Figure i . — Up-and-down sawmill of the 1 3th 

 century. The guide mechanism at lower left, 

 attached to the saw blade, appears to be a 

 4-bar linkage. After Robert Willis, trans, and 

 ed., Facsimile of the Sketch-Book of Wilars de 

 Honecort (London, 1859, pi. 43). 



both in academic circles and in the workshop, noting 

 where possible the influence of one upon the other. 

 If I have devoted more space to particular people 

 and episodes than is warranted by their contributions 

 to the modern treatment of the subject, it is because 

 I have found that the history of kinematics of mecha- 

 nisms, like the history of any other branch of engi- 

 neering, is more interesting and more plausible if it 

 is recognized that its evolutionary development is the 

 result of human activity. This history was wrought 

 by people like us, no less intelligent and no less subject 

 than we are to environment, to a subjective way of 

 looking at things, and to a heritage of ideas and 

 beliefs. 



I have selected the period from the time of ^\'att 

 because modern mechanisms originated with him, 

 and I have emphasized the first century of the period 

 because by 1885 many of the ideas of modern kine- 

 matics of mechanisms were well developed. Link- 

 ages are discussed, to the virtual exclusion of gears 

 and cams, because much of the scholarly work in 

 kinematic synthesis is presently directed toward the 

 design of linkages and because linkages provide a 

 convenient thread for a narrative that would have 

 become unnecessarily complex if detailed treatment 

 of gears and cams had been included. I have brought 

 the narrative down to the present by tracing kine- 



matics as taught in American engineering schools, 

 closing with brief mention of the scholarly activity 

 in kinematics in this country since 1950. An anno- 

 tated list of additional references is appended as an 

 encouragement to further work in the history of the 

 subject. 



James Watt, Kinematic Synthesist 



James Watt (1736-1819), improver of the steam 

 engine, was a highly gifted designer of mechanisms, 

 although his background included no formal study of 

 mechanisms. Indeed, the study of mechanisms, with- 

 out immediate regard to the machines in which they 

 were used, was not introduced until after Watt's 

 important work had been completed, while the actual 

 design of mechanisms had been going on for several 

 centuries before the time of Watt. 



Mechanisms that employed screws, cams, and gears 

 were certainly in use by the beginning of the Christian 

 era. While I am not aware of unequivocal evidence 

 of the existence of four-bar linkages before the 16th 

 century, their widespread application by that tim.e 

 indicates that they probably originated much earlier. 

 A tantalizing 13th-century sketch of an up-and-down 

 sawmill (fig. 1) suggests, but does not prove, that the 

 four-bar linkage was then in use. Leonardo da 

 Vinci (1452-1519) delineated, if he did not build, a 

 crank and slider mechanism, also for a sawmill (fig. 2). 

 In the 16th century may be found the conversion of 

 rotary to reciprocating motion (strictly speaking, an 

 oscillation through a small arc of a large circle) and 

 vice versa by use of linkages of rigid members (figs. 

 3 and 4), although the conversion of rotary to recipro- 

 cating motion was at that time more frequently accom- 

 plished by cams and intermittent gearing. Never- 

 theless, the idea of linkages was a firmly established 

 part of the repertory of the machine builder before 

 1600. In fact one might have wondered in 1588, 

 when Agostino Ramelli published his book on ma- 

 chines,' whether linkages had not indeed reached 

 their ultimate stage of development. To illustrate 

 my point, I have selected the plate of Ramelli that 

 most appeals to me (fig. 5), although the book 

 exhibits more than 200 other machines of comparable 

 complexity and ingenuity. 



There was a vast difference, both in conception and 

 execution, between the linkages of Ramelli and those 



1 Agostino Ramelli, 

 1588. 



Le Diverse et Artificiose Machine, Paris, 



PAPER 27: KINEMATICS FROM THE TIME OF WATT 



187 



