flow of air from the front end through up; therefore, it follows that the Walthe nozzle, and into the cylinders. This schaert-geared engine necessarily has produces that whistling sound that you more lead in full stroke, or full gear, have no doubt heard when the reverse than has the Stephenson-geared engine. lever is carried too high with an engine Excessive lead in full gear is not desirfitted with slide valves. There are, of able, from the fact that it frequently course, certain types of engines in which causes pre-admission, viz., steam will be the reverse lever cannot be carried down admitted to the cylinder before the pisas far as on other types. It is always ton has reached the end of its stroke, advisable, however, to carry the reverse thereby having a retarding effect, and lever down far enough so that the re- again, the exhaust port opens just as lief valves on the steam chests will open, much sooner as the difference in the and remain open, and not be fluttering lead; consequently, with a Walschaertup and down, as is the case with the re- geared engine working in full stroke, verse lever hooked up too high. There steam is admitted sooner and also exis but one exception to this rule, and hausted sooner than from an engine fitted that is on piston valve engines fitted with the Stephenson gear, thereby making with by-pass valves, in which case the them slow in starting. When the reverse air can flow forward and back from one lever is hooked up into the running notch, end of the cylinder to the other through however, both engines have the same the by-pass valves, and little air is amount of lead, and no doubt the correct sucked in through the nozzle. This, how- amount of lead, and consequently one will ever, is not in our opinion good practice, handle the train in the running notch as the churning of the air up and back just as well as the other. in the cylinders has a tendency to heat them and carbonize the oil. 2413. quite a number of engines known as the 'Mallet Articulated Compound Locomotive.' What is the meaning of the word 'Mallet?"-N. S. K. The Word "Mallet."-"We have The Westinghouse Air Brake. Answers by F. B. Farmer. justment With Nos. 5 and 6 ET.-"Please 1045. Why Different Safety Valve Adexplain why the safety valve is set at 53 pounds with No. 5 ET equipment and at 68 pounds with No. 6 ET.”—P. R. B. Answer. The word "Mallet" is a Answer. This difference is due to one proper name, and is the name given to the articulated type of locomotive from the inventor of that type, Anatole Mallet. With of the several improved features in No. 6 as compared with No. 5 ET. With either ET equipment a full service application from 70 pounds brake pipe pressure gives 50 pounds brake cylinder pres2414. Logey Starting Engines.-"Our sure. An emergency application gives 53 engines have two types of valve gear, the pounds or a little more with No. 5 ET, Stephenson and the Walschaert; with the latter valve gear the engines are very lazy but with No. 6 gives 68 pounds, or 15 in starting a train, but seem to be as good pounds more than with No. 5 ET. With as any other after the train gets to going two engines alike except one equipped at a fair rate of speed. With the Stephen- with No. 5 and the other with No. 6 ET son gear they are very good in starting, the driver brake of the first would deand have a very strong exhaust. All have velop practically the same power in a same size cylinders. Some say the Wal- full service as in an emergency applicaschaert has not got as much lead as the tion because this would be based on 50 Stephenson, which is the trouble. What I want to know is, why they are so lazy pounds brake cylinder pressure. starting, and just as good as the others the other one the same driver brake after once getting the train going?"-N. power would be obtained with 65 pounds S. K. brake cylinder pressure, due to difference Answer. With the Walschaert-geared in leverage. Consequently, in any full engines the lead remains constant, and as service application, giving but 50 pounds it is deemed necessary to have a certain brake cylinder pressure, its braking amount of lead when the engine is power would be about 20 per cent. less worked up near mid gear in what is than with the No. 5 ET. termed the "running notch," it follows In practice this means that the No. 6 that as the lead does not increase on a ET brake would be just as effective as Walschaert-geared engine it is necessary the No. 5 in emergency applications, yet to give them the mid gear lead in full in any full service applications would be gear, that is, they must have as much less likely to slide drivers or overheat lead in full gear as is required in mid their tires. As the driver and tender gear. On a Stephenson-geared engine, brake cylinder pressures, also that of the the lead increases as the lever is hooked engine truck brake where used, are the same these advantages would apply equally. Another advantage is that the lower leverage required where 65 pounds cylinder pressure is used as the basis for maximum braking power is that for the same piston travel with the two brakes mentioned the one with No. 6 ET would have more shoe clearance in release. were being held applied independently. Cutting out the driver brake then stopped the loss of main reservoir air. Releasing the locomotive brakes would have had the same effect. When the automatic brake valve was lapped, after train was charged and driver brake cut in, leakage at once commenced to reduce the brake pipe pressure, lap position cutting 1046. Brake Cylinder Leak Emptied off all supply. This operated the equalMain Reservoir. "Please explain the izing piston of the distributing valve, following: Engine equipped with No. 6 causing it to send pressure chamber air ET brake apparatus. Could not pump up into the application cylinder, the same train. Had a bad leak in right driver as in any automatic application. This brake cylinder. Cut out the driver brake caused the application portion to open and pumped up train. Cut in the driver the passage from the main reservoir to brake, placed handle of automatic brake valve on lap and lost all main reservoir the locomotive brake cylinders and the air. Please explain how the air got from leaky driver brake cylinder did the restthe main reservoir to the brake cylinders reduced the main reservoir pressure to with the automatic brake valve on lap." a low amount. -R. S. V. 1047. Compressor Stops When Releasing Brakes.