governor is to suspend a distance
piece on the end of the governor lever, so that at normal speed this
distance piece is interposed between the gas valve spindle and the lever
operating it. In that case the gas valve will be opened. But if the
speed is above the normal, the distance piece will be raised clear of
the valve spindle, and the opening mechanism (driven by a cam on the
side shaft) will simply move forward and recede again without ever
touching the gas valve.

There are any number of movements which have been, and there are many
more which could be, devised to give the same result; and it depends
principally upon the form of engine in question which device we adopt.

The simplest and most direct action is, however, always the best;
complicated mechanism is to be deprecated, especially on small engines.
For this reason is the inertia governor more generally fitted to such
engines.

[Illustration: FIG. 25.]

A simple form of this governor is shown in fig. 25. The gas valve V is
shown on its seating. It is screwed into a pecker block B, and pinned as
shown. The latter should be of cast steel, tempered to a straw colour;
or if mild steel or iron is used, it must be well case-hardened, in
order to resist wear. The pecker P (also tempered hard) is mounted on
the cast-iron weight W, which in turn is pivoted on the valve lever L.
It will be seen that the weight W (which is only held in the position
shown by the spring S) will tend to lag behind when a sudden upward
motion is imparted to the lever L. Thus it depends upon the degree of
suddenness with which L moves whether the pecker P remains in the same
relative position to the lever as the latter travels upwards and engages
with the pecker block B, or whether it misses it and simply slides over
the face of the block. The adjustment of the spring S is effected by
screwing up or slacking out the milled nuts T; and on the degree to
which this spring is compressed depends the sensitiveness of the
governor, and consequently the speed of the engine. To obtain accurate
and steady governing with this type of mechanism it is essential that
the weight be perfectly free on its spindle, and that nothing but the
spring S holds, or tends to hold, it in the position shown. On this
account it is advisable to provide a "lip" on the pecker block, as
shown, to keep the area of contact as small as possible. This
effectually prevents any sticking, should a superfluity of oil happen t