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Extra traction on demand

Extra traction

The Putzmeister M 70-5 is the largest truck-mounted concrete pump boom in the world. To comply with the highway regulations in some states, Putzmeister mounts the large-boom concrete pump onto a 10-axle semi trailer, which houses the pump’s boom, base structure with support, outriggers, pump unit, and 330 kW Deutz 6-cylinder Tier-3 diesel power plant.

The version shown is powered by a 370 kW Kenworth C500B tractor. The front wheels of most on-highway tractors provide steering, but not propulsion. So when the C500B must negotiate rough terrain, front-wheel steering alone just won’t cut it. Therefore, the Kenworth C500B shown uses a hydrostatically powered front wheel drive system from Poclain Hydraulics. Poclain’s hydraulic assistance drive is integrated in the tractor’s two steerable front axles for low-speed travel over rough terrain or in poor traction conditions, while its other three axles are mechanically driven.

A driver can engage the front wheel drive on demand for additional traction and mobility. The system is a joint development between Poclain Hydraulics, Tuthill, Monroe Truck, and Putzmeister.

The hydraulic system was designed for simple installation, versus that of a complicated drive shaft and transfer case system commonly used today. Because this axle assembly is so compact and has no differential gearing, there are no crankcase interference issues. Therefore, the truck body does not need to be raised to install the system, which would be required for installing a conventional mechanical drive. This has a number of benefits, including, but not limited to:
• reduced installation cost,
• lower center of gravity,
• easier cab access, and
• greater ground clearance.

The hydraulic part of this hub is so compact that it is hardly noticeable once assembled. In fact, the OEM turn radius is maintained as is the suspension and ride comfort.

The front wheel motors are powered by a Poclain Hydraulics closed-loop, variable-displacement pump that is driven from the tractor’s power takeoff. A Poclain Hydraulics Addi Drive freewheeling control valve controls engagement and disengagement of the front wheels, which can be done at any time.

In addition to providing other functions, an electronic CAN link controller matches the speed of the front wheels to that of the rear wheels. The front wheels can be deactivated by the operator or they will automatically disengage when the vehicle exceeds a predetermined speed, usually 30 km/h (about 20 mph) depending on tire size. The system can then be re-engaged without coming to a stop once the operator slows down within the operating speed range.

For information on Poclain’s Addi Drive system, visit

TAGS: Construction