From Drivers and Mechanics.
Page 18
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The sender of the followang communication has been awarded the los. prize this week.
[990] " H.11." (West Bromwich) writes :—" Many attempts have been made, not without a measure of success, to improve the injector invented by Mr. Gifford. The general action, however, despite modern improvements, remains unaltered, and depends on impulse and momentum. I enclose sketch [We have had this redrawn—ED.] which explains the internal anatomy of the every-day type of injector ; I hope it may be of service. It often surprises me to find how little many a driver knows of injectors.
" Referring to the sketch A shows the body of the injector, which, in practice, is cast in two parts for convenience ; B shows the steam-regulating hand wheel ; C is a cone-pointed steamregulating spindle ; D is a movable cone for regulating the water supply ; it is actuated by the hand wheel (E) through a rack and pinion ; F is the nonreturn delivery valve
" With regard to the working of the injector, it. should be noted that high-pressure steam has a high initial velocity, when projected into the atmosphere. Taking advantage of this fact, steam is led direct from the boiler through the delivery pipe, .past the coneshaped nozzle and the water supply. Its velocity creates a vacuum in the pipe, and the water rises to avoid creating the vacuum which nature abhors. It is caught up by the rushing steam, which imparts to it an ever-increasing velocity as it passes along the delivery pipe. By this time the boiler check valve is reached, the saturated water and steam will have attained a momentum great enough to lift the cheek valve, even against the pressure in the boiler. "A few tips with regard to the fixing may be of value. The steam to the injector should be taken from the highest possible part of the boiler ; this ensures dry steam entering the injector, which is, of course, important. The stop valve fitted on the steamfeed pipe should always be nearer to the boiler than the injector." A typical injector.
(We believe that the injector is, to many steam-wagon dr'veni, an un• opened hook. They know that the opening of the steam-delivery valve forays water into the boiler in some mysterious way, and they are content not to inquire further. Our correspondent's letter explains the working of the apparatus elearly.—ED.I A Neat Chain Repair.
[991] "E.H." (Nechells) writes :—" As I have seldom seen any hints on chain repairing, I forward an account of a method I have successfully employed from time to time. Many drivers when putting on new hushes or rollers bang the pins out with a heavy punch and a hammer. This method scraps both pins and plates, and makes hard work of what should be an easy job. The following is the best way to effect the repair. Saw through plates near the outer edges of the pins, which can then easily be withdrawn without injury. Fit the new plates and bushes, knock the old pins back into position, and burr over slightly to lock them in place. By this means a quick and cheap, but thoroughly workmanlike repair is effected. There are many other jobs in connection with steam and petrol lorries that can be much simplified by a. little careful thought before the heavy hammer is brought into play'
Using Up Broken Saw Blades.
[992] " S.B.H." (Huddersfield) writes :—" I have often noticed a big waste of hack-saw blades in shops that I have worked in. I do not mean worn-out blades, but quite new ones, which have been snapped off two or three inches from the end, sometimes even at the first or second cut. Although saw frames are made adjustable, yet even at the shortest setting they will not usually take the broken blade, and there is also no provision for clamping. To remedy this state of affairs I thought out the following little wheeze, which I have used for some considerable time with gratifying sucess.
"The enclosed sketch gives an idea of ray device. [We have had sketch redrawn.—En.] The frame is composed of t in. brass or copper tube, and is bent into shape as shown. The under corners are flattened An Ingenious Indicator.
[993:1 " G.S.C." (Slough) writes :—" Herewith I send you some rough sketches—[We have had these redrawn.—En.]—showing a method of finding the dead centres on internal-combustion engines, in which the only access to the piston is through the valve covers and plug holes. The sketches are almost self explanatory. As shown in the top sketch, a small fork piece with two centre points, one rigid and one spring, is substituted for one of the valves, and attached to this is fixed an arm carrying a short quadrant. After this is put in Position, the special-shaped bent needle is put through the portway and is sprung into the centres. It is now a simple matter to get the dead centre and to mark the flywheel accordingly. Then all the setting points can be marked off from this. The same method can be used for cylinders with inverted valves, the only difference being in the shape of the needle."
The Slovenly Appearance of Some Drivers.
[994,1 " S.C." (Glasgow) writes : --" I am sorry to notice that drivers of heavy commercial vehicles are often careless and dirty as regards their clothing. The other day a man came into our place with a splendid steam wagon, and it was painful to observe the difference between the well-kept engine and its driver. He is a smart mechanic, to my own personal knowledge and although his wagon carries a heavy load, and therefore he has a great deal of lifting and delivering of goods to do, yet. that does not seem to me to excuse his slovenliness. The care of expensive and ingenious machinery is dignified work, and if a man must, labour let him be at all events a dignified labourer. Steam-lorry driveis are the greatest oftentiers, They are often undistinguishable from scarecrows, Sonic of our chaps persuaded one of these men In don an old boiler-suit a short time back, and the effect was astonishing. His aspect was changed from that of a sweep to that of a capable workman, At first he objected to being seen in his outfit, but he found the ' chipping ' at his faint-heartedness more than he could put up with. He now, I may remark,, has blue dungarees of his own, and speaks well of the comfort and economy they afford. We workmen. cannot. all wear brass-bound suits and anchor-buttons, but we can all look something like our jobs, and not insult the appearance of the engines we run. I may remark that a smart appearance—I do not mean foppish. is very often likely to pay a man for his trouble, particularly in the engineering line!'
Sandboxes and Pumps.
r9031 " A.K.'" (Royston) writes :— " hava been greatly interested in the recent correspondence appearing in your 'D. and M.' pages regarding winter treads. I do not think it, good policy to groove the road wheels, as the edges are apt to get burred over when the belt is not in position. [Our correspondent refers. to J.G.A.'s ' belt-tread for wheels. See p. 319, 14th December.—En.] I am of the opinion that a decided improvement can be effected by the fixing of sandboxes, fitted with short lengths of pipe, and with a shut-off slide and lever. This would often enable. a trip to be completed in had weather, for the going on the level is generally quite good—it is in surmounting inclines that. the dickens is played with the grip. Personally, I am not fond of rushing about. with a small shovel looking for gravel and ashes. "I wonder if is of your readers complain of theway the pump s arranged on the Foden wagons. I would suggest that the pump eccentric be made a. loose running-fit on the sprocket shaft, and be fastened as required by means of a suitable pin, which could be inserted and withdrawn at the driver's option. This would enable the injector and the pump to be used in combination or separately, and would obviate involuntary stoppages, after climbing a, long hill, owing to the inability to force enough feed-water into the boiler when climbing. INVe consider that the standard arrangement, in all ordinary circumstances, is ample.—Em].
'Regarding the rings on mud plugs, some of the rings on my boiler have been in use for two years and they show no signs yet of wanting renewal. I have used boiled linseed oil and blacklead for such joints
with great success. The great secret of successful joint-making lies in having all the surfaces that are to be jointed properly scraped and cleaned before any new material is inserted. The least possible amount of packing should be used," An Animated Scriber.
One of our artists is not accustomed to mechanical and workshop phrases. The drawing illustrates his idea of the term " An ordinary scriber wobbles all over the shop," which was used in a communications by a contributor to the " D. and M " page. He was temporarily left to evolve an illustration to a letter suitable for this page. The above drawing was the only result. He has been reprimanded.