Technical I press ions of •
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THE PA
IS SHOW
THOSE who control the policy of the commercialvehicle industry in France sprang something of a surprise when they decided to hold a comprehensive display of vehicles and chassis at this year's Salon, because for some time past the arrangement has been for an extensive commercial-vehicle section only every other year. Taken as a whole, however, their decision appears to have been hardly a wise one. It is, of Course, extremely difficult to gauge trade conditions months ahead, but the attendance at this Show was the poorest we have ever seen at a foreign Exhibition of this nature, and it was difficult to find any important innovation in respect of vehicle design.
In one respect, however, France has certainly progressed, that is, in the utilization of (as apart from the development of) oil engines. Practically all the important makers stage oil-engined vehicles, the engines of which are mostly built under foreign licences, England being represented by Ricardo and Gardner, Geri:laxly by Deutz, Junkers and Bosch-Acro, Sweden by Orno, and so on. The Junkers engine is also built in France, where it is known as the L.M., and for a time this type had almost all its own way, but is now being challenged in many directions. Some of the engines built, however, have not given the most satisfactory results, chiefly in respect of the undue emission of smoke and excessive noise, as those who travel on French roads can testify, but this is probably a passing phase.
French chassis, as a rule, axe now clean in design although, as yet, not quite so much progress has been made in this respect as in British designs.
Tendencies in Final-drive Design.
The Berliet is one of the few examples left with worm drive. In most other cases, particularly in the heavier models, double-reduction axles of the bevel-and-spur type are employed, whilst in the Citroen coach the axle centre is set back, and there is a spur gear reduction at each side. The other reductions are mostly incorporated with the axle central casings.
Many of the largest chassis also embody a secondary reduction forming a unit with the gearbox and virtually doubling the number of ratios. Free wheels have not advanced to any great extent, although the Chenard and ,Walcker embodies a device of this type.
Considerable use is made of rubber to reduce vibration. In many cases the engines are supported in this manner, whilst the smaller Berliets have enclosed B32 rubber-cushion drive at the rear of the gearbox. We noted a Citroen in which the silencer is hung by a steel strap carried by a double thickness of rubber-fabric material mounted horizontally.
It is obvious that French makers are accustomed to overloading, because nearly every vehicle has auxiliary springs of one type 5r another. Principally they take the form of supplementary leaves mounted above the springs proper, and, usually, making contact with brackets on the frame, this being either plain or provided with rubber cushions. On one Laffiy, however, the extra leaves are restrained by clips secured to the lower leaves. Unusual springing is to be. found in the special Krupp chassis, which, of course, comes from Germany. This is best explained by the drawing which we include. It has already been described in this journal, but, hitherto, in giving drawings we have not shown the coil spring. The Lorraine-Tatra is also notable for its suspension system.
Great use is made of vibration-damping devices, or shock-absorbers as they are often called. Those for the back axle of the S.C.E.M.I.A. chassis are of the hydraulic type, and each is located inside the channel of a side member at the point where it arches. The only objection to this is that, with certain bodies, it might be somewhat inaccessible, but suitable traps to give access to them could no doubt be provided. In the Chenard and Walcker the front steering dampers are carried on the dudibirons at an angle of about 45 degrees from the direction of travel.
The big S.O.M.U.A. is equipped with a type which we? have not hitherto seen. It is really more of a coinpensatii7r than a damper, and consists of a deep plate joining levers connected to the rear-spring seats, so that if one wheel lifts in relation to the other torsion is imposed on the plate. Perhaps this is a reflection from the private-car side of the industry, where torsion rods are now being used in several chassis in place of other forms of spring.
More attention is being devoted to the improvement of brakes, which are of particular importance in France, that country of long straight roads where the speed depends more upon the vehicle than upon other conditions. Some form of servo is almost a sine qua .nou for the large-capacity types. The Renault still retains its familiar disc-clutch type of servo, the disc being driven from the gearbox, and the actuation being by rods, whereas in the Bernard, which also employs this type of servo, the pull is conveyed by a chain. The originator of this type was Rolls-Royce.
Servo-hydraulic Braking on Heavies.
Dewandre and Westinghouse vacuum servos are utilized to a considerable extent with, in some cases, three of such auxiliaries on a single chassis, sometimes its conjunction with Lockheed hydraulic transmission. Our British experts on braking would probably criticize the multiplicity of cross-shafts on certain models, also the somewhat flimsy cam-type operating gear on several transmission brakes.
Two or three of the hand brakes, as on the Latil sixwheeler, have a cushioning device to avoid shock through too rapid application. That on the vehicle mentioned is a square-section coil spring, which is compressed when the brake is applied.
The favourite scheme appears to be to link up the rear brakes by rods, and the front by cables, with some form of compensator between the two, but there are not wanting examples with cable operation throughout.
