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A NEW CONTINENTAL

13th February 1948
Page 38
Page 39
Page 38, 13th February 1948 — A NEW CONTINENTAL
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INTEGRAL construction of body and chassis, employed with success for many years by certain privatecar designers, is now making some headway in the commercial-vehicle field, despite certain difficulties encountered in . its application. An interesting example is a new 48-seater single-deck bus, now being produced ii, Amsterdam by the commercial vehicle section of the famous Dutch marine-engine concern, Kromhout Motoren Fabriek.

One of the main obstacles to the widespread use of the idea is the fact that many chassis manufacturers do not build their own bodies. In the case of the new Kromhout bus, the design is the result of a combined effort by engineers of Kromhout Motoren Fabriek and those of the Verheul bodybuilding works at Waddinxveen.

, Built in Two Works These two factories are about 38 miles apart, and it was agreed that the basic body structure, to which are attached engine, transmission, axles, and steering gear, was to be built in the Kromhout works at Amsterdam, and the rest of the body at the Verheul works in Waddinxveen. This basic bed structure had, therefore, to be strong enough to make the 38-mile road trip from one factory to the other, under its own power.

The basic structure consists of two longitudinal members in channel-section pressed steel, to which are attached a number of dross-Stays, also of channel section. These are welded to the longitudinal members and extend beyond them on both sides, with tapered ends. Side pillars for the .,uperstructure are welded to these ends, and floorboards are attached directly to the cross-stays. This form of construction presents certain advantages. The cross-stays act both as frame members and floor bearers. The last-mentioned must, in normal independent construction, 'be provided in addition to chassis crossmembers. Apart from weigh: reduction, a sounder and stronger ensemble is claimed, as compared with separate chassis and body.

In a vehicle with a separate body, floor bearers, to be strong enough to prevent bending at the ends must be of dimensions that will tend to increase weight and floor height: If, on the other hand', they are made from lighter sections, stiffening brackets are needed at the outer ends. These may cause a twisting effect on the chassis side member if the position of a floor bearer happens to fall between two frame cross-members. This defect does not occur with integral construction, because the floor bearers form a unit and the longitudinal frame member is held in position by it.

The basic bed structure is obviously not designed to support the entire body load when separated from the upper structure, and side walls ate subjected to additional stress, which fact has been taken into account when designing them.

The accompanying diagram shows longitudinal bending stresses to which the complete structure is submitted when under full static load. Vertical lines in the shaded portion represent bending stress at each point over the whole length, as measured from the base A—B.

The four triangles S indicate positions of front and rear spring brackets v which

are the noints of support. Greatest

stress occurs at the outer rear-spring bracket position, which is only to be expected. With normal independent construction, the frame must be designed to withstand this stress on its own. In the present instance, the basic bed structure only ly a small part of this stress, as w shon by the height A—D or B—C, and the remaining stress, as represented by the height from line C—D to G is taken care of by the body side walls.

Stress Distribution Between D and E the bed structure is strong enough to take all bending stresses, without relying on the superstructure. The last-mentioned, on the other hand, looks after most of the stress between E and H, and covers the shaded portion, E F G-1.1 E. road tests w Severe rere made with the Kromhout prototype vehicle. It was taken out first as a bare skeleton, without panels. It is an all-welded machine, bur, after lengthy tests, close inspection of the joints revealed no flaw in this respect. Since that time, the complete vehicle has been put into passenger service, covering daily distances of 200 miles or more, over give-and-take roads. Up to January last it had covered some 50,000 miles. Such a distance as this should be sufficient to give a very good idea of its capabilities and suitability AKromhout six-cylindered oil engine, with a Roots supercharger, is employed.

This unit develops 150 b.h.p. at 2,000 r.p.m. Engine suspension is designed to cut out engine-to-body reactions so far as possible.

The engine is carried on. two ballbearing trunnions located at its centre of gravity. These bearings are carried isolated from the frame on two arms isol by Silentbloc joints Engine torque reaction is absorbed by a torsion bar with o tw universal joints—one attached to an arm on the engiae and the, other to the front axle. The gearbox, mounted centrally, also rests. on rubber pads and the central bearing of the propeller shaft is carried in a rubber ring. Servo steering is employed. Pneumatically operated doors are locat.c1 centrally on both sides of the bus, whilst heating and ventilation are well looked after. Main dimensions are:—Wheelbase, 20 ft. 6 ins.; overall length. 36 ft. 84 ins.; overall width, 8 ft. The five forward ratios are 6.54, 3.08, 1 76 to 1 and 0.636 overdrive. The spiral-bevel gear ratio is 5.57 to 1. Laden weight is 11 tons. In the two experimental buses so far produced, weight reduction has not been carried to extremes, because of a lack of the right materials. Close attention has been devoted to the production of an ensemble that will give longer life to the body nisi] would independent chassis and body construction. The intention now is to extend this form of construction to other types and adopt it for quantity production, to which it seems especially suited.

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Locations: Amsterdam

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