The engine represented in Figs. 1 to 4 herewith is intended for a mill,
and is of 530 to 800 indicated horse-power, the pressure being seven
atmospheres, and the number of revolutions forty-five per minute. As
will be seen by the drawing each cylinder is placed in a separate
foundation plate, the two connecting rods acting upon cranks keyed
at right angles upon the shaft, W, which carries the drum, T. The
high-pressure cylinder, C, is 760 mm diameter, the low pressure cylinder
being 1,220 mm. diameter, and the piston speed 2.28 m. The drum, which
also fulfills the purpose of a fly wheel, is provided with twenty-eight
grooves for ropes of 50 mm. diameter. With the exception of the
cylinders, pistons, valves, and valve chests, the engines are of the
same size, corresponding to the equal maximum pressures which come into
action in each cylinder, and in this respect alone the engine differs in
principle from an ordinary twin machine.
[Illustration: BORSIG'S IMPROVED COPOUND BEAM ENGINE. FIG. 1]
The steam passes from the stop-valve, A, Fig. 4, through the steam pipe,
D, to the high pressure cylinder, C, and having done its work, goes into
the receiver, R, where it is heated. From the receiver it is led into
the low-pressure cylinder, C1, and thence into the condenser. Provision
is made for working both engines independently with direct steam when
desired, suitable gear being provided for supplying steam of the proper
pressure to the condensing engine, so that each engine shall perform
exactly the same amount of work. The starting gear consists of a
hand-wheel, H, which controls the stop valve, A, and of another h, which
opens the valves for the jackets of the cylinders and receiver. The
hand-wheel, h1 and h2, govern the valves, which turn the steam direct
into the two cylinders. There are also lever, g, which opens the
principal injection cock, H1, and the auxiliary injection cock, H2, the
function of which is to assist in forming a speedy vacuum, when the
engine has been standing for some time.
[Illustration: BORSIG'S IMPROVED COPOUND BEAM ENGINE. FIG. 2]
The drum is 6.08 m. diameter, the breadth being 2.04 m., with a total
weight of 33,000 kilos. The beams are of cast iron with balance weights
cast on. The connecting rods and cross beams are of wrought iron, and
the cranks, crank shaft, piston rods, valve rods, etc., of steel. The
bed-plate for the main shaft bearings are cast in one piece with the
standards for the beam, which are connected firmly together by the
center bearing, M M1, which is cast in one piece, and also by the
diagonal bracing piece, N N1. The construction of the cylinder and valve
chests is shown in Fig. 1. The working cylinder is in the form of a
liner to the cylinder, thus forming the steam jacket, with a view to
future renewal. This lining has a flange at the lower part for bolting
it down, being made steam-tight by the intervention of a copper packing
ring. There is a similar ring at the upper part which is pressed down by
the cylinder cover. The latter is cast hollow and strengthened by ribs.
The pistons are provided with cast iron double self-expanding packing
rings. For preventing accidents by condensed water, spring safety
valves, ss and s1 s1, are connected to the valve chests. The valve gear,
which is arranged in the same manner for both cylinders, is actuated
by shafts, w and w1, rotated by toothed wheels as shown. Motion is
communicated from the way-shafts, w and w1, by the eccentrics, and the
eccentric rods, e1 e2 e3 e4, and the levers and rods belonging thereto,
to the short steam valve rocking shafts levers, f1 f2 f3 f4, and the
exhaust valve rocking shafts, k1 k2 k3 k4, the bearings of which are
carried on brackets above the valve chests, which, being furnished with
tappet levers, raise and lower the valves.
[Illustration: BORSIG'S IMPROVED COPOUND BEAM ENGINE. FIG. 3]
The valves are conical, double-seated, and of cast iron, and the inlet
and outlet valves are placed the one above the other, the seats being
also conically ground and inserted through the cover of the valve chest.
Both inlet and outlet valves are actuated from above, and are removable
upward, an arrangement which admits of the valves being more easily
examined than when the two are actuated from different sides of the
valve chest. To carry out this idea the inlet valves are furnished with
two guides, which, passing upward through the stuffing-box, are attached
to a hard steel cross piece, which receives the action of a bent catch
turning on a pin attached to the levers, t1, t2, t3, t4. The exhaust
valves, on the contrary, have only one guide each, which passes upward
through the seat of the admission valve, through the valve itself by
means of a collar, and through the stuffing-box. It is furnished with
hard steel armatures, through which the levers, z1 z2, Fig. 3, act upon
the exhaust valves.
[Illustration: BORSIG'S IMPROVED COPOUND BEAM ENGINE. FIG. 4]
The governor effects the acceleration or retardation of the loosening of
the catch actuating the steam valve by means of hard steel projections
on the shaft, v1, the position of which, by means of levers, is
regulated by the governor, which in its highest position does not allow
the lifting of the inlet valve at all. The regulation of the expansion
by the governor from 0 to 0.45 takes place generally only in the case of
the high-pressure cylinder, while the low-pressure cylinder has a fixed
rate of expansion. Only when the low-pressure cylinder is required
to work with steam direct from the boiler is the governor applied to
regulate the expansion in it. An exact action in the valve guides and
a regular descent is secured by furnishing them with small dash pot
pistons working in cylinders. Into them the air is readily admitted by
a small India-rubber valve, but the passage out again is controlled at
pleasure.--_The Engineer_.
* * * * *
TO DETECT ALKALIES IN NITRATE OF SILVER--Stolba recommends the salt
to be dissolved in the smallest quantity of water, and to add to
the filtered solution hydrofluosilicic acid, drop by drop. Should a
turbidity appear an alkaline salt is present. But should the liquid
remain limpid, an equal volume of alcohol is to be added, which will
cause a precipitate in case the slightest trace of an alkali be present.
* * * * *