For DRIVERS, MECHANICS, & FOREMEN.
Page 31
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TEN SHILLINGS is paid to the-sender of any letter which we vublislt on this page, and an =RA FIVE SITI,CLINGS to the sender of the one which we select as being the best each week. All notes are edited before being pubtished. Mention your employer's name, in confidence, as evidence of good faith. Address, A, M. and Fâ "The Commercial Motor," 7-15, Rosebery Avenue, London, E,C. 1,
Lamps Alight.
On Saturday, March 12th, light your lamps at 6.26 in London, 6.34 in Edinburgh, 6.36 in Newcastle, 6.37 in Liverpool, 6.31 in Birmingham, 6.36 in Bristol, and 7.20 in Dublin.
Some Useful Tips.
The sender of the following communication has been awarded the extra payment of 58. this week.
[2200] " T.H.W." (Wigan) writes:â" I had a peculiar trouble recently with a single-cylinder O.A.V. magneto, which may possibly be of interest to your readers for, although this particular magneto was a
part of a motorcycle, a four-cylinder machine of the same make might easily develop similar trouble.
"Misfiring having occurred while the bicycle was in use, the magneto was removed and tested. It was found to give 18 sparks regularly and then to miss two or three, then giving another 18, then missing again, continuing thus in regular sequence. As I had had trouble of this kind in the army with motor-bicycle magnetos, I suspected a. flat on the small fibre roller which causes the points on the contact breaker to open. I therefore removed this roller and skimmed it up in the lathe, replaced it and tested the magneto again, but without noting any improvement. I Made a further careful examination of the contact. breaker itself, for I felt convinced that the trouble was there and subsequently discovered that the bore of the roller was not true. It was not a:perfect circle. The elect waa that every time a high part of this inner face came against the pin about which the roller rotated, the points of the magneto did not quite close, and, in consequence, no spark took place until this high spot got clear. After truing the hole up with a small reamer, the trouble entirely disappeared, and has not occurred since.
"Another interesting case of mine recently was in connection with the engine of a Maxwell ambulance. No. 3 cylinder would persistently give trouble owing to oil on the sparking plug, and, in fact, when the
latter was removed, oil could distinctly be seen floating on the top of the piston, while the other cylinders were apparently quite normal in this respect. . As the engine actually required overhauling, it was dismantled and particular attention paid to this point. All the pistons appeared to be on the slack side, but the piston rings were quite good. No. 3 piston, however was not under-cut round the skirt like the others, and No. 3 cylinder was also slightly scored, owing evidently to the gudgeon pin having come loose on some previous occasion.
"After consideration I decided to cut a groove, in the skirt of the piston to match those on the others. I also bevelled off the lower edge of the groove for the lowest piston ring, and, in addition, drilled eight IV in. holes round this bevelled face leading to the inside of the piston, so tbat;as the pistons descended, this lowest ring scraped off all surplus oil, which drained back through the holes into the interior of the piston. The experiment was quite successful, and, on re-assembling the engine, and testing, no trace of oiling up in connection with No., 3 or any other cylinder was noted, notwithstanding the fact that the oil in the sump was considerably more than that normally required.
"Another item of information which may interest your readers is that a piece of strong cord is occasionally useful to compress piston rings when they are being erected. The car+ should be wrapped once round the rings and the ends be held by an apprentice or assistant. This, of course, is not so useful as a properly designed clamp, but can be made to serve the same purpose when no clamp is available."
Rebushing Spring Shackles.
[2201] " H.J.E." (Ealing) writes:â" in overhauling chassis, the spring shackles are frequently found to be so worn as -to make it impossible to re-bush them in the ordinary way.. This is particularly the case where floating bushes are used, and, as a general rule in such circumstances, the shackles are scrapped. An inexpensive and quite successful way of keeping these shackles in use is to serid. them to the nearest foundry and have the hole filled in with solid brass or gunmetal east in place. Silbsequently rebore them to the desired size. 1 have found this method most satisfactory in a good many cases."