American Engine in Seddon's Biggest
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THE largest vehicle to be built by Seddon Diesel Vehicles, Ltd., Oldham. Lanes, has just been completed, and is powered by an Americandesigned Cummins NHB 600 oil engine. The new vehicle, which is a normal-control six-wheeler, is suitable for a gross vehicle weight of 30 tons or with turbocharged engine a gross train weight of 100 tons. The vehicle has been designed for general haulage work overseas.
The Cummins oil engine is a 12.18-litre (743 Cu. in.) unit with a gross power rating of 210 b.h.p. at 2,100 r.p.m., the maximum torque being 580 lb.-ft. at 1,600 r.p.m. The engine has bore and stroke dimensions of 130 mm. (5.125 in.) and 152.4 mm. (6 in.) respectively. Its compression ratio is 15.5 to I.
Aluminium alloy is employed for the crankcase and cylinder block castings, and the cylinder block contains easily removable wet-type cylinder liners. Alu minium alloy is used for the cylinderhead castings also, the heads being cast in pairs with Stellite exhaust-valve inserts. The fuel-injection system is the wellknown Cummins PT type which eliminates the conventional fuel-injection pump.
An 18-in.-diameter single-dry-plate clutch is employed and this is operated by air pressure. In unit with the engine there is a Fuller Roadranger R960 10-speed gearbox. This consists basically of a fivespeed gearbox with an integral two-speed auxiliary section actuated by air pressure. The gearbox gives forward ratios of 7.43, 5.80, 4.48, 3.54, 2.76, 2.10, 1.64, 1.27, 1 and 0.78 to I. The reverse ratios are 11.26 and 3.18 to 1.
Double-drive Bogie
A two-piece propeller shaft transmits the torque to the foremost axle of the heavy-duty double-drive bogie. This has a load capacity of 24 tons (53,700 lb.). Each axle is a double-reduction unit with hypoid primary gearing and epicyclic hub gears for the secondary reduction, the overall reduction being 8.89 to 1.
The bogie suspension consists of inverted semi-elliptic springs centrally pivoted to large chassis brackets, and axle location and torque reaction are provided by rubber-bushed radius arms. A third differential can he incorporated in the leading axle, if required, for on-the-road use.
The front axle is based on an I-section beam, 41 in. deep and 3f in. wide. The front track is 6 ft. 7+ in. and the rear track is 5 ft. 1 lf in.
Bendix-Westinghouse air-pressure braking is fitted, a dual circuit being used for additional safety. Cam-type leadingand-trailing-shoe units are fitted at all wheels and the drums are 16+ in. In diameter, the front facings being 4 in, wide and the rears 6 in. wide.
The chassis frame has eight crossmembers, being secured by fitted bolts in reamed holes. The main members are fabricated of two channel-section pressings, one inside the other. The outer channels, which are of *-in. steel, are 11 in. deep and have 3-in, flanges, whilst the inner members, which are bolted to the outer sections, are of f-in.-thick steel and have a maximum depth of 9 in. with 3-in. flanges. The top flanges of the side members are flat throughout their length.
Marks cam-and-double-roller steering gear is fitted, and assistance is provided by a Vickers Detroit hydraulic-steering servo. Power for this is provided by a Vickers hydraulic pump mounted.on, and driven by, the engine. The steering ratio is 28.5 to 1.
The tyres fitted to the vehicle are 12.0024 in. (14-ply) or Michelin F.24 Metallic equipment, and they are carried on fourpiece 8.37-in. by 24-in. wheels. These are drilled for 10 1-in.-B.S.F.-stud mounting. The spare wheel is carried at the rear of the frame on a winch mounting. An 80-gal. fuel tank is fitted and this is mounted on the right of the chassis frame. A 24v. electrical system is employed, there being four 6v. 184 amp.hr. batteries. The standard cab is an all-steel unit, suitably tropicalized for operation in hot climates.•
The Seddon chassis has a wheelbase of 18 ft. 6 in., and its overall length is 32 ft. 8 in. Its maximum width is 8 ft. 11 in. There is 22' ft. of uninterrupted frame behind the cab, and the laden frame height at the rear is 3 ft. 6 in. The overall height to tbe top of the cab is 9 ft.
The minimum ground clearance is 11 in., the turning circle is 58 ft., and the estimated maximum road speed is 41.5 m.p.h. (66.48 k.p.h.). The maximum permissible front axle and rear bogie loadings are 7 tons and 24 tons respectively.