applied, the pump is allowed to pump up in the main reservoir, the pressure for which the high pressure governor top is adjusted, and thus a heavy pressure is available for the satisfactory release of all brakes. This high pressure is very useful also in handling heavy trains on light grades.

Again all engines equipped according to method No. 1, can be easily changed to method No. 2 should the demands of service require the use of the double pressure system.

The regular governor connection to the brake valves, with method No. 1, is plugged up, and is not used.

Triple Packing Rings.

On short trains there is seldom much difficulty experienced in effecting a satisfactory release of the brakes, because when the handle of the brake valve is placed in the release position, the main reservoir air that flows into the train pipe can increase the pressure in the latter quickly considerably more than it is in the auxiliary reservoir, and consequently the triple piston, if not too dirty, will be forced back to its position for releasing the brakes and recharging the auxiliary reservoir.

When, however, the train is a long one, such as are quite common nowadays on large reads, the main reservoir pressure does not, when releasing brakes, have the effect of increasing the train pipe pressure rapidly, and it sometimes happens, especially toward the rear of such trains, that a brake "sticks," or refuses to release at all.

Aside from the fact that the train is a long one, the conditions likely to bring about failure of brakes to release are, irsufficient main reservoir capacity, dirty condition of triples, and leaking triple packing rings in the triple piston.

The function of the triple packing ring is to form a perfectly air tight joint between the triple piston and the bushing or cylinder in which the latter moves. If this packing ring does not form a good joint in the triple cylinder, there is a chance for the air to leak past it, to the side that has the weaker pressure on it. and if the leakage is sufficient, it is not hard to see that it would be possible to vary the pressure on either side of the triple piston without moving the triple valve at all.

Therefore, to make the triple valve sensitive to slight variations in train pipe

pressure the manufacturer uses great care in making them and in grinding them into the bushings in which they are to work.

The points necessary to observe in making a packing ring, are that it will have sufficient elasticity or spring to keep its ends out against its bushing at the same time not causing any undue pressure in the latter that would make it hard

TRIPLE PISTON

PACKING RING

Fig. 2

to move the triple piston back and forth; that it will fit the groove in the triple piston, in which it is placed, in such a way that it can be turned freely, yet will not allow the air to leak inside and around it; and that when it enters the bushing or triple cylinder, the ends come together, so as to just touch each other.

For the benefit of those readers who may never have seen a packing ring out

VENT VALVE

PISTON PACKING RING.

Fig. 3

of a piston. I am showing in Figs. 2 and 3 cuts of packing rings as they are made both for the triple piston, and the vent valve piston. It will be observed that they are made in the form of a cres cent, and that where the ends come together they are cut diagonally.

The reason why the rings are made in the form of a crescent is to make them strong, and give them sufficient spring to keep pressed out against the triple cylinder.

Fitting a packing ring is a very par ticular job, and requires the assistance of accurate and delicate machinery, manufactured especially for the work.

After the bushing, which forms the triple cylinder, is pressed into the triple valve body, it is rolled and pressed, so that there will be no possible chance for leakage around or under it or for it to get loose; then the interior is ground, not bored out, to a true circle by means of small emery wheels, revolving at high velocity. It may be of interest to know that this method of obtaining a true circle in the bushing is the only one sufficiently accurate for triple valve purposes, the method of boring. leaving a more or less imperfect cylinder.

From this it will be seen that when triple valve bushings need renewing how important it is, that the machinery should be especially adapted to this class of work, and that they be ground so as to form a perfect cylinder.

If triple bushings, and packing rings are renewed in railroad repair shops, trouble is very apt to be soon had with the brakes on long trains refusing to release promptly, on account of leakage past the triple packing ring, and when difficulties of this kind are had, look out for slid flat wheels, as they are the natural result of "sticky brakes."

At the factory where the triple valves are manufactured, some very severe tests are employed to determine the sensitiveness of triple pistons, and the fit of the triple piston rings.

For instance, on a rack having the same number of feet of one and onefourth inch piping and fittings, as is generally had on the average freight train of fifty cars, fifty triple valves are mounted, and a series of tests conducted to detect any possible defect that may exist.

