- Museum number
SUBSIDIARY SECONDS TOURBILLON POCKET-CHRONOMETER MOVEMENT WITH SPRING DETENT ESCAPEMENT AND KEYLESS WINDING.
Tourbillon chronometer watch.
Spring detent escapement; keyless.
Originally with half-hunting case.
- Production date
Diameter: 44.90 millimetres
Thickness: 12.90 millimetres
- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Maker Unknown, but Swiss, c. 1900
Signature: None, but probably made by either Albert Pellaton-Favre (1832-1914) or his son James César Pellaton (1873-1954).
Case: Missing, but was a hunter case.
Dial and hands: Flat enamel dial of canister type and of a greenish blue, with white sunk subsidiary seconds. Blued steel hands, the seconds a later replacement.
Ebauche marks 3009, 38, 1 on the front plate under the dial (see also Charles Suchy et Fils, registration no. 1958,1201.1835).
Front plate diam. 44.2 mm; back frame diam. 42.3 mm; frame th. 8.4 mm; front plate th. 4.3 mm (reduced to 3.1 mm under dial); carriage diam. 19.0 mm; h. over pivot shoulders 7.74 mm; frame h. 4.18 mm.
Frame: Bridge calibre built up on the front plate, the curved centre wheel bridge is characteristic of the work of the Pellatons. The large sub plate on the front plate under the dial carries the third arbor and tourbillon lower bearings and provides a maximum of height within the frame. The movement was fixed in its case by a peg and dog screw in the front plate. The material of the frame is maillchort, a type of nickel brass, or nickel silver as it is usually called.
Going barrel and keyless work: The going barrel, also of nickel brass, with four-turn Geneva stop-work on the cover end. Sliding pinion keyless work, the hand-set mechanism operated by a lever with gold touch piece on the edge of the dial at IV o'clock.
Going train: Arranged for a hunter calibre. The centre arbor hollow for the arbor carrying the cannon pinion. The centre wheel planted below the barrel, the third wheel below the centre and meshing with the fourth pinion on the bottom of the carriage. The escape pinion planted in the carriage and meshing with the fourth wheel fixed concentric with and under the carriage.
Jewelling: The centre upper pivot runs in a jewel with screwed gold setting, those of the third, the tourbillon and the escapement arbors also in pierced jewels. Those of the escapement with endstones. The jewels for the carriage pivots bombé, with convex surfaces against the pivot shoulders.
Tourbillon: Making one revolution per minute and carrying the seconds hand on its extended lower pivot. The carriage top pivot supported by a steel bridge, the jewel in a screwed gold setting. The carriage lightly constructed on a steel plate reduced to a thin rim with three integral arms joining it to the central boss. Three turned pillars at the ends of the arms on the rim carry the three upper arms and integral central boss. The two central bosses have the balance jewelled bearings set inside them. The lower boss also carries the fourth pinion set in a nickel ring and secured by three screws. The escape wheel arbor is carried between cocks branching off one of the arms of the lower part of the frame, opposite it on the rim is screwed a small platinum block acting as a poising weight. The carriage is, however, badly out of poise.
Escapement: Spring detent escapement of developed Earnshaw type. The very light escape wheel with arms sunk below the level of the rim and teeth apparently made of gilded brass. The steel impulse and discharge rollers polished all over and each jewelled radially, the jewels set in straight-sided slots. A most delicate locking detent having its foot at right angles to the main axis, screwed to the rim of the carriage and planted so that the main axis is on or near a tangent to the locked tooth. Both the detent horn and the end of the gold passing spring, itself held by a screw to the detent, are bent towards the balance centre. Banking for the detent provided by an extension of the locking stone below the detent against a narrow arm left standing from the boss of the lower part of the tourbillon frame. The locking stone so reduced that in section it is less than semi-circular. The spring part of the detent consisting of two narrow strips joining the detent body by the passing spring boss to the foot.
Balance: Bimetallic two-armed balance, the arms of sage-leaf shape, set above the bottom of the rim. The screws gold, no quarter screws. Diam. 17.0 mm, h. 1.2 mm.
Balance spring: Blued steel spiral spring of 13¾ turns, with an overcoil and terminal curve. A steel stud held with a single screw and steady pin on a short bracket between one of the arms and the boss of the upper part of the carriage. A round nickel collet. Carried on the central boss of the upper part of the carriage is a regulator index, its tail passing over a sector left integral on one of the arms.
Amplitude limiting device: As the balance swings, a pin standing from the upper side of one balance arm passes between two pins pointing down from one of the arms of the upper part of the tourbillon frame. An arm pointing outwards from a tiny block pinned to the last turn of the balance spring moves out across the two pins in the tourbillon frame and prevents the pin on the balance from passing between the pins a second time in one direction of rotation of the balance. Should the amplitude of the balance increase unduly, the resulting interference between the arm on the block and the pin on the balance reduces the amplitude to the normal and safe limit.
Great wheel (barrel) 96 teeth
Centre pinion 12 leaves, wheel 96 teeth, 5 arms
Third pinion 12 leaves, wheel 90 teeth, 5 arms
Fourth pinion 12 leaves, wheel 72 teeth, no crossings
Escape pinion 6 leaves, wheel 15 teeth, 4 arms
Beats per hour: 21,600
Cannon pinion 12 leaves, minute pinion 10 leaves
Hour wheel 40 teeth, minute wheel 36 teeth
Crown wheel 25 spur teeth, 13 ratchet teeth
Castle wheel (sliding pinion) 13 ratchet, 27 bevel teeth
Intermediate winding wheel 41 teeth
Barrel ratchet wheel 46 teeth
Intermediate hand-set wheels, each 15 teeth
Provenance: Ilbert Collection, purchased by Ilbert from Malcolm Gardner in 1954.
Bibliography: James C. Pellaton, 'Le Tourbillon', Editions des Annales Françaises de Chronométrie, Paris, 1951, p. 355, fig. 13.
- Not on display
Latest: 3 (2017)
3 (Oct 1995) Seconds hand missing. Bolt broken and stem loose.
- Acquisition date
- Acquisition notes
- Following the successful acquisition of the celebrated Ilbert collection of clocks (1958,1006 collection), prints and other related materials made possible by the generous donation of funds by Gilbert Edgar CBE Ilbert's watches were then acquired using funds provided by Gilbert Edgar, public donations and government funds.
- Britain, Europe and Prehistory
- Registration number
- Additional IDs
Previous owner/ex-collection number: CAI.0882 (Ilbert Collection)
Previous owner/ex-collection number: Q267 (Ilbert Ledger)