For DRIVERS, MECHANICS & FOREMEN.
Page 21
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A PRIZE OF TEN SHILLINGS is awarded each week to the sender of the best letter which we publish on. this page ; aaothere are paid for at the rate of a penny a lsne, with an allowance for photographs. All notes are edited before being published. Mention sour employer's name, in confidence, as evidence of good faith. Address, D., M. and F., " The
• Commercial Motor," 7-15, Rosebery Avenue, London, E.G. 1.
Lamps Alight.
On Saturday, the 7th September, light your lamps at 8.3 in London, 8.50 in Edinburgh, 8.13 in New
'castle 8.16 in Liverpool, 8.11 in Birmingham, 8.13 in 'BriskiI, and 9.1 in Dublin.
Fuel Economy Notes for Steam Wagon Drivers.
The sender of the following communication has been awarded the 10s. prize this week.
[1893] " P.S." (Newhaven) writes :—" The steam wagon driver nowadays is beset with many difficulties. He is almost entirely deprived of his favourite Welsh steam coal, and with other classes of fuel it is much more difficult to keep a smokeless fire. In consequence, he finds himselffrequently at variance with the authorities.
"It is, of course, well known—or at least, it should be—that to secure Food results from any fuel, thorough combustion is essential. Otherwise, valu. able heat-giving gases are wasted. Visible stroke contains a not inconsiderable proportion of these gases,. and is, therefore, a direct indication of wasteful firing. It is clear, then, that by careful attention in the stoking department it is possible to serve the dual purpose of smoke prevention and fuel economy. It is not bemusing the readers with unessential tecii• nical details to point out that for complete combustion a free supply of oxygen is necessary. This is admitted to the fire with the air, which enters mainly through the spaces between the firebars. Welsh coal does not require so much air as bituminous coal or coke. Insufficiency of air is the cause of smoke emission. It will be obvious, then, that in a boiler designed for the combustion of Welsh coal, the fire is pre-destined, as it were, when other coal is burned, to give off smoke. If, therefore, it is impossible or inconvenient to fit new firebars with slightly wider spaces, air must be admitted from other directions.
"The admission of air is, as we have seen, regulated in the first place by the spaces provided between the firebars, the proportion of space to firebar area varying, according to one authority, so much as from 12 per cent. of the total grate area when using Welsh coal, to 50 per cent. for coke. Now, if on changing the fuel, the firebars be unduly sluggish, or if a large amount of dense smoke is emitted, it may safely be assumed that a wider-spaced set of firebars is necessary. This change can, of course:, he effected by carefully experimenting with different sets of firebars. As this, however, takes up both time and money, it may be better to communicate with,the makers of the wagon, asking for their advice. They will also most likely be able to supply a set of firebars to meet re-, quirements. Having got the firebars right, the next thing to turn attention to is the ashpan. It is important that this should be a good fit all round, avoiding any air leakages. Furthermore, an easily adjustable damper should be fitted, so that the supply of air may readily be regulated. As to the actual stoking, no hard-and-fast rule can be set down. Not only do boilers vary in their behaviour, but local requirements also enforce different conditions in their working. The generally-accepted maxim of "little and often" may advisably be followed. Take care that no holes are allowed to burn out in the fire, that is to say, keep the firebars fully covered. With bituminous coal, firing must be more frequent than with Welsh coal. The effects of stoking are felt more quickly, but last for a shorter period. With coke, a deeper or thicker fire is' needed, and with soft coal firing must be often. Keep a look out for clinker.
"To keep down excessive smoke, particularly after fresh fuel has been added, air may be admitted through the fire door by the apparatus provided for the purpose. Do not attempt to effect this by leavmg the door ajar, except in the case of Foden wagons, i where the door s specially constructed for that purpose, otherwise the cold air will strike the tube plate, setting up unevenness of expansion and contraction, with resultant leakage between tubes and plates. With the softer coal and coke, more attention is necessary to the tubes, as soot and carbon deposit accumulate much quicker. A good brushing out with a hard wire brush is essential, in addition to the ordinary daily attention which is given with the usual type of brush.
"If after having adoptedthese suggestions trouble is still experienced, improvement may be effected by reducing the size of the blast nozzle with the object of causing a stronger blast. This is usually effected by inserting a thin ferrule into the orifice. Finally, a clean fire, clean boiler, clean and perfectly soft water, steam-tight joints, well-adjusted bearings, gland packings not screwed down too tightly, good lubrication, and careful attention to details are all essentials if good and consistent running is to be experienced."
Securing a Loose Eccentric.
[1894] "S.R" (Mirfield) writes :—" A wagon came in for repair the other day, and at first sight it looked as thought we had a lengthy job before us. This was unfortunate, as, like all transport wagons at the present time, the vehicle was in great demand. An eccentric sheave had worked loose on its key. One s de of this sheave was close to the crank web; the other side butted against a shoulder on the shaft. There was no way of getting at the key without re
moving the crank, and as the latter was, of course, either shrunk or hydraulically pressed on, it was evident, as stated above, a tough job was before us.
"Before going to this trouble, we considered if some alternative means of securing the eccentric were not possible, and eventually hit upon the following simple device, which saved a lot,of trouble, and made quite a good job. The eccentric was first carefully set in its correct position, and two i-in. holes were then drilled right through both crank web and eccentric—see sketch (which we have had redrawn.—ED.). Two distance pieces, also wqh I-in. holes through them, were then made to fit between crank and t_,:centric, and rivets were driven through crank, distance pieoes, and eccentric, thus securing the latter, indepencienriy of the key."