Corrosion of the boiler will be lessened if the boiler is kept
quite full of water when not in use.
A Practical Steam Turbine.
The next step takes us to the construction of a small turbine capable of
doing some useful work. It is shown in cross section and elevation in Fig.
69.
[Illustration: FIG. 69.--Model steam turbine, showing vertical cross
section (left) and external steam pipe (right).]
The rotor in this instance is enclosed in a case made up of two stout brass
discs, D and E, and a 3/4-inch length of brass tubing. The plates should be
1/2-inch larger in diameter than the ring, if the bolts are to go outside.
The stouter the parts, within reason, the better. Thick discs are not so
liable to cockle as thin ones, and a stout ring will make it possible to
get steam-tight joints with brown-paper packing.
The wheel is a disc of brass, say, 1/25 inch thick and 4 inches in
diameter; the spindle is 3/16 inch, of silver steel rod; the bearings,
brass tubing, making a close fit on the rod.
If you cannot get the ring ends turned up true in a lathe--a matter of but
a few minutes' work--rub them down on a piece of emery cloth supported on a
true surface, such as a piece of thick glass.
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