oxygen torque?

[stevieb]

hi
does anyone know what torque an oxygen e mate mtb 13 ah produces ?
thanks

 

[Deleted member 4366]

 

[stevieb]

thanks for that
so at 25kph the torque is 22 nm if i,m reading the graph correctly.
so if a manufacturer advertises a bike at a certain torque would they quote the maximum ? in this case 60nm at a slow speed

 

[Deleted member 4366]

It's an absolute mystery what people claim for torque, especially when it comes to crank-drive bikes. It's completely meaningless. The torque that the rider experiences depends more on the bike and its gearing than the motor. I just converted a Brompton with a tiny 180w Q80 motor. It could drag my 100kg up a 14% hill without pedalling. That's a lot of torque - about the same as a 350w BPM at 22 amps. The difference is in the speed that it does it. Torque times speed is power.

 

[RobF]

It's an absolute mystery what people claim for torque, especially when it comes to crank-drive bikes. It's completely meaningless. The torque that the rider experiences depends more on the bike and its gearing than the motor. I just converted a Brompton with a tiny 180w Q80 motor. It could drag my 100kg up a 14% hill without pedalling. That's a lot of torque - about the same as a 350w BPM at 22 amps. The difference is in the speed that it does it. Torque times speed is power.

Presumably the little wheels helped.

I agree torque figures are meaningless, far too many variables in terms of measurement and interpretation to compare like with like.

The OP mentions 22NM for the Oxygen, Bosch quote 75NM for the CX motor.

Both figures may be correct for all I know, but in use there's no way the Bosch motor is three times as 'torquey' as the Oxygen.

 

[trex]

I think Bosch figures may have been converted to the 44T Classic chainwheel for comparison. 75NM is roughly equivalent to 75NM*34/44=58NM at the rear wheel when 34T cog is selected.

 

[stevieb]

Torque times speed is power.[/QUOTE]
so torque is power divided by speed.
that simplifies things .
thanks

 

[Alan Quay]

Torque times speed is power.
so torque is power divided by speed.
that simplifies things .
thanks

Another way to think about it is that for a fixed amount of power you can have lots of torque at low speed, or high speed with little torque.

Put a bike into its lowest gear. It won't go very fast, but will climb well. Opposite in high gear.

 

[Deleted member 4366]

The power determines how fast you go up a hill or otherwise.

The torque determines how steep a hill you can climb.

Effeciency has a big bearing on power. If you look at that Bafang CST (Oxydrive) chart, you'll see that the efficiency curve is very flat all the way from 15 to 40 km/h, so you get good battery economy and good power at hill-climbing speeds.

With a crank-drive bike, you can have whatever torque you want. You can also have all the speed you want, but not both at the same time.