PART XXV.

WATER-TANKS AND TURN-TABLES.

QUESTION 449. _How are locomotive tenders or tanks supplied with water?_

[Illustration: Fig. 225. Scale ¹⁄₁₆ in. = 1 foot.]

_Answer._ At suitable points, called water stations, along the line of the road, large tanks or reservoirs are located, which are filled either from a natural stream which is higher than the tank and thus flows into the latter, or else the water is pumped in, either by hand or by horse, wind, water or steam power. These tanks are usually, when there is room for them, located near the track, as shown in fig. 225, so that the water can be conducted by a spout, _a_, direct from the tank to the man-hole of the tender. Communication to and from this spout is opened and closed by a valve, _b_, inside of the tank. The spout is usually attached to the tank by a hinged joint, so that it can be lowered to the tender and then raised up out of the way of the engine and train. It is generally balanced by a counterweight, suspended to one end of a rope, which passes over a pulley and is fastened to the spout at the other end. Such tanks are now generally made of wooden staves like a tub or pail, and supported on a heavy frame, _c c c_, made of wood, as shown in the engraving, or on stone or brick masonry.

[Illustration: Fig. 226. Scale ¹⁄₁₆ in. = 1 foot.]

When there is no room for the tank or reservoir near the track, it is placed in any convenient position at some distance from it, and the water is then conveyed by an underground pipe to the place where the locomotive must take water. At the end of this pipe what is called a _water-crane_, fig. 226, is located. This consists of a vertical pipe, _A_, with a horizontal arm, _B_, which is made so as to swing around over the man-hole of the tender when the latter is to be filled with water. In some cases the horizontal arm alone swings around, but in others the vertical pipe turns with the horizontal one in a joint, _C_, underneath the surface of the ground. The latter plan is thought to be preferable to the first, as the pipe is less liable to freeze fast in the joint when the latter is underground than when it is exposed above. A suitable valve, _D_, is also attached to the pipe below ground, so that the stream of water can be turned off or on at pleasure by the wheel _E_.

QUESTION 450. _What considerations should determine the source from which a supply of water should be drawn?_

_Answer._ The first must of course be its convenience to the point where the water is to be used; but more attention should be given to the quality of the water than it ordinarily receives, as the use of impure water, or that which contains a considerable amount of mud or solid matter mixed with it, or in suspension as it is called, or has lime or other mineral substances chemically combined with it, will very soon coat the inside of the boiler with a covering of scale, which is a very bad conductor of heat, and consequently the boiler is much less efficient and much more heat is wasted than if the heating surfaces were clear. Besides this loss of efficiency, when boiler plates are covered with non-conducting scale, they are much more liable to be injured by the action of the fire than when the water comes directly in contact with the metal of the plates. Some water, too, has a corroding effect on the metal of the boiler which is very destructive.

QUESTION 451. _How can the relative amount of incrustating substances in different kinds of water be determined?_

_Answer._ The relative quantity of solid matter or mud which is held in suspension can be at least approximately determined by simply filling vessels, say large clear glass bottles, with different kinds of water and letting them stand for some time until the solid matter settles to the bottom.

An easy method of precipitating the lime and some other salts which are held in solution and which will not settle until they are converted into a solid form is the following: Dissolve in a goblet of pure water (distilled or freshly caught rain water) two or three teaspoonfuls of the _oxalate of ammonia_. Have equal quantities, say a goblet-full of each of the waters to be tested, ranged side by side and marked so as to be identified. Into each of these goblets stir equal quantities of the solution mentioned--about three teaspoonfuls will be enough--and let them stand for a day. The lime and some other salts will be precipitated and fall to the bottom as a powder; and the quantity of this precipitate in each glass will form a very good index of its relative injuriousness in the formation of scale.

When the oxalate of ammonia cannot easily be procured, an experiment may be tried, in the same way, by dissolving common white soap, or other pure soap, in a goblet of pure water, and then stirring into the glasses of water to be tested a few teaspoonfuls of this solution. The comparative amount of lime in the water will be shown by the amount of coagulated matter which will be thrown down.[104]

[104] Correspondent of the Railroad Gazette.

