A MEDIUM-S1ZED COACH CHASSIS.
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A Berliet Production Which is the Outcome of Experiences Gained on the Famous Route des Alpes.
1 N these days of high taxation, and the attempted closing of roads to large passenger-carrying. vehicles by lonal authorities, many shar-a-loanes proprieL tors are casting round for chassis which, while capable of carrying a good number of passengers, are of such dimensions as not to infringe on local restrictions :regarding overall width, loaded weight, etc.
Since 1911 there has been running in the South of France a service-of chars-a-. banes which possibly has to contend with some of the most difficult and arduous road conditions to be found anywhere: this service is known as the Service des Routes des Alpes." The route lies among the snows of the French Alps, and extends from Geneva in the north to Nice in the south. Along this road runs a regular coach service, and the difficulties with which the road abounds will be appreciated by -anyone who has a knowledge of mountain roads. Long heavy gradients and tortuous curves are the order of the day, the nature of the latter prohibiting the use of a vehicle having any very great overhang behind the rear wheels.
When this road was first proposed its use by 'heavy motor vehicles was eons:lamed impossible. This opinion was pot, however, shared by one firm of Feeneh motor manufacturers, and they set out to produce a chassis -which would operate on it successfully. That they have succeeded is established beyond all doubt, for to-day chassis of their construction predominate on the various services running on -the route.
• Not only did they design a vehicle which proved the fallacy of the belief that the road was impossible for motor traffic, but they and their engineers were responsible in no small measure for the lay-out of the road itself. Automobiles M. Berliet, of Lyons (France) and 40, Sackville Street, London, W. 1 (for such is the name of the concern in question), may therefore feel justly proud of the chassis tviiieh is described in this article, for it is the outcome of the experience gained with its forerunners on heavy work an the Route des Aloes since their inception in 1911.
And now to describe the chassis itself. The frame is composed of two side members of pressed channel section steel, slightly inswept at the front to allow -of a greater steering lock. Six s'abstardial cross-members are provided, . giving ample rigidity. A separate sub-frame carries the motor, this sub-frame being supported at three points, thereby safeguarding the engine against twisting stresses due to frame distortion. Long semi-elliptic springs are employedfore and aft, those on the rear axle being underslung, in order to give a lowloading platform.
The motor employed is the well-known Berliet heavy-duty model, having a bore and stroke of 110 mm. and 140 nun. respectively, and developing 33 h.p. at 1,300 r.p.m. The four cylinders are cost in pairs, and have the inlet and exhaust valves (which, incidentally, are interchangeable) located on the left side. The single camshaft is gear driven from the crankshaft, and has mounted on it a worm bevel wheel which drives the oil pump. This latter is located inthe sunup, and delivers oil under pressure to the three main bearings of the drankshaft, and thence to the big-end bearings by means of oil-ways drilled in'the crank webs.
The main and big-end bearings have bronze shells lined with white metal, while the gudgeon pins rock in bronze bnshee in the small ends of the connecting rods, and are locked in the pistons by means of setscrews.
A totally enclosed centrifugal governor is fitted, which operates a separate -butterfly valve in the induction pipe, and cuts in at between 1,250 r.p.m. and 1,300 r.p.m. The governor easing is waled to prevent its being tampered with by unauthorized persons. A high-tension magneto is positioned SertISS the front of the engine, so that the distributor and make-and-break face one on opening the right side of the bonnet. Cooling is by means of a gilled tube radiator with a centrifugal pump to assist the water cir eulation. A multiple-plate clutch, consisting of alternate bronze and steel discs, conveys the drive to a four-speed-and-reverse gearbox. A short c,arclan shaft, fitted with universal joints, connects the clutch and gearbox, which latter is suspended at its forward end from a cross-member by means of a spring-loaded bolt; while at its rear end it is carried on two small arms which rest on a specially dropped cross-member.
The gearbox is of the selective sliding type, with all shafts running on ball bearings. The faces of the gearwheels are large and present ample wearing surface. The ratios are as follow.-21.55 to 1, 18.49 to 1;10.76 to 1, and direct drive, 6.42 to L The change-speed lever works in the conventional gate, and; together with the hand brake lever, is located on the driver's right.
Immediately behind the gearbox is the foot brake and universal joint. The foot brake is of the internal-expanding pattern, the shoes •being fitted with renewable liners. The universal joint is of the star type; and, together with the foot brake, is totally enclosed in a sheetmetal cover.
A small-diameter oil pipe runs from the universal joint to a drip feed on the engine side of the dashboard, and thence to the delivery pipe from the oil pump in the engine. By this means a supply of oil 15 pumped from the engine to the universal joint, the flow of this supply being controlled by the drip feed. The propeller shaft from the universal joint. to the rear axle is enclosed in a torque tube, which absorbs all driving strains, leaving the springs free to attend to the suspension of the chassis.
The rear axle is semi-floating, and ernbodies a double-reduction spur-and-bevel gear. The first reduction is by a bevel pinion on the propeller shaft, which meshes with a larger bevel wheel. On the same shaft as this bevel is a straight. toothed gearwheel, which is in mesh with the differential crown wheel. The differential is of the plain bevel type, and the entire gear is mounted on ball bearings. Provision is made for adjusting the depth of mesh of the various gearwheels, and the whole gear runs very silently. The first reduction is 2.14 to 1 and the second 3 to 1, giving a total re• duetion of 6.42 to 1.
The hand brake drums are bolted to the rear hubs and are of large size. The hand brakes are of the internal-expanding pattern, the shoes being fitted with renewable liners.
The front axle is a drop forging, the swivel pins for the stub axles being mounted on ball bearings, whilst the hubs of the detachable disc wheels also run on ball bearings. The tie rod for the steering gear is placed in front of the axle, thus rendering it very accessible for any adjustment.
The steeling gear is of the irreversible worm and nut type. The column has a comfortable rake and a large hand wheel is provided. On this hand wheel is mounted the quadrant for the throttle control. Fixed ignition is used.
The chassis is fitted with detachable disc wheels, single wheels being used at the front and twin wheels at the rear. The diameter of all wheels is the same, and it is therefore necessary to carry only one spare. Pneumatic tyres 955 mm. by 155 mm. section are fitted to all wheels, and they, together with the resilient springs, help to make a fine passengercarrying vehicle.
The petrol tank is located under the driver's seat, and feeds the carburetter by gravity.
The principal dimensions are :—Overall length, 18 ft.; overall width, 6 ft. 6 iris. ; wheelbase' 12 ft. 8 ins.; length of chassis available for body, 12 ft. 2 ins. The total weight of the chassis is approximately 2 tons.
The price of this chassis, delivered in
London, for commercial purposes is 650; while specially fitted for char-be banes work the figure is £870. The net load which it is capable of carrying is in the neighbourhood of n tons, and it is therefore highly suitable for fitting with 16 and 20 seater coach bodies, this capacity being one which is proving itself very popular during the present season, and one which has already been taken up in considerable numbers in England and particularly in the Isle of Man, where the very large coaches are certainly going out of favour.