feet of grate area. Assuming that the grate area is in the usual ratio to the heating surface, 46.5 square feet, multiplied by 75, would equal 3487.5 square feet of heating surface. Now, applying the formula we have: diameter of safety valve equals .036, multiplied by 3487.5, divided by .1, multiplied by 225. 3487.5 multiplied by .036 equals 125.55. The absolute pressure in the boiler would be 210 plus 15, or 225 pounds. This multiplied by 1 equals 22.5, and 125.55 divided by 22.5 equals 5.5, which would be the diameter in inches of the safety valve were but one used. As it is always advisable to use two safety valves, however, it would require two valves of 2.75 inches in diameter each. Where the figures come out odd, as in this case, the next largest size valve is used, which would, in this instance, mean two valves of 3 inches in diameter. We can therefore see that the engines mentioned are correctly equipped.

1976. Blocking Richmond Compound with High-Pressure Side Disabled.-"How would you block to bring in a Richmond compound, with the high-pressure side disabled?"-4. M.

Answer. We presume that it is desired to bring the engine in under steam. In this case it would be necessary to take down the main rod on the high-pressure side, blocking the cross-head ahead securely; then take the pin out of the back end of the valve stem and fasten the valve ahead so as to open the exhaust port. In this way, the live steam from the boiler passes into the receiver from the high-pressure steam chest, and then forcing the interceptor ahead enters the low-pressure side, converting it into a high-pressure engine. As the low-pressure cylinders and steam chests are fitted with pressure relief valves set at about .4 boiler pressure, care must be taken in starting so as not to get too much steam into the low-pressure cylinder, as while no particular harm might be done, yet it would cause quite a waste of steam at the cylinder relief valves. After starting, the boiler pressure might be reduced to say 120 pounds. It is advisable to disconnect in this manner for the reason

that while the small steam pipe could do the same work if the high-pressure valve was simply disconnected and clamped to cover the ports and steam for the lowpressure cylinder was delivered through the small steam pipe only, yet this pipe

being so small and the cylinder so large, the steam would be so wiredrawn that only slow headway could be made, and in case it were a passenger train where speed is an object it would be almost necessary that the method of disconnecting first mentioned should be adopted.

1977. Sparks Lost from the Stack: Cause and Prevention.-"How can you prevent coal being forced through the tubes and out of the stack? Is there any serious loss from this? If so, what conditions tend to increase or decrease it?"-E. A. M. Answer.-Coal is forced through the tubes and out of the stack by working the engine in very long cut-off when the fire is light or thin, and also by excessive slipping of the engine. The loss has been variously estimated at from 5 to 7 per cent. This loss is serious enough to be taken into account. Carrying too thin a fire and excessive slipping of the engine tend to increase these losses. Carrying a fire of the proper depth and handling the engine in a workmanlike manner tend to decrease them.

1978. Holes and Dead Spots in Fire.-"What will cause an engine to leave holes in the fire? What will cause dead spots with bituminous coal? With anthracite coal?" —E. A. M.

Answer.-Holes in a fire are usually caused by having the fire too thin when the engine is working hard. Dead spots in a fire with bituminous coal can be caused either by letting the fire burn down too low in spots by uneven firing, or by a clinker. With anthracite coal it is usually caused by the grates being clogged, thereby not admitting sufficient air to produce combustion.

tle but very little on that corner. If, however, the engine did come down sufficient to cause the trailer wheel to rub, or make it necessary to block, run the wheel up on a high block or wedge, and block between the forward end of the equalizer, connecting to the main driving spring and the frame.

1981. Broken Valve Stem.-"Stephenson valve gear, slide valve; valve stem broke close to yoke; valve went forward and stayed. Could engine be run half a mile without disconnecting? If necessary to disconnect, please explain how, without taking steam chest cover off. The relief valves screw down through the cover."H. W.

Answer.—It is hardly possible that the engine could be run in this condition for a half mile without disconnecting unless it was down hill, so the steam could be shut off, as with the back port open on one side steam would flow in there and block the piston, preventing it from coming back. This would effectually stop the engine.

