Kullberg's flat-rim balance

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Kullberg's flat-rim balance
Manufacturer	Victor Kullberg
Production years	19th century
Production location	England

A balance invented by Victor Kullberg about 1860 and designed to avoid the middle temperature error, which is present in the ordinary form of bi-metallic compensation balance. Chronometers with this balance headed the lists in the trials at the Royal Observatory, Greenwich, in 1864, 1872 and 1873.

Victor Kullberg (1824–1890) was born in Visby on the Island of Gotland, Sweden. He was trained by the Swedish chronometer maker Victor Soderburg in Stockholm in 1840 and emigrated to London in 1851. He had moved to a permanent address at 105 Liverpool Road, N1 by 1870. During his lifetime Kullberg gained many medals and awards for his work and enjoyed a truly international reputation. As well as supplying many foreign governments, he regularly submitted chronometers for the Annual Trials at Greenwich Observatory, gaining first place in 1864 with a chronometer fitted with his newly invented ‘flat rim’ balance. His inventions included several designs of compensation balance and improvements to keyless winding for pocket watches. He also designed the automatic gas-governor for controlling the temperature of the chronometer testing ovens at the Observatory. More than 500 chronometers by Kullberg were supplied to the Royal Navy alone and he can be said to have been one of the 19th century’s finest chronometer makers. On Kullberg’s death in 1890 the firm was taken over by George and Peter Wennerstrom. They were succeeded by Sanfrid Lundquist who had joined the firm in 1894 and who moved the firm to Cranford in Middlesex in 1938, trading under the name of Victor Kullberg until his death in 1947.

[edit] How it works

The arm and the rims are flat and made up of brass and steel. In the arm the brass is at the top, but in the rims it is at the bottom. A rise of temperature causes the ends of the arms to bend downwards and the free ends of the rims to bend upwards and in so doing to move slightly inwards. The balance weights are mounted on short pillars above the rim and consequently the amount by which they move inward for a certain rise of temperature is greater than the amount they would move outward for an equal fall in temperature, a condition which is necessary to secure continuous compensation.

[edit] Memories

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[edit] In the Science Museum's Records

Inv. No: 1926-251