6. Drivers &Mechanics
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TEN SHILLINGS WEEKLY is paid for the best communication received, and one penny a line of ten words for anything else published, with an allowance for photographs.
Send us an account of any special incident of your work or experience. If suitable, we will edit your notes, supply a sketch when required, and pay you for everything published. Mention your employer's name, in confidence, as evidence of good faith. Address to The Editor, THE COMMERCIAL MOTOR, Rosebery Avenue, London, E.G.
We shall be glad to hear from drivers who have been running. their petrol engines on benzole, as to their experiences. We shall pay for any communications which are published.
How to Re-fit Bearings.
[13151 " H.S." (Busy) writes :—" When overhauling a petrol engine, and it is found necessary to lap in the crankshaft and connecting-rod bearings, I find a powder which will leave a dead smooth surface is a fine grade ca,rborundum, which should be thoroughly mixed with thin oil. If a lapping tool be not available, a satisfactory substitute is F.F. grade emery cloth—also well oiled during use. The method to be adopted is to tear off the cloth in strips of about 1i in. in width, a piece should be once wrapped round the journal and each end given a steady, alternate pull, working the strip from end to end of the bearing. When refitting the brasses, care should be taken to ensure the correct amount of clearance, otherwise the bearings will seize for want of lubricant. A good test for judging when the connecting-rod big-ends are properly fitted is to give the rod a short, sharp push with the hand, when it should revolve round its bearing about one-and-a-half times."
Rig for Grinding-in Pistons and Rings.
[1316] " A.H.H." (Cardiff) writes :—" Hitherto when having occasion to grind in new pistons and rings, I did so by using the connecting rod of each piston for working it to and fro in the cylinder, first wrapping rag round the big-end keep for handling. This method proved too cumbersome, so I send you a sketch—[We have had this redrawn.—En.]—of a readily-made rig, which I have since adopted for the purpose. Procuring a. piece of hard wood about 2 ft. 6 ins_ long, into one end of it I fitted a lead veebearing, then attached alongside the wood a strip of
mild-steel plate l in. wide by in. thick, forming a hook at the end, as shown in the sketch, to clip over the gudgeon pin. For accommodating various sized gudgeon pins I slotted out the two bolt holes in the mild-steel plate to allow for adjustment." A Suggestion for a Rear-wheel Sprag.
[1317] " R. H." (Halifax) writes :—" I send a sketch [We have had this redrawn.—ED.] showing my suggestion for an arrangement of rear wheel sprag which I consider is an improvement upon the usual form of sprag fitted behind the gearbox. That type, if brought into use suddenly, is apt to cause undue stress to be brought into the transmission. From the sketch it. will be seen that the ratchet teeth of the sprag are machined out of the rear-wheel brake-drum casting, which, being bolted directly to the rear wheel, eliminates any possibility of straining the driving mechanism when the sprag is brought into use. The pawl is anchored in a suitable position on the main frame member and is controlled from the driver's seat. by means of a length of cable ; the face of the pawl would, of course, be case-hardened. A. jockey pulley or suitably-formed roller should be fitted, acting as a guide for the cable."
An Ingenious Form of Air-Inlet Valve.
The sender of the following communication has been awarded the los. prize this week.
[1318] " E.F.H." (New York) writes --" To mitigate the poor results frequently attendant upon variable weather conditions, during the running 'Of my machine, I recently fitted a valve to the pipe leading to the carburetter air inlet, so that, when the weather became warm, I could open an air passage and admit cold air to compensate for the rise of temperature. I found this manually-operated valve to give such good results that I decided to make it automatic. For this purpose I fitted a thermostat inside the air inlet pipe so that any varying atmospheric temperature would open or close the extra-air inlet valve at. the reouireJ time. I enclose a sketch [We have had this redrawn—En.] showing the device. The thermostat, co: thermostatic couple, is constructed out of a piece cf
strip steel and strip brass, each piece approximately 6 ins, long by in. thick and in. wide. They are sweated together throughout their length and so bent Suggested thermostatic air control.
that, when, one end is riveted to the inside of the pipe, the other end stands midway in the pipe diameter. The brass strip is fitted on the underneath side. The valve is constructed out of aluminium for the sake of Lightness and is provided with a threaded stem over whichare screwed four lock-nuts which serve to adjust the valve in relation to the thermostat. The action of the device is very simple. When the temperature of the hot air rises above normal, the brass strip expands more than the steel, and causes the couple to bend up, this opening the valve. When the temperature falls, the rod assumes its normal position and the valve closes again. Of course a few trials were necessary to determine the proper adjustment. In the matter of the smooth running of the motor, since fitting the device, the results were far beyond those anticipated."
