THE UPKEEP OF STEAM WAGONS.
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No. 7.—General Overhauling and Repairing.—Shed-day Work.
ANEW WAGON, if made by a firm of repute and well tested, should run for a considerable period before requiring overhauling or repairi4g. But.,in addition to the daily attention when running it will require to be kept in the garage one day per fortnight, commonly termed the "-shed day," for attention to various parts of the mechanism. This shed work should be done in a systematic manner, and the following plan, if followed, will be found to
give good results. .
The work can be divided into three periods, viz :— .Fortnightly.—Clean out the , boiler every shed day.
Do not blow out the water when under pressure, but let it cool downgradually before..emptying. Thenremove all manhole and mndhole covers, as-Ivan and
ftrebars. All the inside of the boiler should now be thoroughly washed out, using a reduced nozzle on the end of the flexible water pipe to get a strong jet, the nozzle being bent at right angles in order to get into all the corners. If the water pressure is not high enough use a. hand force-pump. 'The most important parts are the firebox crown and round the foundation ring. These parts should be scraped with the mud rake, the firebox crown being A accessible from ithe manhole and the four sides of the foundation ring, from the corner mud-holes. In addition to the mud rake, a strand of old wire rope makes a capital tool for loosening dirt, especially round the foundation ring.
Scrape the deposit off all the tubes and surface accessible from the roanhole. The inside of thelrebox should then be cleaned with a wire •brush to reroove all the carben deposits from the plates which would 'otherwise impede the passage of heat through the plates. The cleaning of the insides (or firesides) of the tubes is also of great importance, for the carbon is more easily depoSited here because the gases are rapidly cooled when 'passing through the 'tubes. The wire flue brush used for sweeping the tubes daily removes the loose soot, but does not clean away the hard deposits. A very handy tool for removing this is shown in Fig, 16. It consists of a piece of mild steel bar aboutin. diameter and 4 it. 6 ins. long, with a bent hand grip at one end, and flattened at the other end
• to receive two scrapers made from 1 in. by in, spring steel.' These
scrapers are bent round at their extremities to the inside diameter of the tubes, and formed with a hardened cutting edge, the two cutting edges being set apart a distance equal to twice the diameter of the tubes.
When using the tool, the scrapers are pressed together with one hand to allow them to enter a tube, and then pushed through two or three times, being twisted round to cover the surface of the tube.
the plant is equipped with compressed air, a pneumatic tool for performing this operation can also be obtained from W. II. Willcox and Co. Ltd. If the tubes are ferruled great care must be taken to clean out the ferrules, for these, being smaller in diameter
than the tubes, are not accessible by the tube brush or scraper. They should be scraped out when cleaning the inside of the firebox. The firebars should then be cleaned of all the clinker, also the ashpan ctaned out and both renlaced. The manhole and muilhole should then be replaced, taking care to smear the asbestos joint rings with graphite and grease to enable the-joint to be broken without spoiling them. If any seam shows signs of leaking re:. Caulk it; also re-expand any tubes if necessary. When steam is next raised test the safety valves and the pressure gauge to see that they are in unison. A very good plan for keeping the .inside of the boiler free from scale' is to place', very linely-powdered graphite inside immediately after it has been cleaned. This circulates with the water and polishes the plates, on which scale will not then readily form. If this is done periodically the graphite will soften and loosen any ord scale, which can then be readily • washed out.. The graphite must be of good quality, the t mined in Mexic.'ili being the•best for steam boilers.
