386 KINEMATICS OF MACHINERY.
(normal) conic double-slider chain. We showed that three mechanisms could be formed by it ; two of these appear as chamber-crank gear, and the energy which always seems to accom- pany the search for solutions of the problem of the rotary engine has found for these two a great variety of forms.
89 -
Chamber-gear from the Conic Turning Double- slider.
Plates XXVIII to XXXI.
The rotary steam engine which specially receives the name of disc-engine is represented in Fig. 1, PL XXVIII. It is com- monly known as Davies' * engine, but is sometimes also called after Bishop, who at a later date made some improvements in it. The first inventors are, according to published accounts, the brothers Dakeyne (England), who patented the machine in 1830, and pro- posed to use it both as a steam-engine and as a pump.-f- There are many descriptions of it ; that of Johnson J is very complete, the particular machine he speaks of being the one above mentioned as having been used in the Times printing office, which was constructed with Bishop's improvements. It is in reality the mechanism (<7-^<7 z -) d , the turning conic double-slider, (see 75. No. 15), in which the fixed link d is made the chamber, and the coupler b the piston. It is therefore the same kinematic chain which, placed upon a, forms the Hooke's or universal joint.
The crank a is easily recognised ; it turns upon the pin 1, and is paired by the pin 2 with the coupler b. This carries at 90 from 2 its second pin 3, paired with the block c. The last men- tioned link turns about an axis perpendicular to the plane of the paper and therefore also at 90 to the axis of 3. The cylinder-pair or, more ggnerally, the pair of revolutes, of this fourth axis is not fully constructed ; it consists of the block c formed as a sector, and
- Tn consequence of a misprint in Bernouilli, which has now survived five
editions, this has been known in Germany for years as Darries machine. R.
t Repertory of Patent Inventions, vol. ii., 1831, p. 1 ; Newton, London Journal of Arts, &c., Second Series, vol. ix., 1834, p. 19. The Dakeynes do not seem actually to have constructed any machines under their patent.
Johnson, Imperial Cydopmlit, Steam-engine, p. 19, plates xii. to xiv.
