Longer wheelbase for Scammell Trunker
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• To allow operation with a wider variety of trailers, as well as to afford better accessibility to chassis components, Scammell Lorries is producing a revised and longer version of the current 10ft wheelbase Trunker 2 lightweight tandem-steer three-axle tractive unit. Designated the Trunker 3, it is plated for gross weights up to 36 tons and its wheelbase is 11ft 6in.
A new chassis frame is used, the side-members now being 9.5in. in depth, lin. deeper than on previous models, and this has allowed local box-reinforcements to be eliminated. As a result, brake piping is much easier to trace and all unions and bolts are quickly accessible. The amount of piping has been reduced by grouping the control valves together on the frame-side beneath the cab. The compressed-air 'circuit now includes a condenser with automatic draining.
Relay valves are used in the brake circuits to eliminate delay which normally occurs in air pressure systems, and spring-brake chambers apply the front and driving axle brakes for parking.
The vehicle is powered either by a 200 hp 11.1-litre Leyland 680 or Rolls-Royce 220 hp 12.17-litre six-cylinder diesel engine. With either engine the standard transmission is a 17in. diameter Borg and Beck single-plate clutch and six-speed constant-mesh gearbox. An optional 10-speed semi-automatic gearbox is available. A double-reduction driving axle unit with secondary reduction by epicyclic gearing in the hubs is used.
The brakes on the driving axle are 7in. wide while those on the steering axles are 6in. wide. The total braking area is 1048 sq.in.
With a Leyland engine, the Trunker 3 has a wet unladen weight, complete with fifth-wheel coupling, of 5 tons 16cwt. When fitted with the Rolls-Royce engine the weight is 6 tons lcwt.
The new Trunker will take a maximum permissible imposed load of 11+ tons on its coupling. It will couple to crdinary 40ft trailers within the 15-metre overall length limit and yet its wheelbase is long enough to accommodate trailers with long front overhangs—up to 5ft 4in.