The test applied to determine the sensitiveness of the triple packing ring is: All brakes are applied in full, reducing the train pipe pressure in doing so considerably below the point at which the auxiliary and the brake cylinder pressures equalize; then to release them the main reservoir pressure is maintained at a constant pressure of ninety pounds and is turned into the train pipe through a

diaphragm placed in the train pipe, just below the engineers brake valve, having a 3-32 inch hole through it. The air feeding into the fifty car train pipe through this very small opening, raises the pressure very slowly, and there can be, but very slight leakage past the triple piston packing ring of any triple to cause it to fail to release. Any triple valve failing to release under the above conditions, is sent back to have a new ring fitted and ground into it, and then is tested again.

As all triple valves must stand this test before they are sent out, we may feel sure that if they get an occasional cleaning after they go into service, and the main reservoir capacity is in some degree adequate to the demands of a fifty car train, there will not be much trouble experienced from brakes refusing to release properly.

It has puzzled some air brake students to tell how the packing ring in the vent valve piston is ground into the extended cylinder on the main triple piston, as there is apparently no outlet for the air behind it, during the process of grinding, and for this reason it would be impossi

ble to move the vent piston back and forth freely in its cylinder, as is necessary in order to grind it.

Others, not having in mind the grinding of the vent piston ring, wonder why the large plug is placed in the vent piston.

VENT VALVE

PISTON

Fig. 4

In grinding the packing ring of the vent piston it is first necessary to drill a hole in the piston to allow the air back of it to escape and so not prevent its being worked in the cylinder during the time the packing ring is being ground; after the ring is properly fitted and ground the plug is driven into the hole to make the piston solid. If this plug were left

In Fig. 4, a plan of the train pipe side of the vent valve piston is shown in which A indicates the hole which is drilled in the piston and that is plugged up after the process of grinding the packing ring is finished. F indicates the

Fig. 2 shows the triple piston packing ring, and Fig. 3 shows the vent valve piston packing ring. The triple piston packing ring is somewhat heavier than the vent piston packing ring.

A

YOUNG man, now an engineer, took up the study of air brakes in a systematic way when he first went to firing. He was very ambitious and was filled with that enthusiasm with which this study inspires almost every The desire to learn made him a willing slave to hard and earnest labor after his regular day's work was completed.

one.

I believe that he is a fair representative of that type of young men of which our country may be justly proud, that kind, I mean, who armed with a firm determination to succeed in life, find no labor and no effort too great which might assist them in their upward course.

He made a practice of visiting the air brake instructor connected with the road, at intervals, as opportunity presented itself, during which time they would discuss the various subjects upon which he was seeking more light.

They would go carefully over the various questions that arise and upon his returning home he would attempt to write out all that had been discussed. This he found it best to do by following their dialogue as well as he could recolleet it. On his next visit to the instructor he would bring these sheets and the instructor would revise them, adding to the various points discussed what may have been omitted

In writing out the dialogue he made a practice of putting down the air brake instructor as the "Instructor," and himself as the "Student." I have pruned down these dialogues and will present one each month in this magazine for the benefit of other new firemen.

Dialogue No. 1.

Student. I have just commenced firing on this road and want to learn all about air brakes, so that I will be able

Chief Air Brake and Steam Heat Inspector, also Instructor Boston and Albany R. R., Springfield, Mass.

to pass a good examination, when called upon to do so. I have no doubt but what all the information I require can be found in many books, written on this subject, but I fear that I shall be unable to extract it.

Instructor.-Young man I shall be pleased to assist you for you certainly show a disposition to help yourself. What is one of the things that you have observed that you do not understand?

Student. I do not think that there is anything that I understand correctly. I never had anything to do with an engine before, and in fact never was

on one until I started to learn to fire two weeks ago.

I will say, however, that I understand the atmosphere, that is, the air we breathe, is in some way made to do the work of applying the brakes, but how I do not know.

Instructor. You are right; the air we breathe is made to do the work of

applying the brakes, but not in the unconfined state that it is in surrounding us. Student. Then it must first be confined?

Instructor.--Yes, and that is the duty of the air pump of which you may have heard.

Student.--Yes, I inquired what it was that made the noise which I heard in the fire-box when the engine was not run

ning, and was told that it was the air pump, which I found on investigation was located on the right side of the boiler ahead of the cab.

Instructor.-Yes, that is right The air pump is a steam engine and air compressor combined. The noise you heard in the fire-box was the exhaust of the steam engine part, which drives the air compressing part. The air compressing part may be compared with a common bicycle pump, the piston being moved up, the atmosphere enters and is trapped