_Analytical Essay on the Construction of Machines_, was published about
1820 at London by Rudolph Ackermann (for whom the Ackermann steering
linkage was named), and their synoptic chart was reprinted again in 1822
in Durham.[93] In the United States, _Appleton's Dictionary of
Machines_[94] (1851) adopted the same system and used the same figures.
Apparently the wood engraver traced directly onto his block the figures
from one of the reprints of Lanz and Bétancourt's chart because the
figures are in every case exact mirror images of the originals.
[Footnote 92: Rudolph Ackermann, _Analytical Essay on the Construction
of Machines_, London, about 1820, a translation of Lanz and Bétancourt,
_op. cit._ (footnote 64).]
[Footnote 93: Thomas Fenwick, _Essays on Practical Mechanics_, ed. 3,
Durham, England, 1822.]
[Footnote 94: _Appleton's Dictionary of Machines, Mechanics,
Engine-Work, and Engineering_, 2 vols., New York, 1851 ("Motion").]
In the _Dictionary of Engineering_[95] (London, 1873), the figures were
redrawn and dozens of mechanisms were added to the repertory of
mechanical motions; the result was a fair catalog of sound ideas. The
ferryboat still tugged at its anchor cable, however.[96] _Knight's
American Mechanical Dictionary_,[97] a classic of detailed pictorial
information compiled by a U.S. patent examiner, contained well over
10,000 finely detailed figures of various kinds of mechanical
contrivances. Knight did not have a separate section on mechanisms, but
there was little need for one of the Hachette variety, because his whole
dictionary was a huge and fascinating compendium of ideas to be filed
away in the synthetic mind. One reason for the popularity and usefulness
of the various pictorial works was the peculiar ability of a wood or
steel engraving to convey precise mechanical information, an advantage
not possessed by modern halftone processes.
[Footnote 95: E. F. and N. Spon, _Dictionary of Engineering_, London
1873, pp. 2421-2452.]
[Footnote 96: _Ibid._, p. 2447.]
[Footnote 97: Edward H. Knight, _Knight's American Mechanical
Dictionary_, 3 vols., New York 1874-1876.]
[Illustration: Figure 36.--Typical mechanisms from E. F. and N. Spon,
_Dictionary of Engineering_ (London, 1873, pp. 2426, 2478).]
Many patent journals and other mechanical periodicals concerned with
mechanics were available in English from the beginning of the 19th
century, but few of them found their way into the hands of American
mechanicians until after 1820. Oliver Evans (1755-1819) had much to say
about "the difficulties inventive mechanics labored under for want of
published records of what had preceded them, and for works of reference
to help the beginner."[98] In 1817 the _North American Review_ also
remarked upon the scarcity of engineering books in America.[99]
[Footnote 98: George Escol Sellers in _American Machinist_, July 12,
1884, vol. 7, p. 3.]
[Footnote 99: _North-American Review and Miscellaneous Journal_, 1819,
new ser., vol. 8, pp. 13-15, 25.]
The _Scientific American_, which appeared in 1845 as a patent journal
edited by the patent promoter Rufus Porter, carried almost from its
beginning a column or so entitled "Mechanical Movements," in which one
or two mechanisms--borrowed from an English work that had borrowed from
a French work--were illustrated and explained. The _American Artisan_
began a similar series in 1864, and in 1868 it published a compilation
of the series as _Five Hundred and Seven Mechanical Movements_,
"embracing all those which are most important in dynamics, hydraulics,
hydrostatics, pneumatics, steam engines ... and miscellaneous
machinery."[100] This collection went through many editions; it was last
revived in 1943 under the title _A Manual of Mechanical Movements_.
This 1943 edition included photographs of kinematic models.[101]
[Footnote 100: Henry T. Brown, ed., _Five Hundred and Seven Mechanical
Movements_, New York, 1868.]
[Footnote 101: Will M. Clark, _A Manual of Mechanical Movements_, Garden
City, New York, 1943.]
Many readers are already well acquainted with the three volumes of
_Ingenious Mechanisms for Designers and Inventors_,[102] a work that
resulted from a contest, announced by _Machinery_ (vol. 33, p. 405) in
1927, in which seven prizes were offered for the seven best articles on
unpublished ingenious mechanisms.
