Figure 45. — Paths of 1 1 points on the coupler (horizontal) link are plotted 

 through one cycle. Dashes indicate equal time intervals. From John A. 

 Hrones and G. L. Nelson, Analysis oftheFourBar Linkage (New York, 1 95 1 , p. 635) . 



I / 



hear the author of the statement out. "A drafting 

 machine is a useful tool," he wrote. "It is not a 

 substitute for a draftsman.""* 



The scholarly interest in a subject is fairly repre- 

 sented by the papers that are published in the trans- 

 actions of professional societies and, more recently, 

 by original papers that appear in specialized maga- 

 zines. From 1900 to 1930 there were few papers 

 on mechanisms, and most of those that did appear 

 were concerned with descriptions of new "mechanical 

 motions." In the 1930's the number of papers 

 reported in Engineering Index increased sharply, but 

 only because the editors had begim to include 

 foreign-language listings. 



There has been in Germany a thread of continuity 

 in the kinematics of mechanisms since the time of 

 Reuleaux. While most of the work has had to do 

 with analysis, the teasing question of synthesis that 

 Reuleaux raised in his work has never been ignored. 

 The developments in Germany and elsewhere have 



been ably reviewed by others,"' and it is only to be 

 noted here that two of the German papers, published 

 in 1939 in Maschinenbau, appear to have been the 

 sparks for the conflagration that still is increasing 

 in extent and intensity. According to summaries in 

 EAgineering Index, R. Kraus, writing on the synthesis 

 of the double-crank mechanism, drew fire from the 

 Russian Z. S. Bloch, who, in 1940, discussed critically 

 Kraus' s articles and proceeded to give the outline of 

 the "correct analysis of the problem" and a general 

 numerical solution for the synthesis of "any four-bar 

 linkage." '-" Russian work in mechanisms, dating 

 back to Chebyshev and following the "Chebyshev 

 theory of synthesis" in which algebraic methods are 

 used to determine paths of minimum deviation from a 



'" Mechanical Engineering, October 1942, vol. 64, p. 746. 



"' Grodzinski, Bottema, De Jonge, and Hartenberg and 

 Denavit. For complete titles see list of selected references. 



120 My source, as noted, is Engineering Index. Kraus's articles 

 are reported in 1939 and Bloch's in 1940, both under the 

 section heading "Mechanisms." 



226 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



