42 escapement

The escape wheel is formed by six arms and six pins fixed around a circle concentric to the arbor of the wheel. T & Z are the 2 gravity arms . On T it is pivoted an ell shaped arm L, of which M & N are its arms. L is free to revolve around R until it is locked by O. Fixed on Z there is the escape wheel arm lock B .

Z swing is limited by the lock K which is fixed on the rear face of the back plate. This the action of the escapement

As shown, the pendulum is swinging to the right and has just parted from the impulse pin Q .

The gravity arm T has made contact with the locking arm Z via C and D and has moved enough for the escapement arm A to be released from its jeweled stop B .

The lifting pin 1 has engaged the lipped end F of the lifting lever L whose right-angled extension M is rotating away from its banking pin O.

As the pendulum moves further to the right , the gravity arm is reset with M clear of O , the locking arm arrested by its banking pin K ( fastened to the back plate of the clock), and the next escapement arm E , arrested by B.

On its return to the left ,past the vertical, the pendulum picks up the gravity arm , M drops in its position against O and the system is ready to take up the diagram situation again , with 2 taking the place of 1.
Which one the originality in the action of this escapement ?

Escapement

It is not the pendulum which, as it happens in usual gravity escapement, unlocks B by A ,but ,to the contrary this job is performed by T in touching D and in that handling whatever may came up with the change of friction during this action.

Hope this animated gif created by Daniele Mazza may throw some light on the subject.

Let us say that the escapement gives to the pendulum virtually constant impulse.

I said virtually because other changes could arise: changed conditions of gravity arms pivots lubricating oils or other things which could vary the phase stability of the escapement, just to say a couple. Therefore if the escapement has constant impulse , why not add some complications ?

Also, bearing in mind I never build a perpetual calendar ,you can understand how the temptation was fascinating.


Dumbell inertia device	gravity arms	escape wheel