In ·iL!I. ::n � 14v1,. , KINEMATICS o{Me,cha,n,itm! .�· !tom fhe, ime, of Wa,H UNITED STATES N}ITIONAL .MUSEUM CONTRIBUTIONS FROM THE MusEUM OF HISTORY AND TECHNOLOGY PAPER 27 KINEMATICS OF MECHANISMS FROM THE TIME OF WATT Eugene S. Fergttson JAMES 'WATT, KINEMATIC SYNTHESIST 187 TO DRAW A STRAIGHT LINE 199 SCHOLARS AND MACHINES 209 MECHANICIANS AND MECHANISMS 216 MECHANISMS IN AMERICA, 187S-l9SS 223 ADDITIONAL REFERENCES 229 by Eugene S Ferg11son KINEMATICS OF MECHANISMS .FROM THE TIME OF WATT In an inventive tour de force that seldom, if ever, h(IS been equalled for its brilliance cmd f(1r-reaching conseqi,ences, Jcimes Watt radicctlly altered the steam engine not only by adding a separate condenser but by creating a whole new family of linkages. His approach was largely empirical, as we use the word today. This study suggests that, despite the glamor of today's so­ phisticated methods of calcitlc,tion, a highly developed inttti­ tive .rense, reinforced by a knowledge of the past, is still indis­ pensable to the design of successful mechanisms. THE AUTHOR: Eugene S. Fergruon, formerly cur,1tor of mechanical and civil engineering in the United States Nationcd Museum, Smithsonian Institution, is now p,·ofe.rsor of mechan­ ical engineering at lowa State Univer.Jity of Science and Tech­ nology. 11': E!'o:GINEERl!',;G SCHOOI.S TOD,\Y, a student is intro­ edged in one way or another their debt to those who duced to the kinematics of mechanisms by means of arri,-cd on the scene at an earlier time than they. a course of kinematic analysis, which is concerned There ha,·c been occasional reviews of the sequence with principles underlying the motions occuning in and nature of developrr.ents, but the emphasis mechanisms. These principles are demonstrated by naturally has been upon the r.ecent past. It seems a study of mechanisms already in existence. such as to me that there is som..-thing t<> be gained in looking the linkage of a retractable landing gear, computing beyond our own generation, or even beyond the mechanisms, mechanisms used in an automobile, and time of Franz Reuleaux (1829-1905), who is gen­ the like. A systematic, if not rigorous, approach 10 erally credited with originating many of our modern the design of gears and cams also is usually presented concepts of mechanism analysis and design, and to in S\lch a course. Until recently. however, no serious inquire into the ideas that made possible Reuleaux's attempt was made to apply the principles developed contributions. in kinematic analysis to the more complex problem \\'hile no pretense of completeness is made, I ha,·e of kinematic synthesis of linkages. B,· kinematic tried in this paper to trace the high points in the synthesis is mcam the designing of a linkage to pro­ dc,·eloprnent of kinematic analysis and s,·nthesis, duce a given series of motions for a panicular purpose. That a rational-numerical or geometrical-ap­ proach to kinematic synthesis is possibll' is a relatively Take to Kinemcttics. It will n:ccot idea, not yet fully acct'pted; but it is this idea repay you. It is more fecttnd that is responsible for the intense scholarly interest in than 7,e.ometry; it .,dds a fo1trth e c th kinemati s of mechanisms that has occurred in dimension to space. this couniry within the last 10 years. This sc:holarh·, activi1,·.. has resulted in the rediscovcrr. -·Chcbyshcv to Sylvester, 1873 of many earlier works on the suhjt'ct, and nearlr all the scholars no"" ,,·orkin(( in this field hm·e acknowl- 186 Bt:LLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHI\OLOGV .. :•'--.....7:i,"ro-...�.., ..:�•··· ... , Il matics as taught in American engineering schools, closing with brief mention of the scholarly acti\·ity in kinematics in this country since 1950. An anno­ tated list of additional reforcnces is appended as an encouragement to further work in the history of the subject. James Watt, Kinematic Synthesist James \Vatt (1736-181')), 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 imroduccd until after \Vatt's important work had been completed, while the actual design of m<:>chanisms had been going on for se\'Cral centuries before the rime of \•Vatt. Figure 1.