[ [117] Henry N. Bonis, "The Law of Coriolis," American Machinist, November 18, 1920, vol. 53, pp. 928-930. See also "Acceleration Determinations," American Machinist, November 25 and December 2, 1920, vol. 53, pp. 977-981 and 1027-1029.
Less than 20 years ago one might have read in Mechanical Engineering that "Practical machinery does not originate in mathematical formulas nor in beautiful vector diagrams." While this remark was in a letter evoked by an article, and was not a reflection of editorial policy, it was nevertheless representative of an element in the American tradition of engineering. The unconscious arrogance that is displayed in this statement of the "practical" designer's creed is giving way to recognition of the value of scholarly work. Lest the scholar develop arrogance of another sort, however, it is well to hear the author of the statement out. "A drafting machine is a useful tool," he wrote. "It is not a substitute for a draftsman."[118]
[ [118] Mechanical Engineering, October 1942, vol. 64, p. 746.
The scholarly interest in a subject is fairly represented by the papers that are published in the transactions of professional societies and, more recently, by original papers that appear in specialized magazines. 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 begun 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,[119] 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 Engineering 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."[120] 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 given curve, has also been reviewed elsewhere,[121] and I can add nothing of value.
[ [119] 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."
[ [121] A. E. Richard de Jonge, "Are the Russians Ahead in Mechanism Analysis?" Machine Design, September 1951, vol. 23, pp. 127, 200-208; O. Bottema, "Recent Work on Kinematics," Applied Mechanics Reviews, April 1953, vol. 6, pp. 169-170.
When, after World War II, some of the possibilities of kinematic synthesis were recognized in the United States, a few perceptive teachers fanned the tinder into an open flame.
The first publication of note in this country on the synthesis of linkages was a practical one, but in conception and undertaking it was a bold enterprise. In a book by John A. Hrones and G. L. Nelson, Analysis of the Four Bar Linkage (1951), the four-bar crank-and-rocker mechanism was exhaustively analyzed mechanically and the results were presented graphically. This work was faintly praised by a Dutch scholar, O. Bottema, who observed that the "complicated analytical theory of the three-bar [sic] curve has undoubtedly kept the engineer from using it" and who went on to say that "we fully understand the publication of an atlas by Hrones and Nelson containing thousands of trajectories which must be very useful in many design problems."[122] Nevertheless, the authors furnished designers with a tool that could be readily, almost instantly, understood (fig. 45), and the atlas has enjoyed wide circulation.[123] The idea of a geometrical approach to synthesis has been exploited by others in more recent publications,[124] and it is likely that many more variations on this theme will appear.