Correspondence.
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Ignition for Commercial Motors.
The Editor, " THE COMMERCIAL MOTOR."
Sir :—I was very much interested in reading Mr. De Prelle's article on " Ignition for Commercial Motors " in your issue of August 3oth, and I particularly noticed that his outstanding feature was that his drivers and men were totally inadequate for their calling. For instance, Mr. De Prelle says that if a car breaks down, the drivers come to the conclusion that it is always the magneto that has gone wrong, From his remarks one would think that all drivers are suffering from " magneto on the brain." I consider such remarks are absurd. Whilst endorsing the opinion of Mr. De Prelle that low-tension magneto ignition is more suitable for commercial motor work than other systems,. I was rather sorry to see the manner in which the men were ,spoken of.-Yours faithfully, G.B. London, September eith, 1906.
The Van Trials Deadlock.
We print below sonic further extracts from letters addressed to Colonel Crompton by members of the Motor Van, Wagon, and Omnibus Users' Association on the subject of the proposed van trials. ED.] Mr. II. N. jEFFERY, secretary of the Ackik FLOORING AND PAVING COMPANY (1904), Gainsborough Road, Victoria Park, N.E., writes :-" We quite approve of your _action with regard to the Automobile Club. We cannot see any objection to trials carried on outside that Club."
Mr. W.u:i ER H. Cook, managing director of FASTNUT, LIMITED, bp, Aldermanbury, E.C., writes :—" We consider the way the Automobile Club has met the Association in this matter both wrong and unfair. The course you have adopted certainly meets with our approval, and we fail to see that any benefit is gained by the Association in matters -confined to business vehicles through connection with the Automobile Club of Great Britain and Ireland. We believe, if the Association carried out trials on its own account, they would be well supported and prove a success."
Mr. A. H. CI-meet-nu., 4, Westwell Street, Plymouth, writes :--" I have come to the conclusion that the Automobile Club, in refusing representation to our Association on the committee formed by them to carry out the contemplated motor van and lorry trials, has certainly inflicted an injustice -on the users of that class of vehicle, as I feel that the committee of the Automobile Club is not in such a gocal position to form an adequate opinion as to the merits of this particular class of car as is a committee whose members habitually use the same in their business. I certainly think the trials, if carried out by our Association, would be of great value, and if Messrs. Carter, Paterson and Company, and Messrs. Pickford could be induced to give a thorough test to the competing vehicles under the Association's supervision, I am convinced it would be of greater weight with prospective users of commercial vehicles, in addition to saving the Association's funds."
Improvements in Omnibus Chassis.
The Editor, "TILE COMMERCIAL MOTOR."
Sir :—Now that the daily Press appears to be filled with the views of people who consider that motorbuses are a nuisance, not only to pedestrians, but also to house-owners who occupy preneses along the various routes, I should like to point out that the cause does not lie so much in the construction of the vehicle itself as in the method of driving.
frequently use the buses on the route from Cricklewood to Piccadilly Circus, and am always struck by the apparent ignorance of most of the drivers. When changing gear, which, by the way, appears to require an almost superhuman effort on some makes of omnibuses, the noise of the machinery in the gear-box is most distressing to those who occupy the interior of the vehicle. Then, again, some of the vehicles which ply in our streets appear to suffer from a fierce clutch. I am not connected with the trade in any way, but take a great interest in the motorbus movement, and should be glad to see improvements in the designs .appertaining to the present construction.—Yours faithfully, September 17th, 1906. H. T. C. (Norwood).
Oscillating Front Axles The Editor, " THE COMMERCIAL MOTOR."
Sir :—Referring to the article by Mr. Herbert Guthrie in your issue of the 13th instant, it seems to me that he overlooks what has always appeared to the writer to be the main advantage of a pivoted front axle, namely, that the amount of rise on one wheel going over a road obstruction is exactly halved at the point of contact of the axle to the body of the ear. Mr. Guthrie deals with the oscillating front axle purely from the point of view of the canting effect produced on the body of the ear by one wheel going over a road obstruction, but I submit that this is not fair unless the (elect on the vertical motions and forces is kept in view at one and the same time. I feel confident that a great advance will be possible if a thorough study is made of all the forces that are brought to play on the body of the vehicle, and that the horizontal forces (or forces which tend to cant the body of the vehicle) should be differentiated from those brought into existence in hearing the weight of the vehicle.
If one deals with the horizontal forces by means of a separate system, on the principle ol curtailing them before they react' the body of the vehicle, the amount of rise and tall of a wheel going over an obstruction can be carried to a minimum limit with wonderful results in easy running. With your kind permission, I hope to describe such a system in the near tuture.—Yours faithfully, CitAs. Wst. Fuvrosi. The Glen, Paisley, N.B., September ltith, Igoe.
The Editor, "THE COMMERCIAL MOTOR."
