newtons? but don't have figs...

[Desertprep]

I am reading about motors now and looking at specifications. I often see motors described in terms of "newton meters" Does this measure the same thing as foot-pounds per inch? it is a measurement of torque? And what is an adequate number of newton meters for an ebike with 26" rims - assuming, for the sake of comparison, that the rider will not be pedaling at all.

 

[Ricky_nz]

I am reading about motors now and looking at specifications. I often see motors described in terms of "newton meters" Does this measure the same thing as foot-pounds per inch? it is a measurement of torque?

Yes its a measure of Torque
1 newton meter = 0.737562149 foot pounds

Edit: missed the per inch part. Hadn't had my morning coffee yet :lol:

 

[Miles]

I've no idea what "foot pounds per inch" would represent.

A Nm is a force of 1 Newton acting at a radius of 1 metre.

If you and your 26" wheeled bike weighed 100kg, you would need at least 50Nm at the wheel to go up a 16% gradient (steep hill). Divide this by the reduction ratio of your drive to get the torque required at the motor.

 

[Desertprep]

Thanks! How many fig-newtons, uh newton meters would I need on flat land?

 

[Ricky_nz]

Thanks! How many fig-newtons, uh newton meters would I need on flat land?

How long is a piece of string?

It depends on if your name is luke or if you have a severe dislike for speed and acceleration :lol:

You can work out the NM for an existing system that has similar performance to what you are looking for.
Take its input power at a given wheel RPM and you can calculate its NM. google. should show you how.

I did work out numbers for the Turnigy 80-100 180Kv geared for 50Kph at one point but I can't find the bit of paper at the moment.
If I find my calcs I will post them later.

 

[Miles]

Thanks! How many fig-newtons, uh newton meters would I need on flat land?

As Ricky said....

50Nm at the wheel would get you to around 50mph on the flat but would require over 3000 Watts.
If you met your 16% gradient at 50 mph, you'd need about 100Nm at the wheel and over 6000 Watts to maintain speed....

 

[Desertprep]

thanks!