CHAPTER XIV.

_ACCIDENTS TO CYLINDERS AND STEAM CONNECTIONS._

IMPORTANCE OF THE PISTON IN THE TRAIN OF MECHANISM.

The piston is an autocratic member of the machine. For thousands of miles it toils to push the engine ahead, every thing going smoothly so long as it is confined to its recurring journey; but let any attachment break, or a key fly out that will increase the piston’s travel, and away the piston goes, right through a cylinder-head.

CAUSES THAT LEAD TO BROKEN CYLINDER-HEADS.

The causes which most commonly lead the piston to smash out cylinder-heads, are broken cross-heads, broken piston-rods, and broken main-rods. A main crank-pin or wrist-pin breaking, is almost certain to leave one end of the cylinder a wreck. These may be termed the major causes for breaking out cylinder-heads; but there are numerous minor causes, which are scarcely less destructive. A piston-rod key begins to work loose. It is hammered down occasionally, which does not improve its fit; and some day it jumps out altogether, letting the piston go on a voyage of discovery. A machinist of the careless sort has been examining a piston’s packing, and, in screwing up the follower-bolts, one of them gets a twist too much. Drilling out a follower-bolt is a troublesome operation, so Mr. Careless lets it go. On the road this head drops out, and a broken cylinder-head is the consequence. One of the worst causes of breakage to a cylinder that I have ever seen, was caused by the packing-ring of the piston catching in the steam-passage. Part of the ring broke off, and wedged itself between the advancing piston and the cylinder. The wedge split the cylinder open, and the remainder of the piston acted like a pulverizer upon the fragment of the cylinder.

BROKEN CYLINDER-HEADS OFTEN PREVENTABLE.

The causes which eventually lead to broken cylinder-heads often originate from preventable strains. Thus, cross-heads are frequently fractured by main-rod connections pounding; and weaknesses, that ultimately bring crank-pins to disaster, originate in a similar way. A loose piston-key is liable to crack the piston-rod, if it does not give trouble by jumping out. Loose guides have a tendency to spring piston-rods, and throw unnecessary strain upon them. Pistons lined out of true, are dangerous for the same reason. A pump-plunger working out of line, or badly secured in the lug, throws a distressing load upon the cross-head. And so the list of potential accidents grows. Like the steady water-drop that wears into the adamantine rock, trifling defects, assisted by time’s action, prove stronger than the most massive machine.

When any thing happens to permit the piston to break out a cylinder-head, the engine can be put in running trim by taking off the valve-rod and main-rod, and setting the valve on the center of the valve-seat. Blocking the cross-head is unnecessary, if the break will allow the escaping steam to pass through; for then no further tension can be put upon the piston to cause further damage. If, by an extraordinary freak of good luck, a piston-rod breaks without causing other damage, the cylinder-head must be taken off, and the piston removed. Then cover the ports, and take down the main-rod on that side. Or, if the cross-head is all right, the main-rod may be left untouched. When the cross-head breaks, it generally entails taking out the piston, centering the valve, and taking down the main-rod on that side.

WHEN A MAIN-ROD BREAKS.

With a broken main-rod which does not knock out the cylinder-head, the main-rod and valve-rod should be taken down, the valve secured on the center of the seat, and the cross-head blocked with the piston at the back end of the cylinder.

CRANK-PIN BROKEN.

For a broken main crank-pin, the above method of stripping the engine will do with the addition of taking down both side-rods. An accident which disables one side-rod, requires that the other one shall be taken down also, or there will be trouble when the engine is attempted to be run with one side-rod. The rod might go all right so long as no slipping happened. But, if the engine began to slip while passing over the center, the side-rod would have no leverage on the back crank to slip its wheel; and a broken rod or crank-pin would almost certainly ensue.

A broken side-rod, that is not accompanied by other damage, requires both side-rods to be taken down. All the inconvenience arising from this is, that the engine is more liable to slip. But, with dry rails, an engine can get along very well without its side-rods.

