bers refer to the letter and number used to designate this valve in the different catalogues issued by the Westinghouse company and are used in referring to this valve in the catalogue.

Student. The large pipe connection at the left is the main reservoir connection. Instructor. Do you understand that this should be a separate pipe connection all the way to the main reservoir, and not connected to the delivery pipe from the pump to the main reservoir? Student.-I do.

Instructor.-What connection is made at the bottom?

Student. This is the train line connection, and is the beginning of the train line.

Instructor. To what is the upper connection, looking to the right, made to? Student. To the equalizing, or brakevalve reservoir.

Instructor.-Do you understand the object of having a reservoir connected to the brake valve?

Student.-No; that is one of the things that I do not understand, and I find those I have asked have different views about it.

Instructor. The sole object of this reservoir is to increase the volume of air above the piston valve, which is No. 17 in the cut; a port leads from this chamber, D Fig. 2, to the pipe.connection to the reservoir, and the reservoir is practically part of the chamber for it is always in communication with it no matter where the handle of the brake valve may be placed.

Student. What is the difference between volume and pressure?

Instructor.-Pressure is the force of the air, or the power it has to do work, like moving a piston in a cylinder, and may be registered by a gauge. Volume is the quantity, or amount of air you have, and cannot be registered by a gauge. For illustration, there may be 70 pounds pressure in a chamber no larger than a teacup, or there may be only 5 pounds pressure in a chamber as large as this room. In the first case there would be a small volume and a high pressure, and in the second case a large volume and a low pres

sure.

Student. That is very plain. Instructor. Now, what is the lower right hand small pipe connection made to?

Student.-To the pump governor.

Inspector.-Yes, that is right with this engineer's valve. Now, in regard to the gauge connections; but in the first place what kind of a gauge is connected to the engineer's valve?

Student. It is a duplex gauge; that is, two gauges in one case. There is attached to one gauge a black, or white pointer, and to the other a red pointer.

Instructor. To which one of the gauges is the left hand connection made? Student. To the one with the red pointer.

Instructor. And the right hand connection?

Student.-Five.

Instructor.-What are they? Student. Full release, running position. lap, service application, emergency application.

first understand that main reservoir pressure is always present on top of the rotary valve, which, referring to the sectional cut, Fig. 1, is No. 13, and is the part that is moved by the handle. Again referring to Fig. 1, "a" is a port and "c" a cavity in the rotary valve. In the rotary valve seat "" is a port and "b" a cavity. The

line.

Instructor. Where else may air flow to from the main reservoir with the handle in this position?

Student. To the equalizing reservoir. Instructor. We might say then that with the handle in this position there is open communication to all parts of the brake, except the brake cylinder, so that all the pressures can equalize.

Student.-Yes; that is as I understand it, for the air in the train line may flow into the auxiliary reservoir through the feed port in the triple.

Instructor.-How then should the pressures, indicated by the two hands of the duplex gauge, compare with the handle in this position?

Student. They should certainly register the same pressure, for the pressure they are attached to are equal soon after placing the handle in full release.

Instructor. Suppose you were firing on an engine and the red pointer registered 10 pounds more pressure than the other, what would you think the trouble was?

Student. I should think that one, or both, of the gauges was out; that is, was not registering the right pressure.

Instructor. Then would it be right to say that both pointers of the gauge should register, with the handle in full release, the in the main reservoir, equalizing reservoir, train line, and auxiliary reservoirs?

pressure

Student.-Yes; for these pressures should be all equal at this time.

Instructor.-What would control the number of pounds pressure that may be obtained with the handle in this position? Student. The pump governor, which should be adjusted for 70 pounds.

Instructor.-It is not essential that you should know just how the air passes through the engineer's valve to the train line and equalizing reservoir, but it is well to know if you desire.

Student. I think I should like to know.

Instructor.-All right.

You should

ply port, it is the port that leads directly to the train line, and "a" is a large port through the rotary. Therefore it is only necessary to establish communication between these ports and air may flow freely from main reservoir to the train line. This is accomplished by port "a" being in communication with cavity "b," and "1" being in communication with cavity "c," and cavity "b" and "c" being in communication by one overlaping the other. And air may flow through port "a" into cavity "b" then up into cavity "c" and down into porr "1."

Referring to Fig. 2, it will be seen that port "j" in the rotary valve is in communication with port "e" in the rotary valve seat, which leads to chamber "D" (the cavity above the equalizing discharge piston), from which there is always direct communication to the equalizing reservoir.

Student.-You have made that very plain, and I now understand that the result is just the same as would be had if ports "a" and "" were brought in direct communication with each other.

Instructor. We will now move the handle to running position, which is the next position to the right from full release (which is the extreme position to the left), and I want to know first the object of this position.

Student. It is to obtain excess pres

sure.

Instructor. That is right, and it also permits air to be fed into the train line to supply that which may escape on account of leakage. What do you mean by the term "excess pressure"?

Student.-Pressure in the main reservoir above that in the train line.

Instructor. What is the object of having excess pressure?

Student. I understand that it is necessary to have it to insure the prompt release of the brakes on trains of any considerable length; it also helps to charge the auxiliary reservoirs promptly.

Instructor.

know how it is obtained?

Instructor. With the handle in running position no air can flow from main reservoir to the train line unless it passes by the excess pressure valve. (Fig. 2 No. 21.) This valve is a dividing line between main reservoir and train line pressures. Main reservoir pressure is on the left side, as it is shown in Fig. 2, and has a tendency to open the valve; train line pressure is on the opposite side and, therefore, has a tendency to hold the valve to its seat. On the train line side of the valve there is also a spring, Fig. 2 No. 20, which acts with the train line pressure in holding the valve to its seat. It is evident then that there must be in the main reservoir a sufficient pressure above that in the train line to overcome the tension of the excess pressure valve spring before the valve will be opened. The amount that is thus held back will depend on the tension of the spring.