[Footnote 102: _Ingenious Mechanisms for Designers and Inventors_ (vols.
1 and 2 edited by F. D. Jones, vol. 3 edited by H. L. Horton), New York,
Industrial Press, 1930-1951.]
There was an interesting class of United States patents called
"Mechanical Movements" that comprised scores of patents issued
throughout the middle decades of the 19th century. A sampling of these
patents shows that while some were for devices used in particular
machines--such as a ratchet device for a numbering machine, a locking
index for gunmaking machinery, and a few gear trains--the great majority
were for converting reciprocating motion to rotary motion. Even a
cursory examination of these patents reveals an appalling absence of
sound mechanical sense, and many of them appear to be attempts at
"perpetual motion," in spite of an occasional disclaimer of such intent.
Typical of many of these patented devices was a linkage for
"multiplying" the motion of a flywheel, proposed in 1841 by Charles
Johnson of Amity, Illinois (fig. 37). "It is not pretended that there is
any actual gain of power," wrote Mr. Johnson; and probably he meant it.
The avowed purpose of his linkage was to increase the speed of a
flywheel and thus decrease its size.[103]
[Footnote 103: U.S. Patent 2295, October 11, 1841.]
[Illustration: Figure 37.--Johnson's "converting motion," 1841. The
linkage causes the flywheel to make two revolutions for each
double-stroke of the engine piston rod B. From U.S. Patent 2295, October
11, 1841.]
An Englishman who a few years earlier had invented a "new Motion" had
claimed that his device would supersede the "ordinary crank in steam
engines," the beam, parallel motion, and "external flywheel," reduce
friction, neutralize "all extra contending power," and leave nothing for
the piston to do "but the work intended to be done."
A correspondent of the _Repertory of Patent Inventions_ made short work
of this device: "There is hardly one assertion that can be supported by
proof," he wrote, "and most of them are palpable misstatements." The
writer attacked "the 'beetle impetus wheel,' which he [the inventor]
thinks us all so beetle-headed, as not to perceive to be a flywheel,"
and concluded with the statement: "In short the whole production evinces
gross ignorance either of machinery, if the patentee really believed
what he asserted, or of mankind, if he did not."[104]
[Footnote 104: _Repertory of Patent Inventions_, ser. 3, October 1828,
vol. 7, pp. 196-200, and December 1828, vol. 7, pp. 357-361.]
Although many of the mechanisms for which patents were taken out were
designed by persons who would make no use of the principles involved
even if such principles could at that time have been clearly stated, it
is a regrettable fact that worthless mechanisms often got as much space
as sound ones in patent journals, and objections such as the one above
were infrequent. The slanted information thus conveyed to the young
mechanician, who was just accumulating his first kinematic repertory,
was at times sadly misleading.
From even this sketchy outline of the literature on the subject, it
should be fairly evident that there has been available to the
mechanician an enormous quantity of information about mechanical
linkages and other devices. Whatever one may think of the quality of the
literature, it has undoubtedly had influence not only in supplying
designers with information but in forming a tradition of how one ought
to supply the background that will enable the mind to assemble and
synthesize the necessary mechanism for a given purpose.[105]
[Footnote 105: Some additional catalogs of "mechanical movements" are
listed in the selected references at the end of this paper.]
Some of the mechanisms that have been given names--such as the Watt
straight-line linkage and the Geneva stop--have appeared in textbook
after textbook. Their only excuse for being seems to be that the authors
must include them or risk censure by colleagues. Such mechanisms are
more interesting to a reader, certainly, when he has some idea of what
the name has to do with the mechanism, and who originated it. One such
mechanism is the drag link.
After I had learned of the drag link (as most American engineering
students do), I wondered for awhile, and eventually despaired of making
any sense out of the term. What, I wanted to know, was being dragged?
Recently, in Nicholson's _Operative Mechanic and British Machinist_
(1826), I ran across the sketch reproduced here as figure 38. This
figure, explained Mr. Nicholson (in vol. 1, p. 32) "represents the
coupling link used by Messrs. Boulton and Watt in their portable steam
engines. A, a strong iron pin, projecting from one of the arms of the
fly-wheel B; D, a crank connected with the shaft C; and E, a link to
couple the pin A and the crank D together, so the motion may be
communicated to the shaft C." So the drag link was actually a link of a
coupling. Nothing could be more logical. A drag link mechanism now makes
sense to me.
