Tractor Drawbar Power
Drawbar HP = (pull * speed) / 375; PTO HP estimate from public benchmark.
Example
You enter
- Drawbar pull (lb) 4500
- Ground speed (mph) 4.5
- Surface firm_soil
You get
- Drawbar HP 54.0
- PTO HP estimate 75.0
- Tractive efficiency 0.72
Checked against published worked examples from: ASABE.
Details, formula, and sources
Formula or tableDrawbar HP = (pull_lb × speed_mph) / 375. PTO HP estimate = drawbar_HP / tractive_efficiency, from the ASABE D497 table by tractor type and surface (2WD: 0.87 concrete / 0.72 firm / 0.67 tilled / 0.55 soft or sandy; MFWD, 4WD and track rows higher).
Source and editionASABE D497 (Agricultural Machinery Management Data) by name; Nebraska Tractor Test Lab publications.
Free accessNebraska Tractor Test data free at tractortestlab.unl.edu.
What governsEstimate. AHJ and licensed professional govern.
API field namespull_lb, speed_mph, surface, drawbar_hp, pto_hp_estimate, tractive_efficiency
- Tractive-efficiency table 2WD 0.87 concrete / 0.72 firm / 0.67 tilled / 0.55 soft; MFWD, 4WD and track rows by surfaceASABE D497