-"We have an engine equipped with ET, and when the brake valve handle is put in full release position or when releasing brakes in full release what causes it?"-J. A. K. the pump stops. What is wrong and Answer. With the ET locomotive brake equipment the air supply for the driver and tender brake cylinders in all brake applications, either automatic or independent, comes directly from the main reservoir. The application portion of the distributing valve controls the flow into and out of these brake cylinAnswer. Assuming the case to be one ders and it is governed by the air in its where the air compressor stops while reapplication cylinder. An application leasing the train brakes, with brake either automatic or independent, merely admits air to this application cylinder, and the application portion of the distributing valve then opens a passage for main reservoir air to flow into the engine and tender brake cylinders and keeps the passage open until these cylinders have obtained the same amount of pressure as is had in the application cylinder. The passage will then be closed, but will be opened again as soon as any leakage starts to reduce the brake cylinder pressure, thereby restoring it. valve in release position, but that it soon excess was re In full release position the feed valve pipe will stay at 70 pounds as the feed It will be seen from the foregoing that valve is then supplying nothing but the with a bad leak in any of the locomotive warning port in the automatic brake brake cylinders or their piping it might valve. Feed valve pipe pressure and the easily be impossible to obtain much prespressure spring, totalling 90 sure in the brake cylinders on attempting pounds, act downward on the diaphragm to apply the brakes; hence, that the of the excess pressure governor head, the main reservoir air would then flow to the atmosphere through this brake cylinder leak. On the other hand, such a brake cylinder leak would have absolutely no effect so long as no attempt were made to apply the locomotive brakes as the distributing valve would then have the passage from the main reservoir to the brake cylinders closed. It follows that with the leaky brake cylinder cutting the main reservoir pressure to the out it could have no effect during aptop of the governor piston. plications. If the leaky brake cylinder helped to prevent charging the train in the beginning it was because the engine brakes one having two air pipe connections. Release position admits main reservoir until the 130 pounds had on commencpressure under this diaphragm. Hence, ing release can drop to less than 90 pounds the excess pressure governor head must control the compressor, the higher it upward, lifting its valve and admitpressure under the diaphragm deflecting 1048. voir Pipe Broken.-"With a broken equalBrake Valve Equalizing Reser izing reservoir pipe one would have to brake in the emergency position; that is, make a service reduction in this position that which is cared for automatically by and bring the brake valve handle back to the equalizing piston when the brake lap slowly and carefully. I was asked valve is in good order. why this was done. Please explain."R. R. Answer. With a broken equalizing reservoir pipe it is first necessary to close the pipe end toward the brake valve by inserting a blind gasket in the union at the brake valve. Next remove the service exhaust fitting and screw a wooden plug in its place, thus closing this outlet. If there is but the one large, duplex gauge the braking will have to be done by judgment as its black hand will be useless during a reduction as it will not indicate correctly. If there is also a small duplex gauge its brake pipe hand can be used. 1049. Undesired Quick Action Causes. -"With a triple valve in good condition is there any chance of it going into emertion of the brake valve, in case a hose gency except when using emergency posibursts, the train parts or the like? If so, why?" "I have heard something about the service aplication port in the triple and the service exhaust port in the brake valve being the same size and smaller than the that it would be impossible for the triple emergency port in the brake valve, and to go into emergency. Please explain this."-R. R. Answer. The principal cause of unAs stated in the question, braking will desired quick action is oil or grease lubnow have to be done by careful use of rication between the triple valve slide the emergency position. This care is valve and its seat. Therefore, where just as necessary in starting and mak- such lubricants are used for the slide ing the discharge as in stopping it. If valve, now quite generally known to be made too slow brake cylinder leakage improper, though still used by some grooves will not be covered or passed. If made too rapid, particularly at the start, undesired quick action will occur. Any chance of error should be on the side of a too gradual reduction. roads, a triple valve can be in first-class condition and yet cause undesired quick action. This does not mean that such lubricant will often produce this very undesirable result, but it does cause every valve so lubricated to be harder to move toward application and occasionally with some valves it so increases the resistance as to cause the parts to move to emergency position when they do start. The standard practice now is to remove all oil, grease and gum from the slide valve and its seat, using benzine or gasoline to insure this, and apply nothing but