[Illustration: Figure 38.--Drag link coupling used on Boulton and Watt
portable engines. The link E drags one shaft when the other turns. From
John Nicholson, _The Operative Mechanic, and British Machinist_
(Philadelphia, 1826, vol. I, pl. 5).]
Directly related to the drag link coupling were the patents of John
Oldham (1779-1840), an Irish engineer who is remembered mainly for the
coupling that bears his name (fig. 39). His three patents, which were
for various forms of steamboat feathering paddle wheels, involved
linkages kinematically similar to the drag link coupling, although it is
quite unlikely that Oldham recognized the similarity. However, for his
well-known coupling, which employs an inversion of the elliptical
trammel mechanism, I have found no evidence of a patent. Probably it was
part of the machinery that he designed for the Bank of Ireland's
printing house, of which Oldham was manager for many years. "Mr. Oldham
and his beautiful system" were brought to the Bank of England in 1836,
where Oldham remained until his death in 1840.[106]
[Footnote 106: Oldham's paddle-wheel patents were British Patents 4169
(October 10, 1817), 4429 (January 15, 1820), and 5445 (February 1,
1827). Robert Willis (_op. cit._ footnote 21, p. 167) noticed the
existence of the coupling. Drawings or descriptions of the banknote
machinery apparently have not been published though they probably still
exist in the banks' archives. The quotation is from Frederick G. Hall,
_The Bank of Ireland 1783-1946_, Dublin, 1949. John Francis in his
_History of the Bank of England_ (London, 1848, vol. 2, p. 232) wrote:
"The new machinery for printing the notes, which was introduced by Mr.
Oldham ... is well worthy of a visit, but would be uninteresting to
delineate."]
[Illustration: Figure 39.--_Top_, Original Oldham coupling built before
1840, using a cross (instead of a center disk), as sketched by Robert
Willis in personal copy of his _Principles of Mechanism_ (London, 1841,
p. 167). _Bottom_, Oldham coupling as illustrated in Alexander B. W.
Kennedy, _Kinematics of Machinery_, a translation of Franz Reuleaux'
_Theoretische Kinematik_ (London, 1876, pp. 315-316).]
The Geneva stop mechanism (fig. 40) was properly described by Willis as
a device to permit less than a full revolution of the star wheel and
thus to prevent overwinding of a watch spring. It was called Geneva stop
because it was used in Geneva watches. The Geneva wheel mechanism, which
permits full rotation of the star wheel and which is frequently used
for intermittent drives, was improperly called a Geneva stop in a
recent textbook probably because the logical origin of the term had been
lost.
[Illustration: Figure 40.--Geneva stop mechanism first used in Geneva
watches to prevent overwinding. The starwheel B had one convex surface
(_g-f_, dotted) so the wheel could be turned less than a full
revolution. After Robert Willis, _Principles of Mechanism_ (London,
1841, p. 266).]
The name for the Scotch yoke seems to be of fairly recent origin, the
linkage being called by a Scotsman in 1869 a "crank and slot-headed
sliding rod" (fig. 41). I suppose that it is now known as a Scotch yoke
because, in America at least, a "Scotch" was a slotted bar that was
slipped under a collar on a string of well-drilling tools to support
them while a section was being added (fig. 42).
[Illustration: Figure 41.--Scotch yoke, described as a "crank and
slot-headed sliding rod." From W. J. M. Rankine, _A Manual of Machinery
and Millwork_ (ed. 6, London, 1887, p. 169).]
[Illustration: Figure 42.--A "Scotch" supporting the top member of a
string of well-drilling tools while a section is being added, 1876. From
Edward H. Knight, _Knight's American Mechanical Dictionary_ (New York,
1876, p. 2057).]
It was surprising to me to find that the Ackermann steering linkage,
used today on most automobiles, was patented in 1818 when Detroit was
still a frontier town.[107] Furthermore, the man who took out the patent
described himself as Rudolph Ackermann, publisher and printseller. I
thought I had the necessary clue to the linkage's origin when I noticed
that the first English translation of the Lanz and Bétancourt treatise
was published by Ackermann, but the connection finally proved to be more
logical, if less direct. Ackermann (1764-1834), son of a Bavarian coach
builder, had spent a number of years designing coaches for English
gentlemen in London, where he made his home. One of his more notable
commissions was for the design of Admiral Nelson's funeral car in 1805.
