• Home
• Used vehicles
• Product news
• Dealer news
• Compliance
• Buying advice
• Archive

WHAT THE SHOW WILL REVEAL.

Present-day Tendencies. How the User Is Being Studied. The Development of New Types. Pointers in Design.

OITITE a number of persons connected with the privateWear industry has expressed to us the wish that there were as much initiative and development in that branch as are being displayed to an ever-increasing degree in the constantly enlarging business connected with the production of the commercial vehicle. In fact, from all parts of the world comes commendation of the enterprise of our commercial-vehicle designers and manufacturers, and we have no doubt that this will do a great deal of good in the battle which is being fought for the markers overseas, whilst it is being rapidly realized in our own country, not only that the British-built vehicle is second to none, but that it is now being constructed in so many models and types that the user has a wide field of choice arid can secure the vehicle that exactly fits his requirements. Improvements in design are, of course, not confined to Britishbuilt vehicles, for there are certain outstanding types produced by foreign makers, but the number capable of p'utting up performances equal to the home products is quite limited, whereas, only a few years ago, the user requiring highspeed vehicles of light weight had almost to confine his attention to chassis built in\ other countries; now such vehicles are being turned out in large numbers_by many of our manufacturers.

Remarkable Commercial Vehicle Developments.

We believe that no visitor to the coming Commercial Motor Exhibition at Olympia can possibly fail to be deeply impressed with the extraordinary developments whichlhave occurred since the Exhibition of 1925, and which Will certainly continue to progress, this improvement, moreover, not being confined to a fe* details: it is, in fact, general. One writer in the daily Press, in criticising the private-car exhibits at Olympia (in our opinion rather unfairly), stated that there were practically no developments except in connection with the engines. No one, however, can possibly make such an accusation against the commercial vehicle.

It is interesting to observe the continuing o f tendencies which were first publicly disclosed in 1925, and how pessimistic prophecies regarding certain of them have been proved false.

One of the most striking is the low level of the frame, Which was freely stated to be unmechanical and . which would prove a nuisance from the maintenance point of view through interference with accessibility. 'Contrary. to many expectations, this type of vehicle has not only survived, but has increased. in numbers to such a degree thát. practically every, maker of note 'will exhibit one or more examples embodying this feature, the average height of the frames being in the neighbourhood of 2 ft. when under load.

How the Six-wheeler Has Progressed.

Vast strides will also be noted in connection with the rigid-frame six-wheeler. Many makers who hitherto have refrained from producing chassis of this type while awaiting the result of pioneer experiments have realized that there is hound to be a market for it in the near future; in fact, already there is quite a considerable calk for six-wheeled i,ehicles actually in production. There are naturally, several points in design which may require years of experience to settle; as, for instance, in-connection with the employment of a differential between the bogie axles and the employment of torque members in chassis other than those intended for cross-country service.

One particularly interesting model will be the TillingStevens petrol-electric six-wheeler ; another will be the F.W.D. with optional four-wheel or six-wheel drive, the control for this being at the command of the driver. On this vehicle, as the front wheels need only be driven when passing over SOIL ground, a differential between the front and rear drives is not considered essential, Other interesting types will be the new Sentinel propelled by steam, the Berliet in which the forward bogie wheels only are

driven, and the Garrett_ trolley-bus. Other types which have already been described, bat which are of comparatively recent production, are the Foden, the Associated Daimler, the Guy, the Karrier and the Commer—all sixwheelers—and the Scammell flexible eight-wheeler to carry 15 tons. The names of Karrier and Guy have been associated with this development since the very beginning and their new products embody some exceedingly interesting features.

More Attention Given to Brakes.

The general increase in power and speed has naturally drawn the attention of designers to the improvement of the brakes, and four-wheel, brakes, which at the last Show were something of a novelty, will be' found on a very large number of vehicles, particularly those designed for passenger work: With the spreading use of brakes on all wheels, it soon became apparent that it was asking too much from the driver to expect him to operate them by manual effort, Particularly in the case of the heavier vehicles. This has resulted in the adoption of certain forms of servo device. In a 'few cases, such as the Rolls-Royce pattern on the Dennis, , and the rocking-shoe-fulcrum type on the Maudslay, these devices are constructed by the makers of the chassis, but in the majority of instances it will be found that vacuum-operated servo mechanism, in particular the Dewandre and, to a lesser extent, the Westinghouse, will be employed. The Westinghouse air-pressure-operated brakes are also being used on certain vehicles, such as the Istrrier and Halley six-wheelers.

