Tanker tonnage identified, conception of engine horsepower size, best matched with tank tonnage, carrying big, small engine, oil transport vehicle back force.

Making use of the rig general detecting laboratory to test the deferent maximal feeding force and drawing back force of drill rig, the validity of theoretic accounting value are analyzed in the paper.

We believe that a force of about one hundred pounds was needed to pull the string all the way back on a long bow.