All parts—thickness of the pallet stones, length of pallet arms, etc.—bear the same ratio of proportion. We measure the thickness of the entrance pallet stone on the large drawing and find it to be .47"; we make a similar statement to the one above, thus: 10 : .47 :: .26 to the actual thickness of the real pallet stone. By computation we find it to be .0122". All angular relations are alike, whether in the large drawing or the small pallets to match the actual escape wheel .26" in diameter. Thus, in the pallet D, Fig. 93, the impulse face, as reckoned from B as a center, would occupy four degrees.
MAKE A LARGE ESCAPEMENT MODEL.
Reason would suggest the idea of having the theoretical keep pace and touch with the practical. It has been a grave fault with many writers on horological matters that they did not make and measure the abstractions which they delineated on paper. We do not mean by this to endorse the cavil we so often hear—"Oh, that is all right in theory, but it will not work in practice." If theory is right, practice must conform to it. The trouble with many theories is, they do not contain all the elements or factors of the problem.
Near the beginning of this treatise we advised our readers to make a large model, and described in detail the complete parts for such a model. What we propose now is to make adjustable the pallets and fork to such a model, in order that we can set them both right and wrong, and thus practically demonstrate a perfect action and also the various faults to which the lever escapement is subject. The pallet arms are shaped as shown at A, Fig. 94. The pallets B B' can be made of steel or stone, and for all practical purposes those made of steel answer quite as well, and have the advantage of being cheaper. A plate of sheet brass should be obtained, shaped as shown at C, Fig. 95. This plate is of thin brass, about No. 18, and on it are outlined the pallet arms shown at Fig. 94.
To make the pallets adjustable, they are set in thick disks of sheet brass, as shown at D, Figs. 95, 96 and 97. At the center of the plate C is placed a brass disk E, Fig. 98, which serves to support the lever shown at Fig. 99. This disk E is permanently attached to the plate C. The lever shown at Fig. 99 is attached to the disk E by two screws, which pass through the holes h h. If we now place the brass pieces D D' on the plate C in such a way that the pallets set in them correspond exactly to the pallets as outlined on the plate C, we will find the action of the pallets to be precisely the same as if the pallet arms A A', Fig. 94, were employed.
