A SIX-TONNER WEIGHING UNDER FOUR TONS.
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Details of a New De Dion Product, Taxed at £48 only, with Full Equipment, Including Servo-operated Four-wheel Brakes.
WE WERE recently afforded an opportunity for examining the first examples of a new batch of De Dion chassis which have just arrived in this country. This latest model is known as the K.M., and it has the remarkable distinction of being able to carry a load of 6 tons and yet, compleVy equipped with four-wheel brakes, Westinghouse vacuum servo, starter and electric lighting set, mid platform body with detachable hinged sides, it weighs only 3 tons 19 cwt. 1 qr., and is thus eligible to be rated for taxation at £48.
The new model is actually made for 4, 5 or 6-ton loads, but where less than 6 tons is to be carried, smaller engines are utilized. The unit in the heaviest model is of 125 mm. bone and 150 ram. stroke ; the 5-tonner unit has a bore of 110 mm. and a stroke of 150 mm.; and the engine of the 4-tonner is of 100 rum. bore and 140 mm. stroke.
Pneumatic or solid tyres can he fitted at choice, even to the heaviest type, and that this gives manifold advantages is shown by the fact that a certain user who has taken delivery of a similar chassis is able to average 18 m.p.h. between London and Manchester, and this while carrying 5-ton loads. Such average speeds could certainly not be kept up for long periods if solid tyres were used.
One of the secrets of the light weight of the new model lies in the famous De Dion cardan drive in which the differential is supported from a chassis cross-member, and cardan shafts convey the drive to rack and pinion gears In the wheels. The result of this is that there is very little unsprung weight, for the axle proper is merely a plain steel tube of comparatively small diameter. The housing for the spiral-bevel gearing and differential and the axle tube together weigh less than an ordinary axle, which would have to be of the double-reduction type to be capable of dealing with the loads of a vehicle of this description.
Another excellent feature of the new model lies in the braking. The foot brake acts on all four wheels and through the medium of a Westinghouse vacuum-servo device, which gives exceedingly powerful asaistance to the driver. There are two hand-brake levers the outer acting on the front-wheel brakes only, whilst the inner expands shoes in a transmission brake and contracts bands on the peripheries of the ring gear, in the real wheels. These bands, although open, are well within the rims of the wheels and
are, consequently, protected from mud which might other'wise be thrown direct upon them.
The four cylinders of the engine are cast in pairs, but there is a single exhaust casing, and around the exhaust outlet at the rear is a muff, from which hot air is supplied to the Soles carburetter, whilst the inlet pipe has a tube let into it for operating the servo brake. Ignition is effected by a De Dion Victrix magneto mounted at the rear of the timing case, whilst at the front, and driven from the same pinion, is a oentrifugal pump, which, incidentally, is larger than any previous model of the same load capacity. There is a double pulley for the V-belt drive to the fan and the Victrix dynamo • an eccentric spindle provides adjustment for the fan belt. The fan itself is of cast aluminium with four blades.
A centrifugal governor is carried in a casing at the rear of the engine and driven from the camshaft; it has direct control of the carburetter. The tappets are enclosed by two covers. Circulation of the lubricating oil is by means of a gear-type pump carried in the sump, and the oil is fed under pressure through a drilled crankshaft to all the bearings. The oil pressure can be adjusted by means of a relief valve. The flywheel is open and carries a ring for the Bleriot starter.
One of the points in the construction of the radiator is that the cooling surface is built up in eight detachable see"tions, so that in ease of damage it is a simple matter to replace one or more. Incidentally, the top and bottom water connections are flange-mounted on the tanks, There
are two combined fillers and breathers at the off side of the engine. Between them is a dip-stick, which passes through a nut which, when turned, operates the sumpemptying cock.
To reduce the weight of the reciprocating parts, aluminium pistons are employed, and for the sake of lightness the camshaft is driven by timing wheels having helicoidally cut teeth.
To facilitate starting by hand, if that ever be necessary, decompressor is provided.
The clutch is easy to operate and is of the type having a steel plate tarrying bonded-asbestos friction material at each side contacting with the flywheel and a pressure plate. We examined a similar clutch, which had been running in a De Dion vehicle, under process of overhaul for the first time after three years' continuous and heavy service on solid tyres, and the clutch showed barely any signs of wear. Direct clutch-withdrawal mechanism is used and 'the clutch itself has four toggle levers for releasing the pressure plate. On the clutch shaft is a pinion-type universal joint.
Both engine and gearbox are mounted on a sub-frame, which is itself three-poinz suspended. In addition, the gearbox is carried at three points in the sub-frame, the front connecting point being in a special bearer which, by means of an eccentric arrangement, allows the gearbox to be aligned with the engine.
Pour forward speeds are afforded by the gearbox, and it is noteworthy that the reverse pinion is idle when not actu: ally in use. The change speed is on the sliding principle, internal locking in the different positions being obtained by a ball and plunger device.
Behind the gearbox is an internal-expanding transmission brake with a very simple means of adjustment close to the actuating lever.
A long tube is utilized to enclose the propeller shaft. This tube is carried by a bearing at the front end of the propeller shaft, where is also situated a double-thrust ball race and an adjusting ring by which the depth of the meshing of the bevel pinion can be altered.
The differential casing is, of course, suspended from the chassis frame an consequently, there is'-no movement of the propeller-shaft tube. At the front end of this tube there is a speedometer 'drive from the propeller shaft.
There are 13 leaves in each of the rear springs, which are overslung and have a width of 43 ins. Along the centre of each leaf is a depression which enables the leaf to key into its neighbour, so that there is no possibility of sideslip occurring, between them.
Two unhardened-steel sliding blocks are fitted to each of the cardan joints for the final-drive shafts. These run in slides with hardened-steel renewable faces, and the crosspins upon which the blocks bear have floating steel bushes and hardened-steel end pads. By this means the wear is reduced to a negligible extent and replacements can be made when required. In addition, protecting leathers prevent the ingress of dirt and water and the egress of lubricant.
The ratio of the bevel gearing is 15 to 53, and that of the internal gearing 29 to 81., Inturned channel steel is used for the side members, which are inswept slightly at the front, tapered to each end, have a maximum depth of 8 ins, and have 23-in.
webs. Great strength is afforded by employing six crossmembers.
A worm and complete wheel form the steering gear, and the steering circle is 26 ft. 3 ins. Stops are formed on the steering arms to limit the wheel movement.
Chassis lubrication throughout is on the Tecalemit greasegun system.
The main dimensions of this chassis are : body space, 11 ft. 11 ins, behind driver's seat, which can be increased to 13 ft. 13 ins, to order ; overall length, 20 ft. 61 ins. ; wheelbase, 14 ft. 10-Ains. ; frame. height, 293 ins.
The chassis, complete with lighting and starting system and 970 ram. by 160 mm. solid Dunlop tyres (twins at the rear), is priced at £895. Incidentally, this price includes four-wheel brakes and Westinghouse servo. With seven 38-in. by 7-in. pneumatic tyres (twins at the rear) the price is 1965. In this case. Michelin disc wheels are provided, whereas in the solid-tyred 'model the wheels are of cast steel.