In order to disconnect without taking up the steam chest cover in a case where the relief valve screws through the cover: If the valve could not be fished back with a packing hook after taking off the valve stem gland and removing the broken stem so as to enable you to get in at the valve, it would be necessary to disconnect the main rod and block the crosshead ahead. It would be possible in many instances, however, to disconnect the valve stem at the rocker arm, then remove the valve stem gland entirely, together with the valve stem, and fish the valve back so as to cover the ports, with a packing hook; then drive some thin wedges (brake shoe keys will often answer) either between the top of the valve and the pressure plate, or between the side of the valve and the steam chest, if the stuffing box hole in the steam chest is large enough to permit you doing so; after which the stuffing box or gland, together with the valve stem, should be replaced in order to prevent loss of steam. Where this can not be done it will, of course, be necessary to pursue the other course, namely, disconnect the main rod.

1982. Computing Area of Safety Valves."The usual allowance in computing area of safety valves is to allow 1 inch area to each 2 square feet of grate surface for lever valves; with a pop valve, 1 inch to every 3 square feet of grate sur

face. The question is, why was the difference of allowance made?"-F. J. K.

Answer. The difference in allowance is made on account of the unreliability, no matter how well designed, of the lever safety valves, and on account of the fact that they are so easily tampered with. And also to discourage, as much as possible, the use of this type of valve. Where the lever type of valve is used, men ignorant of the pressure the boiler can safely carry have frequently moved the weight out to the extreme end of the lever; and if they could not then obtain sufficient pressure to get the amount of power desired from their engine, would hang additional weights on the end of the

lever. Therefore, in order to make the proposition as safe as possible, a much lower allowance is used for the lever safety valve than with a spring-weighted pop valve.

1983. Broken Trailer Tire, Pacific Type Engine.-"Will you please explain what should be done in case of a broken tire on the dummy trailer of a Pacific type engine? I would like to know if same could be swung clear of the rail. Kindly explain, and give particulars how it is done."M. S.

Answer. This question is fully answered on page 155 of the August, 1912, issue of the Magazine, in "Our Special Study Course." The method used is illustrated on page 156, Fig. 6, of same issue.

1984. Use of Crude Oil to Prevent Foaming.

"I am using from a quart to three pints of crude oil in my boiler, daily, in order to hold the water down, as it has been treated, and that is the only thing I have been able to find that will keep it from foaming in switching service. Some of the engineers claim that the oil will get on the crown sheet and keep the water off, causing it to burn the crown sheet. Is there anything to it?"—A. A. H.

Answer. As oil is lighter than water, it will naturally remain on top of the water, and, therefore, can not get on the crown sheet unless the crown sheet is exposed; that is, unless the crown sheet becomes bare, in which case the crown sheet would be burned, oil or no oil. The fact that the oil prevents the boiler from foaming; or, in other words, holds the water down, is sufficient indication that it must remain on top of the water. If the oil could get on the crown sheet and so cause it to burn, there would be very few unburned crown sheets in the west

1985. Dimensions of New Rock Island En

gines.-"I am firing on the Rock Island. I understand the Rock Island Railroad Company has bought fifty new freight locomotives and is putting them up at Silvis, Ill. Will you please give us a good illustration and description of these new engines in the Magazine? Many of us are anxious to know what they are like."-E. B.

Answer. We are indebted to Mr. G. W. Siddell, superintendent of Silvis shops, for the illustration and data. These engines are of the Mikado type; that is, having a 2-wheel engine truck, four pairs of drivers and a trailer. Forty engines were built at the Baldwin works, and ten by the American Locomotive Company. The Baldwin engines are fitted with the Baldwin type of air-reversing mechanism, while those built by the American Locomotive Company are fitted with the American Locomotive Company's screw reversing gear. The Baldwin engines have the Baker valve gear, while the American Locomotive Company's engines have the Walschaert valve gear. The Baldwin engines are equipped with Hancock nonlifting inspirators of 4,500 gallons per hour capacity, while the American Locomotive Company's engines are equipped with the Nathan nonlifting injectors of 4,500 gallons per hour capacity. With these exceptions, the following specifications are common to both:

cases of this kind, as there are anti-foaming boiler compounds on the market that serve the purpose better, yet in the absence of these boiler compounds crude oil can be used, and, we believe, with absolute safety.

pany.

