Should Exhaust Systems be Modified?
Page 52
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I EXPECT that by now many modifications have been made, at least in the drawing-board stage, to the design of commercial vehicles in preparation for the launching of new models at the next Commercial Motor Show.
One wonders if any new design will incorporate a modified exhaust system, that is one that will discharge the exhaust gases in an upward direction and at least six feet above road level.
Surely it is time that designers realized that the large volumes of evil-smelling, and often very smoky, exhaust gases liberated sometimes at considerable velocity by the large-capacity engines in use to-day, when discharged from the accepted exhaust-pipe position, which usually is only a few inches above, and often at right angles to the road, are a menace to health and a nuisance to the public.
One has only to drive or even walk among the dense traffic of our cities fully to appreciate the effects of the compulsory inhalation of exhaust fumes.
Quite apart from this, the effect on The health of bus and other drivers who spend the majority, of their working hours in an atmosphere polluted by these fumes, cannot be readily estimated.
Suppose, for example, that the early designers of railway engines had produced types • with their funnels fitted at right angles to the track and belching forth smoke at or near platform level, I feel sure the travelling public would have protested and a modification at once demanded.
Has any designer given this subject any serious thought? If so, why have not any commercial-vehicle manufacturers, either by themselves or in collaboration with bodybuilders, not attempted to fit an exhaust system with its outlet at roof level?
In the case of singleor double-decker buses, the concealment of a suitably soundand beat-insulated exhaust duct, led up to the maximum roof height, should not present any difficulties from the aspects of back pressure, appearance, drainage or cost_ As long ago as World War I, ambulances were fitted with extensions to their exhaust systems which were led up the back of the body, since then I do not think that any attempt has been made, by manufacturers, bodybuilders or transport undertakings to tackle this problem. '
The use of pressure-charged engines makes the need for modification even greater, the effect of being in close proximity to the exhaust of a vehicle fitted with this type of engine, when running at high r.p.m., is very unpleasant.
Let us hope that at the next Show there will be many examples of modified exhaust systems, the fitting of which will help to make our cities and towns cleaner and healthier places in which to live.
Whitchurch, Shropshire. CHARLES TAYLEUR.
EQUIPPING BUSES FOR GREATER SAFETY AS a regular reader of your journal, I have been particularly interested in various articles dealing with the question of promoting the safety of vehicles, with special regard to those employed for public service. May I, therefore, as a young and recent addition to the bus-driving fraternity, voice certain of my observations?
n 8 I believe that from the driver's point of view a lot could be done to help in this matter.
I have noted that the majority of vehicles used in this area carries only one driving mirror, naturally enough, on the off side. It is my opinion, however, that if an additional and larger mirror were fitted at the near side, the driver could observe passengers boarding and alighting, as well as take note of the " fool " cyclist who creeps between bus and kerb at traffic lights, etc.
It also appears that many bodybuilders forget all about those important hand signals when 4:lesigns for cab doors are on the drawing boards. Most drivers can manage to put only a few fingers out of the small window provided, and to give a really clear and easily understood signal they would need rubber arms. The fault could be remedied either by employing a larger opening at that point or fitting a small one somewhat higher in relation to the bottom framing of the window.
I think also that stop lights should be improved considerably. If a red light, say 12 ins, deep and 6 ins, wide, were built into the panelling at the rear off side at about the level of the rear mudguard and extended around the curve of the body, every following driver could see it. As fitted to present vehicles, stop lights would appear to be only a form of decoration—at least, this is how I see them.
These are just three faults out of many winch would take too long to describe in detail.
In my view, everything possible should be done to make a bus as nearly fool-proof as possible. It is not merely a question of improvement, say, by the .use of wider bodies. One life spared as a result of increased safety is worth the trouble.
Southampton. FREDERICK L. AIKM
[Congratulations to our young and enthusiastic reader. Often the man at the wheel of the vehicle can be of great help to designers and operators. It is he, not the chassis designer or bodybuilder, who has to spend much of his life on the road and, therefore, should be in a position to express practical views on convenience and safety.—En.1
WHEN SHOULD THE SPARK OCCUR?
A FRIEND of mine has been having an argument r-Lwith me concerning the firing point of an internalcombustion engine. Although he is a good practical mechanic, he would not believe that the mixture is hied before top dead centre. He seems to think that the firing should be at this or after. Curiously enough, he has successfully assembled dozens of engines, but I think that he must have had a lot of luck. I have explained the point to him and have endeavoured to demonstrate it, but he will not listen to my advice and says he will only believe it when he sees it in "The Commercial Motor."
Wolverhampton. "FAITHFUL READER."
[Your friend is certainly wrong. There is a slight lag before the mixture fires and a longer period elapses before the flame travels throughout the mixture, which is known as the flame propagation. In the old days of fixed ignition. the spark was set to occur a reasonable number of degrees before t.d.e. to allow for this delay, but the advance could not be carried too far because of the danger of back firing, particularly when starting by hand. In modern vehicles with automatic advance, the ignition may be almost at .t.d.c. when starting, but as the engine picks up, the point of ignition gradually advances until it is well before t.d.c.—En.)