THROTTLE DISCONNECTED.

Any accident to the throttle-valve or its attachments, which deprives the engineer of power to shut off steam, is very dangerous, and calls for prompt action. Lose no time in reducing the head of steam to fifty or sixty pounds, or to the pressure where the engine can easily be managed with the reverse-lever.

With the aid of a power-brake, an engineer can get along fairly with a light train, after an accident has happened which prevents the closing of the steam from the cylinders; but constant vigilance and thoughtful labor are needed.

OILING THE VALVES WHEN THE THROTTLE IS DISCONNECTED.

The greatest difficulty will be experienced in oiling the valves, unless the steam-chests are provided with the automatic feeders, which work with steam on.

If he is running on an undulatory road, an engineer can oil the valves from the cab, by letting the steam down at the top of a hill, and running down at a high speed. It can also generally be done on a level track, by letting the fire burn low, getting up the best speed the engine will attain, then putting the feed full on. As the steam drops suddenly, put the reverse-lever in full motion; and the chances are, that the valves can be oiled.

WHAT CAUSES A DISCONNECTED THROTTLE.

The most common causes of trouble with the throttle are the breaking or working out of one of the bolts that operate the valve within the dome, the breaking of a valve-rod, or working off of nuts that should secure the connection. Where the throttle fails with the valve closed, and the engineer finds it necessary to take the dome-cover off to prevent his engine from being hauled in, he will generally find the trouble to lie with the connections mentioned, or with the bolts belonging to the bell-crank, that is located near the bottom of the stand-pipe. Sometimes the nuts on the top of the throttle-valve stem work off: but, in such a case, there is no difficulty in opening the valve; it is when the engineer wants to close it, that the discomfiture comes in. Some steam-pipes are provided with a release-valve near the throttle, to relieve the pipe from intense back-pressure when the engine is reversed. The sudden reversing of an engine sometimes jerks this valve out of its seat, leaving an open passage between the boiler and steam-chest. This acts like a mild case of unshipped throttle, and must be controlled in a similar way.

BURSTING A DRY PIPE.

The bursting of a dry pipe is similar in effect to the action of a throttle becoming disconnected while open; and it may even prove harder to control, according to the size of the opening. Engineer Halliday had a trying time with a case of this kind. While swinging along the E., F., & G. road, with a heavy train of freight, a herd of horses ran in from an open crossing-gate, and started up the track just in front of the engine. As there was a bridge a short distance ahead, Halliday reversed the engine in his anxiety to prevent an accident. The train stopped for an instant, when the engine began to push it back. Halliday tried to throw the lever to the center, but never before had he felt such a pressure acting upon it. Again and again he tried to throw the lever over; but every time it proved too formidable a struggle, and the catch found its way into the full-back notch. Meanwhile, the train was gaining speed in the wrong direction, and a passenger train was not many miles behind. Beginning to realize the true state of affairs, Halliday called for brakes, opened the fire-box door, closed the dampers, and started the injector. Then he directed the fireman to throw some bucketfuls of water upon the fire, while he tied down the whistle-lever, letting the steam blow. The promptest means for reducing the pressure of steam were now in operation, and his next move was to try the reverse-lever again. Both men grasped the lever, and, by a combined effort, forced it past the center; and Samson’s hair was cut. It was afterwards found that a long rent had opened in the dry pipe, letting the full boiler pressure upon the valves, which moved hard through being dry; the hot gases pumped through them in reverse motion having licked off every trace of lubricating unguent.

OTHER THROTTLE ACCIDENTS.

