File:Tidens naturlære fig22.png

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Summary

Description
Dansk: "Tidens naturlære" 1903 af Poul la Cour, Fig. 22. Kompensationspendulet. Bogen findes digitalt på s:da:Tidens Naturlære

English: 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).
Date
Source From the book "Tidens naturlære" (Nature of Time) 1903 by Poul la Cour, fig. 22. The book is digitized at s:da:Tidens Naturlære
Author Morten Bisgaard
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(Reusing this file)
PD-Old

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Date/TimeThumbnailDimensionsUserComment
current03:34, 27 January 2009Thumbnail for version as of 03:34, 27 January 2009564 × 1,856 (261 KB)Chetvorno== Summary == {{Information |Description={{da|"Tidens naturlære" 1903 af Poul la Cour, Fig. 22. Kompensationspendulet. Bogen findes digitalt på s:da:Tidens Naturlære}}<br> {{en|Temperature compensated [[Wikipedia:gridiron pendulum|gridiron pendulu
16:22, 7 August 2006Thumbnail for version as of 16:22, 7 August 20061,500 × 1,856 (277 KB)Bisgaard{{Information |Description="Tidens naturlære" 1903 af Poul la Cour, Fig. 22. Kompensationspendulet.<br> Bogen findes digitalt på s:da:Tidens Naturlære<br><br> "Tidens naturlære" (Nature of time) 1903 by Poul la Cour, Ill. 22. Temperatur compensate
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