TWO NEW DENNIS UNDER FLOOR-ENGINED CHASSIS
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WO new underfloor engined chassis, the Stork 3-tonncr and Lancet U.F. passenger model, will be exhibited by Dennis Bros., Ltd., Guildford, at Earls Court. Apart from its modified engine, the Lancet U.F. bears no resemblance to the Dennis Dominant, which was shown in 1950, and the underfloor-engined 3-tonner is novel in Dennis goodsvehicle design.
The Stork has been built basically for special bodywork, having a dropped extension for a low entrance at the front and affording more body space than normal. Such a chassis would be suitable for a travelling shop or a pantechnicon, a dropped rear extension being an alternative frame arrangement.
In this respect the goods and passenger models are alike, because the Lancet has level and parallel longttudinals between its spring extremities and dropped extensions are bolted on at the front and rear. The passenger model is planned in all respects for weight saving, and single rear tyres arc available. The rear axle is specially designed and weighs only 9 cwt. as a
unit. Built for the 30-ft.-long, 8-ft.wide body, the chassis is estimated to weigh under 4 tons.
New Perkins Engine
The Stork employs the new Perkins four-cylindered horizontal oil engine, and has hydraulic operation for the brakes, clutch 'and accelerator control. It is available with wheellaases of 11 ft. 8 ins. and 10 ft. 6 ins., and the overall length of the frame is 22 ft.
51 ins. The main side members start I ft. 11 ins, ahead of the axle; in front of which is the dropped extension carrying the steering box and driving controls, and providing a frame height of l ft. 4 ins. at the cab entrance.
To stiffen the junction point, a light full-width cross-member of Z section, 1 ft. 2 ins, deep, is employed, forming the riser between the cab and body. A remote-control selector for the gearbox is attached to the stiffener.
A flat-tube radiator with pressed-steel shell and pressed-brass top and bottom tanks is interposed between the stiffener and front axle and is supported by semi-flexible units below frame level. Cooling is assisted by a light six-bladed fan driven direct from the engine and working in a cowl.
Engine Within Frame
The Perkins horizontal fourcylindered oil engine developing
52 b.h.p. at 2,4043 r.p.m. and 123 lb.-ft. torque has a wide sump, with filter attached, and the fuel-injection pump is driven from the rear of the camshaft. It is mounted within the longitudinals, below frame level, and the crankshaft is in line with the centre of the chassis ' A 10-in.-diameter dry clutch and four-speed gearbox are attached as a unit which is supported on a two-point mounting, employing a single bracket attached to the centre of the timing case, and at a single point at the rear.
The clutch pedal is linked to a Dennis cylinder for hydraulic operation of the withdrawal gear, and the fuel. injection pump is controlled through a hydraulic arrangement from the accelerator pedal. A two-piece shaft links the gear lever to the selector cover on top of the gearbox, and the universal joint in the shaft comprises two knuckle pins arranged at right angles.
A hypoid final drive of 5.57 to I is used in the Stork and the axle case is banjo type in shape, formed from tubes attached to a central casting_ The braking system is conventional, employing Girling .hydraulic master and operating cylinders actuating twoleading-shoe units at the wheels. Th.': drums are 14 ins, in diameter and the shoes 21 ins. wide at the front and 3i ins, at the rear. The standard tyres are 32-in. by 6-in, truck type, but 29-in. by 7-in. and 27-in. by 6-in. equipment is available.
The 12-gallon fuel tank is supported on the near side of the frame behind the front wheels and the battery is carried on the opposite longitudinal in front of the rear axle. The dynamo, mounted above the front axle inside the frame, shares the fan drive. The spare wheel is carried below the rear overhang.
The main longitudinals of 6-in. depth, 21-in, flange and P6-in. section arc spaced 2 ft. 61 ins, over the outer edges. Allowing for a bulkhead behind the driving seat, an 18-ft.-long body can be provided. At the twin rear wheels the Stork chassis is 6 ft. 5i ins, wide when fitted with the standard tyre equipment. It is canmated that in licensing condition the chassis weight will be 1 ton 15 cwt..
The Lancet U.F. is fitted with the Dennis 7.585-litre direct-injection oil +engine with normal aspiration. Modifications to the manifolding and governed speed have improved the output to 108 b.h.p. at 2,000 r.p.rn. Its torque is 328 lb.-ft. at 1,250 r.p.m.
A new cylinder block has been designed, to reduce overall height of the unit in its horizontal form, and there has been a rearrangement of components, the water pump and dynamo sharing a tandem drive on top Qf the crankcase. All timing gear is arranged at the flywheel end of the engine. There is an 11-in, clearance below the engine and the clutch
housing, when the springs are fully deflected, and 9.00-20-in. tyres fitted.
