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Laying Out the Escapement (Having decided upon the size)

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.