The generally accepted method of laying out this escapement is shown in Figs. [41] and [42], as follows: “Draw a circle representing the escape wheel; multiply the radius of the escape wheel by 1.4 and set off this as the center distance between the pallet and escape wheel centers. From the pallet staff center describe a circle with a radius equal to half the distance between escape wheel and pallet centers. Set off on each side of the center line one-half the number of teeth to be embraced by the pallets and from the points of the outside teeth draw lines tangent to the circle described from the pallet center. These lines would then form the faces of the pallets if they were left flat.”
We wonder how much information this description and the drawing conveys to the average reader. How long should the pallets be? What is the drop? How much will the escape wheel recoil with such a depthing? What arc will the pallets give the pendulum? Why should the center distance always be the same (seven tenths of the diameter of the wheel) whether the escapement embraces eight, or ten, or six teeth? As a matter of fact it should not be the same. We could ask a few more questions as to other details of this formula, but it will be seen that such a description is practically useless to all but those who are already so skilled that they do not need it.
Fig. 42. Recoil Escapement with Curved Lifting Planes.
Fig. 43. Drawing the Lock Lift and Recoil of the Usual Form.