horsepower assignments

[3rdrailoscaler]

Is there a general equation that railroads use to determine the needed horsepower requirement for a specific train weight?  I understand that more horsepower is needed to counteract the issues of ruling grades and curves in a rail line, but how much horsepower is needed to move a specific train weight on say flat, level and straight track?  Is it a general rule of 1hp per ton or something else?  Thanks

[greyhounds]

3rdrailoscaler

Is there a general equation that railroads use to determine the needed horsepower requirement for a specific train weight?  I understand that more horsepower is needed to counteract the issues of ruling grades and curves in a rail line, but how much horsepower is needed to move a specific train weight on say flat, level and straight track?  Is it a general rule of 1hp per ton or something else?  Thanks

What I know about is the "Davis Resistance Formulas"  that indicate how much tractive effort (which relates to horsepower) it will take to move a given train over a given route at a given speed.

How fast do you want the train to go from point A to point B?  The major element in the formulas is the grade.  (rate of increase in elevation).  It overwhelms the other factors because the locomotives have to lift the freight instead of just move it along.

I understand that a slow freight, i.e. coal, can be powered at around one HP per ton.  If it's a UPS train you're around three HP per ton.  If the train's route is water level, i.e. along the Mississippi River between Chicago and the Twin Cities, you can get by with less than three HP per ton.  If you're going over the Rockies or want to do 80 MPH if required to meet the contract, you'll need more. 

[timz]

3rdrailoscaler

Is there a general equation

That's easy: no, there isn't.

There is no absolute minimum horsepower needed to roll a given train at a given location-- there's a minimum needed to roll it at any given speed, but if 1 or 2 miles/hour is fast enough you can get by with an astonishingly low horsepower. That's what the steel wheel on the steel rail is all about.

On dead level track a modern AC six-axle locomotive can maintain 10 mph with at least 250 cars loaded to 143 tons apiece-- i.e. 0.1 hp/ton or thereabouts. We could haul far more with the same horsepower if we added a slug or two, but we couldn't manage 10 mph.

So there's no use trying to decide what horsepower you need for a given train until you decide what speed you need.

 

 

[Eric97123]

All your answers are here (or most of them)

 

http://www.alkrug.vcn.com/rrfacts/hp_te.htm