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Turbocharged 24-ton artics from Seddon
Page 37
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• A new 24-ton Seddon tractive unit designated the 24:Four powered by the Perkins T6.354 turbocharged 5.8-litre engine will be displayed at the Scottish Show next week. List price is quoted as £3625.
The turbocharger and the associated airto-air intercooler adds comparatively little weight to the 6.354 engine, yet increases power output to I55bhp, enough to meet the autumn 1972 law on performance standards at 24 tons gvw. Maximum torque is 376 lb ft — about 45 per cent more than with the normally aspirated engine.
In designing the new tractive unit reliability has been considered more important than sheer lightness. The engine drives via a 14in.-diameter single-plate clutch and a simple six-speed constant-mesh ENV gearbox with an overdrive top gear to a Seddon hub-reduction axle as used in the 32-ton units. The standard reduction ratio is 7.25 . to 1 and the plated weight is limited to 10 tons by the springs and tyres used. The front axle is plated for 5 tons.
The gearbox ratios are 6.52, 3.74, 2.36, 1.48, 1.0, and 0.85. The reverse gear ratio is 6.79 to 1. A remote change-speed mechanism is used, the vertical gear lever being located beside the driver's seat.
Spring brakes, used for the first time on a Seddon truck, are fitted on the rear axle and replace the parking brake. The footbrake has dual compressed-air circuits. One line serves the tractor brakes and the other line the service brakes. Additionally there is a completely separate third line, operated by a separate lever and connected to the secondary diaphragms of the dual brake chambers on the tractor's front axle and the trailer. Both front and rear wedge-expanded Girling brakes on the 24:Four tractive unit are of 15.5in. diameter and 7in. wide. Laminated copper-steel tubing is used for all the airpressure lines.
The 24:Four's chassis frame is the same as that used for the Seddon 13: Four series of trucks, but the springs are similar to those fitted to the tractive units of the heavier 16:Four range. Typical weight in full running trim with all couplings and spare wheel is, at 4.85 tons, light for a 24-tanner.
Other model changes to Seddon vehicles announced for 1972 include a Burman recirculating-ball heavy-duty variable-ratio steering gear to be fitted to all Seddon 32:Four tractors to improve their handling precision and lighten the effort. Powerassisted steering, when specified, is still Adwest cam and roller.
The facia panel below the windscreen is now flanged and sealed, so the moulding which covers the windscreen-wiper mechanism is more rigid.
A short-wheelbase (I2ft IM.) version of the 22 DD6 V8-engined double-drive sixwheeler has been added to the present six-wheeler wheelbases of 16ft in. and 17ft 7in.