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Hello friends!
Here is all I have recovered:

Maker: H. Kriebel, Berlin
Action maker: Lexon, Berlin

Hammer bore (from bass to treble):
First section: 49 to 47mm
Second section : 41mm
Third section: 41 to 42mm
Fourth section: 42 to 45mm

Knuckles:
Height: 9,5/10mm
Distance to center pin: 18mm
Distance to hammer head: 112mm

Key ratio:
From top of key front to balance rail: 225mm
From balance rail to capstan tip: 115mm

Spread: 112/113mm

Look at the pictures.
Drop screws are also out of range. And is imposible to adjust drop to 3mm from string, for example. Repetition lever hits against hammer flange!! Aftertouch? Nothing! t
Remember: I adjusted key dip to 10mm and hammer blow to 45mm
I begin to think that complete action is to much far from strings...

Enjoy this piano-puzzle!!! THANKS to all you!!!

PD: I couldn´t upload the photos. And I do read FAQ seccion. I´ll try later.

Knuckle is far from center pin, often goes with large spreads as 114 115 mm even 116 (Förster grands, with their 18mm knucke to center dimension, can have 11 mm key dip and 116 mm spread)

The pics should say what is going on better

Very short hammer bore, do you have the string's plane height ? hammer bore is of no value without hammer center height and string's height, they are by evidence very short (45 mm is YET a short bore)

Actions with so short bore should work fine , assuming it is coherent with hammer center height and string's height.

18 mm from the center is really rare, you may need 10,5 mm key dip, have a look at the sharps to white relation, at 10 mm, if your sharps are too high when they are at full dip you can believe that the keyboard need more key dip.

You have a relatively small Key ratio, at 1.95 (but accepteable) 2.03 is considered good for Renner action (why 0,03 ?)

there are mismatched parts somewhere. how did you install the jack to knuckle line ?

change the 16mm shanks on Steinways an you will need thicker letoff buttons

Reblitz cannot help on grand regulation, not really...

On some old pianos, the action brackets are made of an alloy that changes dimensions. This could be the case or the brackets may have been replaced with the wrong size.

An experienced tech would cast an experienced eye over the action and look for new parts and go through a process of elimination. An example being, do the ends of the keys lift the dampers at a reasonably appropriate time? Initial contact at around 1/3 key travel. Does any part look newer? Tell tale signs are, the color of the wood and metal parts, different looking glue joints at the hammers and the trimming of the hammer shank behind the hammer.

If the hammers have not been shaped, you will see the string marks more towards the back of the centre of the tip of the hammer if the hamers are bored too short. This would also happen if the hammers are excessively worn.

How do the notes at the extremes of the action regulate?, there is often far less wear there.

You will most likely find a pencil line on the side of a hammer core at the end of a section that is on centre going through the core tip and extending to the strike point on the felt. Itf not, draw one or imagine oneThis should form a right angle to the strings when the hammer touches the strings unless the original hammers were raked and have been replaced with standard stock. .

I could go on like this for ever. Time for someone else to take over.

The hammer bore varies a lot, which would indicate that the hammers have worn and were filed unevenly. Usually there are only two bore lengths on a cross-strung, for the bass notes and for the treble notes.

sorry but no again , all depends but on most well build old grands the bore follows the string "plane (which is all but plane most often, plus jumps at the break between agrafes and capodastro...)

differences as large a 5-6 mm can be find, but most offten it is in the 2-3 mm range.

other brands consider that the action will accept a < 3mm difference in string height and use a medium dimension, based on the high/medium string's height.

then note 88 you can find some "undercentering", but generally as the medium hammers are bored 3 mm less than the usual distance this sort of auto correct- the higher hammers will be bored 90° then, while the medium ones are 91°

not easy to do so when boring, but it is good to be attentive to that.


good tip from RXD with the action brackets in "zamac" or soft alloy

Here you have a link to the photos
Piano Photos
Now we have to wait some time for me to go and take more measures.
Diference between strings height and shank center pins must be somewhat equal to hammer bore, isn´t it?
Continued later. THANKS!!!

Oh, really? Name one make of piano where the bore changes other than at the bass break!

Nevermind BDB, many European grands (special mention to Bechstein)..

The plates where way less straight beforethen, actually Bechstein still does.

The jump between agrafes and capo is also common, of course today those parameters are more under control (particularely with vacuumed plates, on a Yamaha if you have 200 mm string's height you have them all along.

Steinway have a flexible frame and a crowned keybed, that goes in direction of correction, but I have seen some (very rare) with hammer bore tweaked (at the factory I suppose )

Generally speaking it is just considered normal setup to have the hammer shanks at the same orientation at letoff moment , and hammer centers lining. only the hammer bore allows this (plus little cheats on stack positionning)

"Tolerance" of the action is about 3mm, some sections being more sensitive to bore than others.