The hydraulically operated brake has not yet become really popular in this country, although one in particular, the Lockheed, is of extremely sound design and will be found on the new six-cylinder Graham Brothers' chassis designed for passenger work.

There is an increasing tendency towards the employment, once again, of a transmission brake in addition to those acting direct on wheel drums, and this brake is usually controlled by the hand lever. Its purpose will be explained when it is mentioned that it is sometimes known as a parking brake. One reason given for the employment of this type of brake is that it is entirely unaffected by the state of load. Sometimes alterations in load on a vehicle will cause the brakes acting direct on the wheels to release— possibly with drastic results. It is most important that transmission brakes should not be employed for long Periods as they work at a high speed, give enormous leverage and are apt to fire. It is also becoming the practice to separate the transmission brake from the gearbox, and the drum is often carried on a short portion of the propeller shaft which is mounted in its own bearings on one or more frame crossmembers. In this position it is usually more accessible and receives a better draught of air. It also relieves the forward bardan jtAnts from braking stresses. Good examples of this class of brake will be seen on the Halley and the new Associated Daimler ; in the latter, well-ribbed shoes of light alloy, are employed. It will be found that, in the S.P.A., the brake drum is mounted immediately in front (I the rear axle, thus still further relieving the propeller shaft, but increasing the unsprung weight.

Improvement in .Brake Details.

Rods for operating the brakes have not always proved reliable, and steel tapes are being substituted in many instances. A. neat "type of rod is, however, employed on the new Saurer. Each rod has a hanging weight which prevents it from turning under vibration and it is rotated for adju.stment. Where long rods are still used, they are usually prevented from vibrating, either by being held between pads of fibre or supported in the centres of springs similar to a clock spring. Where shoes of light metal are used they must have surfaces of hard material to take the wear of the cam or other contracting or expanding medium; for instance, in the Vulcan the shoe ends are equipped with pressed-steel faces riveted in position.

There is something to be said for the type of brakeoperating mechanism which provides increasing leverage. Such an arrangement will be found on the F.W.D. sixwheeler.

Efforts are being made to expedite the work of refacing brake shoes, and the employment of T-headed bolts utilized in Karrier vehicles has now been extended to the Comrner. We would like to see further developments such as this, by which riveting is avoided.

Increasing Use of Six-cylindered Engines.

, Another striking tendency of quite recent date is the use of six-cylindered engines, and, apparently, nearly all our bigger makers are expecting large calls for vehicles equipped with this type of power unit. Certainly, from the point of view of comfort through reduction in vibration, rapid acceleration and general smoothness in running, there are many points in favouri of the "six," despite its extra complication.

With the development of these units there have been radical changes other than the mere addition of cylinders. The sleeve type of valve has again come into prominence, and will be found on a Karrier in the form of the BurtMcCollum single sleeve, on the Associated Daimler as the Daimler Knight sleeve in pairs and made of steel, the Panhard with its sleeves lined with white metal, and the Minerva which is also of the Knight design.

Amongst British engines three of the most striking are the Leyland, the Karrier and the Thornyeroft. The first has Duplex roller chain drive to helical spur gears driving the overhead camshaft. The second has the crankshaft in two sections bolted to a central flywheel and with the Burt-McCollum sleeve valves to which we have already referred. In both these engines great attention has been given to lubrication. In the Leyland the whole of the oil is passed through a special felt filter three or four times a day so that it remains green after thousands of miles of use, whilst in the Karrier the oil is passed through the external cooler, a similar filter and back into a large oil reservoir on the dash. As regards the last-named, the Thornycroft six-cylindered model, this has renewable cylinder barrels pressed into the main casting, and the timing gears are at the rear, where they are not subiected to torsional vibrations.

