Tractive Effort conversion?

Can tractive effort be converted into horse power? If it can then how do i do it? If it can't...why not?!

Ta.

 

The very short answer is Yes, since Power is, by definition, Force x Velocity. Tractive Effort is the force applied to the track to move the train in one direction or the other, so multiplying the TE by the speed does indeed give the horsepower. This is what was done with various tests in steam days, BUT the TE declines exponentially as speed rises, so you need to know what the actual TE is at the speed you choose. That was what the dynamometer car was for: to establish the TE, but it established it at the drawbar, not track, so the TE required to move the engine itself wasn't recorded and the power output would be underestimated. In fact, what was established was the Drawbar Horsepower, then an allowance was inserted for the gradient being climbed and the Equivalent Drawbar Horsepower estimated.

But you can't just take the Nominal Tractive Effort as given in the Ian Allan ABC and deduce the horsepower from it. The Nominal TE, in any case, is merely a calculated figure and does not necessarily bear any relationshape to anything the engine could actually produce.

 

Unfortunately, this is not straightforward. To understand the relationships at a basic level one needs to have studied physics to A-level. This link then provides a useful summary:

http://www.twoof.freeserve.co.uk/motion1.htm

A more advanced outline can be found here: (opens Word doc)

http://www.brightlemon.com/ma/what_use/TractiveEffortAccelerationAndBraking.doc

Cheers
Alan

 

The OQ class Peckett 0-6-0ST (The Maerdy Monster) has a TE nearly as much as a Black 5, but the Peckett would never be used to haul The Pines Express.

The OQ that did make it to preservation though is (presumably) more economic to operate than a Black 5 on a preserved line?

 

Hence why you see "Starting Tractive Effort" quoted I.e. TE at speed = 0