How To Calculate Torque And Power?

[Lumpen]

I am wondering how you work out Torque if you're given HP and revs and vice-versa,it was in a motor of mine a while back but I lost the bugger, from memory it was something like:

Horsepower over Revs x Something to do with a circle = torque...no seriously!

I was just wondering if any engineering type fellas or Fact Nerds :idea: actually know what the formula is!

[aniken]

I'm not an enginner, but its a slow day at work today . I found the attached conversion chart on the net. You use a ruler to line up the 2 values you do know (eg, rpm and horsepower) and it tells you the other value (torque). Someone who is more mechanically minded than me may have something better

or check out How stuff works

Edited 21/03/03 02:23 AM by aniken

[svtang]

at any rpm ... the torque (in nm) is the kW at that rpm times the 9549 (or 9459??? I can't exactly remember as I'm only a halfbreed nerd) then divided by that rpm

so 240kw at 5250rpm .....240x9549/5250= 436nm

scratching my head

[rjs]

Damn I actually got the calcs at home.

[Raptor]

Power(watts) = Torque (Nm) x revs (radians/second)

Lets see if I can work this through;

1 revolution = 2xPi (Pi=3.142 etc), therefore

RPM = 2x3.142/60 (rads/sec) = 0.104733333

Power (kW) = Torque (Nm) x RPM x 0.1047333/1000

OR

Power (kW) = Torque (Nm) x RPM / 9548

and

Torque (Nm) = Power (kW) x 9548 / RPM

QED!

(Yes, I did do an engineering degree back in the mid 80's. Amazing what stays in the memory)

[Guest Mr Walker]

Raptor,

I thought you'd be talking Hp back then not kw! Just to remind me, is the conversion for imperial measurement;

Power (Hp) = Torque (ftlb) (or whatever the abbreviation is) x 5250 / rpm?

[Lumpen]

theres actually two different formulas aren't there one relating to HP and ft/lbs and another one for Kw and Nm's.

I remember that HP and Ft/Lbs are the same at 6000 odd revs and Kw/Nms are the same at the 9548Rpm.

And I knew it had something to do with a circle.

[Raptor]

Raptor,

I thought you'd be talking Hp back then not kw!

Gimme a break, the country has been metric for longer than that.

Still HP and mpg means as much to me as kW and l/100kms.

5250 seems to ring some bells but I never could make much sense of imperial conversions and I don't have any reference books handy.

Yes XFwannaBA. It has something to do with that circle thing (Pi).

[Lumpen]

and heres me thinking all those greek guys were just working out new recipies...

[rjs]