QUESTION 452. _How are locomotives turned around on the track?_

_Answer._ The most common means employed for that purpose is a _turn-table_, fig. 227. This consists of two heavy beams made of wood, cast or wrought iron, placed side by side and resting on a pivot in the centre, on which they turn. They are placed in a circular pit below the level of the track, so that when rails are laid in the ordinary way on top of the beams they will be exactly level with the track which leads up to the pit. By turning the beams on the central pivot so that the rails will come exactly in line with the permanent track which leads up to the pit, the locomotive can be run on the turn-table, which is then revolved a half-revolution, which of course reverses the position of the locomotive and brings it opposite the permanent track so that it can be run off from the table. In order to prevent the beams from tipping down when the engine first runs on or off of the turn-table, wheels are placed at their outer ends which run on a circular track and bear any inequality of weight that may be thrown on them if the locomotive is not equally balanced on the central pivot.

[Illustration: Fig. 228. Scale ³⁄₃₂ in. = 1 foot.]

QUESTION 453. _How is the central pivot constructed?_

[Illustration: Fig. 227. Scale ³⁄₃₂ inch = 1 foot.

50-FOOT TURN-TABLE, BY WILLIAM SELLERS & CO., PHILADELPHIA.]

[Illustration: Fig. 229.]

_Answer._ It usually consists of a vertical post, _A_, shown in fig. 228, which is a transverse section through the centre of the turn-table, the end of which rests on hard cast iron or steel bearings. In some cases, as shown in figs. 227 and 228, which represent a turn-table built by William Sellers & Co., of Philadelphia, the weight rests on conical steel rollers, _m m_, which revolve in a circular path formed in the top plates. Sometimes turn-tables are fitted with gearing and cranks, _D_, fig. 228; but if they are made so that the whole weight rests on the centre, and if they are of sufficient length so that an engine and tender can be moved on them sufficiently to be balanced over the centre, gearing will not be needed; but a simple lever fastened to the turn-table will be all that will be required to turn the table and the engine and tender on it. The tables should be of such a diameter or length across the centre as will enable the class of engine in use on any road to be balanced. With light engines the 50-feet table is large enough; with the long, heavy engine now used on the great trunk lines, the engine and tender quite fill up the entire length of 50 feet, leaving no margin for adjustment. In such cases, the 54 feet, 56 feet, or, better, the 60 feet, should be employed. These large tables are also made heavier in proportion. The table should be of such a length that engines, with tender either empty or full, when run on the table can be so placed as to bring the centre of gravity immediately over the centre. When so balanced, one man can turn the loaded table with ease.

In setting up turn-tables it is necessary that the foundation at centre, upon which the pivot rests, should be of the most substantial character, so as not to be liable to settle. The circular track, which may be made of light rails, say 28 or 30 lbs. to the yard, should be level, and the table should be so adjusted as to swing clear of the circular track when loaded. The pit required is quite shallow near the edge and deepens towards the centre. Provision is made for covering the entire pit by a platform turning with the table, but this should be avoided whenever possible, as the best constructed cover does offer some resistance in turning. Even in roundhouses, where a covered pit might be considered preferable as presenting a smooth floor for crossing in any direction, it has been found advisable, in view of the greatest ease in turning and the facility offered by the open pit for cleaning, to dispense with the cover. The centre upon which the table turns is constructed of the best cast steel, and consists of conical rollers of steel between two steel plates grooved out to receive these rollers. This part of the table must be kept clean and well oiled, say with best sperm or lard oil and tallow of such a consistency as not to harden in cold weather. The top cap at centre is held in place by a circle of bolts. These bolts take the entire weight of the table and load; by slacking off the bolts the table can be lowered on the wheels on the circular track and the cap lifted off to gain access to the plates and rollers. These should be opened, examined and cleaned at least once every three months.

Under the cap and between it and the top of the centre box are segments of wood. These can be altered in thickness to bring the table in proper adjustment. If the centre foundation settles, these segments should be thinned sufficiently to enable the table to be screwed up to a proper height. With proper care such tables are practically indestructible.[105]

[105] Wm. Sellers & Co.

QUESTION 454. _Is there any other method of turning locomotives?_

_Answer._ Yes; what is called a ~Y~ is sometimes used. This consists of a system of tracks laid somewhat in the form of the letter ~Y~, as shown in fig. 229, in which _A B_ is the main track, with two curves, _A C_ and _B C_, laid as shown. If now it is desired to turn a locomotive which is standing in the position of the dart _A_, it is run on the curve _A C_ to the position of the darts _a_ and _C_. It is then run backward from _C_ on the curve _C B_, as represented by the dart _b_, and when it reaches the main track in the position of the dart _B_ it is evident that its position will be reversed, as is shown if we compare the direction of the dart _A_ with that of _B_.