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DOUBLE-DECKER
The Introduction of the Lance Chassis for 48-56-seater Bodies. A New Model of Advanced Design and Marked Accessibility
JUST before tne t.,ommercial-vehicle Show last year Dennis Bros., Ltd., Guildford, introduced the now famous Arrow chassis which proved to
be one of the sensations of the Exhibi tion. The latest model, designated the Lance, for 48-56-seater bodies, is a development of the Arrow, and actually embodies an engine of the same design. Readers will remember that this power unit incorporates a very ingenious cylinder head and valve layout.
The valves are carried in the bead, but the rocker mechanism is borne by
a separate assembly, which can be turned over on its pivots so as to clear the valve stems and permit the removal of the cylinder head complete. The valve timing is not disturbed, neither is the camshaft drive in any way upset.
It is thus possible to remove the cylinder head, substitute one from the stores and have the engine running again on the road within an hour.
Wet liners are employed for the six cylinders. These are carried by the cast-iron cylinder block and are remov able at any time, thus facilitating maintenance. The bore and stroke are 100 ram. and 130 mm. respectively and the power output is 100 b.h.p. at about 2,500 r.p.m. No fewer than seven main bearings are employed, and these are 3 ins. in diameter, so that the engine should stand up to proloirged hard service without calling for attention.
The auxiliaries are grouped on the B28 near side because, of course, forward control is employed for this chassis. A. disc coupling is installed between the pinion of the distribution drive and the M.C.L. dynamo. Behind this is antSther coupling and a skew-gear drive to the water pump, which has a vertical spindle and incorporates a patent thrower device to prevent water, which might leak past a neglected pump gland, from entering the skewgear housing. Behind this casing is a vernier coupling, which drives the magneto and permits very fine variations in timing the ignition.
A. Zenith U-type carburetter is bolted to the face of the round inlet pipe, which has flat ends and the usual connection for the servo and Autovac. Above the inlet tract, and in contact with it for a short distance, is the exhaust manifold with a central outlet.
Distribution is by an automatically adjusted duplex chain. This drive also transmits power to the fan, which incorporates a friction clutch in its hub, in order to deal with sudden fluctuations of engine speed. An A.uto-Klean filter attends to the To cope with the arduous work encountered on bus service a 14-plate clutch is employed; it has the exceptional area of 750 sq. ins. On the road we found that this component possessed an extraordinarily sweet action. A drastic test consisted of coasting forwards down a hill with the reverse gear engaged and the clutch pedal depressed. When the chassis attained 5 m.p.h. the engine was speeded up and the clutch pedal released suddenly ; the chassis slowed down, stopped and reversed its motion without a jar.
Unit construction for the engine and gearbox is employed ; four forward speeds are provided and the gears are of chrome-nickel steel and.of really generous proportions. By placing the shafts side by side ample room is allowed for the use of large shafts, bearings and gearwheels. The control is by a lever to the left of the driver, with a single shaft connection between the gate and the selector mechanisnf. A two-piece propeller shaft, equipped with Mechanicsjoints, is arranged to give straight-line transmission under load, and the centre bearing is located in a spherical housing.
An underslung worm is used in the rear axle; the centres have been arranged at 71 ins, to give a greater wearing area than the more usual 7-in, type and to ensure cool running. The shafts are of the fully floating pattern.
Semi-elliptic springs with 12 leaves apiece are used fore and aft. They are equipped with Luvax recoil dampers. An important maintenance feature is that Silentbloc bearings are used for the shackles, thus cutting out 14 points normally requiring attention.
Cam-and-roller steering provides exceptionally light control. The front axle is specially shaped to withstand front-wheel-braking stresses, and the swivel heads have taper-roller bearings. A Dewandre vacuum servo augments the driver's effort id the application of the four-wheel brakes. The hand brake operates only on the rear wheels. All brake facings are interchangeable.
As Will be seen from one of our illustrations the frame is exceptionally rigid and deep, being cross-braced amidships and between the members of the rear platform.
This chassis, which is marketed by one of the oldest commercial-vehicle makers in the country, sells for £1,150 in standard form,
equipped with 36-in. by 8-in. tyres, spare wheel and tyre, Exide 170 amp.-hour batteries and a 600-watt dynamo. Its leading dimensions are as follow ;—Wheelbase, 16 ft. 6 ins.; overall length, 25 ft. 7 ins.; overall width, 7 ft. di ins.; front track, 6 ft. 4 ins.; rear track, 5 ft. 10i ins.; dash to centre of rear axle, 13 ft. 7 ins.; dash to end of frame, 20 ft. 8 ins.; width of frame, 4 ft. 1 in.; frame height (laden), 1 ft. 11i ins.; clearance up to mar axle, 10i ins.; clearance under axle, 7 ins.; turning circle, 58 ft.; chassis weight (dry), 3 tons 6 cwt.
On the road we found that the vehicle ran quietly— the noise from the tyres being the most prominent feature—and that it gave good riding to passengers in both saloons ; there was no vibration when standing for prolonged periods upon the platform in the conductor's normal position.
We subjected to a short road test one of the Lance chassis which was passing through the shops at the time of our visit to the works. When laden with ballast it weighed the full legal 91= tons, and covered the 1.4-mile ascent of the Hog's Back from Ghildford in 5 mins. 10 secs. The stop-and-restart test was accomplished on a 1-in-6i gradient, and the engine proved to have ample power for dealing with' this hill, despite its full load.
When covering 7.6 miles in 20 mins. in top gear on the Gifildford-London road the fuel used was exactly one gallon; this figure was attained with the brandnew chassis. It accelerated from rest to 30 m.p.h. in 50 secs, and from 10 m.p.h. on top gear to 30 m.p.h. in 45 secs. From 30 m.p.h. the brakes brought the vehicle to rest in 91 ft. and from 20 m.p.h. in 3815 ft.
The maker has paid particular attention to the question of maintenance. The engine and gearbox can be 'removed in toto well under the hour, owing to the use of an ingenious split bridge at the rear and a detachable front cross-member. Grouped lubrication is employed, this even extending to the clutch-withdrawal ball race. A very neat point, also having a bearing upon maintenance, is the special M.C.L. switchboard clipped to the steering column. A faulty unit could be renewed in less time than diagnosis would occupy in the ordinary way.
This switchboard is very neatly arranged ; it carries a combined lighting and starter switch on top, together with two coloured lights. The green one indicates by its action that the oil pump of the engine is delivering lubricant to the bearings, whilst the red light shows that the dynamo is charging the battery. The use of the green light instead of an oil gauge does away with a pipe which might give rise to trouble ; in its place is a simple electric wire. On the forward face of the casing is the control for the dimmer—a double-filament device—and the horn switch is handily placed on the right of the set. All wires are led from the casing in a single flexible tube.