Sir :—Mr. Herbert Guthrie, in his article in your last issue, is, I am afraid, quite wrong in his conclusions as to the supposed disadvantage of an oscillating treat axle. He appears to confuse comparatively harmless tilting with positively injurious straining. A tour-wheeled vehicle with pivoted front axle is for all practical purposes a threewheeler. And, in the two vehicles Mr. Guthrie illustrates, the surmounting of an obstruction by a rear wheel will, doubtless, give a bigger platform tilt to that which possesses a front-axle rocker. But the lesser tilt of the other can only be secured at the expense of a straining effort to lift the front wheel off the ground on the obstructed side. And the heavier the front axle load and the longer the wheel base, the greater will this strain be, to say nothing of the temporary disorganisation of steering power. But will you allow me, Sir, to refer to another interesting problem, viz., that of load balance, which is frequently overlooked. In a steam wagon, the load on•the steering wheels is practically a permanent one, whereas that on the drivers is variable. The working load is really balanced over the back axle. And, given ample motive power' the tractive capacity by the vehicle is largely measurable y the weight resting upon the driving axle, the front axle load being, tractively, almost valueless.
Apart, therefore, from other considerations, the most economical .and effective of two vehicles will be that which bears upon its front axle no greater weight than will secure safe steering on the maximum gradient which has to Le negotiated, and which allows to its back axle the biggest working load margin. Any excess front axle load appears to me to really weaken the tractive efficiency of the back axle, inasmuch as the pushing forward by the rear axle of a front axle overload is pretty much in effect the same as trailing a similar load behind.
Now, the law provides a maxinfurn ts-ton gross load, of which no more than eight tons shall be on the back axle, leaving four tons to the front. But, as it also provides a maximum 5-ton total tare, it is evident that to carry a 5-ton net load, there must be no more than a 3-ton back-axle tare, which leaves two tons to the front.
What, therefore, I should like to ask your readers is whether these statutory obligations are conducive to thoroughly efficient commercial motor design, without waste of material after satisfying all requirements as regards strength and rigidity?
Are there any steam wagons in use realising the lastnamed tare proportions? As regards 5-ton carrying vehicles, I do not myself believe that there are any really serviceable modern ones (i.e., after 1904) under 41tons total tare, whilst I am certain that there are many which very far exceed the statutory 5 tons unless their carrying platforms are removed for treatment as part of their load, but which, by the complacency of licensing authorities in not checking loads, are obtaining a tractive credit which they do not deserve.
The question of load adjustment to secure the highest tractive efficiency with any given gross vehicular weight might, I am sure, be dealt with by some of your scientific correspondents, to the great advantage of merely practical readers such as myself.—Yours faithfully, September nth, 1906. DRIVER MECHANIC.
The Editor, "THE COMMERCIAL MOTOR."
Sir :—Mr. Guthrie either has not grasped the true issue at stake with regard to the oscillating front axle, or is seeking to confuse it. No amount of theorising, with false premises as a basis, will alter the concrete facts of the case. No one who has ridden, even for a short time, on the two types of machines referred to, will be in doubt for a moment as to the great value of the rocking axle and, certainly, no user who has owned both types would allow himself to be persuaded contrary to his experience of the great reduction in repair hills due to the oscillating type of axle.
Ihave had the opportunity of testing, over a distance of io,000 miles, two steam wagsns of identical construction throughout except that No. i was fitted with what for the want of a better name I will call the rigid axle; No. 2 was fitted with a rocking axle. No. 1, in addition to a number of minor troubles with pipes and loose rivets in the frame, broke one front axle and two springs during the lo,mo miles test run. No. 2 had no breakdowns whatever, and its general condition was much better than No. I at the end of the period referred to.
What is wanted in a heavy motor is flexibility in as suspension, to enable it to accommodate itself, without undue strain, to the inequalities of indifferent road surfaces. Roads, in general, are not good, and, as it will be many years, if ever, before they are even approximately perfect, the rigid axle, in my opinion, is doomed for use in heavy vehicles. It is no use arguing that, because the rigid axle system is satisfactory on light vehicles, that it will be equally efficient in absorbing shock with the heavy ones. There is no comparison ; it is a question of the relative rigidity of the springs and the frame. In a vehicle, in which the useful load to be carried is a small proportion of the gross toad, the rigidity of the frame compared with the spring may be high. On the other hand, in a vehicle con structed to carry a large load in proportion to the gross weight, the rigidity of the frame compared with the springs will be low. Therefore, it is impossible to get the necessary flexibility from the springs alone. By all means, make the springs as flexible as the governing conditions will allow, but the springs must be supplemented by an equaliser in the form of a rocking axle.
Dealing with the latter part of Mr. Guthrie's article, I am willing to admit that the rigid axle is cheaper, but, if cheapness is the only criterion of value, why not dispense with springs too? I deny, totally, that the rigid axle is lighter. The small amount of weight added by a forecarriage such as that fitted to the St. Pancras wagon can be saved by making the axle, wheels, and springs lighter than they would have to be without it, and for the following reason. With an oscillating axle it is impossible for the weight to be unequally distributed on the wheels, whereas, with a rigid axle, the whole of the weight of the fore end may be concentrated on one wheel, and this wheel, together with its spring and axle, must be made strong enough to carry twice the load it would have to carry were it fitted with a rocking arrangement,of some kind, To sum up, the rough diagram shows, without any need for words, what takes place when the rigid-axle machine surmounts a considerable obstruction.—Yours faithfully, HENRY A. NEAL. Somerville, Lion Gate Gardens, Richmond,