ffers certain geometrical
and mechanical advantages in its construction, which we will notice in
due time. 15 teeth divide evenly into 360deg. leaving an interval of 24deg.
from tooth to tooth, which is also the angle at which the locking faces
of the teeth are inclined from the center, which fact will be found
convenient when we come to cut our wheel.

From locking to locking on the pallet scaping over three teeth, the
angle is 60deg., which is equal to 2 1/2 spaces of the wheel. Fig. 1
illustrates the lockings, spanning this arc. If the pallets embraced 4
teeth, the angle would be 84deg.; or in case of a 16 tooth wheel scaping
over three teeth, the angle would be 360 x 2.5/16 = 56 1/4deg.

[Illustration: Fig. 1.]

Pallets may be divided into two kinds, namely: equidistant and circular.
The equidistant pallet is so-called because the lockings are an equal
distance from the center; sometimes it is also called the tangential
escapement, on account of the unlocking taking place on the intersection
of tangent AC with EB, and FB with AD, the tangents, which is the
valuable feature of this form of escapement.

[Illustration: Fig. 2.]

AC and AD, Fig. 2, are tangents to the primitive circle GH. ABE and ABF
are angles of 30deg. each, together therefore forming the angle FBE of
60deg. The locking circle MN is struck from the pallet center A; the
interangles being equal, consequently the pallets must be equidistant.

The weak point of this pallet is that the lifting is not performed so
favorably; by examining the lifting planes MO and NP, we see that the
discharging edge, O, is closer to the center, A, than the discharging
edge, P; consequently the lifting on the engaging pallet is performed on
a shorter lever arm than on the disengaging pallet, also any inequality
in workmanship would prove more detrimental on the engaging than on the
disengaging pallet. The equidistant pallet requires fine workmanship
throughout. We have purposely shown it of a width of 10deg., which is the
widest we can employ in a 15 tooth wheel, and shows the defects of this
escapement more readily than if we had used a narrow pallet. A narrower
pallet is advisable, as the difference in the discharging edges will be
less, and the lifting arms would, therefore, not show so much difference
in leverage.

[Illustration: Fig. 3.]

The circular pallet is sometimes appropriately called "the pallet with
equal lifts," as the lever arms AMO and ANP, Fig. 3,