Adjusting the Guides.—Put the connecting rod in place on its pins, and
revolve the crank until the guides have taken up that position which
allows the crosshead to move freely. Then mark off the holes for the
guide holding-down screws, and drill and tap them.
Packings.—The glands and piston should be packed with asbestos string.
Don’t be afraid of packing too tightly, as the tendency is for packing
to get slacker in use. The rear end of the cylinder should be bevelled
off slightly inside, to allow the packed piston to enter easily.
Joints.—The cylinder head and valve chest joints should be made with
stout brown paper soaked in oil or smeared with red lead. All screw
holes should be cut cleanly through the paper, and give plenty of room
for the screws.
[Illustration: FIG. 66.-Vertical section of force pump driven by
engine.]
When making a joint, tighten up the screws in rotation, a little at a
time so as not to put undue strain on any screw. Wait an hour or two,
and go round with the screw-driver again.
Lubrication.—When the engine is first put under steam, lubrication
should be very liberal, to assure the parts “settling down” without
undue wear.
The Pump.—Fig. 65 shows in section the pump, which will be found a
useful addition to the engine. (For other details, see Figs. 53 and
54.) Its stroke is only that of the eccentric, and as the water
passages and valves are of good size, it will work efficiently at high
speed. The method of making it will be obvious from the diagrams, and
space will therefore not be devoted to a detailed description. The
valve balls should, of course, be of gun-metal or brass, and the
seatings must be prepared for them by hammering in a steel ball of the
same size.
In practice it is advisable to keep the pump always working, and to
regulate the delivery to the boiler by means of a by-pass tap on the
feed pipe, through which all or some of the water may be returned
direct to the tank.
The tank, which should be of zinc, may conveniently be placed under the
engine. If the exhaust steam pipe be made to traverse the tank along or
near the bottom, a good deal of what would otherwise be wasted heat
will be saved by warming the feed water.
Making a Governor.
[Illustration: FIG. 66.—Elevation of governor for horizontal engine.
Above is plan of valve and rod gear.]
It is a great advantage to have the engine automatically governed, so
that it may run at a fairly constant speed under varying loads and
boiler pressures. In the absence of a governor one has to be constantly
working the throttle; with one fitted, the throttle can be opened up
full at the start, and the automatic control relied upon to prevent the
engine knocking itself to pieces.
The vertical centrifugal apparatus shown in Fig. 66 was made by the
writer, and acted very well. The only objection to it is its
displacement of the pump from the bed. But a little ingenuity will
enable the pump to be driven off the fly wheel end of the crank shaft,
or, if the shaft is cut off pretty flush with the pulley, off a pin in
the face of the pulley.
Turning to Fig. 66, A is a steel spindle fixed in a base, L, screwed to
the bed. B is a brass tube fitting A closely, and resting at the bottom
on a 1/4-inch piece of similar tubing pinned to A.
A wooden pulley jammed on B transmits the drive from a belt which
passes at its other end round a similar, but slightly larger, pulley on
the crank shaft. This pulley is accommodated by moving the eccentric
slightly nearer the crank and shortening the fly-wheel side bearing a
little.
The piece G, fixed to B by a lock screw, has two slots cut in it to
take the upper ends of the weight links DD; and C, which slides up and
down B, is similarly slotted for the links EE. Each of the last is made
of two similarly shaped plates of thin brass, soldered together for
half their length, but separated 3/32 inch at the top to embrace the
projections of D. To prevent C revolving relatively to B, a notch is
filed in one side of the central hole, to engage with a piece of brass
wire soldered on B (shown solid black in the diagram). A spiral steel
spring, indicated in section by a number of black dots, presses at the
top against the adjustable collar F, and at the bottom against C.
The two weights WW are pieces of brass bar slotted for driving on to
DD, which taper gently towards the outer edge.
When the pulley revolves, centrifugal force makes WW fly outwards
against the pressure of the spring, and the links EE raise C, which in
turn lifts the end of lever M. A single link, N, transmits the motion
from a pin on M to the double bell-crank lever O (see Fig. 66) pivoted
on a standard, P, attached to the bedplate. The slotted upper ends of P
engage with pins on an adjustable block, R, which moves the governing
valve V (solid black), working in the tube S through a gland. The
higher M is raised the farther back is V moved, and its annular port is
gradually pushed more out of line with two ports in the side of the
valve tube, thus reducing the flow of steam from the supply pipe to the
cylinder connection on the other side of the tube. This connection,
by-the-bye, acts as fulcrum for lever M, which is made in two parts,
held together by screws, to render detachment easy.
The closer the fit that V makes with S the more effective will the
governing be. The gland at the end of S was taken from an old cylinder
cover.