Page:The Kinematics of Machinery.djvu/412

 390 KIN EM A TICS OF -MA CHINE R Y.

The right-angled links in the conic trains do not, however, differ so widely from the others in form as the infinite links in the cylin- dric chains. We may on this account look for the counterpart of the disc-engine also among the mechanisms (C r gP- L ) d, and among them we find in Lamb's engine one which has a great resemblance to it. In both b is the piston and the driving-link and d the chamber; in both also the piston, on account of the omission of c, is fitted with a slot which moves to and fro upon a plate forming part of the frame ; in Lamb's engine, too, we might replace c by a slotted cylinder similar to that here shown. The comparison is very instructive.

The disc-engine has been introduced into France by Bouche' * and by Molardf in a form somewhat differing from that above described ; the last named engineer, especially, has endeavoured to extend its use as a steam-engine. The form used by both is that shown in Fig. 4, PI. XXVIII. Here the chamber d is extended over the pin 2 of the link b, and encloses a cone which forms part of a. This cone is simply the revolute 1 properly belonging to a. Bishop's external coupler b and block c are not used. Within the slot of the disc there appears, however, to have been used a metal packing-piece corresponding to the block c.J The careful con- struction of the surfaces of the disc and its enveloping cones is relied upon to give a steam-tight joint between them.

Fig. 5 shows an older form of the disc-machine, proposed by Davies in 1837 and intended for a pump. Here again the link c is entirely omitted, the crank a indeed is also omitted, but there is substituted for it an auxiliary mechanism. This consists of a crank with a spheric pin placed upon an axis normal to that of the chamber, and connected by means of a F"-shaped coupler to a cross-spindle forming part of b. This spindle, for constructive reasons, is placed as in Fig. 6, and not at right angles to the slot in the disc, an error which might easily have been avoided. The entire machine is a clumsy approximation to (C^C 1 -)*, which could


 * Propagation Industrielle, vol. iii. 1868, p. 244 (Patent dated 1835).

t Rapport du Jury International, 1868, vol. ix., p. 82.

Tresca, Rapport sur une Machine Locomobile de M. Molard, Bulletin de la Soc. d' Encouragement, 2nd Series, vol. xix, 1872, p. 49. Tresca suggests, too, that the " temporary success " of the disc-engine was not unconnected with the novelty of its method of action.

Newton, London Journal of Arts, &c. Conjoined series, vol. xix., 1842, p. 18.