Page:The Kinematics of Machinery.djvu/395

 SIMPSON AND SHIP TON. 373

Messrs. Simpson and Shipton * employed it in the form of a steam- engine which was shown in action at the London Exhibition of 1851 and attracted no little attention. These inventors are the same as those of the machine shown in Fig. 2, PL XVII. ; the want of any distinct comprehension of the problem which there showed itself appears here in almost greater measure, and accounts for the employment of a special auxiliary train to trans- fer the motion of the link a to an axis turning in fixed bearings. This auxiliary mechanism consists of a pair of parallel cranks, attached at the one end to a, at the other to a fly-wheel shaft, con- axial with 3. The couplers of this mechanism are parallel to the principal coupler 6, and form with it as it were two pairs of parallel cranks. They are quite rightly adapted to transfer to the axis of 3 the motion of a, which as we know ( 69) turns completely round during its motion. Apart from this secondary train the machine consists of a chain (C^'P- 1 -) reduced by d and placed on c, in which the crank a, formed as a cylindric piston, is the driving link, and the block c the chamber. The complete formula for the mechan- ism is therefore (ClP-^l - d + (C"^ } and for the chambering ( V) = a, c. A comparison of this machine with that of Fig. 2, Plate XVII. allows us easily to understand how one and the same inventor devised both of them, for the one, (C^P L ) e d, is simply a direct inversion of the other, (C r gP- L ) b d.^ There is higher pairing between c and a, the preservation of a steam-tight joint is therefore scarcely possible. There would have been no difficulty, had the chain not been reduced, in employing lower pairing and obtaining a good joint by it ; and at the same time the common form of steam-cylinder and piston arranged in any way in two parts could have been employed. I may leave it to the reader to investigate this much more practical form, not advising, however, that even so arranged the machine be again brought forward as a steam-engine. In the form before us, however, the machine is in the highest degree impractical, in no respect so advantageous as the common direct-acting engine. What can we say therefore to the extraordinary assertion of the inventor before the Mechanical

series, 27, 1850, p. 207 ; Repertory of Patent Inventions, Enlarged series, xiii., 1849, p. 287.
 * Johnson, Imperial Cyclopaedia ; Newton, London Journal of Arts, 7. Conjoined

t In his collection of kinematic models at the Gewerbe Akademie in Berlin, Prof. Reuleaux has used the same (invertible) model for both.