Difference between revisions of "Horsepower"

'''Drawbar horsepower''' is the power a railroad locomotive has available to haul a train or an agricultural tractor to pull an implement.  This is a measured figure rather than a calculated one.  A special railroad car called a dynamometer car coupled behind the locomotive keeps a continuous record of the drawbar pull exerted, and the speed.  From these, the power generated can be calculated.  To determine the maximum power available, a controllable load is required; this is normally a second locomotive with its brakes applied, in addition to a static load.

If the drawbar force is measured pounds-force (<math>F / {\rm lbf}</math>) and speed is measured in miles per hour (<math>v / ({\rm mi/h})</math>), then the drawbar power in horsepower (<math>P / {\rm hp}</math>) is: