How the NFC is selecting 8-tonner
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Page 47
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by CM reporter
THE National Freight Corporation, whose design participation led to the development of the Scammell Crusader, is now engaged in a 38-tonne tractive unit project to provide its operating companies with a vehicle for use in Europeincluding the UK.
Last year the NFC started the exercise by consulting with its operating companies to produce a basic spec for a heavyduty two-axle tractive unit capable of operating up to this gross combination weight. It then invited 12 manufacturers to submit detail specifications to meet the Corporation's requirements. With Scania and BLMC submitting two vehicles each, the NFC is now considering 14. The main points of these are listed in the accompanying table.
The NFC specification called for a unit capable of pulling a 12.2m semi-trailer and operating at 38 tonnes gcw (38,000kg). The unit had to be able to carry an imposed weight of 104 tonnes (10,500kg) with the centre-line of the kingpin 11,0m from the extreme rear of the trailer, and all within 15m overall. The design weight of the rear axle had to be not less than 11 tonnes (11,000kg) and the front axle not less than 7 tonnes (7,000 kg).
Road performance was set at a maximum road speed of not less than 60mph (96kph) on the level, in still air conditions, with a gradient ability of 1 in 6.23 (16 per cent).
Manufacturers were invited to state the average mileage life expected of the corn ponents before replacement became necessary.
Cab noise level was not to exceed 89dB(A) measured at the cab centre, at head level. But the NFC stressed that quieter conditions should be attempted.
The minimum power to weight ratio has been set at 7bhp per ton (5.25kW/1000kg) and the fuel tank must have at least a 70-gallon capacity.
The Berliet TR280 and Leyland Marathon have been offered with three optional axle ratios and the Ford HA4230, Scania LB140 and 110, Seddon 280 Mk HI and the Scan-mei] Crusader with two optional axle ratios.
Most manufacturers have achieved the cab noise levels with ease, though Mercedes and Volvo did not quote any figure in their submissions. Others gave only one, either with the windows opened or closed. Chrysler, DAF and Seddon were the only ones to quote two figures. The lowest rating with windows closed was claimed by Berliet at 66dB(A). With the exception of Chrysler, Foden and Scam-, men, all the specs offered tilt cabs.
NFC has not yet settled on its final choice. It could now be delayed pending the outcome of its Middle East vehicle (see page 17 of this issue).
Other points from the NFC's requirement specification include : A cooling system of the "noloss" or "'sealed" type, is preferred and if not standard is to be offered as an option. Systems incorporating additional means of temperature control through the fan drive or by means of radiator shutters are to be offered, if available, as optional extras. Where Varivane and Kysor radiator shutters are not offered as standard options these are to be quoted for as alternatives.
An automatic or semi-automatic transmission may be offered as an alternative to the conventional clutch and gearbox.
The unit is to be equipped with B.8.0 x 20 x 6.8 in offset, three-piece, 10-stud fixing wheels fitted with 11.00-20 H.L.C. radial tyres or alternatively 7.50 x 22.5 single-piece wheels fitted with 11.R-22.5 tubeless tyres.
An engine exhaust brake is to be offered as an additional option. Where the secondary braking system includes braking on the unit rear axle, means of modulation so that the braking force at this axle cannot exceed that obtainable on full service brake application throughout the range of load or road/tyre conditions is to be offered as an alternative, if not standard equipment.