Two 3 Consolidated safety valves. Firebox, 108 inches long, 84 inches wide.

Schmidt superheater.

Cylinders-Diameter, 28 inches; stroke, 30 inches.

Outside steam pipe to cylinder. Piston valve, 16-inch diameter chamber.

Driving wheels, 63 inches diameter.

Wheel Base-Driving, 17 feet 0 inch; engine, 36 feet 2 inches; engine and tender, 67 feet 0 inch.

Weight-On drivers, 235,000 pounds; on engine, 315,000 pounds; on tender, 165,000 pounds; total, engine and tender, 480,000 pounds.

Tender-Vanderbilt

type; capacity, 9,000 gallons water, 16 tons coal. Peters electric headlight. Westinghouse air brake ET 6 equipment; 8-inch Westinghouse cross-compound pump.

Engine No. Baldwin 2500 to 2539. Engine No. American 2540 to 2549. Trailer Truck-American locomotive latest outside bearing truck; journals 9 x 14 inches.

1986. Loose Piston Rod.-"If consistent, I would like to have your opinion on the following subject: A standard American engine, 4-4-0, having that type of crosshead which employs the 4-bar guide, that is, two bars on each side of the crosshead, and where the crosshead pin is cast solid with the crosshead, piston rod taper fit, what would you do if you received this engine with the piston rod working considerably loose in the crosshead? Say it worked an inch? The piston rod key bent considerably and can not be taken out with means at hand, and back end of main rod strap bolts sheared, so as to have a shoulder on them, and bolts slightly bent so they can not be taken out with the means at hand, what course would you pursue to prevent further damage in taking the engine to the shops

under her own steam? The crosshead key, or piston rod key, was bent toward the cylinder and there was no way to secure the rod firmly in the crosshead. I might mention that I took a relief engine to passenger train, which gave up the disabled engine. Your opinion will be appreciated."-D. G.

Answer. The only thing that could be done under the circumstances would be to disconnect the valve stem on that side, blocking the valve to cover the ports, and come in on one side. If the destination was not too great, it would not be necessary to make any provision for oiling the cylinder. If it was necessary to proceed a considerable distance, however, it would be advisable to remove the front cylinder head also. With the ports covered, admitting no steam to the cylinder, the piston would be propelled by the main rod and crosshead. The compression of air in the front end of the cylinder would prevent the piston from striking, except in case the engine were run at a very high rate of speed. The piston could not strike the back cylinder-head, as with it loose in the crosshead it would not be drawn back far enough. It would hardly be safe to try to work steam on that side, as, in that case, there would be some

1987. First Duty of An Engineer.-"What is an engineman's first and most important duty?"-C. W.

Answer.-Safety always. In other words, be sure you are right, then go ahead.

1988. Cross-Feed of Lubricator.-"Is it possible for any lubricator to cross-feed and allow all of the oil to go to one steam chest?"-C. W.

Answer. With the present improved type of lubricator it is not possible. With the older type of lubricator it was possible, however, as the equalizing passage was so cored that a stoppage of one choke plug would allow the oil to pass through the equalizing passage and through the other choke plug, and while the oil would be feeding up in regular drops through both sight-feed glasses, yet it could all pass to one cylinder while apparently going to both.

1989. Broken Side Rods.-"All instruction books tell us in case of a side rod break

ing, to take the opposite one down also, on account of the danger of breaking a crank pin, knuckle pin, or bending a rod, if left up, which I can not understand how this happens. Please explain fully."-C. W.

