380

MODERN STEAM PRACTICE.

fast river steamers, and the screw superseding the paddle wheelalmost universally for ocean-going steamers.

To understand the action of the feathering paddle wheel we haveto consider each float free to oscillate on pins passing throughbrackets forged on the paddle arms; on one of these journals anarm is fixed, and a rod for each float is attached to a pin on the

end of each arm, the arms being all con-nected to a strap (Fig. 259), which is freeto revolve on a sheave (Fig. 260) placedeccentrically with the main shaft. One

Fig. 259.—Eccentric Strap.a, Strap with brass lining pieces. B, Seat fordriving rod. c C, Holes for radial rods.

Fig. 260.—Eccentric Sheave for Paddle Wheel.a, Eccentric. b, Flange for bolting it to the ship’sside.

of these connecting rods is the driver, and is firmly secured tothe eccentric strap in a way similar to an eccentric rod for thevalve motion. When the paddle wheel is overhung, with one

pillow block at the side of thevessel, this bearing being support-ed with a wrought-iron bracketrivetted to the side of the ship, theeccentric sheave is secured at theend of the pillow block; and whenthe paddle wheel is supported withan outside bearing bolted to thesponsons, the eccentric sheave isbolted to the side of the ship direct.In setting out the mechanism,we consider the position of thedriving float, as we may term it; at its deepest immersion it isquite vertical, and as the rod from the arm that is fixed on the floatis secured to the eccentric strap, as the paddle wheel revolves the

Fig. 261.—Boss for Paddle-wheel Arms.a, Boss, b B, Seats for arms. c, Wrought-iron ring.