a special grade of fine, dry graphite. Oil is still used on the main piston, but very little of it. When the "feel" of the train indicates about enough holding power the discharge must be stopped gradually to prevent the head brakes from releasing. While the discharge is occurring the head end of the brake pipe, where the train is of any length, is lower in pressure than farther back. Auxiliary reservoir pressure reduces with the brake pipe pressure up to the point of full application. Hence, the auxiliary reservoir pressure of the head brakes will be lower during the discharge than that of the others, Regarding the porting of triple valve and these head brakes will be heavier and brake valve, the facts are as folapplied. If the discharge from the brake lows: With the Westinghouse autopipe were stopped quickly the pressure matic brake valve in good order the at the head end would rise, due to equal- brake pipe pressure can reduce no faster izing with the then higher pressure at in service applications than the equalthe rear end. This would bring the izing reservoir pressure can be reduced, brake-pipe pressure at the head end and the equalizing reservoir pressure above that in the auxiliary reservoirs cannot be reduced as rapidly as the and thereby cause the premature release service application port in the triple of those brakes. valve can reduce the auxiliary reservoir pressure. Hence, quick action cannot occur under these conditions, even with but one car brake in use, if the triple valve responds promptly when the service application is begun. Bearing in mind that the head brakes were previously applied heavier than the rear ones and thereby would have the slack bunched it will be seen that if they are made to release by stopping the discharge quickly the slack will be run out If the equalizing reservoir volume is rapidly by the rear brakes, possibly reduced by water in this reservoir or if causing a break-in-two. But even if this the preliminary exhaust port in the did not follow some valuable braking brake valve is too large the equalizing power would be lost. The gradual closing of the discharge prevents this. In this it is performing by the hand and the head reservoir pressure can be reduced too fast and undesired quick action is then probable, particularly with a very short equal. train. Also, if the brake valve service the equalizing piston responds, at which exhaust fitting is missing or is replaced time the two pressures will again be by a non-standard type that allows a too rapid discharge the brake pipe reduction can start too fast and thereby cause the same trouble. Another possible cause with the brake valve is the equalizing piston sticking when the preliminary exhaust is started, then opening too suddenly and too wide. This is unusual, but can follow from fitting a new ring into a worn equalizing piston cylinder without the latter being trued up or rebushed. state what The black hand of the large duplex gauge falls in emergency position, but far slower than the brake-pipe pressure reduces. In fact, no gauge can indicate the pressure throughout the brake pipe when emergency position is used with a long train because the pressure falls so much faster at and near the point of discharge than elsewhere. R. R. The red hand of the large duplex gauge is always connected directly with main reservoir pressure. The red hand 1050. Black Gauge Hand Connected to of the small duplex gauge is connected What Pressure. "Please with brake cylinder pressure of the enpressure the black_hand on gauge No. 1 gine and tender, assuming FT equipis connected to. I thought it was con- ment. nected to equalizing reservoir pressure, but am told it is not. Please explain 1051. Brake-Pipe Reduction Before what pressure is shown on the gauge in Releasing.-"With a long freight train each position of the brake valve."-R. R. why should one not attempt to release Answer. Your understanding is right. after making a reduction of 5 pounds?"The black hand of the large, duplex Answer. The customary and proper gauge, designated as gauge No. 1 with instructions in this particular include the ET equipment, is connected directly even an ordinary passenger train and are to equalizing reservoir pressure. In renot to attempt to release after a light release, running and holding positions the duction, say 5 pounds, from the standard equalizing reservoir air is connected with the brake pipe, insuring equal pressures. ther reduction. The reasons are that the pressure carried, but to first make a farIn lap, service and emergency positions high pressure remaining in the auxilthey are separated. In service position iary reservoirs after a light reduction the direct or preliminary reduction de- renders all triple valve slide valves sired is made by the engineer in equal- harder to move to release than after a izing reservoir pressure and is therefore heavier reduction and makes it easier shown by the black gauge hand. The to overcharge head auxiliary reservoirs equalizing piston of the automatic brake valve reduces the brake-pipe pressure in releasing. the same amount. Hence, when the discharge ends after return to Jap position the black hand still indicates brake-pipe pressure, though not connected with it. How much the reduction should preferably be before releasing depends largely on the length of train. For long passenger trains it should be at least 8 pounds. For freight trains up to about 60 cars it should be at least 10 pounds and for longer ones 15 pounds. If lap position is used, say, for a minute or more this may not then be true as the brake-pipe pressure will reduce Note that it is the amount below the from unsupplied leakage. However, as pressure carried that governs. For exthe equalizing piston always allows more ample, if the pressure carried is 70 or less air to leak from the equalizing pounds and, because of not having fully reservoir to the brake pipe when the latter is the lower it is seldom that the and