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SEDDON reduce the weight and standardize on units

ASWEEPING programme of rationalization has been applied by Seddon Diesel Vehicles, Ltd., to their range of goods vehicles, whilst at the same time the adoption of two-spring two-leaf bogie suspension for all sixand eight-wheeled chassis has, together with other less striking modifications, resulted in significant reductions in unladen weight—no less than 1 ton 2 cwt. in the case of one of the eight-wheeled models. Although the Seddon passenger-chassis range remains unchanged, the goodsvehicle programme is now restricted to models of from 12 to 24 tons gross weight.

In view of their specifications, the Seddon sixand eight-wheeled models are among the lightest of their type produced in this country. For example, a single-drive eight-wheeler with Gardner 6LW engine has a wet chassis-cab weight of 5 tons 17 cwt. and this includes the spare wheel, eight-wheel brakes and power-assisted steering. This weight is only 10 cwt. above that of the equivalent single-drive six-wheeled model and a mere 30 cwt. mole than that of a 6LW-engined 24-ton-gross tractive unit.

Before dealing in detail with the new Seddon models, mention should be made of the new system of model-type nomenclature. which has been adopted. In future, each model will be identified by three symbols: the first will indicate the gross vehicle weight, the second the number of wheels and, in the case of double-drive models, the number of wheels driven, and the third symbol will indicate the engine.

Thus the latest Seddon four-wheeled range consists of five load carriers arid eight tractive units which, in turn, are derived from two basic load carriers and three basic tractive units. The load carriers are the 12/4/354 and 12/4/370 12-ton-gross models and the 14/4/400, 14/4/5LW and 14/4/6LW 14-tonners, The 12/4s are available with wheelbases of 9 ft., 11 ft. 6 in., 14 ft. 6 in. and 16 ft. 6 in., the 354 models having the Perkins 6.354 engine and the 370 models being powered by the Leyland 0.370 unit. The 14/4 vehicles have wheelbases of 11 ft. 6 in., 14 ft. 6 in. arid 16 ft. 6 in., and the available power units are the Leyland 400-S. the Gardner 5LW and the Gardner 6LW.

Six-wheelers are the 16/6/354 and 16/6/370 16-ton-gross models, the new 17/DD6/354 17.5-tonner and its 18-ton-gross derivative, the I8/DD6/400—both these models have the Eaton 30DS tandem-drive—the 20/6/400, 20/6/5LW, 20/6/6LW and 20/6/LX single-drive 20-ton-gross chassis and the 20/DD6/6LX double-driye.design. ' There are three eight-wheelers: the singledrive 24/8/6LW. and 24/8/6LX models and the 24/DD8/6LX double-driver. The 20/DD6/6LX and 24/DD8/6LX both have the new Moss two-speed tandem drive.

Tractive Units Tractive units include the 16/4/354 16-tonner and its automatic-coupling equivalent, the 16/4/A354; the 18/4/370

18-tanner and the 18/4/A370 with automatic coupling: the 20/4/400 and 20/4/5LW 20-tonners: and the 24/4/6LW and 24/4/6LX 24-tonners.

AU tlw six-wheelers are offered with wheelbases of 12 ft. Gin.. t4 ft. or 17 ft., whilst the eight-wheeler options are 14 ft. or 17 ft. 9 in. The tractive units have wheelbases of 8 ft., except for the 24-ton-gross models, the wheelbases of which are 9 ft.

Despite the impressive number of models in the latest Seddon range. rationalization has enabled the number of different units employed to be reduced to a marked degree. Only six engines are used (Perkins 6.354, Leyland 0.370 and 400-S. and Gardner 5LW. 6LW and .6LX), three gearboxes (Albion 611241 and David Brown 552 and 657), two single-speed axles (Seddon 8-ton and Moss 10-ton), two two-speed axles (Eaton 16802 and 18802). three trailing axles (Seddon. Moss and Eaton), two sets of double-drive axles (Eaton 30DS and Moss two-speed), two front axles (Seddon 4-ton and Kirkstall 5-ton), one dual-rate front spring, one type of bogie suspension and one cab.