Local Protection during Case-hardening.
[1319] " RT." (Bedford Hill) writes :--" In the matter of case-hardening, principally where the work in hand has to be left uniformly hard all over, the ordinary carbonizing treatment would be quite satisfactory. In other cases, however, where only the wearing surfaces have to be hardened and the parts left soft for machining, riveting, etc.. the proposition is quite a different matter, and it is not. generally well-understood how best to protect the portions which are required to be left soft against the action of the carbonizing element.
"Ordinary fireclay, which is .sometinies used for the purpose has the habit of cracking or peeling off during the purpose, process, with the result that the under lying surface becomes either wholly or partially exposed, and subsequent softening has to he effected with a considerable degree of uncertainty by means of a blow-lamp, "One method which is sometimes employed when making new parts is to allow a surplus amount of material on the particular portions required to be left soft for some further machining operation, and, as the hardening generally has but a skin-deep effect, the superfluous metal may be ground away after the hardening process.
"By far the best way, however, is to use a solution of copper on the parts desired to be left soft, for a coating of copper of even Tess than one-hundredth of an inch in thickness will resist the action of the most vigorous hardening compound. Mechanics who have access to plating vats will find the particular one used for coppernagmost convenient for the purpose. Failing this, a strong solution of copper sulphate, such as is nseci on the marking-off table, will be found to give excellent results ; it provides a far more convenient and effective protection than the old-fashioned method of covering the parts with firecIay."
Instead of Split Pins.
[1320] " J.W." (Warrington) writes :—" With reference to dispensing with split pins, I send you the end of a bolt [From which we have made sketch.—En.] showing a method I have adopted on different
machines for preventing nuts working loose. A sawcut is made in the bolt, the nut screwed up tight, and then a chisel is used to open slightly out the projecting portion of the pin. This method is very satisfactory for road-spring clip-bracket bolts, rear-wheel brake-drum flange bolts, etc.
Detecting Leaky Tubes.
[1321] " H.W.T." (Cardiff) writes Drivers of steam wagons who have occasion to repair leaks in their boilers, often experience some difficulty in-locating the leaky plate or tube, especially in the central rows of tubes. I find a convenient method to detect the damaged part is to disconnect the feed-pump connecting-rod, and replace it by a piece of flat iron about 2 ft. long, by 2 ins, wide, and in. thick. The iron bar should be drilled at One end to accommodate the pump-plunger pin and rigged up with a fulcrum at some convenient position. The boiler can then be pumped up to any desired pressure, and by this method I recently maintained a• water, pressure of 300 lb. to the square inch on a boiler-test for an insurance company. If the leakage proveS to be from a fractured piate, then of course a suitable patch must either be riveted or welded on. In a multi-tubular
boiler, should the leak occur in one of the tubes, a quick method I have sometimes adopted is to "cut out" the damaged tube by hammering in the tube-plate a. steel ball for a depth of about one inch. It can, if desired at some future time, be driven out again by a long rod. During the hammering, it is desirable to use a "holder-up" on. the opposite end of the tube, as there is the possibility of the tube being displaced."
Bristol Co-operatives' Interesting Deliveries.
There are nowadays numerous flourishing co-operative societies all over the country. One of the most enterprising undertakings of this class is the Bristol Co-operative Society Ltd., of which the general offices are situated at Lawrence Hill, Bristol ; it has 25 branches in and around that city. This concern's business extends over a considerable area, and, the management fully recognizes that quick delivery and turnover of goods to its customers, either over the counter or on the send-it-home-for-you principle, is absolutely essential to successful trading of this class. Four machines are in service ; one is a Thornycroft two-tormer, the remaining three are 25-cwt. Albion vans. The respective length of service accredited to each machine is ; the Thornycroft two years ; one of the Alb ions 12 months and the other two six months. The two-ton van delivers heavy goods to the branch shops within a radius of 20 miles ; it also carries flour to the bakery. One of the Allaions is employed to deliver pastry and confectionery, and the duty of both the others is to collect and deliver laundry—a thoroughly comprehensive delivery service it will be agreed.