The Trend of Commercial Motor Design as Disclosed by the Olympia Exhibits.
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The above title may seem somewhat misleading when it has to be stated here at the commencement that the most striking feature at Olympia is the similarity of the main features of most of the heavy vehicles shown. It is true that the working out of derails by various makers differs in all instances, as it is sure to do when numerous designers approach the same subject, but there are hardly any vehicles which can in a real sense be looked upon as " freaks." The present exhibition differs in this respect from many of its predecessors, and this tact may be taken as a sign of the growth of the industry : satisfactory types having limo evolved from the experiments of many makers, all tend to adopt one of these as experience proves parts of each individual design to be unsuitable. One encouraging feature of the exhibits is the good class of the workmanship shown in nearly every case. This means that manufaetti N rs reelise that the best of material and labour alone renders possible the successful mechanical propulsion of1
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roads. It is, perhaps, unnecessary to state that in the omnibuses, which constitute so large a proportion of the commercial vehicle section, the petrol engine is the one adopted for driving by all makers except one. The exception is the Chelmsford steam omnibus, into the design and consO-urtion of which Mr. Clarkson has introduced so lllatIV ingenious arrangements for overcoming the difficulties inherent to this type of vehicle when used for this class of work. This very preponderance makes it obvious that the following notes deal chiefly with the design of the petrol omnibuses on view,
Wheels.
There is no part of motor vehicles which, in the past, have given more trouble, or caused so much serious delay, as the wheel. When the subject was approached, nine years ago, the true functions of a driving wheel were not correctly apprehended, as, except for the short period during which steam coaches were on the road sonic seventy years ago, the wheel had never been called upon to do more than to roil along under the load it supported. All will remember the light, flimsy wheels which failed to endure the little work put upon them by the mechanieally-propelled vehicles of 1896-1898. When, however, about two years ago, the question of the use of motor buses was raised, considerable experience was available—front extended practical use of both light and heavy cars—as to the best wheels to be used, and in the hands of firms who had made a speciality of this point, the question was so readily solved that no serious trouble has arisen since then from failures of this part of the machine. The type of wheel most usually employed is undoubtedly the wooden one of the artillery type, and this, so long as it is souodly built, seems to meet nearly all requirements. There is some little variation in the shape, tanging and placing of the spoke employed, but this must be so considering the variety of the attachments to the inner side of the wheel. It is, of course, necessary to strengthen a portion which has been bored in order to attach a casting to the inner face, and, when this necessary provision is taken into account, there is a great similarity .be tween the wheels used. A point which does not seem thoroughly settled is, whether it is advantageous to employ a dished wheel or not, to withstand side strain. Undoubtedly many of the wheels that are to be seen at the Show, particularly the driving ones, are dished. This is only done, in the majority of cases, to a slight extent, and, compered with previous exhibi liens, it may be said that experience is showing that a spoke, built practically at right angles to the axle, which is strong enough to curry the load and to drive the vehicle, is also strong enough to withstand the side strain put on it, The iron tyre is usually shrunk upon the wooden felloe, this being free from objection where the section is not too heavy for prompt quench_ ing ; hut the wheels fitted with the Peter Union tyres have, in addition, an outer iron tyre, which is fastened by means of a right-and-left-handed screw and which allows of the ready removal of an old tyre and its immediate replacement. An arrangement of this kind will be found a great advantage, as it does not necessitate bodily removal of the wheel. Although the majority of the wheels are wooden, special note should be Laken of cast-sled wheels : Mr. H. G. Burford, of the Milnes-Daimler Company, amongst others, is fitting these to the omnibuses he sells. Whether the satisfactory results obtained by this wheel on the Milnes-Daimler vehicles are due to the fact that the large, internally-toothed wheel of the system has to be fastened to the inner side of the wheel remains to be seen. The east steel centre undoubtedly gives much greater rigidity than wooden spokes, but it is questionable whether such solidity is necessary with other types of drive. A new wheel, shown on a bus chassis in this country for the first time, is that of the Fiat Company, It consists of two dished steel plates riveted together, each being flanged ever at the top so as to allow of the insertion of a wooden felioe to which the tyre is fixed. These wheels, although new to this country, are said to be extensively employed in Italy. The " Stagg " wheel was shown at the
last Agricultural Hall Exhibition, and it will be remembered that it consists of a cast-steel rim and hub, both of which have pockets in them, into which pockets straight spokes are fitted. Wheels of this type are fitted to one of the ScottStirling buses. No other novelties in the way of wheels appear on the vehicle shown, but the cast-steel wheels will undoubtedly be watched closely, as they have the advantage of being unaffected by weather. It remains to be seen how the solid rubber tyres on them last under varied conditions, as compared with the life on wooden wheels.
Springs.