Improved Specifications

Al] the models in the current range are derived essentially from previous designs but, in addition to significant savings in weight as regards the heavier types. specifications generally have been improved, particularly so far as frame strength and braking are concerned.

Perhaps the most changed of the new models is the 24/DDE1/6LX which, in its old form, was known as the DM. The chassis-cab wet weight of the DD8 was 7 tons 6.75 cwt.. and the new version is 1 ton 1.25 cwt. lighter than this in its 17-ft. 9-in.-wheelbase form. Although the basic chassis-frame assembly, engine and gearbox remain the same. most of the other major components are new, the most striking changes being evident at the rear bogie. As with all the current multi-wheel Seddons, the latest version of the Seddon two-spring two-leaf bogie suspension is employed. this having been introduced in its original form at the Scottish Motor Show last November. In addition to the weight saving and articulation advantages of this bogie suspension, the design has another great asset in that it can be used unchanged throughout the Seddon range, the only modification necessary being to allow for the 33.125-in.-wide frames of the lighter models, the heavy frames being 37 in. wide.

Plain Tapered Springs In its finalized form the suspension has plain tapered leaves which, as before, are slotted at their outer ends to engage with shaped pads in the axle brackets. The springs arc underslung and vertical thrust is taken by large buttons. At the centre of each two-leaf assembly a spring-carrier casting is clamped to the spring and this contains two phosphor-bronze bushes with a 1-in, gap between them.

A machined steel sleeve with an outside diameter of 3.5 in.

and an inside diameter of 2 in. passes through the bushes. This is clamp-bolted to the pivot-bracket casting which straddles the spring-carrier. A full-width tie rod passes through the sleeves on each side to give rigidity to the bogie assembly, whilst there are greasers on each of the pivot-bracket castings to permit the sleeves to be filled with EP90 oil.

The pivot-bracket assemblies themselves are considerably different from those of the original design, being now T-shaped steel-plate fabrications with the pivot castings bolted to their tower faces. Originally, the pivot brackets were bolted to the frame to provide a single-point contact above the bogie centre line, but the new arrangement avoids stress concentrations, with obvious benefits to the frame life. Back-to-back channels provide a cross-member at the bogie centre line, also forming the anchorage points for the rubber-bushed torque arms.

Front-bogie Suspension Important changes have been carried out to the front-bogie suspension of this and the other two eight-wheeled models. On the original vehicles the four front springs were all shackled at their rear ends, but this was found to produce steering-geometry complications because the axle steering arms were, linked directly to a relay lever positioned near to the front end of the second off-side spring, this relay lever being used also to directly transmit the power from the steering servo ram.

Whilst this, arrangement gave minimum interference to the second-axle steering through road shocks, in the case of the front axle its arc of travel was opposed to that of the forward end of its draglink. To overcome this the leading-axle springs have,, in effect, been reversed so that their shackled ends are to the front, this layout also permitting the use of a single intermediate hanger bracket. With the newer arrangement both axles move in approximately the same arc as the axle-ends of their clraglinks, so giving far more accurate steering geometry,. with subsequent benefits in respect of reduced steering effort and improved tyre life.

To return to the rear bogie: in the case of the 24/DD8/6LX (and also the 20/DD6/6LX) the new Moss two-speed doubledrive assembly is employed, details of this design having appeared iri our issue of August 17.

As before; eight-wheel brakes are standard on all the 'Seddon eight-wheelers, but whereas the original versions had Kirk stall 16.5-in.-diameter cam brakes, 4 in. wide at the front and 6 in. wide at the rear, the latest models have Girling 15.5-in, cam brakes, which are 4.25 in. wide at the front and 7.0 in wide-at the rear, giving a total lining area of 1,356 sq. in.-over 300 sq. in. more than that of the original design. Handbrake performance has been improved on the new models by 'the use of a Neate NBC 9 multi-pull lever, this type of handbrake being standard on all those of the new Seddons which have full air-pressure braking.