Cases of serious trouble resulting from accidents to throttle connections would be easy to multiply. Two incidents with similar originating conditions, but with very different results, will suffice. Engineer Phelps was pulling a full train of coal over rails that were neither wet nor dry, and had just enough frost upon them to be wicked. He was having a bad time slipping, but was working patiently along, when the throttle became disconnected with the valve open. The engine at once started on a whirl of slipping that threatened disaster, but it was immediately controlled by the engineer pulling the reverse-lever to the center notch. Engineer Cook of the F., G., & H. road, was not so fortunate when the stem of his throttle-valve broke on a slippery day. As the wheels began spinning round, Cook lost his head, and kept working at the throttle-lever to try to stop. Seeing this was of no avail, he grasped the sand-lever, and tugged vigorously at the valves. A season of tumult succeeded; and, when the engine stopped presently, it was found to be a deplorable wreck. It was hard to tell, from the look of the ruin, what part of the locomotive broke first; but the crank-pins on one side were cleaned off, and the piston was out through the cylinder-head. The side-rod on the other side broke close to the strap, and was twisted up like a spiral spring.

POUNDING OF THE WORKING-PARTS.

It is good for an ambitious young engineer, who desires to thoroughly master his calling, to walk occasionally into the room where a well-managed automatic cut-off engine is at work, and watch its smooth, noise-less movements. There he may find an ideal of how an engine should run. The nature of the work performed by a locomotive engine prevents it from being operated noiselessly, and the smoothness of its action must always compare unfavorably with a well-constructed stationary engine; but the connections which transmit the power of a locomotive should be free from knock or jar, if they are properly proportioned, and skillfully put together.

SOME CAUSES OF POUNDING.

To an engineer with a well-regulated mind, a pound about the engine is a source of continual irritation. If a pound arises from a cause which can be remedied by an engineer, the careful man will soon perform the necessary work to end the noise. Sometimes the origin of a pound is hard to discover: very often it is beyond the power of the engineer to stop it. Some makes of locomotives always pound when working in full gear. With such an engine, a nervous engineer will fuss, pushing up wedges until they stick fast, and cause no end of grief to get them down again. He will key up the main-rod connections till they run hot, and he will prophesy that the engine is going to pieces. But the engine hangs together all the same, and is only suffering from want of lead, or want of compression. Where an engine is deficient in the cushioning to the piston, due to compression or lead, the momentum of the piston and connecting-rod is suddenly checked at the end of each stroke. The concussion to these working-parts is so great that pounding will be produced. As the engine gets hooked towards the center, this pounding will cease, because the lead opening increases as the motion is notched back. The most common causes for pounding with locomotives are worn main-rod connections, and driving-boxes too loose in the jaws, or the brasses loose in the driving-boxes. If side-rods are out of tram, or have the brasses badly worn, they sometimes pound when passing the centers. A cross-head will pound when the guides are worn very open. This last defect is liable to cause a bent piston-rod. A piston makes a tremendous pound when a badly connected rod allows it to touch a cylinder-head, and a very ominous pound is produced when the spider gets loose on the piston-rod, and a piston-rod loose in the cross-head will make itself heard all over the engine.

LOCATING A MYSTERIOUS POUND.

Several years ago a very troublesome and mysterious pound caused the writer a great deal of annoyance. He was running an old engine, with cylinders that had been bored out until no counter-bore was left. The piston had worn a seat leaving a small ridge at the end of its back travel. The main-rod was taken down one day; and, in putting it up again, the travel of the piston was slightly altered. The engine started out with a pound, and kept it up. If any of my readers have been working an engine that seemed to hang together merely by luck, away on construction work on the wild prairies, with no machine-shops in the rear to appeal to for aid or counsel, with all his own repairing to do without tools or skilled assistance, they will understand the difficulty experienced in locating that pound at the back end of the cylinder.

A cylinder loose on the frame, or a broken frame, will jar the whole machine; and both of these defects are serious, and demand increased care in taking the engine along with the train. Loose driving-box brasses produce a pound which is sometimes difficult to locate. In searching for the cause of a pound, it is a good plan to place the engine with one of the cranks on the quarter, block the wheels, and have the fireman open the throttle a little, and reverse the engine with the steam on. By closely watching in turn each connection, as the steam through the piston gives a pull or a thrust to the cross-head, the defect which causes the pound may be located. Never run with a serious pound inside of a cylinder. It is an almost certain indication that a smash is imminent.