Altogether Too Many Coach Accidents!
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.SOAIETHING must be done by the passengercarrying section of the industry to put a stop to the " char-a-banes crash" and the "motorbus catastrophe " that fill the columns of the daily papers at holiday times. The reports of these mishaps make bad reading, with their fatal results," "emergency door .broken open to free the victims," "root burst open In vain efforts to escape," and such-like startling phrases in the headlines and flaring captions to the accompanying illustrations.
Immediately after the war we persistently drew the attention of motor. coach operators to the urgent need, for employing vehicles designed in chassis and body expressly for passenger carrying. The growing demand for suitable types encouraged the makers to produce them, and it is correct to say that there is to-day-not the slightest need, for passenger purposes, to use converted lorry chaWs or vehicles that are employed in the main as load carriers. The tendency, when a lorry or van is taken for a pleasure jaunt at the week-end (or at any other time), is for the driver's foot to press hard upon the accelerator pedal, because paSsengers ask for speed, or taunt the-driver whenever his vehicle is overtaken. High speeding means excessive braking, and at the end of a long day under these driving conditions, brake shoes, well worn at the start, become worn to the point where they fail and leave the driver in the lurch.
In the case of the charLa-bancs smash at Greenwich on August Bank Holiday, the driver' S explanation was that his brakes failed, and the cause was , probably as we have suggested, for it is possible that the vehicle being thus engaged for the week-end there , had been no time for, an inspection of brake shoes and that the driver was not aware of their condition.
Under the projected Road Traffic Bill, the Minister of Transport will have power to make regulations under which passenger-carrying vehicles will be subject to inspection. The many accidents of the past eight years have already led to the determination that these inspections shall be thorough, but, if accidents continue as they are doing, there will one day be such an outcry in the daily papers that the Minister will he forced to make the conditions onerous. This would inflict a. serious injury upon the coach industry, :but it is one which can yet be averted if those who, to-day, allow their vehicles to be taken out in a known defective condition or to be driven by men in the least degree incompetent or inexperienced, will see about setting their business in order.
Motor Coaches in Convoy: A Suggestion.
'THERE is a very noticeable fault in the motor 1coach driver (however good he may be and however luxurious, well equipped and well maintained his vehicle may be) in that when he is driving in company he maintains close order instead of opening out. And it may even be that we should not hnve used our parenthetical sentence framed as it is, but have said "because he is a good driver and has a good vehicle." His greater skill and the use of coaches maintained at a high level foster the ability to keep close up to the coach in front, and the net effect is often to be seen on the roads favoured by the average coach patron. It will take the form of a whole terrace of motor coaches—three, four, or half a dozen going along in convoy fashion at a goodly pace, making a column that is exceedingly difficult for the private car driver to overtake. Complaints on this score are always reaching us, and, of course, we have observed the practice ourselves and have condemned it.
Motor coach owners and operators can help to mitigate the nuisance and to eliminate one cause of irritation by instructing each driver to leave a gap of 150 yards to 200 yards between his own coach and that preceding it, to keep open order even when a traffic check occurs and to give overtaking traffic its opportunity to get past.
This is not going to entail a hardship, because, with a convoy of ten coaches, a preserved interval of 200 yards need not. between the first and the last, result in a ,greater difference than two minutes at their destination. 'The observance of the stated interval between coaches, however, will have the effect of facilitating traffic flow, which with the rapid growth of traffic is becoming a vital Principle of highway conduct:
Safety Braking for Fast Vehicles.
WE do not hear quite so often nowadays of serious accidents caused by complete failure of the brakes on a vehicle, but such failures do certainly sometimes occur, although, fortunately, not always with sufficiently drastic results to bring them before the notice of the public. With the increasing number of high-speed vehicles on the road (these being mostly passenger-carrying types), it is essential that the whole subject of braking should receive the utmost consideration, and every important failure be analysed so that information gleaned in this manner can be employed to safeguard vehicles in the future.
There is still much to be done in tracing out the effects of the high temperatures often caused as a result of powerful braking at high speeds. Drums are often too thin and the connection between drums and wheels do not provide sufficient body of material to permit adequate dissipation of the heat ; consequently, distortion is apt to occur. this being either permanent or temporary. Permanent distortion prevents proper initial brake adjustment, whilst temporary alterations in drum shape may easily have the effect of upsetting the initial adjustment and result in inefficient braking effort. Wear of wheel bearings may cause the shoes to be out of centre in the drums, resulting in unequal wear and a reduction in the area of drum surface over which the shoes normally take effect. Such hearing wear also makes adjustment most difficult and unsatisfactory. This does not apply. however, with such force to vehicles in which ball or roller bearings. are .employed for the wheels, as the eccentricity of the drums in such cases is, of course, limited to a comparatively small amount.
It is very difficult to ensure that the braking power will always be equal, as this depends upon factors other than the design of the shoes, drums and operating mechanism. Leakage of oil into the drums is a frequent cause of a great reduction in braking power. Water will also sometimes act as a lubricant in a place where it is not wanted, but this is not quite so important, as it soon dries out when the drums become warm. The entry of grit will often increase the braking power, but only temporarily and at the expense Of accelerated wear in the drums and of the friction material employed on the shoes. Cast-iron usually gives Increased power as compared . with steel, but drums wholly composed of this material are not to be recommended when used in conjunction wifh expanding shoes, as this material is of low-tensile strength, although it will stand high compressive stresses. In some designs which we have seen this difficulty has been overcome by employing steel equipped with cast-iron liners, giving a combination of strength and a high coefficient of friction.
It is not fair always to blame the maker of a vehicle when the brakes fail ; more often than not—in fact, we may say in the great majority of Instances—poor maintenance is at the root of the evil. It is not fair to the vehicle, to other users of the road and to the general public to allow brakes to be neglected. They should be looked upon as the most important part of a vehicle, for even a breakdown is better than a runaway.
Brakes should receive most careful inspection, scored drums should be re-turned if not too thin, or replaced if dangerously so. and brake-shoe facings should receive constant attention. A few shillings spent on these may,'tin the end, save as many pounds. Where .rivets are employed for „holding such facings, these should be carefully 'inspected for looseness.
We have, on many occasions, pointed out that the ordinary form of so-called compensation is practically futile, and it is often introduced rather to please users than for any practical reason. It may produce equal pressure between shoes and drums, although even this is usually not certain, but this does not imply that equal braking effort is obtained on each wheel ; even if this be equal, the condition of the tyres and a the surface being traversed may, and usually does, upset the whole scheme, and, after all, the final braking • does not occur in the drums, but between the tyres and the road surface.
In this connection a rather interesting scheme is being tested out in the U.S.A. This is to balance the wheel pull on the road by interconnecting the brake anchorages instead of the brake-operating mechanism. Thus one brake force reacts against the other, because any unbalanced force produces movement which can be utilised to decrease the pressure of the stronger brake while increasing that of the 'Weaker one.
Much improvement in braking has resulted through the embodiment of some efficient form of servo device in the braking system, so that the driver is not required to expend so much energy in controlling a heavy vehicle. This is all to the good. In our opinion, the driver should be relieved of as much expenditure of his physical strength as possible ; all his energy should be conserved rather. for manceuvring the vehicle than that he should be looked upon as a source of power.
America has gone even farther than us in this effort, for in many instances servo steering now forms part of the mechanical equipment of a vehicle. It may not be very long before the controlling of a road motor will consist of little more than the pressing of a few buttons.