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• 458.—The Care of Fusible Plugs.

11th December 1923
Page 30
Page 30, 11th December 1923 — • 458.—The Care of Fusible Plugs.
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Which of the following most accurately describes the problem?

The fusible plug is one of the most important fittings on the boiler of a steam wagon, and yet this valuable means of safety often receives abuse and is treated with reckless carelessness. If a driver asked himself the question, "What would happen if a plug failed to act? " he would have much food for thought.

Plugs sometimes burn out with the water at the proper level in the glass, but this seldom happens.

Nearly all drivers have had trouble at some time or other owing to the fusible plugs leaking. This is probably because the plugs are made of gunmetal, whilst the boiler plates are usually of steel, and there is a different rate of expansion between the two metals.

The fusible plugs should be changed at least once

in every six months, and some engineers advise changing in three to four months, so that they can more easily be screwed out, for if left longer it is generally necessary to cut them out. Cases have been known in which the plugs have been left in so long that the parts in contact with the water have been completely, sealed over by scale. In other instances, boilers have been found in which the plugs have been replaced by bolts—a most dangerous practice.

Corrosion eventually eats the plate. away around the plug hole. If badly corroded in this manner, the corroded portion should be bored out, tapped to a suitable size and a taper plug screwed fight home, after which the fusible plug must be put in a different position, taking care that it is approximately the same height. •

Another method, which avoids drilling a second hole in the boiler plate, is to fit a screwed sleeve, and this should be tapped for the fusible plug ; it e,16

must be held in position by a special back nut and washer. If it is thought that too much of the boiler sheli has corroded away and that weakening of the crown plate will take place if a large plug he fitted, instead of boring out the hole, it is advisable to fit a plate with suitable packing between it and the boiler, four or more setscrews being used to fasten it down. The fusible plug must, of course, be put in a different position, Used plugs need not be scrapped. They can be cleaned out and refilled, and, in doing so, it is important to note that it is not necessary to fill the portion which projects into the firebox, as the water in the boiler cannot proteet this, and it merely gets burnt or melted away, and it may cause the portion on the water side also to melt.

Very good results have been obtained from the use of Vulcan plugs, but there are many other satisfactory makes on the market.

459.—The Care of Oil-filer Strainers.

After being in constant use for some time, the gauze strainer in the oil filler may become choked, or partially choked, with grit and hardened or burnt oil. As in most cases the filler also acts as a breather, this choking is very important, for not only does it take a long while for the oil to penetrate to the sump while filling, but pressure is set up in the crankcase and the oil may be forced out of the bearings and up past the rings into the combustion chambers. . The strainers may usually be cleaned with paraffin, but if this does not prove effective they can be washed in hot water containing soda. Every care should be taken af the breather cap, but if by any chance this be lost, the breather should net be plugged in any manner., unless the plug can be fluted or drilled in order to allow free egress of air, in fact it is better to run without any cover at all over the breather than to, have it stopped up altogether.

460.—Tightening Peerless Brake Drums.

Following the publication of Hint No. 453, dealing with the care of the brakes on the Peerless lorry, one of our readers points out that, whilst bearing out the statement in this hint, that the foot brake drums on the Peerless are apt to become loose, this fault may be cured in the following manner.

The old bolts should be removed and longer ones fitted, and as it is very difficult to tighten these up, on account of obstruction caused by webs, two plain washers should be put on to each bolt to act as packing pieces, and above these one flat-type spring washer. Ordinary nuts should then be tightened on to these and the lorry run in the usual way. Now use the brakes until they run hot, and the nuts must be tightened up while the drums are in this condition. It will then be found that no further trouble as regards loosening of the bolts will be experienced.

It will be found possible to use bolts h in. longer than standard by filing away one side of the head, so that each bolt can be canted into its hole.

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