Konrad Mauch (KOMA) slowing problem

spiderbobr

Registered User
Apr 1, 2021
8
1
3
74
Country
Doing a restoration of this clock that had been stored for 30 to 35 years. It was bought about 1955 one owner. To start, it is a plate 1395 4 ball pendulum. I have done a full overall and inspection of the movement. Complete tear down, cleaning and polishing everything, plates, pivots, bushings, gears, pallets (did not remove pallets from escape) and all the rest of related parts. I then checked all arbors for straightness, the only gear out in the slightest was the minute arbor by .0015 now sitting at .0005. All escape teeth are good all equal size, and ready to be re-installed. Parts that I replaced are the mainspring with a new 20 x 38 and a new complete unit suspension spring SU Unit 13c at .0033 both from Horolovar. Put it back together, checked before escape arbor to make sure all movement was good with the gear train and it was. Added escape and hand checked drop and lock with a slight winding of the spring, all good. Added the rest of the components and put it in beat. Started the test period and after running for a day I noted that the amplitude of the pendulum was changing as much as 50 degrees within an hour. So I sat down and every 5 minutes noted where the pendulum was on the scale I laid out on the base. Note picture of what I found. This continued exactly the same for the two hours I watched it (I'm actually kind of patient). My thought was there is a lose of power at the same time every hour. Must be the motion works (I'm thinking) so I remove the hour hand and set it to run again. It got much better, now there is only a difference of about 20 degrees in the hour. So I remove the motion works completely. I has been running for a full week at a whooping 375 degrees both clockwise and counter clockwise and very strong. So I put it all back together and the same thing, but while watching it this time, I noted a ⅛" space that the hour wheel can move in and out freely on it's axle screw. Can't figure if that has anything to do with it but it is the only thing so far that I've come up with. Another thought I'm wondering if there was a washer there under the secure mounted wheel to the front place to take up this space but I don't see that on any drawings? I'm at a loss, if anyone has any suggestions I would be happy to check them out. Another odd thing, under the hand nut was two (2) concave hand washers. If I remove one, it does not get tight enough to lock the minute had into the motion works. There is no face plate binding either also notable on the picture.

IMG_7443.jpeg IMG_7472.jpeg
 

KurtinSA

NAWCC Member
Nov 24, 2014
4,389
274
83
San Antonio, TX
Country
Region
Welcome to the message board! As for the minute hand clutch and washers, as long as you have enough tension to hold the minute hand in position all the way around the dial and you can still reasonably move the hand with your finger, then I think you have things correct.

It appears that your power issue is when trying to raise the minute hand. That is quite normal although I've never measured the change in rotation. Note that it's not really about the rotation, but do you have enough over swing as you lose the rotation? You need sufficient over swing in order to sustain the running clock due to variations in the escapement and the need for power to raise the hand. What kind of over swing do you have?

As another test for sufficient power, I usually leave the motion works and hands off and wind the clock to roughly 50%. Then I rotate the pendulum until a tooth drops, maybe a little bit more, then let the pendulum go. If the pendulum gains in rotation and over swing, that's a good sign of sufficient power. I repeat the trial with the motion works and hands. If it runs then for multiple hours, then I consider the clock "done" and do the final oiling and assembly.

Kurt
 

spiderbobr

Registered User
Apr 1, 2021
8
1
3
74
Country
Good point Kurt, I'll check the overswing as I have not done that sense the first time this started happening and at that time I had between ½ and ¾" on one side and ¾" to 1" on the CCW side, (but my diagram on the base could have been slightly to one side giving me the different overswing readings) I have not tried rotating the pendulum until the tooth drops, I 'll try that tonight as well. Thank you
 

Wayne A

NAWCC Member
Sep 24, 2019
674
107
43
Country
Region
I like the chart, and what you found is fairly normal with 400 day clocks unless they have very tiny or ballanced hands. These clocks are very low powered and the extra force to move the hands up the hill must come from somewhere and its as you see in the rotation change. As Kurt mentioned you must have enough over swing for the clock at the highest load area, say 9:45ish.

Its one of things that make setting 400 day clocks with instruments a little difficult because there not the most synchronous clocks out there. I can dial them in fast with a counter but the rate just varies as the day goes by. So you have to tweak these after letting them run a day or weeks to average out the varibility. They can keep very good time though once set.
 

spiderbobr

Registered User
Apr 1, 2021
8
1
3
74
Country
Thanks Wayne, I did a bit more tweaking and got a bit more overswing than before. When I checked I didn't have as much as I had thought in the last post I made. I have this time reattached the motion work and the minute hand to see what I can get, and it has more amplitude already than in my tests shown. Have to wait a while to see the upswing of the hand.
 