Answer.-In order to understand this proposition fully, you must take into consideration the fact that the crank pins and rods on one side of an engine are carried over, or by, the centers by the power applied to the opposite side. You can readily understand that when the crank pin on one side, say the right side, is approaching the forward center there is no steam in that cylinder; and, even if there was, on account of the piston pushing in a straight line, there would be no rotative effort applied to the wheel. The opposite crank pin, however, would be on the quarter, and the steam in the cylinder acting against the piston would, of course, have a tendency to rotate that wheel, and as both wheels are rigidly connected to the axle it would pull the right side over the center. Then as soon as steam was applied against the piston head on the right side the rotation of the wheel would be continued. Exactly the same proposition obtains with reference to side rods; as, for instance, say on a

consolidation engine the back side rod on the left side was broken, making it necessary to take it down. In this case, when the right back crank pin approached either center there would be nothing except the momentum of the wheel, or the movement of the engine, to cause the right crank pin to pass over the center, as the pull or push exerted by the side rods, depending whether it is passing over the forward or back center, would be exerted in a practically straight line. Now, if, through any cause, the engine should slip, and the slipping was taking place just as the right side was passing over the center, which would mean that the slipping was caused by the power exerted on the left side, there is a chance of the three pairs of wheels that are left connected up slipping faster than the engine is moving. This being the case, the back crank pin on the right side may not be quite over the center when the other crank pin ahead has already passed the center; and, therefore, a further slipping of the wheel would break either the rod, knuckle pin or the crank pin, whichever was the weakest.

1990. Broken Main Pin.-"In case of a main pin or main rod breaking, we take down main rod on disabled side. And should

all side rods on both sides or only on the disabled side be taken down, or all left up?"-C. W.

Answer.-In case of a broken main pin, that is, where the pin is broken next to the hub of a wheel, it has been customary on American railroads to take down all side rods on both sides, coming in with one main rod up. The writer has never agreed with this practice, however, as, in his opinion, it is simply necessary to take down all rods, main and side, on the disabled side, and leave all rods up on the good side, as there is no possible way in which side rods left up can become cramped so as to cause them to break, or break pins, etc. While the writer has frequently advocated this method of disconnecting, and has practiced it personally for quite a number of years, he has never been able to get but one man to support him in this view. Therefore, until this method of disconnecting is recognized as good practice, as it undoubtedly will be in time, we would advise all concerned to "carry the stone to the mill" in the old-fashioned way, by taking down all rods except the main rod on the good side. In case of a

main rod breaking, it would simply be necessary to take down the broken main rod on that side; of course, disconnecting the valve stem, covering the ports, and leaving all side rods up on both sides.

1991. Greatest Power of Locomotive.-"In what position should an engine stand to develop its greatest tractive power? Say a right lead engine?"-C. W.

Answer. With the crank pin on one side just back of the bottom quarter or ahead of the top quarter, so as to place the crank pin on the opposite side just over the forward back center.

1992. Test for a Valve Strip Blow.-"The following questions and answers are in the Magazine of January, 1910, page 47, last question in first column; January, 1906, page 66, second column, Question No. 363, by H. L. B.; February, 1906, page 209, second column, Question No. 33: 'How can a test be made for a valve strip blow?' The answers are, 'Put the crank pin on the side where the blow is thought to be, on the forward center, and reverse lever in center notch of quadrant, with valve covering ports,' etc. Now this looks like a misprint, as I think the forward center should read 'on the quarter,' as the ports can not be covered when the engine is on the center if the valve has any lead. Please tell me if I am right or wrong."-C. W.

Answer. You are right. And, in my opinion, if this was not a misprint, it certainly was an oversight, as the writer knows that one of the parties answering the question knew better.

tion."Does the amount of air admitted to 1993. Amount of Air Necessary for Combus. the fire have any influence on the amount of fuel consumed or the heat produced? State why."—E. A. M.

Answer.-Yes. It has a decided influence, as too little air will not supply sufficient oxygen to produce perfect combustion, as too little air simply produces carbon monoxide, a gas with only about one-third the heating properties of carbon dioxide, which is formed when the supply of air is sufficient. Too much air causes a waste, as it is necessary to heat the surplus quantity of air, and the oversupply tends to depress the firebox gases below the igniting temperature. In Sinclair's catechism he states that it takes 2.66 pounds of oxygen to burn 1 pound of coal into carbon dioxide; and as it takes 4.35 pounds of air to supply 1 pound of oxygen, it will take 11 pounds of air to provide the oxygen necessary to burn each pound of coal. As some excess