In the vehicle-mounted hydraulics industry, a standard tipper truck has a relatively simple architecture in which fluid power is channelled to a single function. Road-recovery vehicles, firefighting equipment, hydraulic platforms and special-purpose logistics vehicles, however, require a multifunctional system design. In these vehicles, several hydraulic consumers—such as the recovery winch drum, telescopic lifting boom, stabiliser outriggers that secure the vehicle to the ground, and lower-platform positioning mechanisms—must be supplied from the same power source and controlled independently.

Engineering Challenges of Multifunctional Systems

Distributing the hydraulic flow from a single pump among several functions requires the following design questions to be resolved:

• Simultaneous and Sequential Operation: Will the functions operate at the same time, or must they follow a defined sequence? For example, the stabiliser outriggers must contact the ground and lock before the lifting boom is deployed; this is a fundamental safety rule.
• Flow and Pressure Distribution: The flow required by the winch motor may differ from the pressure required by the stabiliser cylinders. The system must distribute these changing demands among the lines without creating a bottleneck.

To manage this complexity, the system architecture may incorporate multiple-pump configurations such as Group 40 tandem gear pumps, which can generate two independent flow lines from a single shaft.

Precision Management: Proportional Control and Multi-Channel Joystick Systems

Pneumatic controls form the management centre of multifunctional systems in the driver’s cab. Unlike conventional on/off switches, HMLIFT multi-channel proportional pneumatic joysticks give the operator precise control over movement.

• Proportional Air Technology: The air pressure delivered to the valve control ports varies in direct proportion to joystick travel, within the maximum 10 bar limit. This gradually opens the spool inside the directional control valve and allows the recovered vehicle to be lifted or lowered smoothly and precisely, without shock.
• Multi-Channel Architecture: Two-channel, three-channel or multifunction joysticks and air switches make it possible to manage several independent hydraulic circuits—such as boom extension, platform angle and PTO integration—from a single control console.

Safety Limits: Position Locking and Stability

Safety margins must be kept at the highest level during road-recovery operations. When a heavy load is suspended or the recovery platform is held at an angle, a sudden pressure drop or leakage in the hydraulic lines must not create a mechanical hazard. To prevent this risk, closed-circuit directional control valves from the VK3600 series are preferred. In neutral, these valves close all flow paths and retain the fluid in the lines. The resulting hydraulic lock helps cylinders and motors remain securely fixed in their current positions.

Conclusion

The success of a hydraulic system in special-purpose and road-recovery vehicles is measured by how safely and precisely multiple functions can be controlled from one centre. With the correct tandem-pump selection, proportional pneumatic controls and position-locking valve architecture, even complex mechanical movements can be managed in the field with high safety and efficiency.