Norfolk's air suspension
Page 14
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AIR SUSPENSION is a key feature of the large fleet of threeaxle trailers being delivered to Norfolk Line (see p9).
The trailers are built to a common design for two or three-axle operation, and have IMS Osterhout air suspension to improve ride and stability and to remove mechanical linking between bogie axles.
In either form, the 12.2m long, 4m high trailers have capacity for 76cum goods, with internal dimensions of 12.12m length, 2.43m width, and 2.58m height.
By deflating the air suspension, the trailers can be carried on European piggy-back railway services which have a 3.92m overall height limit. It also is useful on ferries as it can be deflated to let the trailers settle rather than bounce in heavy weather.
According to Norfolk Line, the trailers can be converted from two to three-axle layout in about four hours. The trailer is raised from the ground and the two axles are unbolted and loaded on to a special trolley that has been rolled under the trailer, on rails.
The trolley is then removed and the two axles are spaced to make room for a third, new axl between them. The trolley I then returned under the traile raised, and the axles are bolte into position using the holes a ready cut during the origin. construction.
The vehicles were built wit anchor points included for tlthird axle, so re-siting can be ul dertaken quickly.
A single tyre arrangementwi selected, 16x22.5 for tande trailers and 15x 22.5 for the t axle models, although sorr converted tri-axle trailers will r tam n their 16x22.5 tyres un these wear out.