ForDRIVERS; MECHANICS & FOREMEN. . •
Page 29
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TEN SHILLINGS is paid to the sender of any letter which we publish on this page, and an EXTRA_ FIVE SHILLINGS to the sender of the one which we select as being the best each week. All notes are edited bejore being published. Mention pour employer's name, in confidence, as evidence of good faith. Address, D., M. and F., 'The
. Commercial Motor," 7-15, Bosebery Avenue, London, E.C. 1.
Lamps Alight.
On Saturday, August 7th, light your lamps at 9.6 in London, 9.37 in Edinburgh, 9.26 in Newcastle, 9.26 in Liverpool, 9.15-in Birmingham, 9.16 in Bristol, and 10.9 in Dublin.
A Jig for White Metal Bearings.
The sender of the following communication has been -awarded the extra payment of 5s. this week.
[2120] "MM." (Kensington) writes :—" When an engine is down' and -new bearings are to be fitted, it is frequently found necessary to re-grind the crankshaft, which is, as a rule, either scored, or worn oval. In such cases neither the old bearings nor new ones of standard
size are of any use. The accompanying sketch illustrates a standard jig which I have had made, in which white metal bearings may be cast. It
takes about 16 hours to make, including turner's time. The jig consists of two pieces of mild-steel plate and two tubes. One tube should be slightly Jess in outside diameter than the bore of the bearing, so that for a bearing of nominal size 1, the tube size is 11,1. It should slightly taper from one end to the other. The other piece of tube must have an internal diameter slightly larger than the outside diameter of the bearing, and it must be in halves. The base plate has to be carefully grooved, as shown, to accommodate the two pieces of tubing. Both tubes are slightly longer than the bearing, but the inner is longer than the outer by 1 in. (See sketch.) The top plate bears on to the -LIT of the inner tube, and is held by means of a long central bolt passing through both top and base plate. The two halves of the split tube are held down to the base plate by set screws, passing through the top plate, and through angle brackets welded to the base plate, as shown on the sketch. The joints between the tube and the base plate, and between the two halves of the outer tube, must be carefully ground together.
"It will be noticed that the top plate is narrow, and leaves ample 'room for the metal to be poured down either side. In use the jig is carefully erected, the metal run in, and when it in cold may be dismantled by first removing the outer tube, thein slacking back base plate. Place suitable packing washers betweea it and the white metal. Gently screwing up the central bolt will then release the metal from the inner tube.
"It is a good plan carefully to blacklead all parts before running in the metal, so that there will be no risk of it sticking. Owing to the correbt location of) the inner and outer tubes there is very little machining necessary of these bearings after they are cast.
Running with Half an Inlet-valve Spring.
[2191] " (Eye) writes :—" A short time ago, when making an important journey with a fully-. loaded lorry, I had the misfortune to have an inletvalve spring break in halves. Now other vehicles in the same fleet had met with similar trouble, and had made shift to get along on three cylinders, with the result that they arrived late at the market with their loads, which happened to be garden produce. The effect of the tardy delivery was general dissatisfaction all round. As I did not want the same trouble to occur in connection with my load I determined to make an effort to keep all four cylinders working. I had not a washer or anything I could put .between the two halves of the spring to keep it going normally. What 1 did was to. make use of half a spring by removing the valve cap, putting the half of spring on top of the valve, and screwing the valve cap on again.'
An Engine Control Improvement.
[2122] "F.N.N." (Willenhall) writes :—" The following note in reference to the engine control mechanism of a Star chassis may be of interest to drivers of that make of vehicle. As originally turned out, the control for carburetter and magneto is a drive incorporating two pairs of segmental gears. These wore very rapidly, frequently became disconnected, and finally refused to work at all. At the time this occurred I found I could not get new ones, se took them off, with -a view to truing them Up, recutting the teeth, and replacing the wheels. However, I found. that, with the addition of a couple of new in. ball joints and by cranking the levers and coupling rods a little, I was able to make a direct connection between the levers on the bottom of the steering column and those on the magneto and ea.rburetter "In view of the fact that the original gears lasted about nine months and the Connections with which I replaced these gears have been working about three years without any trouble, I think .1 am justified in claiming this rearrangement to be an improvement."
Running a Steamer on One Cylinder.
[2123] " HK." (Newcastle-on-Tyne) writes :—" I venture to put forward the following as my first contribution to your D.M. and F.' page : Like 'W.W.,' I had a mishap while out driving a Foden steam wagon. In my case it was the forward 'eccentric of the H.P. cylinder which went wrong. As I had a full load on board I could not consider running on one ,cylinder only, as it would not have provided sufficient power. What I did actually was to change the two ecCentrio rods, putting the damaged one to the 'reverse end of the link, and letting the old 'reverse ' eccentric rod take its place. " It will be realized, of course, that the rod was only slightly damaged. Had it been badly bent, or had the eccentric strap been broken, I still think I could havA managed, by fixing the reverse end of the link to the coupling rods. In the former circumstances, reversing would have been difficult but possible ; in the latter, impossible. • "I have been thinking over the problem presented by A.J,Da' and am strongly inclined to agree with H.141.' It seems to me that, with the piston in position, and a large block of wood as well, considerable back pressure would have-been caused in the H.P. cylinder had not the L.P. valve been removed in order to give the steam a passage to the atmosphere."