30 Day New Haven Movement Mainsprings

Laurie Kimble

Registered User
Jan 30, 2011
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A New Haven 'Columbia' wall clock with a 30 day movement came into the shop. Its the NH movement that says 'Patented in England' and has the double wheel on the motion works. Upon disassembly I have discovered that the two mainsprings are different. One is .0185 and the other is .0165. Both are 3/4" x 96" long.

Anybody have any ideas as to which is the correct mainspring size? I would think they would both be the same but please correct me if I am wrong.

I have attached pictures - all are taken before movement overhaul.

DSCN7886.JPG DSCN7888.JPG DSCN7889.JPG DSCN7890.JPG DSCN7891.JPG
 

Dick Feldman

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Sep 1, 2000
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Ninety-six inch length springs sound to me like 8 day springs. You will never get 30 day run time from those springs in that clock.
In that application, I doubt if you will notice the difference between .0185" and .0165" thick springs.
Either will operate well.
A bigger factor with that clock movement will be solving wear and thereby reducing friction.
JMHO
Dick
 

Laurie Kimble

Registered User
Jan 30, 2011
65
10
8
Ninety-six inch length springs sound to me like 8 day springs. You will never get 30 day run time from those springs in that clock.
In that application, I doubt if you will notice the difference between .0185" and .0165" thick springs.
Either will operate well.
A bigger factor with that clock movement will be solving wear and thereby reducing friction.
JMHO
Dick
You are right Dick - the springs are 108" long not 96" as I previously stated. My bad!

I looked in Dick Swan's book at a New Haven 30 day Willard style Banjo and he lists the mainspring at .024" That seems really heavy to me. I also looked at Tran du Luy's ST book and there the 30 day #86 movements are listed at 108" and .015 thickness.

Both springs are in very good condition. My concern is mainly the difference in strength between them and how it will affect the running of the movement. And I was wondering which spring was the correct one - the lighter (.0165) or the heavier (.0185).

The movement shows very little wear. Only 2 bushings were needed.
 

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