Heinzmann motor, understanding specs

[mrbike45]

Hello

I'm confused by the specifications given for the Heinzmann Classic RN 120 DC brushed hub motor. It is giving me different values of torque/emf constants, armature resistances and inductances dependent on wheel size. I would think these figures do not depend on wheel size, but that they are inherent only to the motor. Why is this the case? and how would I figure out how much current the motor is drawing for a certain torque and wheel size?

Here is the data sheet:
http://www.ebike.heinzmann.com/images/ebikesystems/phocadownload/Fahrradmotor-CLASSIC_DataSheet.pdf

Thanks.

 

[Deleted member 4366]

The current is set by the controller, not the motor, so you look at the controller and see what's written on it. There's two versions of the motor: 209 rpm, which will do about 19mph; and 180rpm, which'll do about 15mph in 26" wheels. The idea is that you put the lower rpm one in a 28" wheel, and it'll feel the same as the 26" version regarding speed and force . The lower rpm one will be slightly more efficient when climbing steep hills or under heavy loads if you had it in a 26" wheel.

You'll need to hunt around for info on the controllers, but from memory they do a 33amp one, which is not certified as legal. The highest legal one is 28 amps, and then there's a couple of lower ones. How they got approval for their 28 amp system is a mystery because in my calculation, that makes 1120 watts from the battery. No wonder it has a reputation for good climbing ability.

 

[mrbike45]

oh. It would have been nice if it was mentioned somewhere in the data sheet that there are two versions of the motor being described. This had me confused for a while. Thank you for pointing this out...life makes sense again.
So technically the motor (lower rpm one) could provide up to 50Nm of torque when stalled and P = 36*28 = 1008W. That's crazy.

 

[Deleted member 4366]

There was a Heinzmann motored cargo trike at the Bristol show. It had two wheels at the front a bit like those ice cream vendors machines except that it had a massive basket thing on the front instead. He drove up the steepest hills like a car without pedaling.

 

[passpato]

The sticker on the motor has the specs. Nominal amperage , Max amperage, rmp of motor. To stay legal a motor must not exceed 200 watts (250 on a 3 wheeler) in constant use but can use more for short periods . The motor would overheat after a long period at maximum amps. The Heinzmann controller has a heat sensor in the motor (a thermistor) which tells the controller to cut back on power when the motor is hot.The motor should run all day at the lower, nominal amperage. The motor will reach the rmp at its stated voltage. eg 36v or 24volts.