MODERN STEAM PRACTICE.

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The piston for the blowing cylinder should be light, yet strong.It is fitted with a narrow junk ring for pressing down the packing,

and held down with bolts andnuts let into the piston. Thepiston rod has a cone fitting intoa corresponding cone in the pis-ton, and is secured with a plaincotter passing through the bossof the piston and rod.

We will now consider the de-tails for actuating the pistons ofthe steam and air cylinders simul-taneously. The main beam iscast in two halves, and held together by cast-iron distance pieceswith flanges for bolting to the halves. All the holes for the maingudgeons should be accurately bored out, and the gudgeons turnedto fit. The one for the main connecting rod has collars turned onit. and should be placed in position before the beams are bolted

Fig. 164.—Piston for Blowing Cylinder.a, Piston. B, Junk ring, c, Packing space.

Fig. 165.—Main Beam.

A, Beam. b, Steam cylinder end. c, Air cylinder end. d, Boss for connecting-rod gudgeon.

together; all the other gudgeons, excepting those for the feed andcold water pump, have the journals on the outside of the beam,and can be put in at any time; they are held in position withkeys. Some engineers prefer fitting four keys on the main gud-geons, the hole being left larger, and after the keys are fitted leadis run in, filling up the space; but this does not make such goodwork as boring out the hole the exact size. For heavy cast-ironbeams of all descriptions, neat wrought-iron hoops should be shrunkon the main boss, thereby binding the part that takes the wholestrain that is transmitted through the beam.

The pillow blocks are of the usual description, fitted with brasses,