is
completed by an adjusting nut to squeeze the packings, and a lock nut to
prevent slipping. The back end of the valve must be wide enough to just
more than cover the steam port. If the felt proves difficult to procure or
fit, one may use a ring or two of brass tubing, with an external packing of
asbestos cord.

The cylinder wing W should have the top edge turned over for an eighth of
an inch or so to give a good bearing against the cylinder, and be held in
position by a wire while the soldering is done. It is important that the
line of the wing should be at right angles to a line passing through the
centres of the valve tube and cylinder.

Shaft Bearings.--Take a piece of strip brass half an inch or so wide and
3-1/2 inches long. Bore four holes for screws, and scratch cross lines an
inch from each extremity. Turn up the ends at these lines at right angles
to the central part, stand the piece on some flat surface, and on the outer
faces of the uprights scratch two cross lines at the height of the centre
of the cylinder above the bed. Mark the central points of these lines.

Next select a piece of brass tubing which fits the rod chosen for the crank
shaft, and bore in the bearing standards two holes to fit this tubing. Slip
the tubing through the standards and solder it to them. The ends and
central parts of the tubing must now be so cut away as to leave two
bearings, BB--that at the fly-wheel end projecting far enough to allow
the fly wheel, when brought up against it, to just clear the bed; that at
the crank end being of the proper length to allow the eccentric to be in
line with the valve rod, and the crank disc to occupy its proper position
relatively to the central line of the cylinder. Finish off the standards by
filing the tops concentrically with the bearings.

The eccentric may be built up from a metal disc about 3/4 inch diameter and
two slightly larger discs soldered concentrically to the sides. The width
of the middle disc should be the same as that of the eccentric rod. A
careful filer could make a passable eccentric by sinking a square or
semicircular groove in the edge of a wide disc. The centre of the eccentric
must be found carefully, and a point marked at a distance from it equal to
half the travel of the valve. To ascertain this, pull the valve forward
until the steam port is fully exposed, insert a bar at the rear end of the
valve tube, and mark it. Then push the valve back until a wire pushed
t