ark the circles between which the ring must lie.

Bolt Holes.--The marks for these, six or twelve in number, are equally
spaced on the outside of one plate, and the two plates are clamped or
soldered together before the boring is done, to ensure the holes being in
line. If the bolts are to screw into one plate, be careful to make the
holes of the tapping size in the first instance, and to enlarge those in D
afterwards. Make guide marks in the plates before separating, between what
will be the uppermost holes and the circumference.

Bolts.--These should be of brass if passed inside the ring. Nuts are not
necessary if E is tapped, but their addition will give a smarter
appearance and prevent-the bolts becoming loose.

Bearings.--Bore central holes in the discs to a good fit for the
bearings, and prepare the hole for the exhaust pipe. This hole is most
easily made by drilling a ring of small holes just inside the mark and
cutting through the intervening metal.

For A, B, and C cut off pieces of bearing pipe, 1/2, 1/4, and 3/4 inch long
respectively, and bevel the ends of B and C as shown, to minimize friction
if they rub. File all other ends square. (Lathe useful here.)

Bore oil holes in B and C, and clear away all the "burr." Make scratches on
the bearings to show how far they should be pushed through the case.

Now assemble the case, taking care that the edge of the ring corresponds
exactly with the circles marked on the discs, and clean the metal round the
bearing holes and the bearings themselves. The last are then placed in
position, with the lubricating holes pointing upwards towards the guide
marks on the discs. Push the spindle rod through the bearings, which must
be adjusted until the rod can be revolved easily with the fingers. Then
solder in the bearing with a "Tinol" lamp.

The Wheel.--Anneal this well by heating to a dull red and plunging it in
cold water. Mark a circle of 1-1/4-inch radius, and draw radial lines 1/4
inch apart at the circumference from this circle to the edge. Cut out along
the lines, and twist the vanes to make an angle of about 60 degree with the
central part, and bend the ends slightly backward away from the direction
in which the rotor will revolve. (The directions given on p. 189 for making
a steam top wheel can be applied here.)

Bore a hole in the centre to make a tight fit with the spindle, and place
the rotor in position, with piece B in contact on the C side. Get
everything