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 anything else published.
Drivers of commercial motors, and mechanics and foremen of garages or shops, who are engaged in any branch of the industry, are invited to contribute short, personal experiences, oPin ions, or suggestions, on subjects which are likely to prove of interest to our readers. We shall be glad to hear of anything interesting that has come under any driver's or mechanic's notice, either in the shops
• or on the road. Long and successful runs ; services with no " lost journeys" ; workshop tips and smart repairs all are suitable subjects. Send a post-card, or a letter, or a sketch to us—no matter how short, or how written, or how worded. We will " knock it infr sha.be" before publication. When writing, it is as well to mention your employer's name as a guarantee of bona fides (not . for publication), and to state whether you wish your own name, or initials only, to be published. Payment will be made immediately alter publication. Address your letters to The Editor, " THE COMMERCIAL MOTOR," 7-15, Kosehery Avenue, London, EC.
We have replied in full to the following correspondents by post :—Sidney Parr (Manor Park, E.); " F.F." (Clapham Junction, S.W.); and " D.H.P." (Bedford). We would draw the attention of G. P. Haseltine (Portsmouth) and others to the fact that we are not interested to receive letters which contain spiteful allusions to errors of judgment or inaccuracies, that may have inadvertently crept into the columns of any of our contemporaries.
A Cylinder Sight-hole.
The sender of the following communication has been awarded the los. prize this week :— 14291 H. Gu.t., (Reading), in the following letter, gives an • account of a small fitting which be has found very useful, and which has enabled him to test the firing of the various rtypes of petrol engines which he has had in his charge from time to time :—" Some years ago I made a useful appliance, which I venture to describe in the few following paragraphs, and as I have not seen anything exactly like it illustrated, J thought you might consider it worthy of .publication in the Drivers' columns of TUE COMMERCIAL MOTOR.'
" I enclose a sketch of the device, which should render the following description clear to your readers. The base -(A) is one of those fittings which are commonly sold by -accessory firms for the accommodation of two sparking plugs, when duplicate ignition is to be installed on a 'cylinder which is only normally adapted for one plug; B and 131 are the steel body and the brass lock nut of a broken, low-tension magneto, sparking plug respectively; C and C1 are copper and asbestos washers; and D is a piece of the thickest plate glass procurable. The periphery of this glass must be a slack fit in the steel nipple, in order to allow for expansion. It will be noticed that the second plug holder in the fitting (A) is shortened, and the object of this is to bring the sparking plug points sufficiently low in the plug fitting to be visible through the glass (I)).
" I have always, in my experience, found that it is a great convenience to be able to inspect the spark under working conditions, but, as a matter of fact, this aspect of the device was entirely an after-thought when I originally made the fitting. My first intention was to secure an arrangement by which I could at any time assure myself as to the colour of the flame of the exploding mixture, and the need for such information was impressed upon me during the time that we were carrying out various adjustments to some motor-boat engines, which were to run on .760 petrol. At first, during the period of these tests, we were of opinion that we were getting very good results, and a smoky exhaust was attributed solely to over-lubrication. I then applied the little fitting which I have described above, and I soon discovered that the burning mixture was of a dull yellow colour, and that there was a distinct pause between the time of the commencement of the spark and, what I may call, the burst of flame.
"To enable your readers more thoroughly to grasp the circumstances under which we were working, I may add that the spark was actually occurring when the piston was still well down the compression stroke, and an absence of knocking told me that the piston had to travel some distance before the maximum compression was attained. We next considerably increased the supply of air, with a result which showed, through our spy-hole, a bright, violet-coloured flash, and this was practically simultaneous with the spark ; we also found that we could advance the ignition under these new conditions but very little beyond the top of the compression stroke, whilst the exhaust was clear and almost odourless. As might be anticipated, a very considerable increase of power was obtained, and, in fact, we were enabled to increase the number of revolutions from 450 to 600 per minute.
" For the purpose of the tests, we were using a Walker fan dynamometer, and the adjustment of this instrument was never varied throughout the test. After this initial experiment with my little device, the employers with whom I was at that time engaged never attempted to adjust the feed of a petrol carburetter or paraffin vaporiser without reference to the results which were observable through the small cylinder sight-hole."