The Ackermann steering linkage was not actually Ackermann's invention,
although he took out the British patent in his name and promoted the
introduction of the running gear of which the linkage was a part (fig.
43). The actual inventor was Ackermann's friend George Lankensperger of
Munich, coachmaker to the King of Bavaria. The advantage of being able
to turn a carriage around in a limited area without danger of
oversetting was immediately obvious, and while there was considerable
opposition by English coachmakers to an innovation for which a premium
had to be paid, the invention soon "made its way from its own intrinsic
merit," as Ackermann predicted it would.[108]
[Footnote 107: British Patent 4212, January 27, 1818.]
[Footnote 108: Rudolph Ackermann, _Observations on Ackermann's Patent
Moveable Axles_, London, 1819. It was interesting to me to note an
abstract of W. A. Wolfe's paper "Analytical Design of an Ackermann
Steering Linkage" in _Mechanical Engineering_, September 1958, vol. 80,
p. 92.]
[Illustration: Figure 43.--Ackermann steering linkage of 1818, currently
used in automobiles. This linkage was invented by George Lankensperger,
coachmaker to the King of Bavaria. From _Dinglers Polytechnisches
Journal_ (1820, vol. 1, pl. 7).]
The Whitworth quick-return mechanism (fig. 44) was first applied to a
slotter, or vertical shaper, in 1849, and was exhibited in 1851 at the
Great Exhibition in London.[109] Willis' comments on the mechanism are
reproduced in figure 44. I hope that Sir Joseph Whitworth (1803-1887)
will be remembered for sounder mechanical contrivances than this.
[Footnote 109: The quick-return mechanism (British Patent 12907,
December 19, 1849) was perhaps first publicly described in Charles
Tomlinson, ed., _Cyclopaedia of Useful Arts and Manufactures_, London,
1854, vol. 1, p. cxliv.]
[Illustration: Figure 44.--Quick-return mechanism. _Top_, Early
representation of the quick-return mechanism patented by Whitworth in
1849, from William Johnson, ed., _The Imperial Cyclopaedia of machinery_
(Glasgow, about 1855, pl. 88). _Middle_, Sketch by Robert Willis from
his copy of _Principles of Mechanism_ (London, 1841, p. 264), which
"shews Whitworth dissected into a simpler form"; it is as obscure as
most subsequent attempts have been to explain this mechanism without a
schematic diagram. _Bottom_, Linkage that is kinematically equivalent to
Whitworth's, from Robert Willis, _Principles of Mechanism_ (London,
1841, p. 264).]
Mechanisms in America, 1875-1955
Engineering colleges in the United States were occupied until the late
1940's with extending, refining, and sharpening the tools of analysis
that had been suggested by Willis, Rankine, Reuleaux, Kennedy, and
Smith. The actual practice of kinematic synthesis went on apace, but
designers often declined such help as the analytical methods might give
them and there was little exchange of ideas between scholars and
practitioners.
The capability and precision of machine tools were greatly enhanced
during this period, although, with the exception of the centerless
grinder, no significant new types of tools appeared. The machines that
were made with machine tools increased in complexity and, with the
introduction of ideas that made mass production of complex mechanical
products economically feasible, there was an accelerating increase in
quantity. The adoption of standards for all sorts of component parts
also had an important bearing upon the ability of a designer
economically to produce mechanisms that operated very nearly as he hoped
they would.
The study of kinematics has been considered for nearly 80 years as a
necessary part of the mechanical engineer's training, as the dozens of
textbooks that have been published over the years make amply clear.
Until recently, however, one would look in vain for original work in
America in the analysis or rational synthesis of mechanisms.
One of the very earliest American textbooks of kinematics was the 1883
work of Charles W. MacCord (1836-1915), who had been appointed professor
of mechanical drawing at Stevens Institute of Technology in Hoboken
after serving John Ericsson, designer of the _Monitor_, as chief
draftsman during the Civil War.[110] Based upon the findings of Willis
and Rankine, MacCord's _Kinematics_ came too early to be influenced by
Kennedy's improvements upon Reuleaux's work.
