OPINIONS FROM OTHERS.
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The Editor invites correspondence on all subjects connected with the use of commercial motors. Letters should be on one side of the paper only and typewritten by preference. The right of abbreviation is reserved, and no responsibility for
views expressed is accepted.
Coal v. Oil Fuel for Steamers
The Editor, THE COMMERCIAL MOTOR.
[1,761] Sir,—I waa very much interested in your article on oil-fired steam wagon boilers and, being always on the watch for possible improvements, I have compared your figures with those of an actual test of a four-ton Sentinel running on Welsh steam coal costing 50s. per ton. The Sentinel run was for 50 miles, over ordinary roads, and no special arrangements were made, so that the results would represent everyday working.
The fuel used for the journey was 224 lb., which is equal to 4i lb. per mile, at a cost of 1.2 pence per mile, for a full load of four tons.
The fuel cost on the oil-fired Foden works out at slightly over 6 pence per mile, or five times more than that of the Sentinel.
Allowing that the Welsh steam coal has a calorific value of 14,000 B.T.U.s per lb. and the oil fuel has 19,000 B.T.U.s per lbe and the boiler efficiency with coal firing to be 60 per cent, and with oil firing 75 per cent., then the Sentinel used approximately 38,000 B.T.U.s per mile and the Foden 71,000.
In other words, the oil-fired wagon required twice an much heat as the coal-fired wagon—the slight difference in the loads of the two vehicles does not account for such a great variation in fuel.
Either the Foden boiler is not adapted for oil fuel, or it requires much more steam. than a Sentinel, or there is some defect in the oil fuel system. Which is it1—Yours faithfully, THERMOS. Glasgow.
[The makers of the Sentmet claim a fuel consump tion of 7i lb. per mile for their four-ton wagon. The figures given by our correspondent seenillso low that we would like to receive further information on this subject and opinions from other users of steam wagons.—En]
Pneumatics on Front Wheels Only.
• The Editor, THE COMMERCIAL MOTOR.
[1,762] Sir,—A tremendous amount of propaganda appears to have been let loose in this 'country by foreign manufacturers of large pneumatic tyres in order to encourage the adoption of these on heavy commercial vehicles. I am glad to see, however, that our chassis ina,nufacturers are rather too wily to be persuaded into recommending the adoption of these tyres without thoroughly trying them out.
There is certainly a lot to be said for the adoption of the pneumatic tyre on commercial vehicles, but there are many points against it, although in the propaganda these points are usually glossed over.
Personally, I believe the whole question will boil down to the use of pneurna.tic tyres for the front wheels only, where their shock-absorbing properties will be more beneficial, and where they will not be subjected to Kell variations in the load as they would be if used on the rear wheels. The solid tyres used so generally are perfectly reliable, comparatively cheap, free from punctures, have a capacity for being overloaded in exceptional circumstances without undue deterioration, and there is also no risk that a vehicle with a comparatively high centre of gravity will overturn owing to sudden deflation. The tyre manufacturers claim that this deflation, in the case of their largest pneumatics, is a matter of 5 ins, only, but a 5 in. drop to one side in the case of a vehicle • travelling at some speed is not inconsiderable.
When a commercial vehicle, fitted with solid tyres all round, is running loaded to its rated capacity, its riding is usually.fairly smooth, as the springing is then working under proper conditions. It is only when running light that such a vehicle suffers from considerable vibration and, as a matter of fact, high pressure pneumatics under this latter condition, i.e., running light, may be very little better than solids. At the front axle, however, the load variation is comparatively slight and the tyres and their air pressure can be regulated to give the maximum shock-absorb ing capacity commensurate with strength. Pneumatic tyres positioned at the' frolt would certainly have a considerably longer life than if fitted at the rear, and thus would make up to some extent for the increased initial cost.—Yours faithfully, London. OBSTINATE.
A Use for Captured German Transport.
The Editor, THE COMMERCIAL MOTOR.
[1,763] Sir,—I was extremely interested in the article on German lorry and tractor design which appeared in The Commercial Motor dated 9th instant. It appears to me that these lorries and tractors contain so many interesting features in their design that it would be in the interests of the commercial-vehicle trade and, through it, in the interests of the general public, if these vehicles eould be loaned to the chief manufacturers of commercial vehicles in this country so that their details could be intimately studied.
It would be little use planking down 20 or so of these vehicles on one manufacturer and allowing him only a short space of time to make the examination. It would be better to endeavour to treat them as a kind of circulating library of important information, each manufacturer receiving one vehicle and passing it on to the next manufacturer according to instructions issued with each machine. The manufacturers should be permitted to dissemble the machines provided that they are re-assembled again beloved being .passed on.—Yours faithfully, DESIGNER. Birmingham.
Cantilever Springs for Commercial Vehicles. The Editor, THE COMMERCIAL MOTOR. .
[1,764] Sir,—Referring to the leader on page 409 of The Commercial Motor of November 2nd, entitled " Cantilever Springs for Coaches," may,I he allowed to make a, few observations anent some of your remarks, which are apparently based on experience derived from the considerable tests carried out by Palladium Autocars Ltd:, in their endeavoni to equip the Palladium commercial vehicle with a really sensible suspension and to break away from that relic Of the dark ages—the orthodox semi-elliptic spring I Ydu say "that the most experienced bus builders have favoured springs of the semi-elliptic type and there must be strong reason for this preference." I have no hesitation in predicting, Sir, that the remarkable results obtained by the Palladium double cantilever suspension vehicle must compel all progressive manufacturers to alter their spring design at the earliest possible opportunity. One, at least, of our mostsexperienced bus builders —and certainly the most progressive and enlightened one at that—is already investigating the subject closely, and I certainly am confident that, after completing experiments and making exhaustive comparative tests, the concern will be converted. The cantilever is certainly a far more accommo dating suspension for the varying load than the semiIt appears to me, therefore, that this fact is one of the most clinching arguments in its favour. There is no reason, moreover, why auxiliary springs or other supplementary devices should not be employed in conjunction with the cantilever to secure the greatest finesse.