Student. I think I understand. For illustration, if I should start the pump on an engine, without any air pressure, handle of the brake valve in running po

overcome the tension of the excess pressure valve spring before the black pointer would indicate any. If the tension of the spring was such that it required 20 pounds, then we would have 20 pounds pressure in the main reservoir before any would flow to the train line. After this amount was obtained air would flow to the train line as long as the pressure in the main reservoir is 20 pounds or more in excess of that in the train line.

Instructor. That is right, but what will prevent getting more than 70 pounds in the train line?

Student. When the train line pressure reaches 70 pounds the governor acts and shuts off the steam to the pump. With the pump stopped the main reservoir pressure will drop and the valve close, leaving the pressure 70 and 99. or about 90, it will be a trifle less if the spring is adjusted for just 20 pounds.

Instructor. That is all right. I am sorry that I have not time to talk with you any longer this afternoon. Come and see me again soon. Good afternoon. Student.-Good afternoon.

102. Feed Valve Broken Off.-I would like to ask a question on the F-6 brake valve. What would you do in case the feed valve was broken off so you had to plug the ports leading to and from the feed valve. That is, how would you handle the brake valve? I think it would be the same as if the feed valve was all right with the exception that you would have to feed train line leaks by putting the handle in full release for an instant and then back to running position. Am I right?-H. A. Z.

Answer.--Under such a condition there is no way, with other than a very short train, by which the brakes could be operated with any degree of satisfaction. Your plan could be followed with the exception that the time necessary to leave in full release would have to be more than an instant, particularly after a brake application. After a complete recharge the length of time full release would have to be used would depend on the length of train pipe leakage and how

long a time passed between each use of full release.

As running position would feed no air into the train pipe the latter would steadily leak down. This would tend to cause brake sticking and, where this did not call attention to the loss, might result in insufficient brake force when a stop was desired, a dangerous feature.

With a short train the pump governor adjustment could be reduced to 70 pounds and the brake valve be carried in full release. The excess pressure obtained for release and recharging would be only that of the train pipe reduction, but which would be ample with a short train, with the possible exception of an emergency stop where the train pipe had been emptied.

103. Gauge on Freight Brake Cylinder. I understand that the oil plug holes are now omitted from freight brake cylinders.

While this may be a good plan to prevent putting too much oil in the brake cylinders, will it not be objectionable by preventing a gauge being connected to see if there is any leakage.-A. D. T. Answer. The amount of freight brake cleaning and lubricating required and the very generally too limited force for doing it render impracticable the use of an air gauge as mentioned. In fact, such is not necessarily needed to detect brake cylinder leakage on cars as the loss in piston travel will indicate the leakage quite accurately.

However, should anyone desire to determine this by the use of an air gauge it can be done by connecting the gauge to the exhaust port of the triple valve, applying the brake fully and then forcing the triple to release position. This will put the gauge in connection with the cylinder and any leakage will be shown. This connection can be made more readily than by the oil plug hole as, at the most. it merely requires removal of the short piece of pipe between the triple exhaust port and the union in the retaining valve pipe. Generally the connection can be made at the pipe union.

104. Air Pump Governor.-Is the steam valve of the pump governor opened by the steam or by the spring under the governor piston?-X. Y. Z.

Answer. It is opened by the steam, though the spring renders some assist

ance.

105. Running Brake Test.-Should a running brake test be made with all trains, passenger and freight, just previous to meeting points, draw bridges, railway crossings, etc., and before commencing the descent of a heavy grade? J. M. R.

Answer. The running brake test is always desirable where it is practicable to make it for the purpose of determining by an actual trial whether the train pipe connected is as long as presumed and whether the brakes in operation will be as effective as their number, shown by the standing test, would imply; but, like other good practices, it can be abused and rendered of little value by impracticable rules and injudicious use.

There is no reason why this test should not be made with passenger trains at the places mentioned and, as well, soon after leaving the terminal where the train has been coupled to. Another time is when the train has stood for some time at a

station where there is the possibility of an angle cock having been closed.

It is almost if not fully as desirable to make this test with a freight train where the speed approaching the point of possible danger is such as to require good holding power to insure a prompt stop. On the other hand, to invariably require the test on freight trains is to If, beinsure the rule being violated. cause of the grade, low steam pressure or other cause the speed is low approaching such point, to make the running test would almost insure stalling the train. Under such conditions of low speed and level or ascending grade the running test would be unnecessary.

Were a very light application made to test by the length of train pipe exhaust there would likely be brake sticking a little later unless it was soon followed by a heavier one and release.

Under all circumstances the descent of a heavy grade should be commenced at a low speed and a brake application of about eight pounds should be made as soon as to do will not result in stalling the train where the reduction is soon followed by recharging. This combines the running test and "charging the retainers," as it is often termed.

From either standpoint of holding power or length of train pipe exhaust the test will not be of great value unless the train pipe reduction made is about the same in every instance, as a comparatively few operative brakes on a long train would likely convey the impression of ample holding power where a heavy reduction has been made, while under the reverse condition a very light reduction might convey the opposite impression.

of Different Sizes. Does it take any 106. Time to Charge Auxiliary Reservoirs longer to charge the auxiliary reservoir that goes with a big brake cylinder than it does the one that goes with the smaller one?—B. O.

Answer. Speaking generally, it does not, though as a matter of actual fact there will be a little difference in some cases. For example, the same triple valve is used with both 12-inch and 14inch cylinders, it being a plain automatic type for driver brakes and a quick action for passenger cars, yet the auxiliary reservoir for the 12-inch cylinder is smaller than the one for the 14-inch cylinder. The difference in time is not