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_.