What is Dumper's remorse

Dumper22.10.2009, 17:24

Important transport vehicles in the construction and demolition industry are trucks, SKW (heavy duty vehicles = dump trucks), dumpers and scrapers. A tried and tested vehicle is the dumper that we are introducing here.

Technology on the doorstep

Dumper

If hydraulic excavators, wheel loaders and crawlers loosen earth and rocks, the transport facilities for the loosened material are trucks, SKWs (heavy duty vehicles = dump trucks), dumpers and scrapers. If the driving surface is unfavorable (sand, gravel, soft soil), transport with dumpers is advantageous. They are characterized by the following properties:
You own
- All wheel drive
- Low pressure wide belt tires
- an articulated steering.
Dumpers are available in two-axle and three-axle versions (Picture Wikipedia).

construction

The components of the front end are the driver's cab, the drive motor, the gearbox, the front axle and the hydraulic system. The articulated steering is the movable dividing point between the front and rear of the vehicle. The rear section carries the central and rear axles and the trough with the tilt cylinders.

Axle suspension

The suspension of the axles largely determines the quality of the driving behavior: Because the axles oscillate vertically by several degrees, they not only allow higher driving speeds on difficult transport routes; this also keeps shock loads away from the structure and structural components. The pendulum hinged triangular frames with lateral stabilizers guarantee precise guidance of the axles and independent pendulum movements. A rubber buffer system on the front of the car can also be combined with shock absorbers. The front axle and the rear axles are each suspended separately from the frame. With a three-point mounting, both the necessary degrees of freedom and a load-bearing substructure can be achieved.

Hydraulics

The hydraulic system of the dumper supplies the steering, the tilting system and the fan drive. It works with several axial piston variable displacement pumps. Almost all pumps are located on the engine's power take-off.
 

The tilting system is connected both in parallel and in series with the steering system. For safety reasons, a pump always primarily controls the steering. If the steering is not operated, the steering pump, together with the other pumps, supplies the hydraulic oil for the tilting system; the steering system has priority in any case.

Tilt the trough

Example VOLVO: The rocker arm on the dashboard can take four positions: lowering with hydraulic pressure, lowering / floating position (driving position), hold and tilt. According to the positions of the rocker arm operated by the driver, the directional control valve also has four positions: lowering with hydraulic pressure, driving position, hold and tilt.
Both tilt cylinders are double-acting cylinders. The normal rocker arm position when operating the machine is the driving position; the trough is then in the hydraulic floating position, in which the line sides A and B are connected to the tank line, so that no force is exerted on the trough from the hydraulics. When the machine is parked, the rocker arm automatically returns to the holding position.

Driving resistance in dumpers and similar vehicles

In addition to having the power to move a load, a transport vehicle on tires also has to overcome its own driving resistance. They go back to internal friction, tire rolling and tire penetration.
The rolling resistance RW is made up of the internal friction and the tire rolling; in addition, there is the specific rolling resistance RWs due to tire penetration into the ground.
RW is calculated with 2% of the gross weight of the device. With a gross device weight of 1 ton, RW = 20 kg. The RWs is 6 kg per ton of gross device weight and per centimeter of tire penetration depth.

A Sample calculation:
The tires of a dumper with a total weight of 30 t penetrate 8 cm into the ground while driving. What is the total rolling resistance of the vehicle?
Rolling resistance RW per ton 20 kg / t times 30 t = 600 kg.
RWs = 8 cm by 6 kg / t and cm by 30 t = 1,440 kg.
So the dumper alone has to generate RW + RWs = 2 040 kg (= 2.04 t) pulling force for starting.