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.

Regulation of the speed may be effected either

(1) by driving the governor faster or slower relatively to the speed of the crank shaft;

(2) by altering the position of W on D;

(3) by altering the compression of the spring by shifting F;

(4) by a combination of two or more of the above.

Generally speaking, (3) is to be preferred, as the simplest.

The belt may be made out of a bootlace or fairly stout circular elastic.  In either case the ends should be chamfered off to form a smooth joint, which may be wrapped externally with thread.

FINAL HINTS.

All parts which have to be fitted together should have matching marks made on them with the punch.  To take the parts of the valve chest as an example.  As we have seen, these should be soldered together, finished off outside, and drilled.  Before separating them make, say, two punch marks on what will be the upper edge of the valve plate near the end, and two similar marks on the chest as near the first as they can conveniently be.  In like manner mark the chest cover and an adjacent part of the chest with three marks.  It is utterly impossible to reassemble the parts incorrectly after separation if the marks are matched.  Marking is of greatest importance where one piece is held up to another by a number of screws.  If it is omitted in such a case, you may have a lot of trouble in matching the holes afterwards.

Jacket the cylinder with wood or asbestos, covered in neatly with sheet brass, to minimize condensation.  If the steam ways, valve chest, and steam pipe also are jacketed, an increase in efficiency will be gained, though perhaps somewhat at the expense of appearance.