Contributions from Drivers and Mechanics.
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TEN SHILLINGS WEEKLY for the Best Communication Received, and One Penny a Line of ten words for any thing else published.
Drivers of commercial-motor vehic es and tractors, and mechanics and foremen of garages or shops, are invite-1 to send sitar' co iriontions on any subject winch is likely to prove of interest to our readers. W t.rkshop tifs and smart repairs ; long and successful runs; interesting photographs : all are suitable subjects. Send a post.card, or a letter, or a gulch to us—no matter ly,w short, or kow written, or has worded. We will " knock it into shape" and prepare sketches, where necessary, before publication. The absence of a sketch dies not disqualify for a prise. When writing use one side of the paper may and men 'ion your employer's name as a guarani e of bona fides. Neither your °Wit nor your employer's name w ll be disclosed. Payment will be made immediately after publication. Address your letters to IN Editor, THE COMMERCIAL Maros, 7-15, kosebery .1venue. Londim, E.C.
When Replacing Valve Springs.
 " (Slough) writes :—" I enclose a sketch and a description of a small addition that I have recently made to my tool kit. As it has far more than repaid me for the slight trouble of making it, I think, perhaps, it will be useful to many of your readers.
" When it is necessary to compress a valve spring on a petrol engine in order to fix its lower end into the slot in the stem, most of your readers will know that the -spring, more often than not, has an annoying habit of gripping the valve stem and of lifting the valve upwards at the same time. In other words, it is difficult, when replacing a valve spring, to ensure that the valve will remain firmly on its seat during the operation.
" To prevent this lift occurring, I made the little tool which I wish to tell you about. I got hold of a discarded bridge-piece and cut off the pegs at the .ends. I drilled and tapped two a in. Whitworth holes in the same centres as the original pegs, and I screwed therein two pieces of I in. round mild steel, 31 in. long ; one end of each of these pieces was turned back for a length of in. and screwed in. Whitworth, as shown in the sketch [We have have had this redrawn.-En.]. By taking off the bridgepiece on the cylinders and by removing the valve covers, this little tool can be fixed into place. Then by screwing down the nut which formerly held the bridge piece, the legs of this tool can be pressed down on to the tops of the valves, thus holding them securely on their seats. The springs can then be put into place easily."
The Comfort of the Driver.
 " S.I." (New Cross) writes :—" Your correspon dent, " " (Bord es] ey Green) [Letter No. 817.—En.] criticises some remarks of mine which I made in the letter No. 809 which yon published in a previous issue. Your correspondent is mistaken if he thinks I am entirely sympathetic with the motorbus companies. If a driver sits on bare boards it is his own fault; he is not compelled to, and can obtain leather seat cushions if he takes the trouble.
" In reply to F. C. McD.' [Letter No. 819.—En.], I have to tell him that I drove one of the first dozen motorbuses that were licensed for running in London, and I can, therefore, speak with some experience. I do not think the two correspondents that I have mentioned are sticking to the point. Mr. Jarrott, in his suggestions for the alteration of steering design, appeared to me to be more concerned as to the safety of the public than as to the comfort of the driver. He claimed that larger steering wheels and such improvements would lessen the number of accidents. On the other hand. I must take exception to Mr. Jarrott on one or two points. If, by altering the size of the steering wheel, we were to alter the standard that has been adopted in the matter of steering gears, and since at the present time some of our fat drivers have considerable difficulty in getting between the steering wheel and the driver's seat, such men would have to retire from active service. A similar objection could be urged on behalf of men with abnormally long legs, and we have quite a lot of them in the London service.
" I really do not think that motorbus drivers have a
lot to grumble at, as weconsiderably-better conditions than tram drivers, who have to stand the whole time. We can strap on our aprons and make ourselves fairly comfortable under the circumstances.
" The complaint from If..T.' that we have only glass windows on which to lean back our heads, is rather
absurd. A bus driver who wants upholstered cushions. for that purpose would be better in some other job. As a matter of fact, when driving in London, you have to situp very erect most of the time if you want to keep clear of trouble. If anyone is really concerned as to the comfort of the driver, I think one of the simplest things that might be done in this direction is to increase the height of the standard dash ; this alteration would mean a. lot, so far as additional comfort is concerned." Locating a Faulty Cylinder.
837] (Guildford).—To all w ho understand the cycle followed by the ordinary-motor-vehicle petrol engine, the method about which you write us, is by far the most obvious one. Others are to note the marks which are commonly made on the flywheel to show the position of the pistons, or to take off a crank-chamber cover and to notice the position of the cranks. If it be a four-cylinder engine, you can readily ascertain in one of these ways which two must include the faulty one, and the final decision as to which one of these is on compression is a simple matter. We are sorry that your contribution is not sufficiently novel to warrant publication. You must "have another shot."
