^ 



Figure 38. — Drag link coupling used 

 on Boulton and Watt portable en- 

 gines. The link E drags one shaft 

 when the other turns. From John 

 Nicholson, The Operative Mechanic, and 

 British Machinist (Philadelphia, 1826, 

 vol. I, pi. 5). 



patents of John Oldham (1779-1840), an Irish 

 engineer who is remembered mainly for the coupling 

 that bears his name (fig. 39). His three patents, 

 which were for various forms of steamboat feathering 

 paddle wheels, involved linkages kinematically similar 

 to the drag link coupling, although it is quite unlikely 

 that Oldham recognized the similarity. However, 

 for his well-known coupling, which employs an 

 inversion of the elliptical trammel mechanism, I 

 have found no evidence of a patent. Probably it 

 was part of the machinery that he designed for the 

 Bank of Ireland's printing house, of which Oldham 

 was manager for many years. "Mr. Oldham and 

 his beautiful system" were brought to the Bank of 

 England in 1836, where Oldham remained until 

 his death in 1840.1°'= 



The Geneva stop mechanism (fig. 40) was properly 

 described by Willis as a device to permit less than a 

 full revolution of the star wheel and thus to prevent 

 overwinding of a watch spring. It was called Geneva 

 stop because it was used in Geneva watches. The 

 Geneva wheel mechanism, which permits full rotation 

 of the star wheel and which is frequently used for 



lOfi Oldham's paddle-wheel patents were British Patents 4169 

 (October 10, 1817), 4429 (January 15, 1820), and 5445 (Febru- 

 ary 1, 1827). Robert WilUs {op. cit. footnote 21, p. 167) noticed 

 the exislence of the coupling. Drawings or descriptions of the 

 banknote machinery apparently have not been published though 

 they probably still exist in the banks' archives. The quotation 

 is from Frederick G. Hall, The Bank oj IrelandVSS-lQdG, Dublin, 

 1949. John Francis in his History of the Bank of England (London, 

 1848, vol. 2, p. 232) wrote: "The new machinery for printing 

 the notes, which was introduced by Mr. Oldham ... is well 

 worthy of a visit, but would be uninteresting to delineate." 



Figure 39. — Top. Original Oldham coupling 

 built before 1840, using a cross (instead of a 

 center disk), as sketched by Robert Willis in 

 personal copy of his Principles of Mechanism 

 (London, 1841, p. 167). Bottom, Oldham 

 coupling as illustrated in Ale.xander B. W. 

 Kennedy, Kinematics of Machinery, a transla- 

 tion of Franz Reuleaux' Theoretishe Kinematik 

 (London, 1876. pp. 315-316). 



intermittent drives, was improperly called a Geneva 

 stop in a recent textbook probably because the logical 

 origin of the term had been lost. 



The name for the Scotch yoke seems to be of fairly 

 recent origin, the linkage being called by a Scotsman 

 in 1869 a "crank and slot-headed sliding rod" (fig. 41). 

 I suppose that it is now known as a Scotch yoke 

 because, in America at least, a "Scotch" was a 

 slotted bar that was slipped under a collar on a 

 string of well-drilling tools to support them while a 

 section was being added (fig. 42). 



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.'"'' 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 

 Betancourt 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 



' British Patent 4212, January 27, 1818. 



PAPER 27: KINEMATICS FROM THE TIME OF WATT 



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