2013-11-06
The tractive effort graph shows the tractive effort as a function of speed when shifting (up/down). The gears can be specified individually. In the graph, certain grades (slopes) can also be plotted. They show the tractive effort required to move the vehicle at a constant speed.
In the event that maximum tractive effort at the wheels exceeds what can be transmitted to the ground via the driving axle power and ground friction, this will be marked in the Tractive Effort Table (explained below).
On all graphs with performance for certain gears, the gear labels are shown on the graph. This can be turned on/off from Main Menu>>Settings>>Gear labels.
The tractive effort chart gives you an excellent indication of how a truck actually performs on the road. The chart provides information on several characteristics.
How to use the Tractive Effort Graph:
The red "small" curves are the tractive force curves for the various gearbox gear speeds. Each curve represents the engine torque curve multiplied by the corresponding gearbox gear ratio, final drive reduction ratio and the rolling radius of the tyres. The result indicates the tractive force at the rear wheels.
The blue resistance curves show the inclination (in percent) which the truck can climb in each gear. On a level road (0% inclination), the resistance curves represent only the sum of the aerodynamic drag and the rolling resistance.
Examples
Point 1 indicates the speed and the gear in which the truck can climb an 10% gradient.
Point 2 indicates the highest point on the tractive force curve for the highest gear. It shows the truck's maximum hill-climbing capacity in the highest gear. The truck can be driven up an 2 % gradient in the highest gear, and will then travel at a speed of 70 km/h.
Do not use the inclination figures to select a reduction ratio. The road inclination varies all the time and the percentage figures provide no information on the average speed up the entire gradient. Select the final drive reduction ratio taking into account the normal cruising speed, and then check that the recommended hill-climbing capacity requirements are met.
Between point 2 and point 3 is the economy speed range of the truck in terms of good driveability.
Good driveability means that you do not need to change gear when a hill appears.
When specifying a truck, the normal target speed should be in the middle of the sweet spot range (available in Performance Summary and in Product Comparison).
Point 4 indicates the nominal speed of the truck. This is the truck speed at max. engine speed.
If the tractive force curve lies above the resistance curve for an inclination of 0%, the truck will reach a higher practical speed than the nominal speed. If the tractive force curve is below the 0% curve, the point of intersection indicates the practical maximum speed of the truck.
Here we find the steepest gradient which the truck can climb with a maximum load on the driven axles and the corresponding vehicle speed. If the value is marked with an asterisk (*), the traction between the tyres and the road surface limits the hill-climbing capacity, i.e. the wheels spin.
The Table consists of 6 columns:
Gear Shows the gear.
Speed (Km/h) Shows the speed at different enginespeed.
Engine. R. (Rev/min) Shows the engine revolution.
Tractive effort (kN) Shows the Tractive effort that are obtained at the wheels.
Power (kW) Shows the power at driving wheel.
Gradeability (%) Shows what incline the vehicle can cope at that specific engine speed and gear. An * indicate that the tractive force is higher than maximum friction between the tyre and surface.