[Footnote 110: A biographical notice and a bibliography of MacCord
appears in _Morton Memorial: A History of the Stevens Institute of
Technology_, Hoboken, 1905, pp. 219-222.]
When the faculty at Washington University in St. Louis introduced in
1885 a curriculum in "dynamic engineering," reflecting a
dissatisfaction with the traditional branches of engineering, kinematics
was a senior subject and was taught from Rankine's _Machinery and
Millwork_.[111]
[Footnote 111: _Transactions of the American Society of Mechanical
Engineers_, 1885-1886, vol. 7, p. 757.]
At Massachusetts Institute of Technology, Peter Schwamb, professor of
machine design, put together in 1885 a set of printed notes on the
kinematics of mechanisms, based on Reuleaux's and Rankine's works. Out
of these notes grew one of the most durable of American textbooks, first
published in 1904.[112] In the first edition of this work, acceleration
was mentioned only once in passing (on p. 4). Velocities in linkages
were determined by orthogonal components transferred from link to link.
Instant centers were used only to determine velocities of various points
on the same link. Angular velocity ratios were frequently noted. In the
third edition, published in 1921, linear and angular accelerations were
defined, but no acceleration analyses were made. Velocity analyses were
altered without essential change. The fourth edition (1930) was
essentially unchanged from the previous one. Treatment of velocity
analysis was improved in the fifth edition (1938) and acceleration
analysis was added. A sixth edition, further revised by Prof. V. L.
Doughtie of the University of Texas, appeared in 1947.
[Footnote 112: Peter Schwamb and Allyne L. Merrill, _Elements of
Mechanism_, New York, 1904. In addition to the work of Reuleaux and
Rankine, the authors acknowledged their use of the publications of
Charles MacCord, Stillman W. Robinson, Thomas W. Goodeve, and William C.
Unwin. For complete titles see the list of selected references.]
Before 1900, several other books on mechanisms had been published, and
all followed one or another of the patterns of their predecessors.
Professors Woods and Stahl, at the Universities of Illinois and Purdue,
respectively, who published their _Elementary Mechanism_ in 1885, said
in their preface what has been said by many other American authors and
what should have been said by many more. "We make little claim to
originality of the subject-matter," wrote Woods and Stahl, "free use
having been made of all available matter on the subject.... Our claim to
consideration is based almost entirely on the manner in which the
subject has been presented." Not content with this disclaimer, they
continued: "There is, in fact, very little room for such originality,
the ground having been almost completely covered by previous
writers."[113]
[Footnote 113: Arthur T. Woods and Albert W. Stahl, _Elementary
Mechanism_, New York, 1885.]
The similarity and aridity of kinematics textbooks in this country from
around 1910 are most striking. The generation of textbook writers
following MacCord, Woods and Stahl, Barr of Cornell, Robinson of Ohio
State, and Schwamb and Merrill managed to squeeze out any remaining
juice in the subject, and the dessication and sterilization of textbooks
was nearly complete when my generation used them in the 1930's.
Kinematics was then, in more than one school, very nearly as it was
characterized by an observer in 1942--"on an intellectual par with
mechanical drafting."[114] I can recall my own naïve belief that a
textbook contained all that was known of the subject; and I was not
disabused of my belief by my own textbook or by my teacher. I think I
detect in several recent books a fresh, less final, and less tidy
treatment of the kinematics of mechanisms, but I would yet recommend
that anyone who thinks of writing a textbook take time to review,
carefully and at first hand, not only the desk copies of books that he
has accumulated but a score or more of earlier works, covering the last
century at least. Such a study should result in a better appreciation of
what constitutes a contribution to knowledge and what constitutes merely
the ringing of another change.
[Footnote 114: _Mechanical Engineering_, October 1942, vol. 64, p. 745.]
The author of the contentious article that appeared in _Mechanical
Engineering_ in 1942 under the title "What is Wrong with Kinematics and
Mechanisms?" made several pronouncements that were questioned by various
readers, but his remarks on the meagerness of the college courses of
kinematics and the "curious fact" that the textbooks "are all strangely
similar in their incompleteness" went unchallenged and were, in fact,
quite timely.[115]
[Footnote 115: De Jonge, _op. cit._ (footnote 78).]