A Grip-head for a Jack.
The sender of the following communication has been awarded the 10s. prize this week.
 " 3.(1.P." (Luton) writes I am sending you a model of an idea of mine for a special form of head for lifting jacks, and I should greatly value your criticism of it. If you would also not mind telling me how I could go to work to put it on the market I should be further indebted to you. I do not think there is any need for me to bother you with a detailed description of my scheme, as I think you will quite well understand it from the itmdel." fOur sketch was prepared front this model.-Ee.1 In a further letter in reply to a critical communication from us, " J.G.P." writes :—" Many thanks for your suggestion that I should secure a provisional protection for my idea at the Patent Office. This has now been completed, and I shall be grateful if you can put me in touch with anyone who is manufacturing motor jacks, and who would like to 11843 a device of this kind, which absolutely prevents the possibility of an. axle or other part slipping while it is being lifted. It will be seen that the greater the weight that is put on the inner arms of the swivelled jaws, the firmer will the load be held."
I We shall he happy to place anyone, who is interested in this ii. pinions idea, in touch with the inventor.—ED ] To Rid Parts of Rust.
 " H.S." (Bedford) writes:—" Some tin:e ago, in the course of my work as a fitter, I had several articles given me to get ready to be eleetro-plated. Now it happened that they were thickly coated with rust. owing to their being laid by in the stores for some time. After spending the best part of a day on two of them scrapiug and emery-papering—I began to look round for a quicker method of cleaning them. When I had knocked off that night., I happened to tell a chum of mine about the job, and he promptly gave me the following tip, which I now send for the benefit of my fellow mechanics. who may at some time or other have similar work to do.
" First of all, then, I made a strong hot potash bath, am] I dipped the articles in this, leaving them in for about half-an-hour. They were next put into a cold muriatie acid pickling solution, composed of two parts of water to one of acid. This removed the rust in a few minutes, leaving the metal only very slightly attacked by the acid. Soaking them in hot potash was responsible for the rapid pickling, for without the potash it takes about an hour in the acid bath to get the same results, and, of course, the shorter the time that they are in the acid the better. I found that all the articles so treated had a smooth finish. My foreman was so pleased that he had all similar work which was in hand done in the same way. The parts were then painted over with a coating of white lead and oil, before they were put back into the stores. Apparently a chemical reaction is set up in this way which changes the character of the rust, softening it and making it soluble, so that you can rub the rust off with your hand."
The S.A.M.D. (Manchester).
The first annual dinner of the Manchester Branch of the Society of Automobile Mechanic Drivers of the United Kingdom was held at the Albion Hotel, Piccadilly, Manchester, on Saturday, the 28th January. During the course of the evening's festivities, which included a dinner and a smoking concert, speeches were made, amongst others, by Mr. J. Newton (of Newton and Bennett, Ltd.), and by Mr. Leo Swain. The latter speaker urged upon his audience the advisability of ecouraging the drivers of commercial-motor vehicles to join the Association. The industrial side of the movement, he was confident, would before long overtake the pleasure-ear branch. It was going to be ten times as big in fact!
Warming the Induction Pipe.
840] " D.E." (Slough) writes :—"Most drivers of public .service vehicles know something of the difficulty of start mg up the internal-combustion engines of commercialmotor vehicles, especially when the weather is cold. Certain popular types of engines are fitted with low-tension magneto, and it is such models that are particularly difficult to start at this time of the year. With this bother in view, I have this winter fitted several engines in the manner which I describe below, and I am pleased to say that this alteration has had excellent results. Between the joint above the throttle and the induction pipe I have fitted a small tray made out of tin or sheet iron. A small quantity of petrol is poured into this tray end is then lighted. While the petrol is burning and the induction pipe is getting hot the driver always finds plenty of small jobs, such as oiling up, brake adjusting, etc. When the petrol is burning out the pressure should be pumped up, and the carburetter should be flnoded. It will then be found that the motor will start at the first turn.
"It is possible that some of your readers will protest that this method is attended with considerable risk; but I do not think there is cause for alarm if reasonable care is taken, and at any rate I can assure you that a simple arrangement such as this is well worth adopting, as it saves a tremendous lot of trouble on cold and frosty mornings."
This method or its equivalent is one that is not infrequently adopted but it is not approved by Fuverintcnd en 1,, as a ink, et by instrane eorspanies.—En.]