HINTS ON MAINTENANCE.
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How to Get the Best Out of a Vehicle, to Secure Reliability and to Avoid Trouble,
565.—Arresting Band Rattle.
Certain types of vehicle are fitted with band brakes of the floating type, and after some use these often Set up a, most disagreeable rattle, act unevenly, and wear heavily close to the adjusting link. These troubles may be prevented by riveting two slotted guides, diametrically opposite, on each band. Small brackets are then screwed or riveted to the back of the drum cover, each carrying a é-in. setscrew, which can be adjusted to fit into the slot in its respective guide. The guide must be long enough to allow full movement of the brake.
When adjusting the brakes, the setscrews should be tightened on the band until even pressure is obtained, but so that the band is held rigid when in use.
566.—Curing a Leak in the Sentinel Pump.
After some wear the boiler feed pump on the Sentinel steam wagon has a tendency to leak at the -valves so that the water level is not kept at a satisfactory height. The trouble will probably be found in the by-pass valve, which is operated from the footplate by a lever and wire cable.
Upon releasing the by-pass pipe union, the cable and the two 4-in, nuts at the flange, the whole will came away with the spindle, valve and a special spring which fits over the top of the valve. This spring is specially treated to resist corrosion, but in time it may give out, and if the by-pass valve stem is at all tight in its guide, due to the presence of foreign matter from the water, the valve will not seat properly, with the result that some, if not all, of the feed water returns to the tank.
The valve and its spindle should be taken out and thoroughly cleaned—the spindle may be polished with fine emery cloth—the valve reground and the internal spring renewed if at all weak or corroded.
In replacing the parts, care must be taken that the joint ring does not become displaced or broken.
567—Setting Foden Slide Valves.
The setting of the slide valves is as important to a steam wagon as the timing of a petrol engine and makes all the difference between a speedy, economical wagon and a sluggish, wasteful one. When a steam wagon leaves the makers the valves B40 are set correctly by an experienced man and a driver or mechanic should not make any adjustment or tamper with the setting of the valves unless he is forced to do so.
In the fitting of a new slide valve or even a new valve spindle it is necessary, however, to reset the valve and, unless a driver knows how to set about the work correctly, a considerable delay will take place before an expert can be obtained to do the work for him.
There are numerous ways of setting valves, but the explanations set forth in hooks are so complex that the average driver has great difficulty in following the instructions. Moreover, if the wagon be broken down away from the garage and the driver has not his instructions with him he will still be unable to tackle the job.
The following method, however, is simplicity itself and no driver should have the slightest difficulty in following the instructions or foaget how to do the work when once explained.
A valve is set correctly if the distance (A) is equal to the distance (B) when the valve is at the extreme end of its travel each way.
If there be any difference, unlock the locknut (C) and turn the valve spindle (D) until the distances are the same. These instructions apply only when the boiler is up to full working pressure.
If it should be necessary to set the valves when the boiler is cold proceed in the same way, but make the distance (B) Ain. more than (A). This difference is due to the expansion of the boiler when steam is raised.
In fitting a new slide valve or valve spindle make sure that the flanged nuts (E) are not binding against the webs of the valve. They should be adjusted to allow the valve a slight movement on the spindle, otherwise the valve will be held rigid with the spindle and consequently off its seating.