A New Seddon Tractor for 32 Tons Gross
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AN addition has been made to the heavy-duty range of sixand eightwheelers introduced last year by Seddon Diesel Vehicles, Ltd., Oldham, Lancs. This is the SD4 four-wheeled tractive unit with gross train-weight ratings of 24 or 32 tons, depending upon the power Unit.
The new model has a wheelbase of 9 ft., giving an overall length of 15 ft. 7 in. The standard cab offered with it is similar in appearance to that employed on the other heavy-duty chassis and on the Mk. 15/10 14-ton-gross fourwheeler.
A choice of three power units is available. These arc the Cummins HF6, the Gardner 6LX and the Gardner 6LW six-cylindered oil engines. The Cummins develops 178 b.h.p. at 2,100 r.p.m., with a peak torque output of 495 lb.-ft. at 1,450 r.p.m., whilst the Gardner units develop 150 b.h.p. and 112 b.h.p. respectively at governed speeds of 1,700 r.p.m.
With each of these engines a 16-in.diameter single-dry-plate clutch, hydraulically operated, is employed, and there is a wide choice of gearboxes. The Cummins engine may be supplied with the David Brown 557/480 five-speed direct-top or overdrive-top constantmesh unit, or the 557A/480 overdrive-top box, which has an epicyclic auxiliary section giving 10 forward speeds. Other options with the Cummins engine include Fuller Roadranger 10-speed gearboxes with either direct or overdrive top gears.
Choice of Gearboxes The David Brown 557/480 five-speed and 557A/480 10-speed gearboxes are offered with the Gardner 6LX, whilst the two gearboxes available with the 6LW are the David Brown 557/350 or 557A/350 fiveand 10-speed units.
• A single propeller shaft with Hardy Spicer 1700-series needle-roller joints takes the drive to the rear axle. Here, again, there is a choice of assemblies. When the vehicle is to be operated at 24 tons gross train weight and is equipped with either the Cummins HF6 or the Gardner 6LX engine a Kirkstall spiral-bevel-and-helical double-reduction 9-ton-capacity axle is specified, with ratios of 6.28, 7.01, 7.95 or 9.17 to 1.
When the tractor is to be used at 32 tons gross train weight and with either the HF6 or 6LX engine, an A.E.C. spiralbevel and helical double-reduction 13-ton axle is specified, this having a ratio of B24 7.12 to 1 as standard, with alternatives of 6,22 or 7.92 to 1. With the 6LW engine a Kirkstall 9-ton-capacity worm axle with 81-in, centres is supplied, the 'maximum gross train-weight rating then being 24 tons. This axle is available with ratios of 6.75 or 5.5 to I.
When either of the Kirkstall axles is fitted the rear springs are 54 in. long, with 3-in.-wide leaves. When the A.E.C,
axle is employed, heavy-duty rear springs, 5444 in. long and 5 in. wide are installed, the spring assemblies including five helper leaves. To give the necesiary clearance between the inner tyres and the springs the chassis frame is inswept when the A.E.C. axle is used, the frame width being reduced from the standard dimension of 3 ft. I in to 2 ft. 4+ in.
The . front axle is similar to that employed on the other Seddon heavyduty chassis and 48-in.-long springs work in conjunction with 7-in.-stroke telescopic dampers. Marles 861 cam-anddouble-roller steering gear is specified. Turning circles are 37 ft. to 38 ft., according to the tyres.
A Clayton Dewandre dual-circuit airpressure braking system is employed, with two-line trailer-braking couplings. A trailer brake hand reaction valve is mounted on the steering column. S-cam operated brakes are employed in all instances, the standard front brakes measuring 164 in. by 4 in.
When Kirkstall axles are fitted, 164-in. by 6-in, rear brakes are supplied, but the rear brakes with the A.E.C. axle are 154in. by 7i-in. units. Diaphragm actuators are then employed at both axles, as opposed to the cylinder type used on the other chassis. A Neate multi-pull hand brake acts on the rear wheels. The total brake friction area with the A.E.C. axle is 618 sq. in. and with the Kirkstall axles it.is 460 sq. in.
Bolted construction is used throughout the chassis frame, which has four crossmembers. The side-member pressings are of 1-in.-thick high-tensile steel, with 3-in, flanges and a maximum depth of 104in. Standard tyres are 9.00-20 in. (14-ply), mounted on 6,00T rims with 5.6in. offset. but when the tractor is to be used at 32 tons gross train weight. 11.0020-in. (14-ply) tyres are employed on 7.33V rims with 6.2-in. offset, In each case the wheels are mounted on 10 1-in. studs.
Plastic_s Cab Panels A 50-gal. fuel tank is standard equipment and the electrical system is 24 v. Electrical fittings include a master switch and a C.A.V. condenser relay flasher system with wide-angle side flasher lamps and repeaters at the rear. The flashers are included in the standard home cab specification, which also provides for a heater and demister, roof rack and two windscreen wipers. The home-market cab is of composite construction incorporating plastics panelling, but an allmetal cab is available for overseas.
The SD4 tractor has an overall width over the cab of 7 ft. 11 in. and the laden frame heights measured at the rear axle centre line are 391 in. when the A.E.C. axle and 11.00-20-in. tyres are fitted, and 36 in. in all other cases. Specimen chassis and cab kerb weights are as follows:— With 6LW engine, 557/350 gearbox and worm axle, 4 tons 144 cwt.; with 6LX engine, 557A/480 gearbox and Kirkstall double-reduction axle, 4 tons 17 cwt.; with 6LX engine, 557/480 gearbox and Kirkstall double-reduction axle, 4 tons 16+ cwt.;. with HF6 engine, 557/480 gearbox and Kirkstall double-reduction axle, 5 tons 31 cwt.; and with HF6 engine, 557/480 gearbox, A.E.C. axle and 11.00-20-in. tyres, 5 tons 9 cwt.