| Photos below show the escapement. The escape wheel looks just like a
conventional Graham type deadbeat escape wheel. The third photo shows an exploded view.
The two triangular shaped steel pallets each act to alternatively lock the escape wheel
and lift each gravity arm. The pendulum acts against the lower portion of the gravity arms
causing them to unlock the escape wheel. The flat springs which hold the gravity arms
require careful adjustment. They are not a passive holding system, but exert a bit of
downward force. However, adjusting too much force (by straightening the spring) causes the
escape wheel to occasionally jam up. Too little, and the gravity arms will tend to bounce
upon the impact of the escape wheel locking against the pallet. This is especially
dangerous with this kind of escapement as a slip of the pallet could result in a 'runaway'
causing damage to the escapement. Overall, this was one of many attempts that were made by
many horologists in this period before Dennison has perfected his design in 1860. It is
not particularly distinguished as it still needs oil on the pallets, is subject to
tripping and catastrophic runaway. All of these which were overcome in Dennison's design.
For another pre-Dennison example of gravity escapement see Dent exhibition clock. The second to the last photo shows the bell system hidden under the hood of the clock. The last photo shows the signature on the reverse of the porcelain dial. Anyone who can shed light on this signature would be most appreciated.
Illustration from Practical Clock Escapements, Laurie Penman, pp. 172-73 |
