Q. Name some other types of fire-door.

A. Some types of doors are made to slide, and are moved by a lever or handle. Swinging doors have a handle and a chain fastened to the boiler-head for convenience in opening and closing. There is a catch or notched rod, on various points of which the door handle may be set, to regulate the amount of air admitted above the fire. Some doors are operated by a rod moved by the piston of a small air cylinder, the valve of which has a foot lever, by which the fireman opens and closes the door.

(See chapter on Motion Records.)

CHAPTER VIII

THE BLOWER AND PAN DAMPERS

Q. How can the fire be urged when the engine is not running and there is no exhaust blast?

A. By a steam jet sent up the stack from a pipe connected with the steam-space and controlled by the blower-cock. Also, in some engines, as on the New York Central Railroad, there are steam and air jets in the firebox above the grate.

Q. How does the blower act?

A. It directs a jet of live steam up the stack, causing, by friction between that jet and the surrounding air in the stack, an air current to pass through the tubes to supply the deficiency.

Q. When should the blower be used?

A. In starting a fire; in clearing out dust and ashes in cleaning fire; in preventing black smoke at times; in enabling certain inside repairs to be made while the fire is burning.

Q. When should the blower not be used?

A. When the fire is drawn or dead, as that would draw cold air into the hot tubes and make them leak. Q. Where is a good place to put the blower discharge? A. Around the top of the exhaust-pipe.

Q. What are the chief uses of the dampers?

A. To prevent cinders and burning coals being dropped where not desirable, and to enable the draft to be completely checked when doors or dampers are closed. Q. How are the ash-pan dampers worked?

A. By a bell-crank and rod communicating with a handle in the cab.

Q. Why is it necessary to have the dampers on a woodburning locomotive shut air-tight, while on a coal burner

the dampers are not tight and some of them cannot be closed?

A. Wood requires so little air to keep it burning, and a wood fire is so open, that air will readily pass up through it and keep it burning so freely when engine is shut off, that the dampers must be air-tight to control the fire. With coal a strong draft is required to burn it; so the natural draft does not have the same effect on a coal fire. If the fire is thick, very little air will draw up through it. However, it is a mistake to allow the dampers and ash-pan to be so open that the draft cannot be controlled, especially with free-burning coal. Some little air is said to be needed constantly to keep the grates cool with a thin fire. This is a matter on which there is a difference of opinion. English engines have very tight ash-pans and dampers. The English find it pays to keep them so.

Q. What is the effect of working a long distance with closed dampers?

A. To warp ash-pan and dampers.

Q. What is the Hale ash-pan?

A. A device on the bottom of the ash-pan hopper, consisting of a lever or hanger, pivoted at its upper end to a frame or bracket, and fastened at its lower end to the hopper bottom. When the hopper is closed the upper end of the hanger is back of the center of the hopper. Consequently, when the dump lever is operated, the hanger pushes the bottom away from the hopper. It facilitates dumping the ash-pan should the hopper be frozen.

Q. What is the ash dump in a stayless boiler?

A. A cylindrical chute or pipe, usually 18 or 20 inches in diameter, leading from an aperture in the bottom of a corrugated fire-box to the outside shell below, to discharge the ashes into the ash-pan.

CHAPTER IX

THE CROWN-SHEET

Q. What is the most effective heating surface in a locomotive boiler?

A. That of the crown-sheet.

Q. How is the crown-sheet kept from being forced down by the steam-pressure between it and the boiler top?

A. By sling-stays or by crown-bars.

Q. In what direction do sling-stays extend?

A. As nearly as possible at right angles to the surfaces which they connect. (See Fig. 30, page 43.)

Q. What is the objection to staying crown-sheets by sling-stays?

A. That to be of the greatest effectiveness, they should be perpendicular to both the surfaces which they connect. Now ordinarily, if at right angles to the crownsheet they will be oblique to the shell, except right in the center line of the boiler.

Q. How can this trouble be got around without discarding sling-stays?

A. By making the boiler-shell over the crown-sheet flat and parallel therewith, so that each stay-bolt will be at right angles to both the surfaces which it connects, as shown in Figs. 57 and 58.

Q. What name is given to this type of fire-box?

A. The Belpaire.

Q. What other advantage has this fire-box?

A. That its sides can spring a little when the inner sheet is heated more than the outer one.

Q. What is the advantage of having the fire-box top curved?

A. To enable the use of more radial stays than other

wise possible, and to give a good surface for reception of the radiated heat. The curved crown-sheet gives more full threads than the flat one, and affords less lodgment for impurities in the water.

Q. What is the disadvantage of curved crown-sheet? A. They necessitate either throwing out too many tubes in the upper corners of the furnace, or else increasing the boiler-diameter.

Q. Where is the Belpaire fire-box undesirable?

A. On roads where there is bad water, by reason of it. affording too good lodgment for scale.

Figs. 57 and 58. Belpaire Fire-box, Matanzas R. R.

Q. For what class of engine is the Belpaire box least desirable?

A. For eight-wheel and ten-wheel engines, as it throws too much weight on the leading truck.

Q. What is the reason of this?

A. The necessity of having a large waist for steam

room.

Q. What other objections are raised to the Belpaire fire-box?

A. The difficulty of keeping the crown-stays tight near the ends of the braces which run from the back head to the top of the fire-box shell.

Q. How may this difficulty be done away with?

A. By substituting for the round back-head braces,