The question of side-sway and roll is one to which great attention is necessary in designing a really flexible suspension. It is undoubted that with the single cantilever side-sway and roll are experienced. It is for this reason principally that my firm eventually adopted the double cantilever suspension design, with a considerable distance between the upper and lower springs on each side. The effect of this arrangement in the Palladium design in diminishing side-sway is, perhaps, as remarkable as the improvement in the smooth running of the vehicle which has been compared with that of a well-sprung vehicle on pnetunatic tyres. In "cornering," for example, less side-sway is apparent than with the serni-elliptic and the feeling imparted is a rather curious compromise between steadiness and well controlled "give," which is altogether peculiar to the double cantilever. There is not the slightest semblance of a lurch. This extraordinary feature is undoubtedly due to the space between the two springs of each side, and will probably be more marked in proportion to the amount of space allowed. The arrpagement in the Palladium design resists distortion and side displacements of the springs and accounts for the steadiness and the controlled " give" just referred to.
Farther, Sir, why should improved suspension be confined to passenger vehicles only? We already claim that the Palladium double cantilever vehicle is -the "Friend of the Fragile Load." Certainly, most forms of merchandise would be the better for escaping the unmerciful pounding to which they are subjected with the present-day vehicle.
The importance of suspension improvement is too great and momentous a question to be evaded any longer. The number of economies which will follow in the wake of improved suspension will force themselves, in the very near future, on to the long-sffffering user who will have to face competition more and more severe as time goes on.
Decreased petrol consumption, considerable saving in the repair hills, and freedom from breakdown are instances of the advantages and economies to the vehicle use-r.The question of the reduction of urnsprung weight is of itself sufficient justification for the adoption of cantilever springs. Undoubtedly the deleterious effect of heavy unsprung weight hammering and pounding the road surface accounts to a very large exteat for the atrocionsly bad roads that are found in all parts of the country, and particularly in those parts where heavy traffic has to 'be dealt with. The cost to the country for road repair would be considerably reduced, and the damage to adjacent property owing to the bad roads and badly-sprung vehicles, which is undoubtedly assuming a serious aspect, would be greatly diminished.—Yours faith fully, For PALLADIUM AIITOCARS, LTD., J. Ross MACMAEON, Managing Director.
Giant Pneumatic.—Information Wanted.
The Editor, THE COMMERCIAL MOTOR.
14765] Sir,—I observe that a gentleman who signs himself (1 II. Maxwell, Editor, News Service Bureau, United States Rubber Co., Ltd., is interested in my new semi-pneumatic-cushion tyre. I wonder why ? Maybe he is the head of his firm's propaganda department. (He is, of course.—En., " C.M."3 In that event it would be his " business" to squash anything, likely te interfere with the progress of the " Giant. '
Mr. Maxwell suggests that my reason for disliking the-" Giant" is because I am working on a rival tyre. That is rather amusing, for, being already in the pneumatic tyre trade, I see nothing to prevent my making a larger edition of my present tyre and selling it for use on heavy commercial vehicles. if I did so, I should have to supply spares, just the same as the others. Instead, I prefer to strike out on new' lines.
I cum Ira' Lancashire. Some of my friends from Wigan' St. Helen's, Warrington, etc., asked me to go to the commercial motor Show, collect all the literature I could, and obtain for them answers to certain questions: 1. Q.—Can " Giant " pneumatics be fitted to existing lorries?
A.—Yes, but such a course is not recommended. " Giant " pneumatics give best service when fitted to specially built .chassis.
2. Q.—Is it necessary to carry spares? A.—Yes, one for the front and one for the rear.
3. Q.—But why two spares? Would not one do, as in the case of an ordinary plea.sure car ? A.—No, because we recommend a different size tyre behind from that in front.
4. Q.—Are these spares fitted to wheels, and blown up ready for use ?
A.—No, we recommend that covers and tubes only should be carried.
5. Q.—But in the event of a puncture or burst, would it not take a very long time to change the cover and tube and inflate same?
A.—No, because we only recommend the tyres to be fitted to those clia,ssis which are fitted with engineoperated pumps. 6. Q.—In the event of a puncture, as the " lift " from the deflated' to wheel-changing position is rather exceptional, what jack do you recommend? A.—Two jacks. The necessary height can be obtained by using first one then the other. Some firms supply a special jack. 7. Q.—Seeing that a 10 in. Giant, inflated at., say, 150 lb. to the square inch, contains something like 60 tons pressure of air, what would happen to the driver of a vehicle fitted with such tyres,. if one were to burst just when he was working on AI A.—The risk of burst is very remote.
S. Q.—Do you guarantee it against burst? A.—No.
O. Q.—Then the risk is not so remote as you suggest. Now give me a definite answer to my query No. 7.
A.—The reply to that would be in the infirmary I The foregoing represent but a few of the queries and answers I received during my visit. For instance, one enterprising American salesman declared his particular tyre was capable of reaching 20,000 miles without being touched. "Two years running mark you, Sir, and, with ordinary luck, no need to even touch a spare." Had I been alone, I should certainly have asked that salesman what use the spares would be when brought into use after lying idle for two years, but being in the trade I forgot to.—Yours fsithfully,
BRITISH LION.