Al's sliding bogie
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An extra axle has been added to the original tandem axle trailer which incorporates a sliding bogie subframe that extends 990mm (3.2ft) to the rear, ensuring the unit complies to the legal spacing requirement of 6.9m (22.6ft) between the rear axle of the tractive unit and the rearmost bogie axle when running at 38 tonnes. When discharging from ISO containers, the bogie can be moved forward to remove any overhang behind the container.
The sliding bogie incorporates four air operated spring loaded locating pins which engage automatically. To extend the trailer, the locating pins are retracted using the emergency air line on the tractive unit which then moves forward until the bogie subframe locks in its new position. To shorten the trailer the pins are retracted and the tractive unit simply reverses back towards the stationary bogie whereupon the locking pins re-engage.
Rubery Owen parabolic threeleaf mechanical suspension is used on the tri-axle bogie conversion and Al claims the sliding bogie conversion, which is the first on a tipping skeletal trailer, has not increased body height.