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[Mathurin]

3.2 Nm * 80/11 * 28/19 = 36 Nm at the rear wheel.

Subtract efficiency losses and you get about 34.7 Nm at the rear wheel.

You really think you're gonna get anywhere near 96% of the power through two geardowns?

Check out the cyclone, a very similar design:
http://endless-sphere.com/forums/viewtopic.php?t=506&start=15

 

[TylerDurden]

The way I read the motor spec, is peak torque of 2.9Nm @ 2201 rpm with 75% eff.

Yer gonna need some watts to push that bike up a 6% grade. At 75% eff, yer gonna make a bit of heat.

 

[safe]

You really think you're gonna get anywhere near 96% of the power through two geardowns?

Something in the 94% - 96% range is about right. Don't forget this is my actual bike that I ride, so all the numbers have been verified by real world experience. I keep the chains in very good condition (clean them every 500 miles) and lubricate them every other ride. I also make certain that the bearings are clean and well adjusted. I used to work at a bike shop and am pretty good at this sort of thing.

 

[safe]

The way I read the motor spec, is peak torque of 2.9Nm @ 2201 rpm with 75% eff.

The Unite website says 3.2 Nm for the 1000 Watt motor. I burned out the old 750 Watt and upgraded. I can now pull 3-4 mph faster in every gear, but my range has dropped from about 18 miles to about 13 miles. It depends on how I ride of course. On the flat I can pull 40 mph pretty easily, whereas it used to be a struggle to get to that speed. It's a good motor and it seems to handle the heat a little better than the original 750 Watt motor used to. (the workmanship appears better)

I did 50 mph on the downhill today... and it wasn't even working that hard... (of course that's downhill)

MY1020 36 Volt, 1000 Watt, 3000 RPM, 35.6 Amp, permanent-magnet motor.

20 mph seems about right for a 6% slope at peak rpm... (based on my personal experience on the bike)

http://www.cn-dcmotor.com/productShows.asp?ArticleID=276

But all this "chit chat" doesn't advance the question of "Battery Current Limited" control verses "Motor Current Limited" control. Right now my old bike uses the standard battery side control... so at present I'm not really testing the theory yet.

 

[safe]

Fetcher

With one of these comparators, when the input voltage rises above a certain level then it "toggles" and at that point you would know that you need to cut the throttle voltage. This happens very fast and the result would be a "PWM" - like effect on the throttle signal because the throttle would suddenly go to 0 volts which cuts the motor power and current, which instantly is fed back to the comparator which then opens the throttle voltage to back to normal and it repeats over and over again hundreds of times a second.

Is that a terrible (but simple) idea?

The "feedback loop" becomes the motor itself... would that damage something?

 

[fechter]

That's basically how all my limiter circuits work. When the ouput of the amp goes low, it pulls the throttle signal to the controller down. This instantly reduces the current, which allows the amp to go high again. It's a closed feedback loop. If you lift the rear wheel off the ground it will never get enough current to limit, so it runs open loop.

 

[safe]

That's basically how all my limiter circuits work. When the ouput of the amp goes low, it pulls the throttle signal to the controller down. This instantly reduces the current, which allows the amp to go high again. It's a closed feedback loop. If you lift the rear wheel off the ground it will never get enough current to limit, so it runs open loop.

So you don't dampen the "cutoff" of the throttle at all?

Is the resulting throttle signal oscillating rapidly?

Doesn't this create something like an AC current coming from the throttle rather than a DC current? It's almost like adding PWM between the throttle and the controller. Wouldn't it?

That's very simple... 8)

 

[fechter]

I put a capacitor in the negative feedback loop to slow down the response. With a slow amp like a TL082, you don't need it. The controller has a ramp up delay built in, so that slows the throttle up response. I haven't had any oscillation issues with the slightly delayed response.