368 KINEMATICS OF MACHINERY.
The form of steam-engine given in Fig. 2, PL XX., which was designed by Smyth,* shows how far men may be led by the delusive fancy that there must be some special advantage in the rotary steam- engine. We have here a combination of four trains of the class (C^P- L ) a> - 1, the blocks c are in their usual form, the higher pairing rendered necessary by the omission of the coupler is supplied by cylindrical bars working in a circular ring, and the steam expands only in the spaces enclosed between the moving cylinders. Its uselessness is obvious ; it is only astonishing that it should ever have received any serious treatment at all.
Fig. 3, PL XX. Steam-engine consisting of two mechanisms of the class ( C^P- 1 )*. Here for the first time we have d used as the piston; the coupler b is a drum, touching the inner wall of the chamber and revolving about the axis 2, the bearings of which are not shown. The block c forms a joint at the place where the slide d passes through the drum b. Lechat has both designed and constructed (1866) a machine on this plan which had one piston only, i.e. which contained only one train (C'^P- L ) & .'f- Hick, of Bolton, had already obtained a patent for it in England in 1843.J Both, however, were long preceded by Lord Cochrane, who in 1831 constructed the machine both with two pistons (as shown in our sketch) and with one only, and at a later date added some small improvements to it-. The American Root has recently (1863) re-invented the same machine, using, however, three pistons instead of two. ||
In Fig. 4 we have the same machine used as a three-armed ventilator. It was patented in this form in England (1855) by BellfordjIT and quite recently Root has again brought it to light ** in very much the same form. We have here a striking example of the waste of inventive energy which has so often occurred in
- Practical Mechanic's Journal, vol. xvii., 1864-5, p. 261.
t Genie Industriel, vol. xxxii., 1866, p. 27.
+ Practical Mechanic's Journal, vol. xix., 1866-7, p. 249.
Propagation Industrielle, iii., 1868, p. 181. Newton, London Journal of Arts, &c., Conjoined Series, vol. viii., 1836, p. 404, and vol. ix., 1837, p. 216.
|| Scientific American. New series, vol. viii., 1863, p. 63. This particular rotary engine, in a form either complete or reduced as in Fig. 1 . PI. XXJ, has lately been repeatedly patented, e.g., by Works and Reynolds (1870), Higginson (1872) and Myers (1873). Its original inventor seems to have been Trotter (1805). See Engineering, Jan. 1 and June 11, 1875.
T[ Newton, London Journal of Arts, &c. New series, vol. v., 1857, p. 112.
- Scientific American, Nov. 1872, p. 354.