-Up-and-down s;:,wmill of the 13th :rv[echanisms char employed screws, ca ms, and gears century. The guide mechanism at lower left, were certainly in use by the beginning of the Christian attached to the saw blade, appears to be a era. \Vhile I am not aware of unequivocal evidence 4-bar linkage. Aft.;r Rob<:rt Willis, trans. and of the existence of four-bar linkages before the 16th ed .. Facsimil, of the Sketch-Book of Wilars d, century, their widespread application by that tin-:e Ho;,ecor/ (Lond�n, 1 859, pl. 43) • indicates that they probably originated much earlier. A tantalizing 13th-century sketch of an up-and-down both in academic circles and in the workshop, noting sawmill (fig. 1) suggests, but does not prove, that the where possible the influence of one upon the other. four-bar linkage was then in use. Leonardo da If I have devoted more space to particular people Vinci (1452-1519) delineated, if he did not build, a and episodes than is warranted by their contributions crank and slider mechanism, also for a sawmill (fig. 2). to the modern treatment of the subject, it is because In the 16th century may be found the conversion of { have found that the history of kinematics of mecha­ rotary w rcciprocating motion (strictly speaking, an nisms. like the history of any other branch of engi­ oscillation thr-ough a small arc of a large circle) and neeri�g, is more interesting and more plausibk if it vice versa by use of linkages of rigid members (figs. is recognized that its evolutionary development is the 3 and 4), although the conversion of rotary to recipro­ result of human activity. This history was wrought cating motion was at that time more frequently accom­ liy people like us, no Jess imelligem and no less subject plished by cams and intcrmit1cnt gear-,ng. Never­ than we are to environment, to a subjective way of theless. the idea of linkages was a firmly establish<>d looking at things and to a heritage of ideas and , part. of the repertory of the machine builder before beliefs. 1600. In fact one might have wondert'd in 1588, I have selected the period from the tirr.e of \Vatt when Agostino Ramelli published his book on ma­ because modern mechanisms originated with him, chines.' whether linkages had not indeed reached and I have emphasized the first century of the period their �ltimate sta«e-0 of devdoprm:nt. To illustrate because bv 1885 rnanv of the ideas of rr.odern kine­ my point, I have selected the plate of Ramelli that matics or' mechanism� were well developed. Link­ most appeals to me (fig. 5), although the book ages a.re discussed, to the virtual exclusion of gears exhibits more than 200 other machines of comparable and cams, because much of the scholarly work in complexiry and ingenuity. kinematic synthesis is presently directed toward the f There was a vast diference, both in conception and design of linkages and because linkages provide a execution, between the linkages of Ramelli and thost' convenient thread for ,i narrative that would have become unnecessarily complex if detailed treatment of gears and cams had been included. I have brought r Agostino Ramelli, Lt Dh·er.,Y rt Ar1ijiciMe ;\/ochint>i Pari;.;, the narrative clown to the present by tracing kine- 1588. PAPER 27: KINEMATICS FROM THE TIME. Of WATT 187 "J-- �• - ,a, ,...., ...... 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It is interesting, how­ a bench lathe, hand wols, and superb handw<;rk. ever, lo see how \Van and others grappled with The rapid advancement of machine tools, which the solutions of problems that resulted from the greatly expanded the scope of the machine-building advance of the steam engine. art. began during the Boulton and ·watt partnership During the I 770's the demand for continuous, (1775-1800). dependable power applied to a rotating shaft was In April 1775 the skirmish at Concord between becoming insistent, and much of Boulton· s and American colonists and British redcoats marked the \Vatt's effort w as directed toward meeting this beginning of a war that ,vas lO determine for the demand. t.1ills of all kinds used water or horses . future the course of political events in the \Vestern to turn "wheel-work.. but, while these sources of Hemisphere. power were adequate for small operations, the Another event of April 1775 occurring in Binning­ quantity of water available was often limited, and ham now appears to have been one that marked the the use of enormous horse-whims was frequently beginning of a new era of technological advance.