The engine is offset in the frame, with the cylinder block below a side member, and the crankshaft is in line with the final drive of the rear axle. The engine-oil filter, neck and radiator filler are extended to the near side of the frame and a 35-gallon ftiel tank is arranged on the same side. The new Dennis passenger chassis employs a two-plate 'dry clutch and five-speed gearbox having a preselective overdrive, with a ratio of 0.69 to 1.
These units are attached direct to the engine, but the clutch is hydraulically operated from the pedal and the Dennis standard gearbox is turned from the normal horizontal position so that the selector cover is nearer the 'op. This provides an easier linkage with the selector.
A special two-piece axle case with spiral-bevel gear offset from the centre. and epicyclic gear reduction at the outer ends of the driving shafts, has been designed for the Lancet CIF., and it has saved a great deal of weight. According to the manufacturer, three axles of this type have been fitted to buses operating in a hilly northern area and an aggregate mileage of 900,000 has been covered without failure. The overall ratio of the double reduction is 6.06 to 1.
Dennis Bros., Ltd.. intends this vehicle to be available with either single or twin tyres at the rear, consequently the spring perches are not exceptionally widely spaced, as they would be if single tyres were standard equipment. With single rear wheels having fully offset rims, the brake drums are not covered and this should prevent overheating.
Hydraulic Reservoir
A Lockheed continuous-flow braking system is employed, with an accumulator having the nitrogen under pressure in a bag contained in a metal cylinder. The pump is mounted forward with the engine radiator and shares the belt drive for the fan. A large header-tank reservoir, supplying the clutch and brake hydraulic system, is mounted adjacent to the driving seat.
The rear brake shoes are camshaftoperated, the cross-shaft and levers at the rear being attached to the axle, whilst at the front the hydraulic cylinders are mounted on the stub back plate. The drums are 17 ins, in diameter, with 3-in.-wide shoes at the front and 61-in.-wide shoes at the rear.
The radiator for the passenger model is similar in pattern to that used in the Stork, having pressed-brass top and bottom tanks, a light cowl and sixbladed pressed-steel fan. It is a flattube-stack type, flexibly mounted in the frame ahead of the front axle, and has a frontal area of 6 sq. ft: The cooling system is arranged for pressure operation. It is shielded from mud by the deep cross-member which forms the riser between the front platform and main-saloon floor level.
A light sheet-steel assembly encases the steering column, instruments, juncB6 tion and fuse boxes, wiring, tubing and other equipment associated with the facia and electrical control panels. This assembly also includes an inclined floor in front of the driving seat and the pedal gear is carried on brackets outrigged from the front extension.
Maintaining Headroom
By employing the dropped extensions at both ends of the frame, the front and rear of the roof of the Lancet can be swept lower without impeding headroom. Passenger visibility is improved by raising the saloon floor 1 ft. 14 ins. above the front platform.
In the plans for the body, the front entrance is 2 ft. above ground when laden and there is an 114-in, riser between the platform and gangway. The saloon floor is inclined by 24 ins. from the entrance to a point above the front wheels. At the rear the dropped extension is 1 ft. 4 ins, above the ground when laden, and the mainframe level is 1.ft. 74 ins, above the extension. The rear cross-member of the main frame is shaped for a sunken gangway, so providing a single step from the rear platform.
At the rear, the frame extension is secured in conjunction with the outriggers, spring hanger brackets and a cross-member, and is tied at the rear by a tubular member. The front extension is similar in its arrangement, but acts as a simple dumbiron for the spring eye.
The spring pin employed is of the non lubricated type, having a chromium-plated pin working in a hardened-steel bush with a running clearance of 0.040 in. Silentbloc units are used in the front spring shackles, but the rear springs have normal lubrication, chromium-plated pins being secured in conventional phosphorbronze bushes.
Reduced Weight
The main frame is level and parallel, and is braced by five pressed-steel cross-members which are pierced for lightness. It has the same overall width as the front extension (3 ft. 34 ins.) and outriggers are provided at the front and at the eight spring anchorage points. These outriggers extend to the full width of an 8-ft. body.
The Lancet U.F. has a 16-ft. 4-in. wheelbase, with 9.00-20-in. tyres of 12-ply rating as standard. Optional equipment includes 10.00-in.-section tyres with twins at the rear, or Michelin Metallic D 20. tyres (singles all round). The higher rating for the Metallic tyre (2 tons 11 cwt. for the D.20.) ensures that neither axle is overloaded.
Rear overhang is 7 ft. 5 ins., but. a further 3 ins, could be added in the body, within the legal limit, and the frame extension is 5 ft. 2 ins. long. At the front the overhang is 5 ft. 6 ins., for a body extending 6 ft. beyond the front 'axle, and the frame extension is 3 ft. 31 ins: long. There is 25 ft. 91 ins of body space behind the dropped front extension.