The two single-drive eight-wheelers have an almost identical specification' to the double-drive model: the 6LX-engined version differs only in respect of the rear axles, a Moss 10-ton singlespeed assembly being. employed in conjunction with a Moss trailing axle. The standard ratio for the driving axle is 6.14 to 1. The less powerful 6LW-engined model has an Eaton 18802 two-speed axle and Eaton trailing axle, the ratios being 5.14 and 7.02 to 1. Unlike the LX versions, which have the David Brown 657. six-speed overdrive-top gearbox, the 24/8/6LW has the David Brown 552 five-speed direct-top box. The 17-ft. 9-in.-wheelbase version of the 24/8/6LW has a chassis-cab weight of 5 tons 17 cwt., while the equivalent weight of the 24/8/6LX is 5 tons 19.5 cwt.: 14-ft.-wheelbase versions of all three eight-wheelers weigh 1 cwt. less than the double-drive models.

Five 20-tonners The five 20-ton-gross six-wheelers are very similar in general design to the eight-wheelers, having the same basic chassis frame, rear bogie, braking system, cab and so forth. The lightest of these six-wheelers is the 14-ft.-wheelbase 20/6/400, which has a Leyland 400-S engine, Albion five-speed constantmesh gearbox (with the option of a sixth overdrive ratio), Moss 10-ton 6.83-to-1 spiral-bevel axle and Moss trailing axle, a braking area of 1,092 sq. in., 10.00-20 (12-ply) front tyres and 9.00-20 (12-ply) rear tyres. In chassis-cab form, this weighs 5 tons. The 17-ft.-wheelbase version weighs 1 cwt.' more.

n36 To compensate for the reduced governed speeds, the 5LWand 6LW-engined versions have the Eaton 18802 two-speed axle with the same choice of ratios as are available in the 24/8/6LW. The gearbox also is different, being the David Brown 552 five-speed direct-top unit. The 17-ft.-wheelbase model with the 5LW engine weighs 5 tons 6.5 cwt. and the 6LW-engined version weighs 2 cwt. more than that.

When the Gardner 6LX is fitted, the David Brown 657 six-speed overdrive-top gearbox is used in conjunction with the Moss 10-ton driving axle and Moss trailing axle, whilst the double-drive 6LX-engined model has the Moss two-speed tandem set-up. The double-drive six-wheeler has a chassis-cab weight of 5 tons 15 cwt., whilst the single-drive version with the LX engine .has an equivalent weight of 5 tons 9 cwt.

Lighter components are used in the two new double-drive six-wheelers, the chassis-frame side members being 9.I25-in. by 2.75-in. by 0,3125-in. channel-section pressings, compared with the 10.875-in. by 3-in. by 0.3125-in, members of the heavier sixand eight-wheelers. The frame width also is different: 33.125 in. compared with' 37 in.

The braking system too is different, being of the Clayton Dewandre-Girling air-hydraulic type with an Airpak air actuator. The front brakes are 16-in. by 3-in, units and the rear15.5 in. by 6 in., all being, of the two-leading-shoe type. The total effective frictional area is 908 sq. in.

Eaton Tandem Drive

When the Perkins 6.354 engine is fitted, a David Brown 552 five-speed direct-top gearbox is employed and the gross weight is limited to 17.5 tons. With the Leyland 400-S the Albidn fiveor six-speed gearbox is specified and the gross weight is 18 tons. Apart .from the allowance for the reduced frame width, the bogie suspension is identical to that of the heavier models hut the driving axles. are the Eaton 30DS spiral-bevel tandem type incorporating a lockable third differential. This is believed to be the first time that this tandem-drive combination has been employed in a British production vehicle. As used by Seddon in their two six-wheelers, the reduction ratio is 7.17 to

1-the lowest available. .

Both these six-wheeled -types have 8.25-20 (12-ply) rear tyres and 9.00-20(1 2-ply) front, and the chassis-cab weights range from 4 tons 7.5 cwt. for the -14-ft.-wheelbase 17.5-tonner to 4 tons 10 cwt. for the 17-ft.-wheelbase 18-tonner.

The two 16-ion-gross six-wheelers have the same chassis frame assembly as the double-drive models, this assembly being appreciably heavier than that employed on the versions which they replace, which had 8.125-in. by 2.75-in. by' 0.25-in. frames and York third axles. The 16-tanners, which are available with either Perkins 6.354 or Leyland 0.370 engines, have a similar type. of braking system to that of the double-drive chassii, except that the rear brakes are 15.25-in. by 5-in, units, giving a total frietional area of 776 sq. in.