The piston rod, slide valve rod, stop valverod and pump, plunger glands should be tightened up, taking care to screw both nuts equally. Do not make them too tight or the rods will-get too hot and score. If they still show signs of blowing, it is an indication that they requirere-packing. To do this remove the glands and the-old packing; a scriber with a bent point, will be found very useful for removing the latter, but if'this ails replace the glands anchauts, leaving them slack, and run the engine slowly ; the movement of, the rod and the steam pressure will loosen the packing. Next cut the new packing (which should be of the right section to fit between the.rod and gland) into suitable lengths, so that when pressed round the rod, the ends are in. apart, as shown in Fig. 17 ; three or four rings are usually suffieient for each gland. Soak them in-thick cylinclei oil and press 'each one separately iikto the gland with a piece of wood, arranging the joints atclifferent points round the rod. Replace the gland and screw up, gently at first
tightening it up further when the engine short time. has run a
Monthly.—Re-expand all the tubes in the boiler. Wash outtithe water tank and clean the strainers on the pump and injector suction pipes. Remove all the syphon wicks freca the lubricators and wash them0 paraffin, replacing where necessary. Clean the, driving chain by the method already described in a previous article. Clean out the pump and injector check valves, and the water gauge cocks, with a stiff wire; screwed plugs are fitted in front of the passages into the boiler for this purpose. Re-grind the check valves, pump valves, double h.p. three-way cock, and the injector and water-lifter steam valves. These valves are best re-ground while steam is up to allow forthe unequal expansion of the different parts. Metal polish will be found an excellent material for giving a good face to the valves and seats. Clean out the nozzle of the exhaust blast. pipe and scrape inside -of funnel. If these become choked it willeause slow
■ steaming and curtail the power of the engine.
Adjust the brakes to compensate for the wear of the: linings, testing the brake to make, sure that it can be immediately, and securely applied. A wise plan would be to perform half of the above duties alternately on each shed day.
Quarterly—Take out and examine The fusibleplug • in the firebox crown ; if it!is furred up a new one should be fitted. It; is important that this plug should not be tampered with. Teat the pistons and: slide valves for steam tightness. Examine the wheels for any defects.
If steel wheels are fitted loose rivets, should be tightened or replaced. If wood wheels are employed tyres should be pressed up-and wheels re-painted. -It is advisable to have a'spare set of wheels so that this operation can be performed Nyithout keeping the wagon oft the road ; the wheels should be interchangeable with any vehicle. Some types of wood wheels are adjustable, thus obviating the,tnecessity' for removing them to have tyres pressed up. Rubber tyres. Should be changed over with the wheels to compensate for uneven wear due to camber of roads. • Test for alignment and adjusta necessary. Adjust all the brasses andibearings. Take Up any unnecessary slack • in the steering. chains. Re-pack or regrind any of the following cocks which show signs of leaking :--Blow-off cock, gauge cocks, testcocks, cylinder cocks-a II d safety valves.
Locating Faults. •
The preceding routine u-,ork • is arranged to cover ordinary wear and tear, but of course accidents will. happen,' due teeeither faulty material and workmanship, faulty design,. or carelessness and neglect of-the driver, Which will require.. immediate attention or repair: Or defects may develop, such as loss of propelling power,or increased fuel and water consumption,which should be investigated.
Lose of power may be due to either or both of the two following Causes Engine not developing its maximum power, or increased resistance of the transmission gear, the latter causing engine power to be wasted in friction. •
Taking the former, the., first pointeeto settle is whether the boiler is steaming properly' and_producing a constant, supply, of steam at.ithe'rell working pressure. If not it may be due to the .boiler being dirty ; ashpan and smoIxe-lifox. not airtight, .causing loss of draught; chimney choked with oil. and soot; tubes :choked, especially at the-firebox end ifferruled ; firebars clogged with clinker or unsuitable for the Fuel • exhaust blast nozzle -too large and not giving, sufficient draught: .Also the fuel itserf may be unsuitable, especially if it is too wet and the boiler is producing steam inside Fate fireboxinstead of in the barrel. Good Welsh steam -coal should. always be used ; anthracite coal -is useless under a steam wagon.boiler. Coke is only suitable with water-tube boilers, as already explained. On the other hand, even if no difficulty is experienced in keeping the pressure gauge up to the red line, it is not absolute proof that the steam pressure is correct. Test the gauge by cornparing it With a gauge' known to be correct ; a special g-angei shouAd:.be Itentlor this purpose. If the fault is not with the boiler the engine should 'then be examined. Commencing with the cylinders, -ascertain' if the pistons and slide Valves are steam 'bight. The pistonrings may bebroken or too slack,, or the cylinders may be worn oval ; leaking glands will .B42 .
also cause a drop of pressure, especially in the 1.p. cylinder. Another place where steam may be leaking and, escaping its duty is the three-way cock which diverts the h.p. exhanst when working double h.p. ; the h.p. exhaust steam may be escaping straight into the exbaust-blast pipe instead of passing through the 1.p. cylinder. This would only affect the power when working compound. There is bound to be slight leakages in these parts, for a perfectly steam-tight joint has never yet been devised; but if they arenot serious the fault must be looked for elsewhere and the slide valves should be tested for correct setting.
