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IMPROVING THE t

2nd October 1923, Page 18
2nd October 1923
Page 18
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Page 18, 2nd October 1923 — IMPROVING THE t
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Which of the following most accurately describes the problem?

p OF THE COACH.

Some of the Problems 'Which Call fo the Passengers. Modern Tend Promoting the Safety and Comfort of :he Design of Chassis and Bodies.

MOTOR COACHING was, —for many years, considered as a hobby of the poor man, but gradually the lure of the road and the glamour of endless vistas of glorious scenery proved an irresistible attraction to the many millions, apart from the poorer classes only, who cannot afford to maintain private motor vehicles for their own use. Coaching is now recognized not only as an enjoyable pastime, but also as a comfortable means of transport which can, in a great degree, take the place of the Journey by train and, at the same time, provide refreshing draughts of pure air to the jaded toiler, whether he be a member of the artizan or professional classes.

It is essential, however, that the vehicles employed on the work should keep pace with up-to-date requirements, and this is all the more necessary when the increasing numbers of vehicles using the roads are considered. The coaching public must not be allowed to regard itself as neglected in this respect, otherwise its interest will begin to wane, particularly in view of the reductions in excursion fares and the increase in excursion faciltties which have been instituted by the railways.

Safe Travelling Essential.

It is important that travelling by coach should be considered almost, if not quite, as safe as travelling by train; at the same time, there must be no invidious comparison , between the fares charged. in our opinion, it is not necessary so to reduce fares that they aye equal to, or even as low as, those charged on the railway, for, except in the matter of speed over long distances, coaching presents attractions which can never be afforded by the lastmentioned means of transport. Certain small advances have been made in coach design, but not, in our opinion, to a degree which merits full approbation. We do not wish to hang at the heels of the alarmist Preis, for, considering the vast numbers of coaches which have been placed on the road during the past few years, the accidents which have occurred have not been very numerous, and the proportion is probably considerably less now than it was a year or two ago, but there is still a lot to be done before we can point to the coach as representing the finest example of a product built to fulfil all requirements. Both in chassis and body there are many features which call for improvement on the scores of safety, comfort and economy. Many of the vehicles now running are far too cumbersome and occupy an unreasonable width of road. Such vehicles have brought on the heads of their owners their own punishment, for it is they which have caused much of the outcry against coaches being permitted to use narrow roads. If, in the first instance, their size had been restricted and their weight limited to that which could effeetually and safely be carried on pneumatic or cushion tyres, hundreds of roads now debarred to all owners of commercial vehicles might still be open. We do not wish to harp upon this subject, as we have often stated our views on the matter, and we are glad to note a decided tendency in the direction of the development of the smaller coach.

Many of the fears regarding the increased cost of running on pneumatic or semi-pneumatic tyres will certainly be allayed with the employment of lighter vehicles. Very few coaches suitable for running on pneumatic tyres only have yet been constructed. The majority, even of the smaller vehicles, are obviously constructed strong enough to stand the minor and major shocks transmitted through solid tyres, and they are consequently too heavy. It is certainly false economy to carry so much useless weight as is done in so many instances. This not only means extra tyre wear, and the risk of bursts if pneumatic tyres be employed, but it also deducts from the amount of paying load which can be carried. This applies just as much in the passenger vehicle as in the case of that designed for goods.

There is no doubt that vast improvements can be made in the matter of chassis suspension. In very few springing systems, at present employed, is any consideration paid to whether the vehicle be running light. To obtain uniform comfort while running lightly or fully loaded, the springing should be able to adjust itself to the load, and that. this can be effected has already been shown in one or two machines, of whidh we can specify the Bristol in particular. In this vehicle, the ends of the laminated springs are supported on curved slippe'rs. Lightly loaded, the springs are clear Of the slippers for their whole length, but, as the load increases, they come in contact with the slippers and thus their effective length is reduced. This action is also useful for damping out spring oscillations. Efforts have been made to obtain the same results with springs in which certain of the leaves are separated at their ends from the others, so that a. progressive action is obtained. In other cases, spring shock absorbers have been utilized, but not with any great measure of success. For damping out the minor vibrations, rubber cushions which take the place of the ordinary shackles have proved fairly effective, but there is no doubt that further effort will have to be made in this direction.

Isolating the Body from Shock.

A new development which presents many potentialities is that of utilizing some form of cushioning device between the chassis and the body, or an auxiliary frame to which the body proper is secured. Space has already been given to descriptions of such devices in previous issues of this journal, but we may refer, in particular, to the Strachan and Brown system, in which laminated springs are employed, an American device in which steel balls supported in large cups allow relative movement between the body and chassis, and the Holden pneumatic suspension by which the body is supported on the chassis through 'the medium of inflated rubber tubes.

Many coach designet's do not appear to have realized that the average speed of the coach is, normally, considerably in excess of that of an ordinary commercial vehicle, and whilst it is possible that the maximum speed of the engine of the goods vehicle may be reduced, that of the coach may actually be increased, and it Will probably become more akin to the power unit employed on the private car, particularly as the use of smaller vehicles becomes more general.

There is certain to be an increasing divergence between the design of the coach and that of the ordinary goods vehicles, quite apart from such minor alterations as the employment of higher final drive gear ratios and lighter springing. .