Semi-eiliptical springs are used in all cases, and in the majority they are fitted under the frame against which the ends bear. Some slight variation exists as to the manner in which the end of the spring bears on the frame, and many makers adhere to the old system of flattening the end and letting it slide in an inverted channel iron, fastened to the frame, which keeps it in position. The disadvantage of this method is the difficulty of lubricating the rubbing surface. To overcome this drawback, several firms use properly-designed slides, or have a pin at the end of the spring which slides in the slotted sides of a small frame. Both of these methods admit of easy lubrication. The design of the car renders it necessary, in some instances, to have the spring outside the frame, and in these cases they are, of course, hung by means of suitable links to allow of the necessary movement when the springs are, from any cause, compressed. On the De Dion bus, shown by the Motor Car Emporium, in order to obtain a longer sus pension and yet to allow of the front axles being placed well forward, the back end of the front spring is carried by a link to a supplementary spring, composed of inyertcd half leaves, fastened to the frame.
Early motor vehicles frequently had double springs, the second coming into play when ihe first was considerably compressed, the idea being that with a smal load, or on a level road, the easy riding of a light spring was available, whilst the ear did not suffer when the opposite conditions occurred. The De Dietrich bus, shown by J arrott and Letts, Limited, is fitted with a somewhat similar arrangement of " bumping " springs. On the chassis on the Thornycroft stand, the rear ends of the springs of the back wheels are carried by a third spring lying across the vehicle; the advantages of a spring of great length is obtained, by this means, in what must of necessity be a confined space without the frame is to have a large overhang. On the whole, the strength of the springs used seems to be proportionate to the loads they have to carry, and. it is seldom that they appear too light for their work or too heavy for comfortable
As affecting the suspension of the body, iL may not be out of place to mention the efforts made by two makers to render the starting of the vehicle more steady. The floating axle and spring of Messrs. Straker and Squire's system is well known, and over twelve months' experience has led them to adopt it on all the petrol passenger vehicles they build: the driving axle is free to move, within certain limits, along the underside of the frame, and its motion is restroined bv jointed rods, on each side of the vehicle, the ends of which rods pass through and are fastened to helical springs fixed at the ..end of the frame. When the engine starts, its first tendency is to cause the wheel to run by itself along the frame, but this being prevented by the rods the springs are compressed and motion is gradually and gently transmitted to the frame itself. The Wolseley Company achieves the same object by placing springs in the radius rods; when the car starts, these springs become Compressed and transmit motion to the I Nimes.
Frames.
These are fairly evenly divided between examples of pressed steel and steal channel bars of standard sections. '['he sectional shape is, of course, the same in Loth cases; with the pressed steel it can be deepened and strengthened as required, whereas the only means of doing this with rolled channel steel is by supplementingwith extra plates, as is done on the end of the Straker chassis, to take up the extra strain due to the spring drive. Until recently, frames have generally been set in at the engine end, in order to allow the wheels to have sufficient lock without a risk of exceeding the maximum legal width, but the greater legal v, id th under the 1903 Act has removed this necessity. The esult is that ninny of the frames on the vehicles shown are parallel throughout all their length. This has had the :Aditional advantage of allowing more room round the engine, and, therefore, of giving a greater ease of access. Against this, however, must be put the necessity of fresh arrangements for supporting the engine body; when the trames were brought closely together, this was a comparatively simple matter, but with a straight frame some more romplicated means of support is necessary. This has been met in two ways : the first is to fasten on each side of the frame, to which the engine bed is attached, one or more brackets, and this 'will be found on several chassis, hut probably the more usual course is to build a supplementary frame a few inches below the main one, and to put the engine and other mechanism on this. Either of these has the advantage of giving more head room for the engine and
its fittings. The method of fastening the lower frame is one of those details y% hich designers have approached in various ways.
At the other end, by far the most usual method of connecting the main axle xvith the frame is by means of radius rods, although the ,Milnes-Daimler Company still uses a perch frame, and in this they are followed by one of the latest companies—Straker and MacConnell, Limited. Suitable precautions are taken to stiffen the frames against the cross strains they are subjected to. In the case of the SimmsWelbeek chassis, a long cast-iron frame, reaching right across the car and containing the gear and differential, forms a very effective " stiffener " for the frames.
Transmission.
Inre, as may be expected, there is the greatest variety of design 7 yet one type predominates. The system which has for its main features a changing gear of sliding toothed wheels, a propeller shaft driving a transverse differential gear shaft, and the power transferred to the rear wheels by means of chains, is in the ascendant. Many small differences in the method of carrying out this arrangement are to be seen, but undoubtedly the trend is towards the adoption of this type—copied though it may be from the lighter passenger vehicles. The large toothed chain-wheel is usually fixed on a steel casting fastened to the spokes, or the spol«-s and felloes, of the rear wheels. This casting is often utilised externally iS the drum for a band brake, Or internally to enclose an expanding one. It is particularly noticeable that the arrangement of these sprocket castings is very much neater and more workmanlike than for those seen 12 months ago. Of the ge.ari varying from the above, the Milnes-Daimler closely resembles them, driving, as it dees, by means of a pinion and large internally-toothed gear ring fixed to the driving wheels. The Wolseley, with its slow-running type of horizontal engiiie and Hans Renoltl silent chain to the counter-shaft, is too well known to require more than a mention. The James and Browne onmibus is fitted with a special gear, which discloses much in
genuity of design and arrangement. The engine is a hair-cylinder one, with the cylinders placed longitudinally in the car. The change gear is fixed between this and the differential shaft, which lies well to the front of the vehicle. On each end of the differential shaft is a small pinion, which works into an internally-toothed wheel bolted to a collar on a short shaft, which runs in a bearing and bracket ; I he chain sprockets are keyed to the outer end of this short shaft, the system providing a neat form of second reduc. tion. The object of this arrangement on the differential shaft is to give suitable ratios for heavy work. The Simms chassis are fitted, in the large gear-box already referred to, with change gear of the jaw clutch type.
