A David Walter Double Pendulum Clock – Part 3, The Suspension

Jul 02, 2015,23:07 PM
 

A David Walter Double Pendulum Clock
            – Part 3,  The Suspension





David Walter's new double pendulum perpetual calendar clock is advancing every day.
For those of you who didn't see the earlier installments of this series, you can catch up by looking here:
    - Installment 1 – Introduction and Cutting out the plates
    - Installment 2 – Making the Barrel

Next we will see David making the suspension of the clock.  The suspension of a clock is the pivoting part connecting the top of the pendulum to the clock movment.  There are several different ways of making a suspension, the most common being with a flexible spring or with a knife edge.  Both are capable of producting a clock with excellent timekeeping capabilities.  David has chosen to use a spring suspension for this clock.

As you can imagine, I'm sure, the suspension for a double pendulum clock is not a trivial matter, there being two independent pendulums that both need equally good support and adjustment capabilities.

Let's start with a picture of the complete suspension unit.  This is ready to be bolted on to the back of the movement with the two bolts at the top left.  We can see the separate adjusting screws for the two pendulums.  These screws allow positioning the suspension so that the virtual pivot point is exactly in line with the axle of the anchor and that the pendulum hangs perfectly straight, parallel with the force of gravity.  If this is not the case the pendulum will not simply swing back and forth in a plane, but will swing in a figure-8, not only back and forth, but also a little front and back, which adds a possible source of errors for the timekeeping.






The spring assembly itself pictured alongside some standard modern clock spring assemblies for comparison.



Now down to some part making.  Threading the suspension frame support hole.



Milling the slot in the suspension frame.



The suspension springs are made from precision carbon steel bands.  The holes are punched out with a simple hardened steel punch.  A simple but very effective tool.



Milling the square on the shaft of the beat setting screw.



Cross drilling the square.  This will accept a conical pin to hold the nut.



Knurling the nut on the lathe.



To make the square hole in the nut first a clearance hole is drilled.  Then a hardened steel drift is pressed through to make the hole square.



Two nuts with the resulting square holes and the drift used to make them.



Shaping the shoulder of the lower chops of the suspension.  This piece holds the pin for the pendulum hook.



The suspension plates ready for matting.



The suspension plates after matting.  In these two pictures we can see the secret for success to get a clean uniform matting.  Before a piece is matted, it is first polished to remove all imperfections that might blemish the matting.  So never believe that matting means less work than polishing, it is the contrary!



Here we see all of the parts for this double pendulum suspension ready to be assembled as in the first picture.  Note that we see here two sets of suspension springs.  As the springs are easily damaged when a clock is moved David delivers two sets from the beginning.


Let's all thank David again for taking us along during the creation of this work of art and precision engineering.


This message has been edited by DonCorson on 2015-07-02 23:25:00 This message has been edited by cazalea on 2015-07-03 12:09:13

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Thank you fo rthis 3rd part, David and Don! :)

 
 By: blomman Mr Blue : July 3rd, 2015-00:22
Very interesting journey to follow! :) Looking forward to more! Best Blomman

Is knurling one pass or more?

 
 By: MTF : July 3rd, 2015-23:28
Thanks Don and David for the update. Is the lathe knurling process done in one pass or more? Instintively, I guess in one pass for crisp cuts but the forces required must be huge. Multiple passes would nibble away but the precision required in X-Y-Z axes ...  

yes it is.....

 
 By: David Walter : July 4th, 2015-08:34
Knurled in a single pass and quite a lot of pressure is required for a clean knurl,it is done at a fairly slow speed of 260 rpm when done correctly it is quite fast, taking perhaps about 10-15 seconds. You got it ! Fitting a square peg into a round hole c... 

How long did suspension design take?

 
 By: Ophiuchus : August 1st, 2015-16:18
A bit ashamed, I've been following these posts of David's clock avidly from the beginning, but felt so many complex questions coming on, I wanted to wait a while before asking anything. Of all the clocks I have seen and studied in the world, David's after... 

I dont remember............

 
 By: David Walter : August 4th, 2015-13:18
how long the original design took, quite while as I recall. Breguet softened the suspension by removing material making the support slightly felxible, I saw problems with this concept and created a support as "soft" and flexible as possble allowing me to ...