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 vehicles and tractors, and mechanics and foremen of garages or shops, are invited to send short contributions on any subject which is likely to prove of interest to our readers. Workshop tips and smart repairs; long and successful runs; interesting photographs: 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 into shape" and prepare sketches, where necessary, before publication. The absence of a sketch does not disqualify for a prize. When writing use one side of the paper only and mention your entPloyer's name as a guarantee of bona fides. Neither your own nor your employer's name will be disclosed. Payment will be made immediately after publication. Address your letters to The Editor, THE
COMMERCIAL MoroR, 7-15, Rosebery Avenue, London, E.C.
Will the writers of a letter about a steam wagon at Sutton, and of an inquiry about motorcabs, signed A.B.C.D., send their full names and addresses ?
Cutting a Keyway in a Lathe.
The sender of the following communication has been awarded the 10s. prize this week.
[640] A correspondent, who signs his letter " CONTRIBUton " (Sparkbrook), writes to us as follows :—" Cutting a keyway on a shaft is often a difficult and tedious job when it has to be undertaken in an ordinary repair shop. It is, of course, very seldom that small workshops possess much more, in the way of machine-tool equipment, than a lathe or two and a drilling machine; a milling machine of any sort is often a luxury that cannot be afforded. There is invariably, however, a good strong lathe in a shop of any pretensions at all, and it may, therefore, be usef ill to describe a method of cutting a keyway in a lathe, which, although it may be familiar to many of your mechanic
readers, may have some novelty for others. In the sketch which I have enclosed Le have had this redrawn.—En.], a short shaft is shown swung in the centres of an ordinary lathe; we will assume that it is required to cut a keyway,
in. wide and in. deep, at one end of this shaft. An ordinary stiff parting tool should be procured, and the width of this should he about 3-16 in. Having fixed the shaft between the centres, and the poppet centre having been screwed up tight, the tool should then be fixed in the slide-rest sideways, so that its top edge will be in above the centre of the shaft, as shown in the sketch. I omitted to mention that a.* in hole should be bored into the shaft just where it is intended that the end of the keyway should come, in order to allow clearance for the tool and the metal cuttings. The saddle of the latter must be adjusted fairly tight, and the cut may then be taken horizontally by winding the saddle along with the hand feed ; the depth of cut may be regulated by means of the cross-slide. After the top cut has been completed, the packing should be removed, and the bottom edge of the tool should be lowered until it is f in. below the centre of the shaft ; the cut should then be repeated. If ordinary care be taken with the fixing of the tool, and a stop be used to determine the depth of cut, an even fiat seat will be obtained. When the two 3-16 in.-wide cuts have been made, a in. strip will be left down the centre, and this, of course, may be removed in a similar way, by means of placing suitable packing under the tool again. This method, of taking the two outer cuts first, leaves the centre strip to act as a guide and to steady the tool, so that it has even pressure on both sides of it. In the event of the lathe at our disposal being sufficiently strong, then a keyway up to in. wide may be formed with the full width of the tool. If a slot has to be cut in a shaft which is not sufficiently strong to prevent springing, a steady should be used to slide along the back of the shaft; a piece of hard wood or other suitable material should be used to prevent injury to the shaft. With ordinary care, a much-quicker and better finish may be obtained in this way than by the hammer-and-chisel method, which calls for a higher degree of skill in order to secure a well-executed job."
Trouble with Slotted Valve Stems.
[641] " M.W." (Durham) writes —"I am driving a three-ton petrol motorbus of a certain make, and I must admit that I have had a lot of bother with the valves on the engine. The principal trouble has been due to the breaking of the valve stems at the cotter holes. These particular velvet are 81 in. long and their stems are only a shade over 5-16 in., whilst the slot is in. by 3-16 in. It will be seen, therefore, that the stem is left very weak at this point, as the net area is so small. I, at first, thought of boring out the guides in the cylinders, so that I could lit new valves with thicker stems, hut this appeared to he too expensive a job. I eventually decided to weld a new piece on to each broken valve. When I had done this, 1 cut them to the right length, screwed them 5-16 in. Whitworth and tempered the ends. A couple of nuts were then screwed on to the stem, and I was then able to adjust the tension of the spring; I had thus secured an ample fastening without unduly weakening the stems. 1 'TIOW have had all the valves on this engine treated in the same way, and I get no trouble at all in this direction." [Our correspondent would have been wise to have screwed
the stems with a fine thread, but, perhaps, he had not the necessary dies. Various ingenious devices, which do not weaken the stems to any considerable extent, have been adopted on modern engines. Two flats on the stem, with a small horseshoe locking-piece held in place by the pressare of the spring, is as satisfactory a method as any.—En.] Payment of Extras on Taxicabs.
1.642] " TACKSEE (Nunheacl) writes:" As a reader of your paper, and a taxicab man. I notice that your leading article in the issue of the 16th December dealt with the vexed question of the payment of extras on taxicabs. Under the present system, you say that the men put these extras into their own pockets " surreptitiously," and your proposal is put forward as an idea for the prevention of this. Personally, I would venture to suggest that the bast way to prevent this pocketing of extras surreptitiously would be to cease from expecting them to be paid in at all. Then, if the companies maintain that they cannot afford this, I am afraid that the only alternative will be to raise the fares, for I am quite certain that the drivers cannot afford to have any more taken out of their pockets.
" Furthermore, with respect to the amount which you suggest should be claimed from each driver every day, I do not believe, for one moment, that every cab upon the streets of London averages I s. exl. per cab per day under this heading, yet that is what you suggest should be paid in. I should certainly like to know the name of the firm which is so fortunate as to get is. per cab per day under the present system."
Bringing Home a Cripple.
[643] " W.W." (Dartford) sends us an account of the method he adopted in order to bring home a petrol vehicle on which the engine had sustained somewhat severe damage.—" You were recently good enough to publish some tips of mine in THE COMMERCIAL ?vlorou, and I now take the opportunity of offering you a description of some trouble I had with a vehicle, together with the means I took to remedy it. I had to go to a breakdown ; the driver had stated that he did not know what was the matter, except that water was coming out from the engine. This motor was of four-cylinder 30 h.p. and of a well-known make. The ear was a long way from home at the time of the breakdown, and, as it had happened on the Saturday afternoon, there was considerable difficulty in getting assistance of any kind. When I got to work and made an examination of the engine, I found that an exhaust-valve head had broken, and had worked its way in on top of one of the cylinders, and so had broken the piston 'head and water jacket. So considerable was the damage, that it was difficult to see how this could be sufficiently repaired to enable us to get home. After a while, however, I thought that I might be able to cut out the damaged cylinder and its fellow, and run home on the remaining two. I therefore disconnected the inlet water-circulation pipe, which was attached to the pair of cylinders I was going to cut out, and I blanked up the flange on the casting with cardboard. I also blanked up the outlet on the top of the cylinder in the same way. I next removed the cylinder caps on top of the exhaust valves, in order to rekase all compression, and I poured plenty of lubricating oil down into the cylinders of the affected pair, in order to allow the pistons to work easily. I took down the carburetter, and cleansed it from all signs of water. When I had filled up the radiator with some water that I ob • tamed from a shopkeeper near by, I had no trouble in starting the engine on the two cylinders. I travelled slowly home in this way, of course; the vehicle was empty, and there were no hills of any moment. Had the engine had separate cylinder castings I should have been able to arrange for three of them to drive, instead of the two in the case I have described, where the castings were of the twin-cylinder type. At any rate, I got home in reasonable time, and it is possible that this method may interest some of my fellow readers, and save them from spending a night out on the roadside on some occasion."