Big D is in town
Page 18
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YORK TRUCK Equipment has begun full production of its latest Mk V Big D fifth wheel coupling, which was shown for the first time at last year's Motor Show.
Although similar to previous couplers, the standard 120kg (2.36cwt) Mk V unit has a new top plate pressing with revised grease pockets designed to give a greater spread of grease between the rubbing plate and trailer pick-up plate.
The gather angle on the Mk V
is reduced from 500 to 40° between the tails of the coupler. According to York, this reduction forms a more acute angle when coupling up, making it more difficult for the trailer kingpin to dig in to the coupler tails.
The coupler throat has also been increased in depth providing an improved kingpin bearing area.
A deeper 90mm (3.5in) skirt on the 8mm (0.31in) thick rubbing plate, compared to an average 75mm (2.95in) skirt on other couplings, gives the Mk V additional torsional stiffness. Fore and aft oscillation on the new fifth wheel unit is increased from 12° to 15°.
The operation of the Mk V coupler has been simplified, with positive automatic locking of the safety handle.
The dog clip has been eliminated, while the locking mechanism with hook and wedge assemblies now includes a patented spring loaded handle lock.
To unlock and release the kingpin, the driver lifts the handle against the retaining spring and pulls out the handle releasing the kingpin.
The cocked coupler remains ready to accept the kingpin as normal and closes around it when it enters the coupler throat.
The handle springs closed and the spring bias automatically locks the handle into position.
The Mk V Big D coupling has a choice of mounting feet with heights from 154mm (6.1in) to 224mm (8.8in) and two mounting plates.
With a standard mounting, the York coupling can be used on vehicles with a gross combination weight of up to 44.7 tonnes, with a maximum kingpin load of 16.27 tonnes. With a heavy duty mounting, this increases to 65 tonnes gcw and 25 tonnes imposed load.
A seven position 2 4 6kg (4.8cwt) slider version of the Mk V fifth wheel is also available with up to 600mm (23.6in) travel, which supplements York's existing 450mm (17.7in) slider unit.