Precision Regulator / Piece Ecole

Jacob Curtis

Registered User
Oct 20, 2015
7
22
3
Just wanted to share a few pictures of the clock I built in the second year of my schooling (2017). It serves as a great reminder of how far I have come since then. It is built in the style of Glashutte Precision Pendulum Clocks. It is 8-day running, with Harrison's maintaining power, a compensating pendulum with invar rod, and solid sapphire pallets. The driving weight is 800 grams (1.7lbs) and the pendulum bob is 8kg (18lbs)
Performance has been in the neighborhood of 2 seconds a month, I suspect it is slightly overcompensated in its current state.

I produced every component with the exception of the dial engraving and the case.

IMG_1572 (1) copy.jpg IMG_1752.jpg IMG_1737.jpg IMG_1759.jpg IMG_3656.jpeg IMG_4333.jpeg IMG_1302.jpg IMG_4343.jpeg IMG_1754.jpeg
 
Last edited:

Hessel Oosten

Registered User
Apr 26, 2017
45
9
8
The Netherlands
Country
Hi Jacob,

Superb (bis) ! Thanks for posting this.

Can I ask you a few questions ?

* What material did you use for the anchor pallets ?

* Did you use a sort of device (using the contol-circles) for grinding them ?

* You have (i.m.o.) a special longitudinal effect on the frame plates ("platines"). How did you make that ?

* The hands ? Are they made of titanium (if I see it right the blue is somewhat less intense, in comparison to blue-ed steel) ?

Hessel
 

Jacob Curtis

Registered User
Oct 20, 2015
7
22
3
Hi Jacob,

Superb (bis) ! Thanks for posting this.

Can I ask you a few questions ?

* What material did you use for the anchor pallets ?

* Did you use a sort of device (using the contol-circles) for grinding them ?

* You have (i.m.o.) a special longitudinal effect on the frame plates ("platines"). How did you make that ?

* The hands ? Are they made of titanium (if I see it right the blue is somewhat less intense, in comparison to blue-ed steel) ?

Hessel
The pallet are made from synthetic sapphire, I started with a 3mm thick disc. They were ground using a conventional lathe with a grinding attachment. I made simple fixtures to hold the stones by their inside and outside diameters and then ground the impulse planes using the pallet body as a holder.

The plates are just grained using a straight edge and 80 grit abrasive paper.

The hands are O1 tool steel, though they are brushed finish rather than polished before bluing. This gives them a little more subdued blue tone.
 

Jacob Curtis

Registered User
Oct 20, 2015
7
22
3
Jacob, could show/talk about the details of your pendulum design and the math behind it?
Thank you,
-Greg

The pendulum is based on the design by Wilding, it uses an Invar 36 rod (sourced from Eagle alloys) a 12L14 bob weighing approximately 18lbs and a brass compensating tube. The bob is supported at its midpoint by the compensation tube. With a known coefficient of expansion for the invar and the particular alloy of brass used you can calculate the length of the compensation tube.
 

John MacArthur

NAWCC Member
Feb 13, 2007
426
51
28
Taos, NM
laplaza.org
Country
Jacob - I am perplexed: in your picture of the pallets it appears as if you have two entry pallet nibs pointed in opposite directions. Is that just an optical illusion? Or was that a setup for a photo that wasn't the final orientation?
Johnny
 

Jacob Curtis

Registered User
Oct 20, 2015
7
22
3
Jacob - I am perplexed: in your picture of the pallets it appears as if you have two entry pallet nibs pointed in opposite directions. Is that just an optical illusion? Or was that a setup for a photo that wasn't the final orientation?
Johnny
Good catch, at that point just the inner and outer radiuses had been polished, the impulse planes were cut and polished at a later stage.
 

Christopher Doehlert

NAWCC Member
Jun 18, 2019
6
0
1
Lovely work.

Did you compute the pendulum sleeve length such that the top of the sleeve stays at a fixed distance from the pivot point?

Decades ago I made a similar clock when I attended the Bowman Technical school in Lancaster (before Lititz) and the sleeve was computed that way but the pendulum was not isochronous with respect to temperature change. I've come to the conclusion that's because the rest of the invar also expands, changing it's radius of gyration thus keeping the bob suspension point constant isn't sufficient.
 

svenedin

NAWCC Member
Jan 28, 2010
1,751
485
83
Surrey
Country
Region
Superb work. It reminds of the clocks by Erwin Sattler of Munich.
 

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