Figure 15. — Oliver Evans' "Columbian" en- 

 gine, 18 1 3, showing the Evans, or "grass- 

 hopper," straight-line linkage. From Emporium 

 of Arts and Sciences (new ser., vol. 2, no. 3, 

 April 1814, pi. opposite p. 380). 



engines.'^ The practical advantage of the Evans 

 linkage, utilizing as it could a much lighter working 

 beam than the Watt or Freemantle engines, would 



not escape Oliver Evans, and he was not a man of 

 excessive modesty where his own inventions were 

 concerned. 



Another four-bar straight-line linkage that became 

 well known was attributed to Richard Roberts of 

 Manchester (1789-1864), who around 1820 had built 

 one of the first metal planing machines, which ma- 

 chines helped make the quest for straight-line linkages 

 largely academic. I have not discovered what occa- 

 sioned the introduction of the Roberts linkage, but it 

 dated from before 1841. Although Roberts patented 

 many complex textile machines, an inspection of all of 

 his patent drawings has failed to provide proof that 

 he was the inventor of the Roberts linkage.'* The 

 fact that the same linkage is shown in an engraving 

 of 1769 (fig. 18) further confuses the issue. '^ 



The appearance in 1864 of Peaucellier's exact 

 straight-line linkage went nearly unnoticed. A 



33 Grevllle and Dorothy Bathe, Oliver Evans, Philadelphia, 

 19.'^5, pp. 88, 196, and passim. 



34 Robert Willis {op. cit. [footnote 21] p. 411) credited Richard 

 Roberts with the linkage. Roberts' 1 5 British patent drawings 

 exhibit complex applications of cams, levers, guided rods, 

 cords, and so forth, but no straight-line mechanism. In his 

 patent no. 6258 of April 13, 1832, for a steam engine and loco- 

 motive carriage, Roberts used Watt's "parallel motion" on a 

 beam driven by a vertical cylinder. 



3= This engraving appeared as plate 11 in Pierre Patte's 1769 

 work {op. cit. footnote 24). Patte stated that the machine de- 

 picted in his plate 1 1 was invented by M. de Voglie and was 

 actually used in 1756. 



Figure 16. — Modified Freemantle linkage, 

 1 81 9, which is kinematically the same as the 

 Evans linkage. Pivots D and E are attached to 

 engine frame. From Abraham Rees, The 

 Cyclopaedia (London, 181 9, "Parallel Motions," 

 pi. 3). 



PAPER 27: KINEMATICS FROM THE TIME OF WATT 

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