Schatznut

NAWCC Member
Sep 26, 2020
305
133
43
SoCal
Country
Region
The Konrad Mauch standard-sized clocks are exceptionally sensitive to the tension on the hand nut. It must be only tight enough to retain the minute hand. Any tighter and it can result in the clock stalling. The clock that got me started on this whole clock repair madness is a Konrad Mauch my grandfather gave to my grandmother as an anniversary gift in 1950. It didn't work, so I fixed it, and I fixed it and I fixed it again until I learned about this sensitivity of the hand nut tension. It runs perfectly, keeps good time and has over 360 degrees of rotation. Unless I get that hand nut ever so slightly too tight...
 

spiderbobr

Registered User
Apr 1, 2021
8
1
3
74
Country
Yes, I have heard and read about the sensitivity of the hand tightness. Good point to make Schatznut. For the last few hours of running, I've been losing only 25 degrees of amplitude, it's been right at a maximum of 375 and a minimum (with the hands going uphill) of 350, in either direction. I'll check it again tomorrow and am hoping it's still running at the same rates, or at this point running. I'm going to give it through the weekend and first of next week remove the hands again and put the face back on.
 

KurtinSA

NAWCC Member
Nov 24, 2014
4,389
274
83
San Antonio, TX
Country
Region
So what is the over swing?

I suspect that the way a tight hand nut stops a clock is that the hand nut actually deforms the cannon pinion such that it adversely contacts the hour pipe. Seems like this situation would also be the case with any clock. My way of thinking is that the cannon pinion can be glued to the minute arbor and the clock would still run...you just wouldn't be able to move the hands to set the time. So the hand nut...or taper pin...needs to be sufficient to keep the hand from falling by it's own weight but not so tight as to tight as to make it difficult to turn the hand.

The hand nut or the taper pin have pros and cons. I like the hand nut because when I drop it on the floor, I can still find it! It's easier to put on. But it's a PITA when you move the minute hand CCW and you loose all your tension. :banghead: Taper pins are difficult to get on, sometimes needing a third hand, and if the stack up of tension washers is correct, moving the hand backward or forward is a breeze!

Kurt
 

spiderbobr

Registered User
Apr 1, 2021
8
1
3
74
Country
Kurt, that is an interesting view :) Oh, I just went out to the my shop and it is still running strong. I'm still going to wait a day or so before I put the fact back on.

Overswing - is ¾" measure in a straight line on my bottom paper gauge. both CW / CCW.
 

KurtinSA

NAWCC Member
Nov 24, 2014
4,389
274
83
San Antonio, TX
Country
Region
I can't really see what 3/4" is...can you convert that to degrees? You can visually see what 90 is and then cut that in half to 45...that's easy enough to make out...can estimate smaller amounts from there.

Kurt
 

spiderbobr

Registered User
Apr 1, 2021
8
1
3
74
Country
Sure, from the picture I'm looking at 90 at the point I added pallet drops 4 marks from center or 27 degrees from center. Full swing of pendulum is 380°

So looking at the two pictures, where the ball support shows is its full swing in both directions making it just a bout 380 degrees, where the pallet is dropping is on the 4th line from my center point making them both about 27 degrees from center. I measured from center point to pallet drop, which is ¾" or about 32 degrees

IMG_7478.jpeg IMG_7479.jpeg
 

spiderbobr

Registered User
Apr 1, 2021
8
1
3
74
Country
Just had to share this bit of information, as I wrote all the pendulum amplitudes down again (as I did the first post) and made the graft. The green was the first as I was trying to explain my problem, the blue is from today after some tweaking was done over the last few days.

IMG_7480.jpeg
 

spiderbobr

Registered User
Apr 1, 2021
8
1
3
74
Country
Thought I would come back and give the results, it's now been over a month (only by a day) and I have lost one minute. I'm not trying to do any better than that as I feel good to get it that close. I actually prefer the slower mode than faster, as it is easier to move the hand one minute ahead than taking the chance of going backwards and loosening the hand nut. I suppose I could just stop the clock and start again, but it works where I am happy with it.
 
  • Like
Reactions: Wayne A

Forum statistics

Threads
166,141
Messages
1,447,312
Members
86,684
Latest member
ds23pallas
Encyclopedia Pages
1,101
Total wiki contributions
2,883
Last edit
E. Howard & Co. by Clint Geller