A David Walter Double Pendulum Clock – Part 2, Making the Barrel

Jun 24, 2015,23:11 PM
 

A David Walter Double Pendulum Clock
                 – Part 2, Making the Barrel



David Walter's new double pendulum perpetual calendar clock is advancing as the parts making goes on.
For those of you who didn't see the first installment of this series, you can catch up by looking here:
    - Installment 1 – Introduction and cutting out the plates

David has decided to continue with the making of the barrel.
The barrel is an often overlooked part of a clock, although it is an eminently important part that must guarantee a  uniform, consistant and uninterrupted supply of power to the escapement at all times.  No problem, you say, for a weight powered device, gravity remains always the same.  But what happens during the time you are winding the clock?  No power?  What happens if the weight cable gets crossed up on the drum increasing the effective diameter of the drum?  You guessed it, not good.  These and other possible problems must be taken into consideration.

So let's see how David solves these problems.  And at the same time imagine the sounds of the machines, the sight of the chips flying and the smell of cutting oil.  (Don't you just love it in the shop ?)

Cutting the the raw brass bar for the barrels to length.




The hardened steel shafts are soldered in the barrels



To ensure that the torque driving the clock is always constant it is important that the weight cable is always at the same distance from the center of the barrel (torque=force x lever arm, in this case radius), we assume that the force caused by gravity on the weight is constant.  To this end a spiral groove is cut in the suface of the barrel so the cable always winds correctly and never crosses over itself.




Now it is time to lay out the next parts and cut them out.  Note the recess cut in the end of the barrels and the small slot in the rim.  The weight cable is wound around the drum and its end goes through the small slot into this recessed space.  This is space to properly tie up the end of the weight cable.  It is clear that if the cable isn't properly held at the end it will slip and the weight will fall.  And it is also clear that if this happens it only happens when the clock is fully would so the weight falls the farthest and causes the most possible damage.


The maintaining springs are made from guage plate, carbon steel.  Here are two blanks ready for turning the outside diameter.


Here we see cutting the inside diameter, the blank held in a stepped chuck.


The maintaining spring in its raw state.  The job of the maintaining spring is to to keep the clock working while the barrel is being wound.  It is the connection between the barrel and the great wheel of the clock.


After initial filing.


After filing, by hand, hardening and tempered to blue which makes a reliable spring.  These springs now have the form and hardening state needed to keep the clock running during winding.  There is, of course still a complicated mechanism with clicks and ratchets that go along with the spring.


Some of the parts going into the barrels.  They include clicks, shoulder screws, springs, and cocks.


The barrel cocks are layed out and cut out of brass bar.





David mills a shallow recess in the foot of each cock.  This is to make sure that the cock will sit perfectly flat and square against the plate without rocking.


That is it out of the shop for this installment, but the planning continues for the clock case.


As you can see this wll be a stately clock.  I can't wait to see how the work continues.


This message has been edited by cazalea on 2015-07-17 07:14:16 This message has been edited by cazalea on 2015-07-17 07:18:30

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Comments: view entire thread

 

This is good stuff...Thanks David, Thanks Don.

 
 By: tick tock doctor : June 25th, 2015-03:30
Hello Don So many details. Kind regards Anthony

Wonderful to see how the parts are ...

 
 By: blomman Mr Blue : June 25th, 2015-03:52
Coming along! :) Thank you, David and Don for this enjoyable report! Best Blomman

Torque = Force x Radius?

 
 By: MTF : July 3rd, 2015-15:49
Don and David, Having taken so much trouble ensuring that the dropping weights' torque and force are constant by controlling constant radius from the pivot, what happens to the torque applied during winding (weight lifting) by that skimpy albeit pretty bl...  

The concept of............

 
 By: David Walter : July 4th, 2015-09:31
The maintaining spring as invented by John Harrison is to provide equal energy during winding. When a weight driven or fusee clock does not have a maintaining ratchet the train will reverse during winding thus making a mokery of timekeeping. The purpose o... 

Matched pair of springs

 
 By: MTF : July 4th, 2015-20:17
Thanks for the explanation. The springs' torque are matched to that produced by the driving weights. How do you adjust that? By manipulating the spring itself or added external mechanisms? Regards, MTF

The spring is controlled...........

 
 By: David Walter : July 5th, 2015-12:35
in two ways. The first is by changing the strength of the spring by making the spring thinner or narrower so it produces less energy, this can also be done by altering the temper of the spring to make it "softer" to produce less energy. The second is to l...