A Broken Back Axle on a Steam Wagon.
 " J.C." (Parkhead, Glasgow), in the following letter, describes a temporary repair which he successfully carried out on the broken back axle of a steam wagon :— " Some while ago I was driving my steam wagon, which is of a well-known make, along a busy street in Glasgow, and, as the mishap I had, and the subsequent repair I was able to make, may be of interest to some of your readers, I venture to send you an account. At the time of the accident, I was carrying a load of 7 tons, and the broken axle let down one side of the wagon so badly, that I was afraid the load would slip off the platform. With as little delay as possible, I procured blocks and screw jacks to lift the body of the wagon and made things safe for the time. I found, upon examination, that the flange of the driving sleeve had broken through, and that the driving shaft itself was completely fractured. I need not trouble you with an account of the examination, and the subsequent decision I came to, in order to make a temporary repair, but it should suffice if I tell you that I had a clip made to go round the broken flange, and by screwing this tightly .up in position, I was enabled to keep the axle shaft in alignment, and to take the wagon home under its own steam. The fillet on the shaft prevented it from coming out of the sleeve."
What Gives Most Trouble? Ignition ?
[4311 We have recently received a number of communications, intended for publication on this page, in which drivers and mechanics have drawn attention to certain deficiencies in the construction of their vehicles ; and the letters invariably voice a desire for improvement in some small eon-. structional detail, which is constantly giving trouble. It is occasionally the case that a large number of temporary stoppages On the road are due to the constant recurrence of similar troubles on certain chassis. These troubles could often be obviated by means of a slight mechanical alteration. Frequently, however, manufacturers do not hear of these minor troubles and they are therefore not always in a position to take steps to improve -their models in this direction. With a view to affording drivers and mechanics an opportunity of pointing out what are, in their opinion, the details which give them most trouble on the road, we shall publish a selection of letters dealing with this subject, as occasion offers, with the abject of obtaining practical suggestions for the possible structural improvement of minor details on chassis from the point of view of the driver and mechanic.
Amongst other letters dealing with this subject we have received the following from " K.D.L." (Southampton) :— " It has often occurred to me, in the course of five years' driving experience, that a great many roadside troubles are due to a comparatively small number of causes, and that a general enquiry as to what the driver and mechanic find gives them most trouble on the road, could not fail to yield interesting information and should lead to the decided improvement of many small and comparatively neglected details on commercial motor vehicles. I have found that about seventy per cent, of my small worries have been due to ignition defects. I have had to drive machines fitted with all types of ignition, but, in almost every case, I have had cause to curse the designer of my ignition gear. Other trouble I have had, of course, in common with every other driver, but if I had been able to say that, during the course of my career as a motor driver, I had had no trouble with my ignition gear, I should seldom have had to report a broken journey. I have only driven petrol and paraffin lorries and cars, so that I cannot say whether drivers of steam wagons have any small worry which causes them similar trouble and which is peculiar to the type of vehicle upon which they are accustomed to work.
" Terminals, fittings for holding the cables, couplings for the ends of the wire, and the hundred and one little details of the electrical equipment of a car propelled by an internalcombustion engine, are almost universally flimsy and are designed on a niggardly scale. Many magnetos are constant sources of trouble, once they have had a little wear. Distributors, commutators, and contact-makers—well, the less said about many of the patterns the better.
" If, Mr. Editor, you can only persuade the makers to pay more attention to the fitting of a strong and not easily deranged system of ignition to their vehicles, you will save many a driver an anxious hour on the road with a machine which has come to a standstill through an ignition mishap. The trumpery nature of these mishaps makes them all the more annoying. I think all drivers of petrol vehicles will agree with me that no detail gives them so much trouble as the ignition system."
[Many of the later types of petrol-propelled chassis are fitted with admirablyuhemcd ignition systems of a sturdy description, but, in some cases, our corre. spondent's complaint is not groundless. 'The now United Motor Industries (toil, described in our issue of the 18th Tune last, is an excellent sample of what the electrical details should be on commercial motor vehie]es.—ED.1