Some commercial-vehicle chassis are not at all suited to coach work; the balance of the rotating parts, although it may be satisfactory for moderate speeds, often sets up disagreeable vibrations if the speed be increased. This applies particularly to such parts as the propeller shaft, and here, again, much damage is caused by running unsuitable chassis, Unladen, at speeds above those which are attained with the full complement of passengers.

A Call for a Lower Load Line.

There is an increasing call for vehicles with a lower loading line. For many years, the excuse for the high body has been that the passengers desired to see over the high hedges which bordered many roads. The argument is neither sound nor of very great importance, and it would apply even more to the lowbuilt touring car than to the touring coach, and the possibility of evolving new designs of the low-chassis type should be investigated very closely. With the drive transmitted through the rear wheels, the Matter presents a somewhat difficult problem, but that much can be done in this direction is shown by the great reduction in the height of the N.S.-type buses recently placed on the streets of London, and in which there is an intermediate drive by an underslung worm and a final drive by pinions at the ends of the axle shafts which mesh with internally toothed rings in the rear wheels. There arealso certain advantages in driving through the front wheels, even although this is complicated by the fact that these have to steer as well as drive,. We have expectations of very great developments in the matter of front-wheel driving.

The maximum attention possible should be paid to the promotion of safety. We know of only two coaches in which three efficient brakes are provided. These are the Sauna., in which, by a special: arrangement, the engine can be made to function in the capacity of a brake so powerful that the vehicle can be pulled up by it on the steepest hills ; and the Renault, described elsewhere in this issue.

Braking the Four Wheels.

Front-wheel braking has not received the encouragement by the coach owners which it deserves. It has certainly not been fully tried out on the highspeed heavy vehicle—at least, not in this country— and there may be fears that braking the front wheels may accentuate the tendency to skid. We believe that this would actually, be the case if the brakes were applied to the front wheels only, but we think that the solution of the difficulty will be to couple the brakes to the front and rear wheels and arrange them so that the effort is always greater on those at the rear. These brakes, with one on the transmission, should provide all the stopping power necessary, particularly if they be power-applied by the Westinghouse or some other system. of this type.

We have always advocated the provision on commercial vehicles of some device which would 'prevent backward running from any cause, except when the vehicle is being reversed under the control of the driver. This applies even more strongly to coaches operating in hilly districts. We have dealt with this matter at length in previous articles, and have given designs of special forms' of automatic brake which would serve the purpose. The ordinary form of drop-sprag has proved of very little use as, unless brought into action instantaneously, it is highly probable that it will be jumped.

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High speeds necessitate really satisfactory methods of lubrication, and we are inclined to the belief that oil lubrication should be employed throughout, as is done in at least one well-known make of chassis. The number of points requiring attention for lubricating purposes should be reduced to the minimum' otherwise they merely call for neglect. Reliability and goodlubrication may be said to go hand in hand, and it must be remembered that in these days coaches are often away on tours lasting from a few days to months, and so cannot be attended to at what might be called their base depots. It is a very serious matter to a coach owner if he strands his passengers hundreds of miles from their destination, and where the vehicles are used for Continental touring, the factor of reliability becomes of even greater importance.

One point in design which strikes many passengers is that the clatches are often far from ideal. It should not be possible for a driver to engage a clutch fiercely, as this throws enormous stresses on every part of the mechanism, besides being most uncomfortable to those riding in the vehicle. It is possible that some form of hydraulic clutch will eventually come into use, or possibly an ordinary form of clutch may be provided with an hydraulic buffer which would give smoother engagement than is possible to the driver, particularly if he is being bumped about over rough roads. It is somewhat surprising to find that so little use is made of the power starter. The motor required for the heavy engine certainly consumes a lot of current, but there appears to be little reason why the smaller vehicles should not be so equipped, although not necessarily with electrically operated devices.

Imnroving the Coach Body.

Now we will pay a little attention to the matter of coach bodies. Here there is decidedly considerable room for improvement,. although some of the faults which have developed in certain types are laid to the blame of the chassis builder.

The coach body has to be practically rigid, yet it is often mounted on what is actually a flexible framework which can twist to a very perceptible degree -when the wheels are not all on the same plane.

In many coaches the demand of the owners for the largest possible seating capacity has enforced a large overhang, and although this is limited by law, even the proportion permitted is, in our opinion, excessive and apt to produce tail swinging, apart from the difficulty of securing the necessary frame rigidity.

Many bodies quickly work loose at all the joints and warp to such a degree that it is impossible to keep the doors closed with the ordinary catches. A• partial solution to this problem has been found in reducing the number of doors to the minimum and providing a central gangway between the seats, although there are certain objections to this type of body because of the tendency to create draughts.

So far as seating accommodation is concerned, we think that no body should be built to seat more than four people in any one row of cross-seats, and theoverall width of bodies, even on small vehicles, can be reduced by utilizing some form of folding running hoard or step, such as that employed in the latest Bristol coach.

The knee room is often quite inadequate, and this also applies to the space provided for the feet. It is extremely tiring to passengers to remain in a cramped position on long journeys, and there is little reason why these points should be overlooked.

Even such a comparatively small detail as the. right angle for the back squab has a great influence on the comfort of the passengers, and we have seen coaches in which the seats were so arranged that persons under the average height were continually sliding off them. As the coach improves, it may be found possible to make each seat adjustable to suit individual requirements.

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Locations: Bristol, London

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