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, whic