Explanations of time-keepers, constructed by Mr. Thomas Earnshaw and the late Mr. John Arnold / Published by order of the Commissioners of Longitude.

  • Thomas Earnshaw
Date:
1806
Catalogue details

Licence: Public Domain Mark

Credit: Explanations of time-keepers, constructed by Mr. Thomas Earnshaw and the late Mr. John Arnold / Published by order of the Commissioners of Longitude. Source: Wellcome Collection.

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    wise cause the Ballance to swing so much farther to clear the Wheel-; consequently a Check in the motion of the Ballance may stop the Watch; and this, in my opinion, may cause time-keepers, so construct- ed, to stop. The face of the pallet should run in a line of equal dis- tance between the centre of the pallet and its extremity, and not in a right line to its centre, as this causes an increase of friction, and a loss of that power which is obtained by the Wheel acting on the extremity of the pallet: This is clearly proved by time,, by the holes worn by the points of teeth in all pallets that run in a line to the centre. The Scape Wheel teeth should form the same direction as the face of the pallet, under cut for the said purpose of avoiding friction, and maintaining the power, and for safe locking. The points of the Wheel teeth must not be rounded off, but left as sharp as possible. The pivots of the scape Wheel are to be a very little larger than the Ballance pivots. The Wheel is locked by a spring instead of a Detent with pivots, as the French have made them, for those pivots must have oil, and when the oil thickens then the spring of the pivot Detents is so affected by it as to prevent the Detent from falling into the Wheel quick enough ; the consequence of this is irregular time and stoppage of the Watch ; and if ever such a watch went well for Twelve Months, Chance must have had by far the most hand in it.. When the Spring is planted on the side of the Wheel, as in my Es- capements, the part on which the Wheel rests should be a little short of a right angle, so that the Wheel may have a tendency to draw the Spring into it, for if sloped the other way, or beyond a right angle, it will have a tendency to push the Spring out; in that case the Wheel will have liberty to run : the Wheel should take no more hold on the Spring than just sufficient to stop it; for if more, friction will be in- creased. The small return spring should be as thin as possible at the end fastened to the other spring, but at the outer end a little thicker ; the spring should be planted down as close to the wheel as to be just s free o'f it. The discharging pallet about one-third, or near one-half the size of the large or main pallet, the face of it in a right line to the ; /
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