Classic Escapement - Recoil (Common)

grabcad

This project is based on the book CLOCK AND WATCH ESCAPEMENT MECHANICS by Mark V. Headrick (Copyright 1997) as a fine source. The book is public (http://www.nawcc-index.net/Articles/Headrick-EscMechanics.pdf), so you can read and compare (with the book) everything I present here. Actually, you can use my projects as accurate simulations for understanding the book. I recommend you to download the book in order to use it when your computer is offline. All parts, assemblies and simulation/animation are made with Inventor 2014, so some specific references are bonded to this software. As you can learn from the book, there are three classical kinds of escapement mechanisms: Graham (dead-beat), Recoil and the Swiss Lever. My former projects present the Graham (dead-beat) escapement, and now I present the Recoil escapement. This project is explained in the book in the page 16. The difference from the Graham escapement is that the wheel have also a backward movement, not only forward. This is due to the fact that the left arm of the palette have no positive effect - to feed the pendulum with energy - but to push back the wheel. This effect can be interpreted as a recoil, like someone would coil the clock's spring, isn't it? That way a small part of the energy of the pendulum is returned to the reel. The problem is a loose of accuracy, since the backward movement is somehow difficult to control. There are some variants of the Recoil escapement. Here is presented the most common one, where the pallet looks like a bended bar. The design of the mechanism is based on the design of the Graham (Ideal) escapement, as seen in the pictures in the page 16 of the book. Included in my project is the „Basic Sketch.jpg” picture. Here you can see the important halves of the active lines from the Graham (Ideal) design - the ones dimensioned 3°. In the book is written „Shorten the entry pallet slightly and move the exit pallet slightly outwards, parallel to the impulse face of the Graham exit pallet”. The enter pallet is the left arm, and the exit is the right one. That „slightly” shorten and move are dimensioned by me as 2.5 mm, and respectively 2 mm. The pallet is created and you can see that the mass center is a bit eccentric (Classic Escapement - Recoil (Common) - Palette.jpg). To reduce the eccentricity a characteristic dimension of the left arm was reduced to 60 mm. Again, if you use Inventor (2014, 2015...), by entering Environments / Dynamic Simulation you can make your settings to change the way the system works. For instance, you can change the torque applied on the reel from 6 N mm to other value. You can also change the length of the rod from 400 mm. Watch what happens and try other values till you obtain a stable, uniform movement, of the pendulum for a long period of time. To see some real construction look here: Rudimentar: https://youtu.be/pOie2rMdN6k (little recoil) Professional adjustment of the entrance drop: https://youtu.be/Q6hC31fEN2I (noticeable recoil)