If these aremuch out of truth, in all probability it will be noticeable in the beat of the. engine ; this should sound even and rhythmical. Take oft the valve sheet covers and test the setting. The valves may be slack on the spindle, due to the nuts becoming unlocked, and also the link motion may be yery slack, .causing the valves to move only a portion of their proper travel and not openimg the _steam ports sufficiently. See that the cylinder lubricator is working properly, for .if it, is not the pistons Will get hat and probably seize up in the cylinders. Examine also' the crankshaft,: and connecting rod bearings, and the crosS-head slides, to see that they,are not getting too hot. Another important point is the exhaust blast nozzle ; if this gets choked, it will cause excessive back pressure in the, 1.p. cylinder and rob the engine of much of its power. It naighbhappen that the cylinder itself is cracked, buVthis will be very difficult to :deteet without taking an indicator reading.
Any fault in the transmission gear will be noticeable in the yclistance the engine will travel after the steam is shut off; also the ease with whieh it travels when running down hills. If the fault, appears to be here the lubrication of the:axle-boxes, gearshafts and front wheels should be attended to, and particularly the driving chain. The latter may be too dirty, eausing the rollers to bind, or the chain may be too tight. The gearing should also be examined to see that the teeth are not too deep in mesh, and also that they are bearing evenly across.the full width of the faces. If the road wheels are not in correct alignment a considerable amount of powepwill be wasted ; for the wheels, insteathof simply rolling on the ground, will be continually being pushed sideways, causing excessive friction between the wheels and the' road. This will be especially the case with rubber tYres, owing to their greater adhesion. It must be borne in mind, hovirever, that heavy, muddy roads, a big body offering considerable wind resistance, and a windy, clay will all affect the running of the wagon ; and one or more of these adverse conditions may just Overload thp vehicle and prevent it doing its duty on fast gear.
Fuel and Water Consumptions.
The fuel consumption of a machine should be very carefully watched, Lir this will be an indication of its condition; it will also indicate the ability of the driver if the vehicle is known to be in good condition. Bad stoking will cause the carbon in the fuel to pass away unconsumed in the shape of 'smoke from the chimney. Steam leakages, if they become excessive will also have a noticeable effect on the fuel and water consumption.
The greatest cause of increase, however, will be the condition of the boiler. If it is not washed out properly on the shed days, the sediment from the water will form, a hard scale on the plates, which impedes the passage of heat through them. With a low type boiler the graphite method, previously described, should be adopted, but when the tubes or •the firebox are removed for repair, the inside should be well cleaned. Most water-tube boilers are soarranged that the internal parts can be realily removed for cleaning purposes. Forcing the boiler beyond its normal capacity will also cause the fuel consumption to be increased, for the boiler efficiency will be lowered by too much heat being thrown away up the chimney. Evidence of this will be shown by the paint being burnt off the smoke box and the chimney.
It may be that the design of the boiler is at fault, being too small for the work it has to perform. If the fault appe,ars to be excessive water consumption only, examine the water tank and the pump and injector for leaks. The state of the roads will also have a considerable effect on the fuel and water consumption, for the resistance on roads covered with slush and mud or snow is often double that when the roads are dry. Priming of the boiler will cause the consumption, especially of water, to be heavy. Any unusual sound such as knocks, squeaks, or rattles should be immediately investigated and the defect rectified, the sense of hearing being the keenest guide for detecting faults in the steam lorry as in all other machinery. Failure to repair a minor defect may lead to a serious breakdown ; the old adage "A stitch in time saves nine" is very ap
plicable in this case. HEMESTUS.
(To be continued.)