hub motors for a while now and I understand pretty much what they can do and how they behave. I don’t have a lot of space, and my pockets are not gold-lined. A table-top solution would be great!

With that, I am considering using a known device, a 9C 2806 hub motor that I would like to use and be able to place a load on it as if it were stuck in regen-mode. I could then take another 9C 2806 hub motor (I have several in great condition) and use it to run through a series of tests as a motor against the hub-dyno in order to build up a profile of the known-quantity: 9C against 9C mano a mano.

Once that research is completed, then when I finish the construction of the first of several prototypes, I could run through the same or like tests, and be able to compare and contrast the performance. Make sense?

So the question is, has anyone made something like this before, and could it be as simple as placing a controller onto the hub with ebrake=on and measuring the resulting wattage during regen as the hub is rotated?

Naturally there would have to be a dummy load, though I am less worried about that. However - I can’t think of how to make the device any more simple or vastly cheaper.

Floating the balloon, KF

[amberwolf]

Pretty sure ebike.ca's dyno is based around a hubmotor. If it isn't now, it was once.

[liveforphysics]

It's been done, at least twice that I've seen, and it works great.

[Kingfish]

Awesome - the idea is valid and others have made them!

Below is the basic functional block diagram of the Dyno I had in mind:



Regen Load
For the moment I was thinking of dumping the power back into the battery because it will never equal the draw, however at some point I'll need to create a constant power supply to feed the motor. I have read about some interesting posts on inexpensive off-the-shelf resistive loads: water heater & stove-top elements cooled in water and so forth. Frankly I am open to ideas.

The Practical Study
Features that I would like to explore with this static apparatus are as follows with priority given:

1. Get the basics working
   
   • Test 9C 2806 and develop a behavior model for compare & contrast
   • Programmatic throttling for automated test runs and repeatability, and other logging features
2. Evaluate new motor designs
   
   • Efficiency and output (natch)
   • Evaluate enhanced cooling (presuming a more powerful motor will require it)
3. New Controller developments
   
   • Practicality of voltages above 100
   • Variable Regen on non-variable regen controllers
   • Digital Throttle
   • Digital Positioning of hub (no HE sensors)
   • Trap vs. Sinus on ironless cores if practical

Instruments
Digital Oscilloscope - I don’t own one, but there was one listed on Amazon that appealed to me: Rigol DS1052E 50 MHz.

That’s pretty much all I had for equipment at the moment. The mechanical design of the Dyno is perking along in my head, though I am not quite ready to cut metal.

Scheming - and inviting others to conspire with me, KF

[amberwolf]

http://www.youtube.com/watch?v=epIz7P3viio
Bottom of page:
http://www.ebikes.ca/simulator/
Can't find a dedicated page to the sim anywhere, but I think there is one here on ES about it that I just havent' located.

[salty9]

Subscribing.

[Jozzer]

I've just built one for testing Agni motors (some info here viewtopic.php?f=30&t=33440).
I had been thinking about putting together a kit to handle the data aquisition and software side, if there is enough interest..

Steve