Gasparis Schotti, Technica Curiosa, sive Mirabilia Artis, Libris XII. … [Curious works of skill, or marvelous works of craftsmanship] (Nuremberg (Norimberga), (Germany): Johannes Andreas Endter & Wolfgang Endter, 1664), Liber IX. Mirabilia Chronometrica, … (Book 9. Marvelous Clocks, … ), Caput V. Signa chronometrica optica, seu indices. (Chapter 5. Marvelous visual clocks, or clocks with hands), pp. 664-665:Propositio XX. Indicem sinuosum & obliquatum per anfractus quosvis, sine Rotis dentatis quocumque lubet educere. (Proposition 20. [How], without any gears, to lead the twisting, turning pointer [i.e., the shaft that drives the clock's hands] through any bend one pleases.) In the margin is printed: Vide Iconism. VII. Fig. 32. (See Plate 7, Figure 32.), which depicts Schott's universal joint. Schott first notes that there may be occasions when a clock's gear works and its face can't be conveniently aligned; e.g., public clocks installed in towers. He then mentions, in the description of its construction (Technasma, the Greek word for "artifice"), that the universal joint resembles a gimbal that is used to hold an oil lamp so that it won't spill oil. Schott's joint consists of two forks (fuscinula), each of which consists of a shaft to which a metal strip, bent into a semicircle, is attached to one end. Near each end of the semicircle, a hole is drilled. A cross with four perpendicular arms (crux sive 4 brachia) is also made. The holes in each semicircle fit over the ends of an opposing pair of arms. The angle between the shafts must be greater than a right angle. In discussing the joint's motion (Motus), Schott claims that the two shafts move at the same speed (i.e., they form a constant-velocity joint): " … horum autem ductum necesse est sequatur & altera fuscinula, parique cum priore illa feratur velocitate: unde si fuerit unius fuscinulae motus regularis circularis, erit similis & alterius … " ( … but this driven [fork] must follow the other [driving] fork, and it be born at a speed equal to the former: whence if one fork's motion were regularly circular, it will be similarly with the other … ).
For a (partial) history of universal joints, see: Robert Willis, Principles of Mechanism … , 2nd ed. (London, England: Longmans, Green, and Co., 1870), Part the Fifth: On Universal Joints, pp. 437-457.
Hooke first described a universal joint in Hevelius' instrument in: Robert Hooke, Animadversions on the first part of the Machina Coelestis … (London, England: John Martyn, 1674), p. 73. Here he calls the joint a "universal Instrument". From page 73: I shall show " … what use I have made of this Joynt, for a universal Instrument for Dialling, for equalling of Time, for making the Hand of a Clock move in the Shadow of a Style, and for performing a multitude of other Mechanical Operations." The joint is depicted on Plate X, Fig.s 22 and 23, which are available at: Posner Memorial Collection - Carnegie Mellon UniversityArchived 2015-11-17 at the Wayback Machine
Robert Hooke, A Description of Helioscopes, and Some Other Instruments (London, England: John Martyn, 1676), p. 14. From p. 14: "The Universal Joynt for all these manner of Operations, having not had time to describe the last Exercise, I shall now more particularly explain." Illustrations of Hooke's universal joint appear on p. 40, Fig.s 9 and 10; available at: ETU Library ; Zurich, SwitzerlandArchived 2015-09-23 at the Wayback Machine.
Review of Ferdinand Berthoud's Treatise on Marine Clocks, Appendix Art. VIII, The Monthly Review or Literary Journal, Vol. L, 1774; see footnote, page 565.
Willis, Robert, Principles of Mechanisms, … (London, England: John W. Parker, 1841), pp. 272-284.
J. V. Poncelet, Traité de mécanique appliquée aux machines, Part 1 (Liége, France: Librairie scientifique et industrielle, 1845), pp. 121-124.
Hooke first described a universal joint in Hevelius' instrument in: Robert Hooke, Animadversions on the first part of the Machina Coelestis … (London, England: John Martyn, 1674), p. 73. Here he calls the joint a "universal Instrument". From page 73: I shall show " … what use I have made of this Joynt, for a universal Instrument for Dialling, for equalling of Time, for making the Hand of a Clock move in the Shadow of a Style, and for performing a multitude of other Mechanical Operations." The joint is depicted on Plate X, Fig.s 22 and 23, which are available at: Posner Memorial Collection - Carnegie Mellon UniversityArchived 2015-11-17 at the Wayback Machine
Robert Hooke, A Description of Helioscopes, and Some Other Instruments (London, England: John Martyn, 1676), p. 14. From p. 14: "The Universal Joynt for all these manner of Operations, having not had time to describe the last Exercise, I shall now more particularly explain." Illustrations of Hooke's universal joint appear on p. 40, Fig.s 9 and 10; available at: ETU Library ; Zurich, SwitzerlandArchived 2015-09-23 at the Wayback Machine.
Mills, Allan, "Robert Hooke's 'universal joint' and its application to sundials and the sundial-clock", Notes & Records of the Royal Society, 2007, accessed onlineArchived 2015-09-25 at the Wayback Machine 2010-06-16
Mills, Allan, "Robert Hooke's 'universal joint' and its application to sundials and the sundial-clock", Notes & Records of the Royal Society, 2007, accessed onlineArchived 2015-09-25 at the Wayback Machine 2010-06-16
Hooke first described a universal joint in Hevelius' instrument in: Robert Hooke, Animadversions on the first part of the Machina Coelestis … (London, England: John Martyn, 1674), p. 73. Here he calls the joint a "universal Instrument". From page 73: I shall show " … what use I have made of this Joynt, for a universal Instrument for Dialling, for equalling of Time, for making the Hand of a Clock move in the Shadow of a Style, and for performing a multitude of other Mechanical Operations." The joint is depicted on Plate X, Fig.s 22 and 23, which are available at: Posner Memorial Collection - Carnegie Mellon UniversityArchived 2015-11-17 at the Wayback Machine
Robert Hooke, A Description of Helioscopes, and Some Other Instruments (London, England: John Martyn, 1676), p. 14. From p. 14: "The Universal Joynt for all these manner of Operations, having not had time to describe the last Exercise, I shall now more particularly explain." Illustrations of Hooke's universal joint appear on p. 40, Fig.s 9 and 10; available at: ETU Library ; Zurich, SwitzerlandArchived 2015-09-23 at the Wayback Machine.
