Drawbar power (Dbhp) is power measured at the point implements are attached to the tractor, drawbar or 3 point hitch. During tractor testing a load cell is placed between the tractor and a load. The drawbar pull and the speed of travel are recorded and used to calculate drawbar power. Using measurements of pull (pounds) and speed (miles per hour) eliminates the PTO power equations. Because force is measured in pounds and velocity (V) measures both distance traveled and the time required to travel that distance (miles per hour), the best equation to use is:
where F = Force (lb); V = Speed (mph); 375 = Units conversion constant. This equation is derived by modifying the standard power equation.
t hr min 33,000 375
Problem: How much drawbar power is a tractor producing if it develops 1,500 lb of force at a speed of 5.5 miles per hour?
Hp 375 375 375 F
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