Gradeability

IMPERIAL

Obviously, the tractive effort available at the wheels must be greater than the sum of the rolling resistance encountered. If this is not so, the transmission must be shifted to a lower gear in order to increase the tractive effort. The percentage of grade which can be negotiated is given by the formula.

Where:

100 = A constant expression percentage grade and inches

T = Motor torque in lb inches

R = Overall gear reduction including both axle and transmission

r = Rolling radius of loaded driving type in inches

GVW = Gross vehicle weight in pounds

RR = Rolling resistance expressed in percentage grade.

Example:

What percentage grade can be negotiated by a vehicle having a hydraulic motor torque of 1000 lb inches, an overall gear reduction in high of 12 to 1, a tyre rolling radius of 15 inches and a gross vehicle weight of 10,000 lbs driving over good concrete?

METRIC

Obviously, the tractive effort available at the wheels must be greater than the sum of the rolling resistance encountered. If this is not so, the transmission must be shifted to a lower gear in order to increase the tractive effort. The percentage of grade which can be negotiated is given by the formula.

Where:

10200 = Factor

T = Motor torque in newton metres

R = Overall gear reduction including both axle and transmission

r = Rolling radius of loaded driving type in millimetres

GVW = Gross vehicle weight in kilograms

RR = Rolling resistance expressed in percentage grade.

Example:

What percentage grade can be negotiated by a vehicle having a hydraulic motor torque of 117 Newton metres, an overall gear reduction in high of 12 to 1, a tyre rolling radius of 400 mm and a gross vehicle weight of 4,500 kg driving over good concrete?