A PRIZE OF TEN SHILLINGS is awarded each week to
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the sender of the best letter which we publish on this page; all others paid for at the rate .of a primly a lime, with an allowance for photographs. All notes are edited before bang publithed. Mention pour employer's name, in confidence, as evidence of good taith. Address D., 111, and F., "The Commercial Motor." 7-1.5, Rosebery Avenue, London., E.C.
Lamps Alight.
Light your "lamps at 9.23 in London, 10.29 in Edinburgh, 9.47 in Newcastle, 9.44 in Liverpool, 9.S5in Birmingham, 9.33 in Bristol, and 10.25 in Dublin.
Exhaust Valve Cam Renovated.
The sender of the following communication has been awarded the i08. prize this week.
[1741] "J.11." (Leyland) writes :—" Recently when investigating the reason for lack of power from what was in all other respects a good, serviceable engine, I discovered that one exhaust valve was practically without lift. A closer examination revealed the fact that the particular cam which would normally operate this valve had worn very badly; evidently owing. to some error in hardening, it had been left soft, It seemed a pity to throw away a shaft which was otherwise in a perfect state of repair. I, therefore, set myself to discover some suitable means of renovating it, and eventually adopted the •following method, whiCh has proved fo be most successful. " I first of all thoroughly softened the remaining portion of the worn cam, and in order to ensure that this softening was local only, I so arranged the shaft that lengths of it on each side of the cam passed through water contained in clay troughs. I thew trimmed the worn surface of the eam and cut a dovetailed groove in it, this groove running parallel to the axis of the shaft, as shown in the sketch [We have had this redrawn.—En.]. I cut material for a new piece of cam from a gear shaft which happened to be, made of the right kind of steel, and after forming a tongue on this to fit the dove-tailed groove in the cam, 1 trimmed it up to the right shape. I made the new portion of cam T1 t in. narrower than the old tale, so that the outer edges of the groove could be nveted over, thus serving'as an additional means of securing the earn in place-. Both cam and shaft were drilled right through for a in. rivet, and each end of the hole was countersunk. The piece of cam was then case-hardened, refitted, and a good sound rivet driven into the hole. A fidal cleaning up on the grindstone was all that remained to be done."
A Hand.-brake Lever Breakage.
[1742] "JO." (Deptford) writes :—" One Saturday morning recently I was unfortunate enough to fracture tke pawl release handle on the side brake of my lorry. The tiro' e at which this mishap occurred was pa-rticularly unfortunate, as arrangements had been made to work through the week-end on an urgent job. I invariably used-the side brake in preference to the foot brake when driving, and felt that if I went out with the brake in this condition I might meet with an accident It was ,impossible to have it repaired in time, I therefore endeavoured to devise some means of providing a substitute. On the scrap heap I discovered
a piece of i in. sheet steel, triangular n shape, and of such a size that by bending it and cutting it, as shown on the sketch •herewith [We have had this redraww—En.] I was able in a, little over an hour to replace the lever with a very satisfactory substitute."
A Metallurgical Hint.
[1743] "GB." (1-lornsey) writes:—" The following mixture is handy for use when it is desired to restore steel that has been burnt or has lost its temper from some cause. The metal should be heated to a cherryred colour, and then dipped for an instant in the preparation :—
12 parts Tartaric acid ;
4 „ Charcoal powder.;
16 Bone black ; 20 „ Suet ; 20 „ Ferro cyanide potash ; Hartshorn.
" This is particularly suitable for restoring the te-raper of such articles as saws and chisels."