release, a reduction of 5 pounds is recharged from a previous application black hand shows more than a few pounds above actual brake-pipe pressure made without any farther reduction if made from but 60 pounds release may be while the automatic brake valve is on sufficient main reservoir pressure is had. lap. How much can be determined by Do not overlook the great importance of noting the difference between the black high main reservoir pressure in releasing hands of the two gauges. Check against and recharging. It gives the needed gauge error by comparing them in run- drive to force the air into the brake pipe ning position, at which time the pres- rapidly. sures they are connected with are certain to be equal. The black hand on the small or No. 2 duplex gauge is con- "Was asked to give a little talk on the 1052. Handling Long Freight Trains. nected directly with the brake pipe. handling of long freight trains and how With no second gauge make very short to keep them together. Would like some and successive service reductions until enlightenment on this."-R. R. Answer. This is too big and too im- brake pipe and auxiliary reservoir presportant a subject to be treated compre- sures at the desired amount until the hensively in the question and answer col- next application is required. If any umn. It is so important that no one brakes are not released while in release should pretend to give instructions on it position running position aids in releasuntil well and correctly informed. Much ing them, though not so certainly with a has been covered from time to time by long train because of the slower flow into answers to specific questions, limited to the brake pipe. The exception referred certain stated conditions, and also by to under release position is with full LN contributed articles. All will be repeated passenger equipment, at least on some in time, so each issue of the Magazine railways, as the rule is to release and should be read. Any specific questions recharge in running position, mainly belimited to stated conditions will always cause it gives a better control of gradube answered promptly. ated release. LAP POSITION: It cuts off all com Speaking broadly, to avoid damage in handling long freight trains, assuming munication through the brake valve, closdraft gear in fair to good condition, requires merely that the slack be controlled-never allowed to run in or out harshly. The details of how to accomplish this under the varying conditions of service are interesting and should be understood by every engineer as other wise he cannot be classed with the efficient ones. ing all ports directly controlled by its rotary valve. It is used after an application to hold the brakes applied. Another use of it at this time and also just before coupling to cars is to cut out the low-pressure governor head and allow the compressor to increase the main reservoir pressure to the maximum so as to insure releasing and recharging as quickly as possible. Yet another use is to save the main reservoir pressure for the same purpose in case of a burst hose, a break-in-two or an open conductor's valve. 1053. Automatic Brake-Valve Positions. "Please explain the five positions of the automatic brake valve."-J. D. H. Answer. The automatic brake valve with five positions is known as the G-6 SERVICE POSITION: It prevents main and is the one used with the A-1 loco- reservoir pressure from flowing through motive brake equipment that was stan- the brake valve and makes an opening dard for many years before the introduction of the ET equipment. Commencing at the left, facing the brake valve, these positions and their uses are: RELEASE POSITION: It makes a large and direct opening from the main reservoir to the brake pipe and is used to release and, to a variable extent, to charge the brakes. An exception is given under the next position. With freight trains while descending steep grades it is used on some roads to raise the brake pipe to 90 pounds just before starting down and to so recharge during the descent. Another minor function is to open the warning port, indicating that the brakes will be charged above the adjustment of the feed valve if release position is used too long. RUNNING POSITION: It makes a smaller and indirect opening from the main reservoir to the brake pipe, being through the feed valve. Hence, when the flow into the brake pipe has raised the pressure in the latter to the adjustment of the feed valve this device stops it, but reopens when leakage from the brake pipe and its connected parts starts to reduce the pressure. Therefore, its general use is to complete recharging after the handle is moved from release to running position and thereafter to maintain the from the brake pipe to the atmosphere, but through a restricted port. It also, after return to lap position, stops the discharge of brake-pipe pressure gradually when the desired reduction is being completed, thereby preventing the then higher pressure at the rear from causing a rise in pressure near the engine and which would release the head brakes if it occurred. The restricted discharge has two objects: first, to avoid quick action and, second, to prevent reducing the head end of the brake pipe too rapidly. The faster it is reduced, and it could be reduced faster with long trains without causing quick action, the heavier and faster will head brakes apply than rear ones. At the best this causes the slack to run in, and with a more rapid reduction would greatly increase the shocks. The brake valve design enables the engineer to make a reduction from a fixed volume, the equalizing reservoir, through a fixed size of opening, the preliminary exhaust port, thus preventing a too-rapid reduction and rendering it far easier to do good and uniform work with long and short trains. The equalizing piston then reduces the brake pipe pressure an equal amount, never faster than equalizing reservoir pressure can be reduced, and stops the discharge gradually. |