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OPINIONS and

3rd December 1943
Page 31
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Page 31, 3rd December 1943 — OPINIONS and
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Which of the following most accurately describes the problem?

UERIES

LEADED FUEL SABOTAGING THE WAR EFFORT

MUCH has been written concerning the pros and cons inof leaded fuels, and numerous suggestions have been .put forward with a view to overcomingthese difficulties,

i.e. increase valve clearances, advance ignition and grind-in valves every 2-3,000 miles. That is all very' well in peace-time, but what is the harassed transport manager or fleet engineer to do without the necelpary staff to carry out these additional duties, when he is already overtaxed in the repairs department? How is it possible to maintain a routine schedule when' it is found that vehicles cannot be started up or a driver telephones miles from his base to say he 'cannot start through loss of compression?

One writer goes so far as to suggest' that we should rule out the possibility of leaded fuels being responsible for valve burning. Also in the same article, that the older the engine the more frequent the valve burning. My experience is the reverse. Do the petroleum authorities realize the amount of inconvenience which appears to have been caused, and the increase in the use of valuable material for replacing valves and gaskets? I suggest that the quicker we return to a clear fuel or some effort be made to improve its quality, the better it will be for all concerned. We cannot, at this juncture, afford to slow up the " turnround," which may impair the war effort.

Hatch End. S. C. WALKER, M.I.T.A.

EARLY EXPERIMENTS IN IORSION-BAR SPRINGINGt

SEEING the illustration and description of the latest torsion-springing development on page 198 of "The Commercial Motor" of October 15, I am reminded of early experiments carried out by the late S. F. Edge at the A.C. Works at Thames Ditton some 17 or more years. ago.

I do not know whether his experiments were the first ever made with torsion bars, but I remember that I did actually drive a car fitted not only with torsion bars but with these lying along the inside channel of the longitudinal side members of the frame.

Had there been the same knowledge of metallurgy as prevails to-day, it is possible that the experiments might have been considered worthy of further development.

I remember that the bars used ,try A.C.s were much longer than those used, say, on the modern Vauxhall or Citroen cars. I thought perhaps you might be interested to hear this.

HUBERT W. EGF.wrax.

Ipswich. Driver and motorist since 1896.

01L-ENGItIED VEHICLES OF LIGHT WEIGHT

WITH reference to the paragraph " The Load Capacity " of Oil and Petrol Vehicles " under the heading "Passing Comments." It is rather surprising to know that anyone connected with the industry should have so little knowledge of the facts. Most of the vehicles now being produced in the 30 m.p.h. class and fitted with the Perkins P6 oil engine have 'a platform equal in size to that fitted on any petrol-engined vehicle in the same class. The Seddon vehicle, introduced in 1938, had a rated capacity of 6 tons and was equipped with a platform 16 ft. long. It is'in the 30 m.p.h. class,

and at that time its unladen weight was 50 cwt. Owing to the shortage of the lighter alloys the unladen weight has increased, but it is still under 3 tons.

So far as we are aware, it was the first vehicle produced in this class with a platform equal in size to contemporary petrol-engined vehicles.

Other manufacturers are now producing oil-engined vehicles in the 30 m.p.h., class with full size platform

bodies. R. H. SEDDON,

for Foster and Seddon, Ltd.

Salford, d.

OPERATORS WOULD APPRECIATE SERVICE BULLETINS

HiWAVING read with deep interest the articles under the heading of "Let the Operator Advise the Maker," I have been duly impressed by the various suggestions and recbmmendations made therein, but the general title could be turned round to read "'Let the Maker Advise the Operator" to some good effect, p'articularly in relation to the widespread .troubles of leaded petrol.

This frouble has been with us for SOITIC time now, and I have seen only two sets of recommendations from a manufacturer. In a recent article there was a mention of the sending ont of a monthly service-bulletin to dealers. Why could not this be extended to operators with, say, 10 or more of one make of vehicle? This would greatly assist the maintenance staffs of operators who do all their own repairs' and deal with the agents only for the necessary spares. I am sure thatsuch assistance would give. satisfaction to both maker and

operator. R.H. Sheffield.

VALVE BURNING AND ITS TREATMENT

WITH considerable interest I have followed the cor" respondence on the subject of "Leaded Petrol." For some time previous to the outbreak of war we were using Ethyl petrol experimentally in both cars and.commercial vehicles, with an undoubted advantage in respect of power output, which was of considerable value in view of the many stops which our work requires. We experienced exactly the same, troubles as are now being d discussed through your columns, such as burned valves, etc.

I cannot lay claim to any great chemical knowledge, but it' seems obvious that greater power output would require a more powerful explosion, which in turn means greater heat. The exhaust valve has the unenviable duty of standing up to this additional heat while raised . off its seating, and is thus most vulnerable. Following this theory, we replaced all exhaust valves with Vacrom . and at the same time slightly increased the width of the seats, in order that as much heat as possible might be dissipated while the valves were at rest. ' Your correspondent, Mr. Ward, seems to have arrived at a similar solution in giving a greater clearance, thus slightly lengthening the time the valve is seated. It was also found advisable to inspect all cylinder-head nuts at frequent intervals to eirsure that they . were kept thoroughly tight.

These measures made a very definite improvement, but fritfortunately the outbreak of war, and the incidence of Pool petrol, put an end to our experiments.

I feel I must disagree with Mr. Anthony High in his statement that a valve could not suffer to the extent shown in the illustration, from burning alone, and that all compression would be lost long before the valve reached that condition. Obviously, a definite time is required to empty a cylinder of its charge, and whilst his remarks mightbe true in respect of slow speeds, there would still be.quite a considerable compression at high revs. This would rapidly lower as the valve burned, but would be offset, to some extent, by the loweredresist,ance -of the valve to burning, as it gradually lost cooling area.

. I hope that my remarks. will serve to show that these troubles are not new. No doubt Measures will be taken in the future by manufacturers to make valves, etc., more resistant to the added. complication of the new fuels. Meanwhile we shall "certainly pay more than usual attention to any complaints of persistent misfiring.

I wish " The Commercial Motor " every success.

H. G. HOWARD, •

. Engineer and. Transport Manager,

London SW .19. for Charles Douglas and Co. ANOTHER EXPLANATION OF EXHAUST-VALVE BURNING

HAVING read the articles and letters which have ',appeared in your journal regarding exhaust-valve trouble, 1 feel compelled to write and point out that

• all your writers appear to me to have overlooked the real reason for this trouble, and have attached far too much importance to "corrosion."

The reason why "-lead." is added to petrol is well known, namely, to prevent " pinking," butwhat actually happens does not seem, to be understood. Pinking is caused by a sudden instantaneous rise of prewure in the cylinder due to part of the charge exploding instead of burning, and the effect of adding lead (or other dope) is to slow down the rate of burning, which prevents the detonation, but slowing this down causes very much•hotter exhaust gases, with the result that the exhaust valves are burnt " and not corroded or overheated by insulation due to corrosion.

The solution in theory is easy, but not quite so in -.practice—that is, to inerease the compression ratio,

ca.using more useful work to be obtained from charge with consequent decrease in exhaust-gas temperature. Any operator contemplating increasing the compression ratio by machining the cylinder-head -would, however, be welt advised to check carefully piston and valve clearance and, in an o.h.v.• job, that there is sufficient tappet adjustment, S. F. PILE, director, WilmingtOn. for A. Pile and Son, Ltd.

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Organisations: M.I.T
Locations: Sheffield, Salford

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