and of the crescent being on the line
A′ A2
, we plant the compass on the pallet center and the center of the face of the ruby pin and draw
k k
, which will be the path described by the horn. The end of the horn is therefore planted upon it from 1½° to 1¾° from the ruby pin; this freedom at the end of the horn is therefore from ¼° to ½° more than we allow for the guard point; it depends upon the size of the escapement and locking angles which we would choose. It must in any case be less than the lock on the pallets, so that the fork will be drawn back against the bank in case the horn be thrown against the ruby pin.
When treating on the width of the ruby pin, we mentioned the Savage pin roller escapement, which we illustrate in Figs. [26] and [27]. This ingenious arrangement was designed with the view of combining the advantages of both wide and narrow pins and at the same time without any of their disadvantages.
Fig. 26.