Hydraulics in the mud
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HYDRAULIC MOTORS mounted within the wheel hubs of trailers can help improve the traction performance of articulated vehicles under extreme off-road conditions.
For two years Poclain Ecodyn, a French company with its UK base at Marlow, Buckinghamshire, has had prototypes running in Europe which have now covered over 150,000km (93,750 miles).
The Ecodyn drive system uses a simple'fluid pipe to apply hydraulic power generated by a gearbox-attached multi-outlet pump to individual wheel hubs.
Engaged only in adverse running conditions, the independent drive can account for 40 per cent of the total tractive effort.
The slow speed hydraulic motors comprise radial pistons within an external cam which is said to give a smooth and continuous torque output. Power from the hydraulic pump can be used to supply the hydraulic tipping equipment_ Extra electric controls are needed within the cab to select either forward neutral or reverse modes. In the event of failure the motors remain in freewheel.
The £5,000 estimated to be the cost of adding power to two axles can be recovered by improved performance, it is claimed.
Friction losses due to freewheeling motors are similar to that of normal wheel bearings, accounting for 0.45kW (0.6bhp) at 100km /h (62rnph).
In terms of increased fuel consumption each wheel modification is said to be the equivalent of adding an extra rear-view mirror.