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Koma standard

Dells

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Oct 18, 2019
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Hi all
I have had this koma for about 40 years and a few months ago I stripped cleaned and repaired the barrel because of a bulge and as the mainspring had two cracks in it fitted a new mainspring, although it had been running each time I had to regulate it it would stop and take a few tries to get it running again but this last time it would not keep running so I thought I had better have a look .
The first thing I have done is to remove everything of the front and see if it would run and it does, so I had a look in the 400 day book because there is an exploded diagram of the very clock and it only shows one flat washer on the centre arbor but I have the flat washer and the cup washer , so as I had put it back together originally exactly as I had taken it apart I am wondering if someone before me had added the washer or would it have been there from new, does anyone know what is correct?
Dell
 

tracerjack

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Jun 6, 2016
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Dells, you need to be more specific about which Koma standard you have, plate #? or a photos?
 

Dells

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Oct 18, 2019
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Sorry I had the picture ready to add but forgot to add it , it’s an age thing, plate number 1393A
5E5238FC-7768-416A-A17B-1496AE11A2FA.jpeg
 

Dells

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Oct 18, 2019
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Well without the hands or motion work it runs fine so either there is a problem in the motion work or something in the movement is robbing power so I will take movement apart to check that first.
 

Dells

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Oct 18, 2019
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I can’t understand what the problem could be as I put everything back together including motion works and hands but without the cock and anchor and 4 clicks on mainspring and away goes the escape wheel so it’s not lacking power, tried moving fork down and up checked fork gap and it’s definitely in beat.
So if anyone has any suggestions as to what the problem could be it would be much appreciated.
Dell
 

KurtinSA

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Nov 24, 2014
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Locks and drops OK? What about the pivot holes...any extra wear there? With power completely removed, use your finger to turn one of the lower wheels back and forth...do you see any of the pivots jumping side to side in their holes?

Kurt
 

Dells

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Oct 18, 2019
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Hi Kurt
Yes I have checked all that this morning, stripped it checked everything I could think of and rebuilt it, it seems strange that when I put 4 clicks on the mainspring the escape wheel and hands fly round, to me that points to the fork although I haven’t had a look at the frork under magnifying glass I will have a look just in case it has a burr.
Dell
 

KurtinSA

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Nov 24, 2014
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I've discussed the "2-click" test like you mention with a friend...I do it as well and have always used that as a test in overhaul to proceed with things. It's been mentioned that might be a bit misleading as it doesn't really put all the load on the arbor. When you get full power on the train, there are forces which not only turn each arbor but also push them away from each other and this puts extra force on sides of the holes in the plates. Over time, the holes can wear and if enough, then there could be a meshing problem from wheel to arbor. When I am testing successive arbors in the movement, I try and put a little load on the arbor towards to next arbor to see if there's any issues. Not sure if I'm doing it right, but so far I haven't felt anything unusual.

One thing that I've felt with using my smoothing broaches on the holes is if the turning of the broach is either smooth or jerky in feeling. If there is a jerkiness, that almost certainly is due to the fact that the hole is not circular but a bit oblong...if bad enough it might need a bushing.

I guess what I'm saying...and now learning...is that just because a "test" has been performed and "passed" it, doesn't mean that you can eliminate that from any future problems with the clock. One thing I'm trying to judge in my overhauls, is that if I can set the beat, wind the clock to half power, and turn the pendulum so that an escape wheel tooth just falls off the pallet, then if the rotation increases over a short period of time that is a strong indication there is sufficient power to run. If the clock won't run at half power, I have to relook at the work.

Kurt
 
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Dells

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Oct 18, 2019
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I was told when checking for bush wear that you put gentle push on arbor then rock previous wheel then put gentle pull on arbor and rock previous wheel , I have done that and can see or feel no play ( if play present you should be able to feel difference) told this by someone who works in a museum, but what you say makes sense.
Dell
 

Wayne A

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Sep 24, 2019
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Fork and pin contact points are often a problem because its a sliding contact point and any small friction robs power. I polish the fork so its smooth under high magnification and polish the pin as well. Check for clearance at extents of rotation since binding often occurs there when its fine in the center of rotation.
 
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Dells

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Oct 18, 2019
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Hi Wayne
There was a slight burr on fork when I had a look through a loope that I removed with 1200 then 2000 and a small piece of paper just slides between fork and pin at full left and right.
Dell
 

Wayne A

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Sep 24, 2019
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Hi Wayne
There was a slight burr on fork when I had a look through a loope that I removed with 1200 then 2000 and a small piece of paper just slides between fork and pin at full left and right.
Dell
The burr might be all it takes to get it going. After the 2000 I hit the fork with simichrome and dremel polish wheel for a mirror finish.

Wayne
 
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