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?