The bogie is available with either a Seddon 8-ton spiral-bevel axle and Seddon trailing axle or an Eaton 16800 two-speed axle and Rubery Owen trailing axle: the ratio for the Seddon driving axle is 6.83 to 1, whilst the Eaton axle has ratios of 5.62 and 7.82 to 1. The 14-ft.-wheelbase chassis with the Perkins engine has a chassis-cab weight of 4 tons, whilst the 17-ft.-wheelbase model with the Leyland unit weighs 4 tons 2.5 cwt.

Four-wheelers

The various four-wheeled models in the latest Seddon range do not differ greatly from designs which had previously been produced by this concern. The 14-ton-gross models, however, have 37-in.-wide chassis frames and full air-pressure braking with Girling cam-actuated units giving a total lining area of 666 sq. in. With the Leyland 400-S engine the Albion gearbox is employed in conjunction with the Moss 10-ton 6.83-to-1 spiral-bevel axle: with either of the Gardner engines (5LW or 6LW) the David Brown 552 direct-top box is employed with the Eaton 18802 two-speed axles, the recommended ratios of which are 5.14 and 7.02 to I. The chassis-cab weights of these I4-ton-gross four-wheelers range from 4 tons .3 cwt. in the case of the II-ft. 6-in.-wheelbase Leyland-engined model to 4 tons 11 cwt. for the 16-ft. 6-in.-wheelbase chassis with the 6LW engine.

Both 12-ton-gross four-wheelers have vacuum-hydraulic (Continued on page 83)

braking and 33.125-in.-wide chassis frames and are equipped with 9.00-20 (12-ply) tyres as opposed to the 10.00-20 (12-ply) equipment ot the 14-tonners. Power-unit options are the Perkins 6.354 or the Leyland 0.370 and Seddon 8-ton or Eaton 16800 two-speed axles can be•speeified. The 9-Ft.-. 11-ft. 6-in.and 14-ft. 6-in.-wheelbase versions have 8.25-in. by 2.75-in. by 0.3125-in, chassis frames, but the 16-ft. 6-in.-wheelbase versions have 9.125-in, by 2.75-in. by 0.3125-in, side-members: these frames are heavier than those of the Mk. II model, which these new 12-boners replace the earlier design having had a 0.25-in.thick frame. Chassis-cab weights range from 3 tons 6 cwt. to 3 tons 10.5 cwt.

The new series of four-wheeled tractive units follows the same basic pattern as the range of load carriers, except that the Iwo models for use with automatic coupling gears have vacuum-hydraulic braking. The 16and 18-ton models are available with singleor two-speed axles, whilst two-speed axles are standard in the 20-tonner with the Gardner 5I.W engine and in the 24-tonner with the Gardner 6LW unit.

Front these brief descriptions it will be seen that the latest Seddon goods-vehicle range very fully covers the payload capacities from 8 tons to 17-5 tons with a comprehensive choice of specification and size, despite a reduced number of available units. All the new models follow the usual Seddon pattern of providing good value for money and good driving conditions. the latest cab being a comfortable, attractive assembly which was originally introduced last year on the old Mk. II I2-tongross four-wheeler. This cab has plastic panels over a timber frame and a recent innovation is the use of a one-piece curved windscreen in place of the former two-piece screen. As a further concession to the driver, hydraulic steering servos are standard equipment on 01 rigid vehicles of 20-tons-gross rating and above, this servo being available at extra cost on the smaller rigid models and tractive units.

Six examples from the new range will be seen on the Seddon stand at Earls Court, these being a 14-ft. 6-in.-wheelbase 12/4/354. a 17/DD6/354 and a 20/6/400, a 24/DD8/6LX in chassis-only form and two tractive units—a 24/4/6LX (in special 8-ft. 9-in.-wheelbase form for British Road Services) and an 18/4/8370. Other Seddons at the Show will include a 12/4/370 four.wheeler and a special recovery vehicle based on a 12-ton chassis built for Adams and Adams, Ltd., both of which will be in the Demonstration Park, a 12/4/354 on the Homalloy stand. and a 16/6/354 on the Pilot stand.