- Museum number
- 1958,1201.1743
- Description
-
Movement of a pocket chronometer
Fusee with Harrison's maintaining power.
Earnshaw-type spring detent escapement.
Pendant operated half-quarter repeat.
Pennington brass balance with screwed-on bimetallic compensation. screwed
Blued-steel helical balance spring.
Silver engine-turned dial gold hour and minute hands, blued-steel seconds hand.
Case missing.
- Production date
- 1805-1815
- Dimensions
-
Diameter: 51.20 millimetres
-
Thickness: 8.10 millimetres
- $Inscriptions
-
- Curator's comments
-
5/12/2008. Tip of hand refixed by gluing parts to a steel batten. Dial cleaned using soft eraser.
-
Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Robert Pennington, c. 1810
Chronometer
Signature: On the back plate and barrel bridge 'Pennington London 426'.
Dial and hands: Engine-turned silver dial with sunk subsidiary seconds, the figures printed on, attached by screws in the edge of the dial plate passing into rectangular feet soldered to the underside of the dial.
Red gold minute and hour hands, steel subsidiary seconds hand.
Movement:
Dial plate diam. 51.2 mm; front plate diam. 45.8 mm; back plate diam. 43.6 mm; frame h. 8.1 mm.
Frame: Full plate construction with detachable barrel bridge, four turned pillars, the back plate retained by pins. A deep dial plate carrying both case catch and spring and the movement hinge. The dial plate attached to the front plate by three screws under the dial, and a positioning peg. Minute and second divisions marked on the upper surface of the dial plate which is considerably cut away to leave room for the repeating work. A large dust-excluding pipe with oval foot of characteristic shape around the winding square. All the brass parts gilded, with little on the front plate under the dial or on the inside surfaces of the dial plate.
Fusee: Keywind fusee with the usual stop-work and maintaining power, the maintaining ratchet wheel brass. The setting-up-work mounted on the barrel bridge, the barrel arbor with an extended square on that end only. The barrel with a flange on the cover end.
Going train: A well-made and finished train, rather smaller than usual and grouped towards the fusee to leave room for the repeating train and hammers. The brass wheels gilded, the polished steel pinions and arbors with rather small undercuts.
Jewelling: Only the fourth arbor lower pivot in a pierced jewel. The escapement arbor pivots in pierced jewels with endstones. A diamond endstone set in a polished steel ring on the balance cock.
Escapement: A development of Earnshaw's spring detent escapement. The brass escape wheel with short straight-backed teeth left standing proud of the sunk-out rims and arms. The bottom of the wheel and tops and backs of the teeth burnished. The leading edges of the teeth and the outside of the rim left with the original fine cutter marks. The steel impulse roller with rounded polished impulse face leaning away from a radial. This face, the edge and bottom of the roller polished. Jewelled discharge roller, the jewel dovetailed in place, with two adjusting flats on the edge of the roller. A very light solid foot detent with steel passing spring held by a single rivet and the locking stone dovetailed in a slot. Banking for the detent provided by a gilded brass piece held by a blued steel screw in the middle, and with a blued steel plug carrying an eccentric peg passing into a slot in the end of the banking piece, and with a screw head for adjusting the banking.
Balance: Bimetallic 'Pennington' type of balance built up on a brass three-armed wheel. Two bimetallic rim sections screwed and pinned to blocks left standing on the edge of the brass wheel. Two large compensation screws set near the free ends of each rim. Four brass quarter screws acting also as a protection for the bimetallic rims. Their heads are outside and clear of the rims, the threaded portions passing through clearance holes in the rims and into tapped holes in the brass wheel. Scribing marks for the arms of the wheel are visible on the underside, the wheel is riveted to a brass collet on the balance staff. The steel parts of the rims blued. Diam. 23.0 mm, h. 2.0 mm.
Balance spring: Large diameter blued steel helical spring, of 4½ turns, with terminal curves, free-sprung to a brass stud head with a brass screw on the balance cock. The collet a brass bar with two holes to lighten it and a central boss left standing round the balance staff.
Repeating work: Half/quarter repeating work of typical Stogdon type. The train and hammers pivoted in the frame, the steel parts fitted on the front plate under the dial. The steel parts are well and robustly made and with a grained finish. There are no gongs or provisions for them on the movement, and there is no means of adjusting the throw of hammers. The watch was probably a dumb repeater against blocks on the inside of the case.
Going-train counts:
Great wheel (fusee) 60 teeth
Centre pinion 12 leaves, wheel 64 teeth, no crossings
Third pinion 8 leaves, wheel 60 teeth, 4 arms
Fourth pinion 8 leaves, wheel 64 teeth, 4 arms
Escape pinion 8 leaves, wheel 18 teeth, 4 arms
Beats per hour: 17,280
Motion work:
Cannon pinion 4 leaves, minute pinion 36 leaves
Hour wheel 36 teeth, minute wheel 48 teeth
Repeating train:
Great wheel 42 teeth, second wheel 36 teeth, third wheel 32 teeth, fourth wheel 30 teeth, fifth wheel 24 teeth
The pinions of 6 leaves each except the fly pinion of 8 leaves
Provenance: Ilbert Collection; purchased by Ilbert from Mal¬colm Gardner in 1953.
Bibliography: Vaudrey Mercer, 'The Penningtons and Their Balances', AH, Spring 1981, pp. 514-22.
- Location
- Not on display
- Exhibition history
-
Exhibited:
2008 Dec 17-2010 Dec 17, Australia, Canberra, National Museum of Australia, 'Australian Journeys'
- Condition
- Latest: 3 (2017)
- Acquisition date
- 1958
- 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.
- Department
- Britain, Europe and Prehistory
- Registration number
- 1958,1201.1743
- Additional IDs
-
Previous owner/ex-collection number: CAI.1743 (Ilbert Collection)
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Previous owner/ex-collection number: Q225 (Ilbert Ledger)