For a description of the remarkable unit employed on the new Sewer chassis we would refer our -readers to another section of this issue. It is sufficient to mention that the crankshaft is built up of six sections. Incidentally, roller bearings are employed for it.

With six-cylindered engines, rigidity of the crankcase is of vital importance, and to assist in this it will -be found that, in most cases, the cylinders and upper half of the crankcase are east in one, the casting being carried well down below the level of the main bearings, the bottom portion really forming nothing else but a sump.

In the Guy engine a similar cylinder head and valve arrangement are employed to that of the four-cylindered model, the valves being inclined and operated by rocker arms direct from a camshaft in the crankcase. The method permits the use of a very efficient combustion chamber.

While mentioning this point we may refer to the general improvement in the form of combustion chambers. These arekusually of the Ricardo, or what is ,known as the semi

Ricardo, type, often machined all over and thus allowing -a much higher compression than was formerly permissible.

The use of six-eylindered engines is not confined to the larger models. There are, for instance, the Vulcan 20seater, the Star passenger model and the Bean, which is of 17.9 h.p, and has a gross load capacity of 50 cwt.

Of considernble interest to many visitors will undoubtedly be the Mercedes-Benz 5-ton lorry, which is equipped with a crude-oil engine developing 80 b.h.p. This is we believe, the first time that such an engine has been exhibited on a commercial vehicle in this country. Incidentally, a lowframe passenger chassis of thiel make with a six-cylindered engine of normal construction will also be on view.

Higher Engine Efficiency.

Engines, on the average, are vastly more efficient than formerly. The power curves rise steadily to speeds which, at one time, it would have been thought quite impossible to achieve with an engine designed on a commercial basis, and yet these same engines provide a powerful torque at comparatively low speeds; the LeYlAnd, for instance, enabling a laden vehicle to be accelerated from 3 m.p.h. or 4 m.p.h. on top gear. . At one time engine noises and vibration were usually hidden or absorbed by transmission noises, but with the general quietening of the latter, the miner noises and vibrations from the power unit have become of greater import

ance, and a new development which is spreading-rapidly is to insulate the engine from the chassis by mounting it on, rubber blocks or in rubber bushes, the rubber often being of considerable thickness. A ssimilar procedure is now being adopted for gearboxes and -with much snccess.

In the Thornycroft, even the centre bearing of the propeller shafthas no metallic contact with the chassis, it being mounted in a Hardy disc.

Shock-insulating and noise-preventing compressed rubber bushes are also used on the spring shackles, etc., of the new Saurer, and it may well be that in a short time the use of rubber throughout chassis will increase amazingly.

Methods of Mounting Radiators.

In many instances in the past the mounting of radiators has proved unsatisfactosy. They were subjected to' racking stresses causing breakage and leakage, and the movement prevented the use of well-fitting bonnets. At the Show it will be found that, in some cases, radiators are mounted en the same sub-frame as the engine ; in other cases on the front) cross-bearer of the frame, where the movement is not so great as it is on the side members. In the Leyland the, radiator is secured tel the engine and is made quickly detachable. In nearly every case where this is not done, large rubber cushions are used under the feet. For goods vehicles the cast-aluminium pattern is still being employedalmost exclusively, but, for passenger vehicles, outer shells of nickel are often used. In the new Pagefield the radiater, which, incidentally, slopes back at the top, is mounted,. together with the engine and gearbox, on a subframe which can he rolled out of the chassis, as was done in the case of the Lucre. • Gearboxes are, in the main, more compact and certainly quieter. The shafts are now short and stout and sometimes centre bearings are employed. In practically all cases th6 gears are ground after hardening.

There have been big alterations in the method of gear changing, with a view to reducing complication, and whereas the Bristol was at one time practically the sole exponent of the single-control -rod, such a device is now used on a number of makes, including the Aisociated Daimler, the Halley, the Leyland and others.

There is also an increasing tendency towards a central change-speed lever mounted in the gearbox cover.

Propeller shafts are now mostly. in two' and often three, sections, the latter, as explained previously, being mainly where a transmission brake is employed.

There has been a large increase in the number of vehicles utilizing all-metal joints in place of flexible discs, and where such discs are still used some form of centring device is usually fitted.