In the Rochet Schneider the front-brake cam-operating spindle has a universal joint at the outer end, whilst the inner is supported by a ball joint in a short arm swivelling from a bracket attached to the side—rriember. This is shown in detail by a drawing. The Centaure 12tonner of this make (which, incidentally, has an oil engine built under Oberhansli licence) has two vacuum
servos to permit several applications of its three Dewandre servos when the engine pump is not operating.
The Citroen employs a curious transmission brake consisting of a ventilated plate which is gripped between two shoes mounted at one side. This is situated amidships. A similar type is used on the Bernard, but, in this case, the brake is immediately in front of the rear axle.
We noticed no examples of actual servo steerings, but on a large Renault chassis there was a note to the effect that this could be equipped with servo steering if required. Central lubrication does not appear to be used to any great extent on the commercial designs, except on the Citroen.
The Delahaye utilizes a by-pass from the exhaust to warm the tank of its oiler, the heat being controlled by a hand-operated valve situated at the junction.
Much interest was aroused by the new Lorraine chassis built under Tatra licence, but the type has often been described by us in connection with its appearance at German motor shows, although, it is, of course, not a German innovation.
There has been an interesting development in connection with Mithelin tyres. It has been the practice for some time to improve the non-skid properties of old covers which have become almost smooth, by making cross cuts of a maximum depth of about 3 mm. at the sides of the tread. This has been found so effective, particularly on such slippery surfaces as asphalt, wood paving, etc., that the maker decided to incorporate this system in its • new tyres, consequently the Michelin tyres fitted to many of the vehicles at the Show are of this pattern. The tread consists of fairly widely • spaced non-skid indentations, between each pair of which are nine cuts. It seems a complete reversal of the order of things to make cuts in a tyre when, but a few years ago, such a cut would have caused in the mind of the vehicle owner.
Electric vehicles were represented by two Sovd. . models, 3-ton and 5-ton capacities. The batteries are slung at each side of the frame, and the controllers, which are under the driver's seat, give five speeds each way. The larger model is chain driven from two motors suspended from the rear of the frame, whilst the 3 tonner has a single motor bolted at its front to the centre casing of the rear axle and suspended at the back by a coil compression spring mounted on a bolt attached to the rearmost cross-member of the frame. A slightly lighter model is made, but,France has not yet gone in for the very light inexpensive electrics which are being produced in England.
Tipping gears are displayed in a remarkable variety of types for both hand and power operation. One Marrel model has five tubes telescoping into the base cylinder. The same maker shows a three-stage telescopic type complete with cylinder rocking frame and tipping-body frame in duralumin.
The only mechanical unloader we observed was the Hardy, giving a 30-ton push and driven by chains enclosed in the body at each side.
Georges Regis shows a refrigerating van with an unusual cooling equipment known as the Glacia. It consists of two rotors mounted on the same shaft, and each
[ZOLLER STOPS
consternation provided with dozens of gilled cross-tubes. One rotor is within the refrigerating chamber, the other outside the insulation, and with free access to the air. The tubes are filled with a special liquid, and the only action required is-to rotate the device by means of a small motor, when a high degree of refrigeration is obtained. Alfol is used as insulation for the body.
The same bodybuilder displays an exhibition van with boots and shoes shown at each side in three compartments, whilst the interior is equipped as a cinema, apparatus also being provided for broadcasting.
Lagache and Glaszmann and Chenard and Walcker now produce special trailers in which small flanged wheels project from the road wheels. These trailers are pushed on to platformtype railway trucks equipped with lines, when the flanged wheels run on the lines and are chocked at each side. These trailers are built to the special order of the Soc. l'Union des Transports U.F.E., which, as its name indicates,• has been formed with the idea of co-ordinating road and rail operation, the trailers being carried long distances by train and makIng short journeys by road, when they are hauled by tractors.
On the passenger side, improvements have certainly been effected in bodywork and finish, although streamlining is not being carried out to nearly such an extent as is indicated by the paintwork.
On buses, forward con trol is becoming much more popular, whilst we noted that in almost every instance safety glass is utilized for all windows on these and on coaches.
A neat device on the Citroen coach shown by Grange Freres is a combined direction indicator and front lamp mounted on each front wing. The casing is a polished aluminium casting, and the arm is curved out at the front so that it shows a little white light forward. It is pivoted to the front end and shows mostly red when open. This novelty is known as the FUP.
In several of the coaches is a new type of gangway seat. Each seat is carried on its own pedestal. When the squab is down, the seat is locked in the forward position, but as it rises it releases a catch and a spring then turns the whole seat around, so that the back is in line with the gangway and to one side of it.
On one Latil eight-cylinder coach with a Currus body, we saw on the windscreen a guarantee that the vehicle was capable of doing 70 m.p.h. A Renault bus has its sidelamps mounted in the dash instead of on the wings.
Another Renault bus, with forward control, has the driver's seat mounted at the front end of a box-section girder projecting from the bulkhead. The seat can be unlocked and revolved, whilst three positions are afforded to accommodate the driver's length of leg.
Few wood-built bodies are utilized, the majority being metal-panelled and some of all-steel construction.