It will be evident on a little thought,
that if the tooth _A'_ impelled the exit pallet to the position shown,
the outer angle of the pallet must extend down to the point _v_, on the
arc _v' v'_; consequently, we define the impulse face of this pallet by
drawing a line from point _x_ to _v_. To define the outer face of the
exit pallet, we draw the line _v e_ parallel to the line _x z_.
There are no set rules for drawing the general form of the pallet arms,
only to be governed by and conforming to about what we would deem
appropriate, and to accord with a sense of proportion and mechanical
elegance. Ratchet-tooth pallets are usually made in what is termed
"close pallets"; that is, the pallet jewel is set in a slot sawed in the
steel pallet arm, which is undoubtedly the strongest and most
serviceable form of pallet made. We shall next consider the
ratchet-tooth lever escapement with circular pallets and ten degrees of
pallet action.
DELINEATING CIRCULAR PALLETS.
To delineate "circular pallets" for a ratchet-tooth lever escapement, we
proceed very much as in the former drawing, by locating the point _A_,
which represents the center of the escape wheel, at some convenient
point, and with the dividers set at five inches, sweep the arc _m_, to
represent the periphery of the escape wheel, and then draw the vertical
line _A B'_, Fig.
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