The object was to calculate journey time, speed, fuel consumption, and gear change, engine load and rpm statistics for heavy vehicles of different gross weights, engine ratings and final gear ratios, for two model journeys. The model was derived from the force equation relating to inertia and traction forces, and air, rolling and gradient resistances acting on the vehicle. Engine rpm was determined from the speed by aggregating gearbox and rear axle ratios. At speeds lower than the maximum permitted, only the vertical alignment and engine power resources determine the speed. The effect of bends and other traffic was ignored. Road description contained gradient or vertical radius. Speeds limits were also included. Computer calculations were made for every 5m of road for three speeds regarded as maximum possible for a certain vehicle type. At any point, the lowest of the above speeds and the speed limits was taken as maximum permitted speed. After each step, speed was checked and, if found higher, reduced to maximum speed. When the maximum speed changed, vehicle speed was reduced in one step, limited to 20 kph. Calculations comprised 70 combinations of the different variables for each journey. Details of the results are given.
Samenvatting