How much torque

Tonight at work we got on the subject of trains and just the sheer power they produce. It got one of us thinking, how much torque do the motor produce? I know they dont need the torque like a car does to get moving since its all electrical, but im sure the motors still generate torque.

Is it just as much as the HP rating?

A passenger unit like the P32acdm maxes out at 42 000 lbs on coupler

DutchRailnut wrote:A passenger unit like the P32acdm maxes out at 42 000 lbs on coupler

Ummmm....that value you mention is "drawbar pull", not torque!

Torque is different animal entirely. And torque depends on WHERE in the locomotive power system you measure it.

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At the prime mover figuring torque is straightforward:

Torque = Horsepower/RPM x 5,252.

Example: A 4,000 HP diesel running at 975 RPM will develop 21,547 ft-lb of torque at the crankshaft at maximum power.

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For traction motors it's a bit more complex. Torque depends on horsepower, motor-to-axle gear ratio, rail wheel diameter, total number of traction motors and locomotive speed.

Example (neglecting electrical and frictional losses and doing the math offline...): A 4,000 HP, 6 axle locomotive with 61:16 gearing, 42" wheels, and a speed of 8 MPH, the torque developed by each traction motor will be a bit over 14,000 ft-lb.

Note that for a 6 axle locomotive 8 mph is a typical maximum drawbar pull point. This then is also the point where max traction motor torque occurs. At lower speeds input horsepower must be reduced proportionally - otherwise wheel slip and/or traction motor overload will occur. And at higher speeds and constant input HP, torque decreases as speed increases as described in the equation above. ...FB

I was thinking straight from the actual motor (Crank). But damm that is alot of Torque.

Yeah, V-dub, we don't use torque as a measurement, but Tractive Effort is what we use to calculate what will pull the train. The drawbar pull, or effort is measured in pounds of pulling effort, although the newer motors rely on Kbs of effort, with an engine pulling in the 8th notch, at 8 MPH showing an unusual number, like 66 Kbs, whatever that means. I prefer watching the amps, and converting the HP/Amps and tonnage, into a close approximation of what will bust the knuckles. Somewhat harder to calculate, with the new engines, wheel creep systems and no conversion chart for Kilos to Amps, etc...... And remember, to account for the approximate location of the Node, when making these calculations, and locations of loads/emptys, etc.......