Figure 41.—Scotch yoke, described as a "crank and slot-headed sliding rod." From W. J. M. Rankine, A Manual of Machinery and Millwork (ed. 6, London, 1887, p. 169).
Figure 42.—A "Scotch" supporting the top member of a string of well-drilling tools while a section is being added, 1876. From Edward H. Knight, Knight's American Mechanical Dictionary (New York, 1876, p. 2057).
It was surprising to me to find that the Ackermann steering linkage, used today on most automobiles, was patented in 1818 when Detroit was still a frontier town.[107] Furthermore, the man who took out the patent described himself as Rudolph Ackermann, publisher and printseller. I thought I had the necessary clue to the linkage's origin when I noticed that the first English translation of the Lanz and Bétancourt treatise was published by Ackermann, but the connection finally proved to be more logical, if less direct. Ackermann (1764-1834), son of a Bavarian coach builder, had spent a number of years designing coaches for English gentlemen in London, where he made his home. One of his more notable commissions was for the design of Admiral Nelson's funeral car in 1805. The Ackermann steering linkage was not actually Ackermann's invention, although he took out the British patent in his name and promoted the introduction of the running gear of which the linkage was a part (fig. 43). The actual inventor was Ackermann's friend George Lankensperger of Munich, coachmaker to the King of Bavaria. The advantage of being able to turn a carriage around in a limited area without danger of oversetting was immediately obvious, and while there was considerable opposition by English coachmakers to an innovation for which a premium had to be paid, the invention soon "made its way from its own intrinsic merit," as Ackermann predicted it would.[108]
[ [107] British Patent 4212, January 27, 1818.
[ [108] Rudolph Ackermann, Observations on Ackermann's Patent Moveable Axles, London, 1819. It was interesting to me to note an abstract of W. A. Wolfe's paper "Analytical Design of an Ackermann Steering Linkage" in Mechanical Engineering, September 1958, vol. 80, p. 92.
Figure 43.—Ackermann steering linkage of 1818, currently used in automobiles. This linkage was invented by George Lankensperger, coachmaker to the King of Bavaria. From Dinglers Polytechnisches Journal (1820, vol. 1, pl. 7).
The Whitworth quick-return mechanism (fig. 44) was first applied to a slotter, or vertical shaper, in 1849, and was exhibited in 1851 at the Great Exhibition in London.[109] Willis' comments on the mechanism are reproduced in figure 44. I hope that Sir Joseph Whitworth (1803-1887) will be remembered for sounder mechanical contrivances than this.
[ [109] The quick-return mechanism (British Patent 12907, December 19, 1849) was perhaps first publicly described in Charles Tomlinson, ed., Cyclopaedia of Useful Arts and Manufactures, London, 1854, vol. 1, p. cxliv.