Bechstein does not alter their bore distance. Neither do Bösendorfer nor Blüthner.

Had a look at the photos. In the hammer close up photo #10 it shows a lot of material has been used up off that hammer set. The strike point is missing more that 50% of the original felt material.

Proper regulation cannot be completed; you will have to leave some of the tolerances wide unless the hammer set is changed out.

Shaping this hammer set will make the measurements even wider.

I am wondering if there are shims underneath the action brackets to compensate for hammer wear....

Bdb , I am not there to change your mind. For Bluethner I agree, not for Boesen nor Bechstein (factory sheet for a very recent grand in hand) strings height are took in consideration and that is why.

Not an absolute necessity however, just a way to deal with the plate shape.. Section by section.

As I understand it, Bechstein machines their V-bars as well as their agraffe section with CNC machines to ensure the string height is perfectly even everywhere. I learned this from a Bechstein rep. very recently.

Even if it were the case that some manufacturers change the bore distance, which is expensive and wasteful, and offers no benefit, it is hardly common practice, and definitely not pertinent to this particular piano. I am trying to give basic information to someone who is struggling to get help in a remote part of the world, and I do not think that it is something that should have been brought up. It is just confusing to someone who needs help.

What is the most practical way to measure string plane heigth and hammer center pin heigth?

How much is too high for the sharps at full dip? I remember about 1 or 2 mm over white tops.

I aligned rear face of jacks, with tip and wood core of knuckles.

First sentence: this is also related to individual damper lever adjustment, isn't it?

Second: Right now I can't tell you. Sorry.

Third: I will look for this next time I see the piano.

Fourth: Surely hammers were replaced. I saw some carelessness at the joint with shanks.

Thank you, rxd!

They look like original hammers. They have probably been filed once or twice, and have worn a lot since then. This would explain why the hammers are longer at the top and bottom notes, and shorter in between, where most of the wear would have taken place. I would not be surprised if the piano is at least 100 years old. Some of the hammers may have come loose and were reglued, and that may not be as neat as a new installation would be.

I think you need to take Dan Silverwood's advice to heart: Unless the hammers are replaced, and they would undoubtedly have to be bored much longer than the existing hammers, this action is not going to regulate properly.

There are things that you might do that could ease the problem, but you should not do anything that will cause problems if the owner might get new hammers later. But the safest bet would be to regulate the piano so that the let-off of all of the hammers are the same as the hammer that has the greatest let-off, and adjust the drop accordingly.

I would recommend starting with the keyboard, and setting the key dip over the front rail pin to 10mm, and the sharps 12 mm above the white keys measured at the same point. Set the let-off as described, set the drop 1.5-2.0 mm below that, and see how the backchecks work the best.

Hello Silverwood!
Is this always so? When one have hammer felts 50% used, is no more posible normal regulation?
Which tolerances are you refering to?

Actually, action brackets are INSERTED in the key frame. I can't realize if this is original or not. What do you mean it would happen if there were shims under the action brackets?
One of the photos shows the distance between action top and pin block. Does it looks ok?
Do you think I can inprove global regulation making some changes on bracket support heigth on that piano?

Thanks!!

Well, I saw same empty space between hammer hole and shank end, revealing that the shank was rudely sanded before gluing. That"s why I think are not original.
Changing hammers is like an odyssey to me! Starting on how to acquire them, how to do trans-national payment, and so on...Not imposible, but...Also, I am sure the owner don't want going so far. What she is actually asking for, is good repetition. Do you think we can get it, doing regulations as you described? What about hammer stroke? 45mm or more?
Do you say 10mm key dip over front pin line, instead of over key front line?
And about sharps, I don't understand what you mean. Excuse me!!
THANKS!!!!

You are not going to get the best repetition possible, but you should be able to get it fairly even.

The hammer blow distance should be set so that you have an aftertouch about the thickness of a coin. With the let-off set low, it may have to be set with a bit more aftertouch than ideal.

Over the front rail pin is one place key dip is measured. The key front is another, but it does not translate well to sharps, while the front rail pin works for both. The difference is small. You could adjust for it if you like, by reducing the dip a bit, say, half a millimeter.

Hello sorry for the OP, they certainly do the difference in height is small, and hammer bore adjusted to the half mm level, then backchecks height as well - anyway that was the case in 2011.

Due to grey iron casting they probably cannot obtain more than a certain level. Possibly it is also simply left because of the soundboard shape.

Pianosur I did not see the pics yet but the strings height at each section is necessary, as the hammer scenter height note 1 and 88 (taken from the keybed, so the action on a flat bench, or by measuring all single heights and adding them)

10 mm is a standard dimension for modern pianos, yours can have 11 mm key dip but you may be able to discover that by yourself by deduction with keys level, mortise position vs the front pin (and balance pin) level of the keys with 10 or 11 mm dip (to be checked with a small bubble jauge)