A feature which cannot be overlooked is the fact that three or four types of chassis have live axles, notably the ScottStirling cars, the vehicle shown by the British Automobile Development Company, and the Ducommun chassis of the Motor Car Emporium. Many cars are now fitted with a gear-changing lever with the gate, which has been used for so long by the Cannstatt Daimler Company, and which undoubtedly was first seen in this country on the petrol lorries of this type at the Automobila Club trials of heavy vehicles held at Uxbridge in 1899. The question of the wear of teeth which have to be thrown into gear receives considerable attention by the selection of special steels for the wheel blanks, into which chromium, vanadium, nickel, etc., enter.
Brakes.
As vehicles of the type \ye are dealing with are generally used, in busy traffic, where means of readily stopping or of slowing down the car at a moment's notice are absolutely necessary, the fact is scarcely to be wondered at that great attention has been paid to brakes. A short time ago it was
tl.cught sufficient if one of the brakes, supplied to any vehicle with a solid tyre, was of the shoe type. Now it is recognised that, in case of accident to the gear, etc., it is absolutely necessary in a passenger vehicle to have an efficient brake on the driving wheels. This is supplied to-day by means either of .rtaband brake or -one of the expanding type working upon the casting already referred to as carrying the large sprocket wheel. It need hardly be pointed out how efficient a brake of either description can be made. In addition to a brake on the back wheels, it is usual in most cases to have one, worked by a pedal, to operate on one of the gear shafts : this is either a band brake or expanding blocks. In many cases three separate brakes are fitted. In the F.I.A.T. omnibus there is a band brake, which, with one action, applies band 'brakes to both the propeller and differential shafts in an ingenious manner : a double brake, actuated by a single lever, applies band brakes to two separate drums on the propeller shaft on one of the -chassis shown by the Motor Car Emporium. Again, the Maudslay omnibus has internal expanding blocks inside the small chain sprockets. The band brakes are usually of a flat type, but one Thornycroft vehicle has a V groove cut into the brake drum. At one time wire rope was extensively employed to apply the brakes, but the tendency seems to be to use rods : this is undoubtedly a change which will be looked upon as a satisfactory one from an engineering standpoint.
Steam Vehicles.
One of the most noteworthy features of the Show is the comparatively small number of steam lorries shown. Whether this is due to the anticipation of a large wagon display at the Agricultural Hall in March cannot be definitely stated, but less than one-third of the steam vehicle builders show their types at Olympia. Although the numher is small, the variety is good, the makers including Straker, Coulthard, Ellis, Foden, and the Thames Engineering Works. All types of boilers—water tube, fire tube, and locomotive—are included in the exhibits, but, horn the number shown, and from enquiries, it is safe to conclude that the locomotive type is coming into favour. There is litale variation in the pressure of steam used, or in the type of engine. The latter continue to be of the compound type, and no striking alteration has taken place in the gear employed. Wcx)den, built-up steel, and solid cast-steel wheels are shown, no type appearing to be particularly favoured. It seems a pity that the question of running on steel tyres during snow or frost has not been more satisfactorily solved. Many likely users are undoubtedly deterred from purchasing these vehicles, in the dread that they may be useless. The withholding of orders is hardly consistent with the absence of a heavy fall of snow since 1893, except on a few (lays during the year, but a cheap and certain solution of the difficulty must be brought about when more attention is given to it than is indicated at the exhibition. One lorry does, indeed, show non-slipping wheels, this being the Hay steamer, which is fitted with massive wooden wheels. This vehicle has many points of interest, vet it cannot be satisfactorily dealt with from a mere brief examination on a stand. The front wheels have the centre of rotation, for turning corners, situated hi the central vertical plane o; the wheel itself, and it is claimed that this gives great steadiness
over stones, very easy steering, and prevents oscillation of the wheels. A fire tube boiler is used, and the engine is a single cylinder one, which rotates the back axle through the medium of two connecting rods furnished with pawls.
The Car and General Insurance Corporation, Limited, has taken a new departure. A department has been added for the insurance of motor vessels driven by " fuel vapour." We note with pleasure the introduction of a new term, which, we believe, may be ascribed to Mr. Linton Hope, the naval architect to the corporation. Although such business strictly comes under the heading of marine insurance, the corporation has neither the wish nor the intention of undertaking marine business as generally understood.