Lancaster, c.1826 No. A. 23/27

1 day marine chronometer in brass bowl

Lancaster….

Box/Mounting

Simple cylindrical barss bowl with bezel and glass, measuring 92mm high and 96mm Ø.

The flat base, soldered into the seamed bowl, has fine decorative turned rings and a circular, sprung, brass winding shutter centred on the base (spring now missing), and a narrow, straight-sided brass friction-fitting bezel, secured with 2 side-screws. The bezel has a thin, flat, bevelled glass, retained with a narrow copper band, and seated on a straight-sided sight-ring, over the dial. The inside of the bowl has a long fusee pipe screwed in from the base. The sight ring has three large plugged holes spaced 90 apart from one another, just perceptible on its inner surface.

Dial and hands

The 91.0 mm Ø, engraved and wax-filled, silvered-brass dial has three small riveted feet which fix to the pillar plate with side-screws and the dial itself seats in the recess in the bowl, a pin at XII and a notch in the bowl orientating it correctly. The dial has roman hour numerals and there is a large seconds dial at VI o’clock having arabic ten-second figures with straight batons at alternate five-second intervals. The dial is signed below XII: “LANCASTER. / Chronometer / A / 23/27”. Gold demi-lune and poker hands, with a blued steel pointer seconds hand with counterpoised tail. The gold hour and minute hands are each fixed to a brass collet with three steel screws. The cannon pinion has a radial threaded hole in the square at the back of the the minute hand, possibly intended to fix a small counter-weight for the hand.

Movement

Finely constructed and heavily jewelled full-plate fusee movement with four baluster pillars with moulded flanges at either end and one fin in the upper middle, screwed to the potence plate. The set up ratchet wheel and click are polished and blued in a ringed decorative pattern. The click and maintaining power detent each have a polishing point on the underside. There is a single drilled dot on the barrel bridge by the ratchet wheel to mark set-up positions against a nick on one edge of the square. There is a turned spot under the balance cock table, directly above the centre wheel pivot. The barrel bar is engraved on its upper surface: “Lancaster. / A / 23/27”. The balance cock is engraved: “Lancaster’s / Improved / Balance”. The upper side of the pillar plate is stamped: “IW.1826”. The later, signed, blued steel mainspring has a steel square hooking in the barrel and the arbor has squares on both ends. There is a fine, five-wheel train including great wheel, the fusee with Harrison’s maintaining power and with a later, fabricated, straight-sided fusee pipe, slightly flared at the upper end and push-fitted to the square. The train wheels are brass with the third, fourth and escape wheels run on a bar on the pillar plate.

Escapement, balance, spring and jewelling

Earnshaw-type spring detent escapement, the grey-finished detent with later foot. The detent banks against a later steel screw in the original brass banking foot. There is a (later) small unused threaded hole by the opening in the potence plate for the detent, directly above the escape wheel teeth, probably for locking the train. The rest of the escapement is probably the original, including the highly polished impulse roller with its raked, light pink impulse jewel and the discharge roller, which also has a light pink stone inset. The gold escape wheel is probably original but is now mounted so as to be adjustable in depth, running in the eccentric jewel setting.

The “Lancaster’s Improved” bimetal, oversprung balance has parallelogram-shaped brass compensation weights clamped to the bimetal rim segments. Guiding the position of these weights, to ensure they are exactly opposite each other (and hence keeping the balance poised) is a steel arm, pivoted at the centre of the balance and running across the balance diameter with the tips cranked up and run freely into grooves on the top of the compensation weights, covered, but not clamped, by a polished steel plate on top of each weight. There are blued steel mean-time screws positioned in the rim at the ends of the balance arms. The light-coloured gold helical balance spring has terminals on both ends, the upper terminal clamped to a brass stud on the cock table, the fixing screw for the stud having been moved slightly and the earlier screw hole being plugged. The jewelling, which all has dot-marked brass settings and steel screws, extends to the fusee, and is in red or pink stones for the smaller train pivots, clear sapphires for the larger holes and a facetted diamond in a blued steel setting for the balance cock endstone.

Alterations/condition

The brass bowl is in sound condition but with a number of slight knocks and has been quite heavily over-polished and lacquered in relatively recent times. surviving. The steel parts of the \hinges and lock are now quite rusty (some mechanical cleaning done to reduce the corrosion products).

The dial silvering is sound, but has been heavily restored and the engraving is now thin in places and crudely deepened in other areas. The seconds hand is a modern replacement.

The movement is in generally clean condition, though it was found to be thick with old, solidified oil (it has only been very lightly cleaned, and has been re-oiled, during inspection). and has been subject of poor workmanship and damaging repair work in the past. The brasswork was probably all finely curled originally and there is evidence the movement has been quite heavily over-polished and refinished in the past. The barrel arbor square is bent over at a slight angle and the mainspring has been distorted into a conical form by being pulled straight from the barrel. The barrel bar has one crude new fixing screw. The escape wheel upper pivot is broken (wheel now blocked with a tissue wedge) and its later upper jewel hole is now mounted in a rather roughly turned eccentric brass setting. The original foot detent has lost its foot and is now mounted in a crude brass-footed clamp by the base of its spring. The locking stone is also replaced with a steel D-section pin. Some of the jewel setting screws have been replaced and one of the upper fusee setting screws has been broken off, leaving the thread in the hole. The balance staff has been replaced.

Commentary, Provenance, etc

The initials IW and the date 1826 may well have been placed there by the jeweller; it is unlikely Lancaster would have jewelled the movement himself….




Potence Plate Ø: 75.0

Pillar Plate Ø: 75.0

Plate distance: 15.7

Inside barrel Ø: 34.0

Arbor Ø: 11.35 steel, unsnailed.

Thickness: 0.33 – 0.38

Height: 13.8

Signature: “F Scott 15th March 1867” (15cms from end) and : “3 67 F Cotton” (35cms from end)

(6 full turns output from barrel)

Set up: 3 teeth (24 teeth as found!).

TRAIN COUNT


Wheel / Pinion (+ext dia) Comment:

Fusee/Great: 70 / 35.2 No.of Turns: 6 (Chain 50.0cms, 103 links)

Ratchet: 35 / 16.6 Brass, 2 steel clicks

Maintaining Power: 120 / 32.8 Steel

Centre/2nd: 90 / 30.0 + 14 / 7.2 5 tapered crossings. V. finely finished pinion

Third: 80 / 23.0 + 12 / 4.2 “ “

Fourth: 80 / 19.7 + 10 / 3.2 “ “

Escape: 12 /12.5 + 8 / 2.2 Gold. 3 curved crossings “

Balance Frequency: 14,400 vbs/ hr (2 beats every second)

Hour: 54 / 18.7 Brass

Minute Wheel: 56 / 19.8 “

Minute Pinion: 18 / 6.7 Highly polished steel

Cannon: 14 / 5.5 Polished steel

Set up ratchet: 25 / 14.4 Blued steel with polished circles

Impulse pallet tip Ø: 6.0

Discharge pallet tip radius: 1.7

Detent length: 26.0

Balance Ø: 30.7 Balance Mass (incl. b/spring & stud): 6.8g

Balance spring Ø: 13.4 Material: light coloured gold alloy

Turns incl. terminals: 12 ½ (c/w down)