Fig. 411.
THE SILSBY ROTARY STEAM FIRE ENGINE.
The distinguishing feature of this engine will be found in the fact that, in both the cylinder and pump, the rotary type is substituted for the reciprocating or piston principle.
Fig. 412.
The larger sizes of these engines, Fig. [411], are hung on platform truck springs in front and on half-elliptic springs in the rear, and are braced and stayed to withstand violent shocks in the rapid driving over pavements. Although fitted to be drawn by horses only, they can be supplied with rope reel and drag rope.
Fig. 413.
The Silsby steam cylinder consists of two rotary pistons or cams, mounted on steel shafts and working together within an elliptical steam-tight case. Live steam from the boiler enters at the bottom of this case, and in its passage presses apart their long teeth or abutments, causes the two cams to rotate, and exhausts from the top into the tank and feed-water heater; these cams are provided with teeth or cogs, adapted to mesh with corresponding recesses in each other, so that a steam tight joint is maintained between them and leakage thereby prevented from passing directly upward into the exhaust.