Improvements in axles have 'been mainly in detail design, direeted towards the prevention of leakage of oil or grease, hut a somewhat startling development is in connection with the new Leyland models, which have semi:flcrating axles in place of fully floating ,types. 'It is claimed for these that it is easier to remove the wheels for inspection of the brake shoes and without interfering with the wheel bearings. The axle on the Snorer is also of particular interest, in that it permits slight canting of the wheels and ihas anal drive by helical spur gears.

Improvements in suspension are also chiefly concerned with the detail design of laminated springs, such as those embodied in the latest Woodhead patterns, as, for instance, the type in which the main leaf is divided, the halves ending in Solid lugs. rigidly secured to the spring .seats, oe, in the case of a six-wheeler spring, on its fulcrum bracket. 'Another Woodhead improvement is the method of bolting. the clips through holes in the ends of the plates.

In the Kerner sixheeler the bogie springs tire located. by snugs

formed in the leaves. ' Several vehicles will be found to include spring jag variable to load, as in the Bristol, where the ends of the springs roll over cams, which give the effect of shortening the spring and stiffening it under load. In the latest Thornycroft a rubber buffer is mounted over the ends of each spring, and these, incidentally, have an effect somewhat resembling that of the cams in the Bristol.

One important tendency is in the direction of lessening the effort required to lubricate the chassis. Experiments have been made with what is known as the one-shot system, hut this is not always entirely satisfactory, and much use is now being made of batteries of oil or grease nipples arranged at convenient points around the Chassis.

In. the Karrier, another interesting method is utilized. There are two oil reservoirs bracketed to the frame side members, each holding enough oil for a week's supply to its particular points and equipped with a piston which, when pulled up against the pressure of a spring, supplies a constant How of oil for a day. In connection with the use of such devices, Pet-08ex piping has been found satisfactory.

We have not yet made reference to clutch design. It Would appear that the single-plate type is more than holding its own, and where the cone type is still employed it is practically always faced with asbestos fabric. One very successful clutch on lighter vehicles is the cork-insert typb employed on the Morris.

The increasing use of low floor levels has resulted in the production of certain chassis with an off-set drive line. We may refer in particular to the Leyland, the Bristol and the W. and G., the last-named being specially intended for low-built ambulance bodies.

It will be found that further use is being made of light alloys for brake shoes, spring brackets, back-axle covers, etc., this being particularly apparent in the latest Associated DaimlOr. In our opinion, there will be a much grsister spread of their use in the near future.

There have been great strides in connection with the

type of vehicle in which the. driver is situated beside the engine, and for this reason most of the engines used by makers who --employ this forward construction are so built that all t h e important auxiliaries are at the near side. Some makers have gone still farther from• the point of view of accessibility, and we may recall, as a particularly good example, the Garner, with a patent cab eonstruetion which allows a greater portion of the cab to he hinged forward together with the front wings, whilst, in the Mbi.on short wheelbase overtype 4-ton model, the cab is SiO arranged that it can be removed entirely in a few minutes.

A source of trouble with some engines is lubrication of the clutch spigot. To effect the. lubrication in the case of the Commer, a valve is provided, communicating with the force-feed system of the engine.

A point in connection with the cooling systems of certain engines is that arrangements have been made whereby water is specially directed to the valve ports. This is done in the Guy six-eylindered engine by pipes cast in: the jackets, whilst in the Cm:rimer, baffles achieve the same purpose.

We must not conclude without a reference to the employment of gas-producers • several vehicles will be found with these in situ. One will he a 5-ton Berliet.

A sign that the User is being Studied more than formerly is the effort which is made in some chassis to centralize means for adjustment of the brakes, etc., in some easily accessible position. This is a particularly important point where low-level chassis are concerned.

Reverting to the subject of vehicle suspension, we may .mention that there appears to be au increasing use of springdamping devices, particularly for the front, as at this point a bouncing effect is often noted. There is a new Houdaille commercial damper for this purpose, whilst on the Renault there is one built by the. maker.

Oif the latest Karrier six-wheeler there is a special type of pneumatic stabilizer to reduce cel-tain vibrations experienced with multi-wheelers