Well not eMTB I have 2 hybrids

saneagle

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Oct 10, 2010
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How are torque and cadence related to power?
Torque, together with cadence, is a component of power. If you compare two drive units with the same maximum power and different maximum torque, you will see that maximum power is achieved with the motor with the higher torque at a lower cadence. Conversely, this means that to achieve the maximum power of the motor with the lower torque, you need to pedal faster.
That's not generally right. You can always increase torque by lowering gearing, but if your talking about internal gearing, it would need new parts. It's much easier to increase the current. In the old days most ebikes were 36v and the batteries struggled at 15 amps. Now batteries can do 40 amps and have a lot more capacity, so a motor designer, like Bosch that was constrained to 15 amps and about 40 NM, can get 170% more current that would equate to 107nm.

They probably rate their motors according to the speed. The 250w and 350w motors are identical apart from a software setting. The 250w one is limited to 15.5 mph and the 350w one 28 mph, though it doesn'thave enough power to ride around at that speed. 250w is approximately the power you need to propel an MTB type bike with a normally clothed rider at 15.5 mph.
 

guerney

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Sep 7, 2021
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80nm of torque is quoted for my 36V BBS01B. Does 80Nm = 0.737 horsepower? If so, and if 250W is ≈ 33.5% of a horsepower, 80Nm = 550.3W. Stock amperage for my 36V BBS01B controller was 15A = 540W. Almost works out.
 
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saneagle

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Oct 10, 2010
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80nm of torque is quoted for my 36V BBS01B. Does 80Nm = 0.737 horsepower? If so, and if 250W is ≈ 33.5% of a horsepower, 80Nm = 550.3W. Stock amperage for my 36V BBS01B controller was 15A = 540W. Almost works out.
Except that your motor is only about 70% efficient, so that 80nm is an exaggeration. My experience of your motor and comparing it with other CD bikes, I'd say it's closer to 50nm.
 

guerney

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Sep 7, 2021
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Except that your motor is only about 70% efficient, so that 80nm is an exaggeration. My experience of your motor and comparing it with other CD bikes, I'd say it's closer to 50nm.
343.7W?
 

saneagle

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Oct 10, 2010
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36 x 15 x 0.7 = 378 when I was at school; however, that promotes the culture of white supremacy, so your answer would be considered more equitable.
 

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