To represent this in our model we take a lever as shown at Fig.
99, with the elongated slot for the pallet staff at _g_. To facilitate
the description we reproduce at Fig. 102 the figure just mentioned, and
also employ the same letters of reference. We fancy everybody who has
any knowledge of the lever escapement has an idea of exactly what a
"short fork" is, and at the same time it would perhaps puzzle them a
good deal to explain the difference between a short fork and a roller
too small.
[Illustration: Fig. 102]
[Illustration: Fig. 103]
In our practical problems, as solved on a large escapement model, say we
first fit our fork of the proper length, and then by the slot _g_ move
the lever back a little, leaving the bankings precisely as they were.
What are the consequences of this slight change? One of the first
results which would display itself would be discovered by the guard pin
failing to perform its proper functions. For instance, the guard pin
pushed inward against the roller would cause the engaged tooth to pass
off the locking face of the pallet, and the fork, instead of returning
against the banking, would cause the guard pin to "ride the roller"
during the entire excursion of the jewel pin.
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