Efficiency of hub motors at higher powers?

[jag]

I have build a dyno. Seen here http://www.youtube.com/watch?v=XdjQ445WoJw and as a mater of fact it will work for low power ebikes.

Nice work, though as you mention a brake dyno would likely be better for the ebike. We woul dlike the measured for torque/power under sustained load.

As for an ebike like mine a motorcycle dyno would likely work. It is a matter of what type of dyno it is what we want to test for acceleration is inertia dynos. But if we could vary the load it would help to test efficentcies at different levels like simulate different hills. So a brake dyno is best for this other wise It is possible to add weights to my inertia dyno as well. As for the program I have and the dyno mesureing equipement it is for inertia. But for acurate variable load tests one could use a brake mounted to a old cheap tourque wrench to hold it at a certain speed and increase load and the tourque wrench will tell you the tourqe!
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Not a bad idea. I hadn't thought of using an external static torque measure and a brake. An electric brake may as you say below, be smoother than a mechanical. A lever and a scale could be more accurate than a torque wrench.
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As for most motorcycle dynos dynojet ect. alot of them have eddy brakes so they are a light drum that spins up easy and to add load for higher power bikes they use the eddy brake at a load percentage.

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I still wonder if a regular dyno can accurately measure in the 10 or even 100w range. Given that most are designed to hundreds of hp, it would mean they have 0.1-0.01% accuracy. That would be better than my multimeter!

[Arlo1]

I think the thing to remember is we all have big torque! Me bigger then most. But lets say a 300w motor runing at 300 watts and say its 75% efficent. 300x.75=225w then lets convert that. 225/746=.3hp doesnt seem like much but lets say its at 100rpm (100rpm in a 20 inch wheel is ~10 mph) .3x5252/rpm= torque so .3x5252=1575.6/100=15.756ft/lbs or at 10rpm 157.56ft/lbs torque now most motorcycles dont even produce that torque so I think alot of them would work. I deffinatly want to try it. Mine has to have huge torque to be able to flip people off like it does. And I do plan to dyno it!