New Seddon Short-wheelbase Model Appears
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Built for Tipping and Semi-trailer Haulage, a g-ft. Chassis with Perkins Oil Engine Weighing Unladen Under 3 tons SINCE the Seddon lorry, introduced in November, 1938, went into production, almost precisely a year ago, no fewer than 75 have been sold. The actual vehicle which The Commercial Motor road tested (the report appeared in our issue dated June 9, 1939) has now completed 50,000 miles.' Judging by reports from operators and repeat orders that have been received by the maker, Foster and Seddon, Ltd., Pendleton, Salford, Lancashire, the Seddon has proved eminently successful.
Now a new type has made its appearance. It is a short-wheelbase chassis for serviee as a tipping lorry, weighing under 3 tons, or as the tractive unit of a 9-10-ton articulated outfit. The production model has a .9-ft. wheelbase and is standardized with a five-speed gearbox. Basically it follows closely the original design, and is, of course, powered by the Perkins P6 sixcylindered 85 b.b.p. 4.73-litre oil engine.
For the sort of service for which this type of chassis is destined, sturdiness is of first importance. This has been fully realized by its designer, and evidence of the fact is plentiful. For instance, from their virtual mid-points to the extreme rear, the frame side members have an undiminishing depth of 8 ins., whilst the two cross-members completing the square over the rear axle are of the same dimension.
In a forward direction they taper gradually to 4 ins, at the front. For constructional strength the main crossmembers are gussetted, above and below, to the longitudinals. To support the power-unit a V-shaped subsidiary frame is employed.
The rear springs are shorter than on the long-wheelbase model and are of the progressive type. The front ones are identical with those of the fellow chassis.
Changes have been made to the brake system of both models. Vacuum assistance is no longer used, the Bendix shoe-assemblies being actuated directly —by Lockheed hydraulic means in the case of foot application and mechanically by the hand lever. In the latter connection, an improved rear hook-up has been incorporated.
Between the near and off-side rear brakes a compensator has been introduced and this, with its bell-crank, is now carried roughly in line with the rear-axle centre instead of being at a -lower level as formerly. No trouble should be experienced with the new .compensating link, and fitments on unsprung parts, as maintenance engineers are well aware, are by no means unidentified with wear and tear.
Brake Compensator Features
Composed of a high-grade alloy, it is of girder section, and the anchor-pin and arm-spindle bearings measure in. diameter by 2i ins, long. Each comprises two bronze bushes, with an annular space between into which lubricant can be fed from a grease nipple.
A new design of brake drum is also used at both front and rear. Here again no attempt has been made to cut down weight: Of chromidittm iron botls drums are sturdy castings provided with adequate circumferential ribs for rigidity and heat dissipation. That at the front is now dished and should be even stronger than formerly. Friction areas are wholly adequate.
Remarkably compact, the new fivespeed gearbox provides an overdrive top ratio and an emergency first gear. All constant-mesh wheels, which include the third_ and fifth-speed pairs, have helical teeth. The over-all ratios afforded in conjunction with the 6.28 to 1 axle are 4.83, 6.28, 12.81, 21.85 and 38.37 to 1 whilst reverse is 37.45 to 1.
With regard to the final drive, the spiral-toothed crown-wheel and bevel. areof copperized steel. The feature of this material is that the soft-surfacing results, according to claims, in an ultimate tooth bed of an accuracir approaching more nearly to perfection than is practicable by other commonly used means. The teeth measure (in a straight line) approximately 2 ins, long, whilst the crown wheel is no less than in thick, measuring from tooth tip to back face. There should certainly, be a minimum of distortion. To relieve the bearings of excessive thrust, under conditions of momentary overload, a crown-wheel pad is provided.
Transmission from gearbox to axle is by a one-piece Layrub shaft with rubber-type universal joints.
First of the new Seddons to be built, and, incidentally, not strictly standard in that its wheelbase is 10 ft., the vehicle pictured is a tipper with Edbro hydraulic gear, made by Edwards Bros. (Tippers), Ltd., Bolton. It is in the service of S. Taylor Frith and Co., Ltd., and is being operated under particularly arduous conditions. It is working in connection with quarrying operations in the exceptionally hilly country in the vicinity of Buxton, Derbyshire.
: Some of our illustrations show it taking on a load of limestoiZ from a hopper. This, we understand, is used for mortar for the building trade, and for agricultural purposes.
After loading, the vehicle was weighed in our presence and scaled 9 tons 9 cwt. gross, representing a payload of 6 tons 6 cwt. This is a typical normal load, and at this weight figure, according to the information imparted to us, it consumes oil fuel at a rate equivalent to 21.6 m.p.g.
Excellent Hill-climbing
From the driver's cab we gained an impression of its hill-climbing capabilities. A gradient of about I in 6-7 was ascended at a steady 3-4 m.p.h. in first gear with power to spare. In reply to a few questions relating to his own views on the vehicle the driver told us
that he was well satisfied with its performance and experienced no difficulty in negotiating any of the hills that abound in that locality. He spoke in favour of both engine and gearbox, saying how be appreciated the over• drive when running with no load.
As mentioned earlier, this new chassis, in respects other than those mentioned as distinctive, follows the original design, and certain of its features are worthy of recapitulation. One of the most outstanding is the spaciousness of the •cab.
Considerably greater area of floor than is usual has been obtained by the simple, but ingenious expedient of shaping the wing valances to match the movement of the front wheels as they are locked from one direction to the other. Commonly, the shortest distance of the tyre from the frame, when the wheel is at full lock, governs the position of the valance for its full length.
On the Seddon the valance, viewed from above, resembles a wide V, with the angle close to the line of the swivel pin and only the ends near the frame longitudinals.
Another point of special interest is in connection with the steering gear itself. The reduction between steering wheel and drop arm is unusually small, with the result that the action is notably quick. No more than three turns swing the stub axles right through their angular travel which is entirely ade
quate. Nevertheless the steering is anything but heavy, a fact which, no doubt, may be largely ascribed to the tapered-roller swivel-pin bearings which are a feature of the Timken axle standardized.
. We referred above to distinctive : features of the new chassis. This requires a: little clarification. A number of modifications of the old design constitutes improvements wl.ich are also now incorporated in the long
wheelbase model. For instance, the various changes effected in the brake systems apply to both chassis.
In general, however, the original design has proved so successful that the need for alterations has been small.