Laying Out the Escapement
Laying Out the Escapement names 2 different subjects across the 6 encyclopedias on this shelf. Each is set out below.
Laying Out the Escapement In laying out the escapement we must first determine
American Watchmaker and Jeweler (1892)
In laying out the escapement we must first determine the size of the escape wheel and also the number of teeth it is to have. We will make our drawing larger than the actual work is to be, and then after taking our measurements direct from the drawing, reduce them to the actual working size. In Fig. 5 the diameter of the escape wheel is three inches and has thirty teeth revolving to the right, so that we may mount a seconds hand upon the arbor if used with a seconds pendulum. In making a draft of any kind all the lines should first be drawn in with a lead pencil, and then those lines which are to remain are to be inked in with any good waterproof India ink, Higgins' American drawing ink being an excellent article for the purpose. With the dividers set with a radius of one and one-half inches, draw a circle which will represent the diameter of escape wheel. The distance between one tooth and the next equals three hundred and sixty degrees (the number in a complete circle) divided by thirty, the number of teeth in our escape wheel, which will give us twelve degrees as the required distance (360<??>30=12). The distance between the center of the escape wheel and the center of the anchor equals the radius of the escape wheel plus four tenths of this radius, 1 1/2 = 3/2, 4/10 of 3/2 = 6/10 and 3/2 + 6/10 = 21/10 = 2 1/10 the distance required. This distance is to be increased or diminished inversely according as it is desired to reduce or increase the oscillation of the pendulum. Draw a line joining the center of the anchor and the center of the escape wheel, which is the center line of the escapement. In laying off the teeth begin at this center line, laying them off on either side until completed. The back of the teeth are to be radial, while the front faces are to be of an angle sufficiently great to give the teeth strength, yet not so great that more than the point of the tooth will at any time strike the pallet. When this angle has been decided upon, draw a line representing the front face of a tooth and extend it beyond the center of the escape wheel. Now draw a circle to which this line will be a tangent, and all that is necessary in order to draw in the rest of the teeth is to place the straight edge so as to coincide with the point of a tooth and this circle. From the center of the anchor draw a circle of a radius equal to half the distance between the anchor and escape wheel centers. As the anchor is to embrace eight teeth, we draw lines which are tangent to this circle, and touching the points of the fourth tooth on each side of the center one, which will give the pallet faces, if they were left flat. By curving the faces of the pallet and giving an angle to the front faces of the teeth, the friction is disengaging, consequently will wear better. This escapement is sometimes made to embrace ten teeth instead of eight.
Laying Out the Escapement Having decided upon the size of escape wheel and
American Watchmaker and Jeweler (1892)
Having decided upon the size of escape wheel and the number of teeth the anchor is to cover, draw a circle representing the escape wheel and divide it into thirty equal spaces, or whatever number of teeth the wheel is to have. If the wheel is to have thirty teeth, the space between two of them will be twelve degrees. The front faces of the teeth are to be drawn at an angle of ten degrees to a radial line. This inclination of the teeth is marked off by laying the base of the protractor so the center of it will coincide with the point of a tooth and mark off ten degrees from the radial line in the proper direction to form the faces of the teeth. Having located this ten degree point, join it with the point of the tooth by a straight line, continuing it past the center of the escape wheel, and from this center draw a circle to which the line forming the front face of the tooth is a tangent. The front faces of the other teeth may be drawn at the same angle as the first by simply drawing a straight line through the point of the tooth and tangential to the circle drawn last. Draw a line from the center of the escape wheel through the point of a tooth, and to the right of this draw another line passing midway between the tenth and the eleventh teeth. From the points of these teeth erect perpendiculars, and where these cross will be the center of motion of the anchor. From the anchor center draw a straight line forming an angle of from one to two degrees to the right of the lines drawn from the points of the teeth. These lines will locate the lifting angle, the smaller amount being used in regulators and astronomical clocks. From the anchor center draw an arc passing through the points of the teeth which locates the opening of the pallets. Now draw another smaller circle concentric with this one and at a distance equal to one-half the space between two teeth, less the drop, will give the thickness of the pallets. From the point of the tooth to where this last arc crosses the line of the lifting angle will be the impulse face of the pallet. All that remains to be done is to fill in the arm of the anchor. The form shown in Fig. 153 is very convenient, as slight inaccuracies in making may be corrected by means of the two adjusting screws.
What Has Changed in the Last Century
The geometry the American Watchmaker and Jeweler set out in 1892 is still the geometry of the recoil anchor escapement: thirty teeth twelve degrees apart, tooth faces raked about ten degrees off radial, pallet centre spaced roughly four-tenths of the escape-wheel radius beyond its rim. A student at a horological school today would draw the same lines, and the escapement itself dates back to the late seventeenth century. What has gone is the method and the market: the oversized pencil draft inked in with waterproof India ink and measured with dividers and protractor has given way to CAD, and after Seiko's quartz Astron of 1969 the mechanical clock became a luxury and hobbyist object rather than the ordinary way of telling time. The instructions remain sound for anyone repairing or building one, which is now the main reason to lay out an escapement at all.
Written for this edition, 2026.