e centers are to be in straight line.
The lock is to be 1 1/2deg., the run 1/4deg., making a total lock of
1 3/4deg.; the movement of pallets from drop to drop is to be 10deg.,
while the fork is to move through 10 1/4deg. from bank to bank; the lift
on the wheel teeth is to be 3deg., while the remainder is to be the lift
on the pallets as follows: 10 1/4 - (1 3/4 + 3) = 5 1/2deg. for lift of
pallets.

The wheel is to have 15 teeth, with pallets spanning 3 teeth or 2 1/2
spaces, making the angle from lock to lock = 360 / 15 x 2 1/2 = 60deg.,
the interval from tooth to tooth is 360 / 15 = 24deg.; divided by 2
pallets = 24 / 2 = 12deg. for width of tooth, pallet and drop; drop is
to be 1 1/2deg., the tooth is to be 3/4 the width of the pallet, making
a tooth of a width of 4 1/2deg. and a pallet of 6deg.

The draw is to be 12deg. on each pallet, while the locking faces of the
teeth are to incline 24deg. The acting length of fork is to be equal to
the distance of centers of scape wheel and pallets; the impulse angle
is to be 28deg.; freedom from dart and safety, roller is to be
1 1/4deg., and for dart and corner of crescent 5deg.; freedom for ruby
pin and acting edge of fork is to be 1 1/4deg.; width of slot is to be
1/2 the total motion, or 10 1/4 / 2 = 5 1/8deg.; shake of ruby pin in
slot = 1/4deg., leaving 5 1/8 - 1/4 = 4 7/8deg. for width of ruby pin.

Radius of safety roller to be 4/7 of the theoretical impulse radius. The
length of horn is to be such that the end would point at least to the
center of the ruby pin when the edge of the crescent passes the dart;
space between the end of horn and ruby pin is to be 1 1/2deg.

It is well to know that the angles for width of teeth, pallets and drop
are measured from the wheel center, while the lifting and locking angles
are struck from the pallet center, the draw from the locking corners of
the pallets, and the inclination of the teeth from the locking edge.

In the fork and roller action, the angle of motion, the width of slot,
the ruby pin and its shake, the freedom between dart and roller, of ruby
pin with acting edge of fork and end of horn are all measured from the
pallet center, while the impulse angle and the crescent are measured
from the balance center. A sensible drawing board measures 17 x 24
inches, we also require a set of good drawing instruments, the finer the
instruments the better; pay special attention to the compasses, pens and
protractor; add to this a