Draw Bar Pull

IMPERIAL

The torque on the driving axle creates a force between the tyres and the road which is used to propel the vehicle. This gross force is termed the tractive effort and the net force, that is, gross force minus rolling resistance is the drawbar pull.

Where:

DP = Drawbar pull in lbs

T = Motor torque in lbs in

R = Overall gear reduction including both axle and transmission

r = Rolling radius of loaded driving tyre in inches

RR = Road rolling resistance in pounds

GVW = Gross vehicle weight of motive vehicle in pounds

Example:

What is the drawbar pull of a vehicle with a motor torque of 1000 lb in, an overall gear reduction of 10:1 and rolling radius of the driving tyre is 15 inches and a GVW of 10,000 lbs over good concrete?

METRIC

The torque on the driving axle creates a force between the tyres and the road which is used to propel the vehicle. This gross force is termed the tractive effort and the net force, that is, gross force minus rolling resistance is the drawbar pull.

Where:

DP = Drawbar pull in newtons

T = Motor torque in newton metres

R = Overall gear reduction including both axle and transmission

r = Rolling radius of loaded driving tyre in millimetres

RR = Road rolling resistance in newtons

GVW = Gross vehicle weight of motive vehicle in kilograms

Example:

What is the drawbar pull of a vehicle with a motor torque of 115 N m, an overall gear reduction of 10:1 and rolling radius of the driving tyre is 400 millimetres and a GVW of 4,500 kilograms over good concrete?