Kyvadlové hodiny

Huygens first pendulum clock - front view.png
Drawing of the first pendulum clock, designed by Dutch scientist Christiaan Huygens in 1657. Huygens contracted his clock designs to clockmaker Salomon Coster of The Hague, who actually built the clock. The pendulum had a wider swing than modern clocks, perhaps 80°-100°, due to its verge escapement. The drive force for the clock was provided by the two weights at bottom in an ingenious "endless rope" mechanism.

Maquinaria de un Ansonia C-1904.jpg
Autor: Ivan2010, Licence: CC BY 3.0
Mechanism of a Wall Clock Ansonia

Huygens first pendulum clock.png
The first pendulum clock, invented by Dutch physicist Christiaan Huygens in 1657, and built by clockmaker Saloman Coster. This drawing is from Huygens' 1658 treatise on the clock, Horologium. The pendulum was driven by a verge escapement mechanism, so it had a very wide angle of swing compared to modern clocks, perhaps 80° to 90°. The clock was weight-driven, using an ingenious arrangement of two weights linked by a loop of cord. In order to "wind" the clock, the larger weight was simply lifted to the top. Alterations to image: removed caption.

Grandfather clock pendulum.png
Drawing of a typical grandfather clock pendulum, from a 1901 physics book. It is a seconds pendulum, with each swing of the pendulum taking one second. Slightly less than 1 meter (39 in.) long. It consists of a metal weight suspended on a wooden rod, since wood expands and contracts with temperature less than metal, keeping the period of the pendulum more constant. Under the weight is a knurled rate adjustment nut, which adjusted the rate of the clock by moving the weight up and down on the pendulum rod. The weight has a streamlined disc shape to minimize air resistance. Alterations to image: removed caption.

Anchor escapement animation 217x328px.gif
Autor: Chetvorno, Licence: CC0
Animation of an anchor escapement used in pendulum clocks. An escapement is a mechanism in a clock which gives the pendulum pushes to keep it swinging, and at each swing releases the gear train to move forward a fixed amount, thus moving the clock's hands forward at a steady rate. The recoil or anchor escapement, invented by Robert Hooke around 1658 and first applied to clocks around 1680, was the standard escapement used in pendulum clocks until the late 1800s, when a more accurate variation called the deadbeat escapement superseded it. It consists of an "escape wheel" (yellow) which is driven by the clock's gear train. The pivoted "anchor" piece above it (grey) is attached to the clock's pendulum (not shown) which hangs below it. The anchor has flat angled surfaces on each side called "pallets" which the escape wheel's teeth alternately catch and push on, giving the pendulum impulses to replace the energy it loses to friction, keeping it swinging.

This animation shows a typical anchor escapement found in a grandfather clock. The clock has a seconds pendulum, with a period of 2 seconds, so each swing takes one second. The escape wheel has 30 teeth and thus rotates once per minute, so the clock's second hand can be attached to its shaft. The amplitude or width of swing of the pendulum in this example is about 8°, a little wider than many quality anchor clocks, which have amplitudes of 3° - 6°. Of this angle, the "lift" or "drive" angle, the angle of forward swing over which the pendulum receives drive force, is 5°, while the remaining 3° consists of the "recoil".

The animation illustrates one of the disadvantages of the anchor: "recoil", which means the pendulum pushes the escape wheel backwards during part of each cycle. Recoil reverses the clock's gear train all the way back to the driving weight each swing of the pendulum, causing increased wear and inaccuracy.

Tidens naturlære fig22.png
Gridiron pendulum from a precision regulator clock, in the book "Tidens naturlære" (Nature of time) 1903 by Poul la Cour. The gridiron pendulum, invented 1726 by John Harrison, was a temperature-compensated pendulum that stayed the same length with changes in temperature, preventing the variations in timekeeping that occurred with ordinary pendulums when their pendulum rods expanded or contracted with changes in temperature. In the gridiron the pendulum bob is supported by a "grid" of rods of two different metals, in this case steel (dark rods, R & S) and zinc (light rods, T). The rods are connected by a frame (a,b,f,g) so that expansion of the steel rods makes the pendulum longer, while expansion of the brass rods pushes the bob up, making the pendulum shorter. By making the rods of the correct length, the greater expansion of the zinc compensates for the greater length of the steel rods, and the overall length of the pendulum stays constant with temperature. Zinc-steel gridirons like this example only required 5 rods, while brass-steel gridirons required 9 rods due to the smaller difference between the thermal expansion of brass and steel. It is a "seconds pendulum", with a period of 2 sec so each swing took one second, with a length from suspension to bob center of approximately one meter (39 inches).

Mercury pendulum.png
Drawing of a mercury pendulum used in precision regulator clocks, from a French physics book from 1878. The two glass flasks are filled with mercury which expands with an increase in temperature, compensating for the increase in length of the pendulum due to thermal expansion of the rod, keeping the period of swing constant. About 10 inches (25 cm) long, this type was used in a style of mantle clock called a 'crystal regulator'. Alterations to image: Removed caption, rotated to compensate for scanning error, converted from JPG to PNG.

Pendulum-with-Escapement.png
Drawing of a pendulum with anchor escapement, from a 1906 physics book. Labeled parts:(a) pendulum rod, (b) pendulum bob, (c) rate adjustment nut, (d) pendulum suspension spring, (e) crutch, (f) fork, (g) escape wheel, (h) anchor. Alterations to image: altered brightness slightly to optimise contrast, replaced original part labels with colored labels in different order, and added labels a, b, c, and d

GB-3-Gew-Pendeluhr (Luekk).jpg
Autor: Luekk, Licence: CC BY-SA 3.0
German 19th century wallclock made by Gustav Becker

Galileo Pendulum Clock.jpg
Drawing of pendulum clock designed by Galileo Galilei around 1641. Part of the front supporting plate is removed by the artist to show the wheelwork. Although the source says the drawing is 'by' Galileo, it is undoubtedly the one drawn by his student Vincenzo Viviani in 1659, since Galileo was blind by the time he had the idea. Probably the first design for a pendulum clock, it was partly constructed by Galileo's son, who died before he could finish it. For more information see Al Van Helden (1995), Pendulum Clock, The Galileo Project. Alterations to image: none.