Page:The Kinematics of Machinery.djvu/393

 SMITH, COG HE AN E, FLETCHER. ,371

were a pump. The joint between piston and chamber can without difficulty be made steam-tight, as only lower pairing is used. Geo. Smith * used four connected turning-block trains, and placed the couplers inside the chamber a. Fig. 1, PL XXII. shows his arrangement adapted for a pump. The block c is omitted, and the pairing of the reduced chain (Fig. 268) is therefore used. The formula runs 4[(tf;'P- L > - c].

Lord Cochrane gives us still another form of chamber- crank gear based on (C" S P%, Fig. 2, PL XXII. Here the link d is the chamber, and might at the same time be called the piston. We should, however, perhaps rather call the drum-shaped coupler b the piston, as has been done in the formula.

The coupler may also be made the piston with lower pair- closure, to show which I add the, arrangement of Fig. 3, PI. XXII., where d is made a drum and c a joint-piece. A similar solution has also been employed in practice by Fletcher (America ?) in 1843, in a rotary steam-engine which I know only by description and have represented in Fig. 4. It contains three mechanisms of the form (CIP^- The form of the coupler b here is remarkable, and it was principally to explain it that I added Fig. 3. Instead of using a circular pin of the common form at 2, the pin is ex- panded until it reaches the wall of the chamber ,.and the pair 2 consists of a ring-shaped channel in a and a portion of a cylindric ring (A+} in the piston b. Although this construction disguises the real nature of the machine in the most extraordinary way, our analysis places it at once in its proper position without the least constraint.

8: ">-

Chamber-crank Trains from the Swinging Slider-

crank.

(Plate XXIII. Fig. 1.)

The swinging slider-crank (C^P^ is applied least often as a mere mechanism of the four trains formed from the chain (Og'jP- 1 ), and it has also least often been used in chamber-crank gear. I know indeed only a single case in which it has been employed.


 * Tim Engineer, Jan. 1871, p. 56.

B B 2