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Hello everyone,

I have 2 years ago bought a used upright Petrof 125, from Soviet era. I had a thread here about voicing before.

I have been slowly learning and regulating the piano on and off. Learning some new things, applying it, etc. Though it was better every time, it was never spot-on even.
Evenness was what I was looking for mostly and the piano being so old, without any parts changed, of course needed a very thorough regulation.

Let-off, capstans, key height, key-dip - I was going in circles

Then I came up with this idea, that worked perfectly for me and wanted to share it here, for the experienced people to criticize the approach, etc. However, the results are great and the piano is very well regulated now (not 100% perfect, but close :)).

So, my approach was to use the action geometry to my advantage. I thought that evenness will be perceptible, when the keys have the same feel, when pressed. So, my let off, may be 2 mm on two keys, but if one of the key travels to its let-off a bit faster than the other, then the feel wont be even.
Since the dip is 10 mm and the blow distance is 46mm, it means that every mm of a key travel results in 4.6mm of hammer travel. So if the key height is 0.1mm different, it will result in almost half a millimeter of hammer travel, which is perceptible.

So first, I levelled all keys with the ruler as perfect as I could. Then I adjusted the key dip, to exactly 10mm. For that I used the tool I made myself. I took a wine cork, which I cut at exactly at 10mm, made a hole in it. Then I would put it on top of the punching's, if the key dip were 10mm, the key would be level with other keys and would have no travel. If it was higher, i removed the punching's, if it was lower, I added the punching's. I adjusted every key to that.

Now when my height and dip were all very even throughout, I had to adjust capstans, let off, dampers and backchecks.

For those I used that idea that I wanted to share:
I took a wooden block (straight edge), that would cover 5 keys. I put the block on the keys and attached a clamp to it (between the block and the piano itself). Since the clamp had a screw, I could screw it slowly and those five hammers would rise slowly simultaneously. So, for adjusting the capstans, I screwed my clamp until the keys were halfway to the strings and adjusted the capstans, so that keys were in a straight line (because of 4.6 times multiplication, evening out at this stage is much more accurate, than evening out when keys are at rest).
Then I adjusted the let off by screwing the clamp further, so that keys hammers are 3mm away from the string and adjusted all the let off buttons to make the hammers drop there. All even throughout.
That I adjusted the damper spoons. I clamped until the hammers were 22mm from the strings. Adjusted the damper spoons, like you adjust the lost motion: slightly pressing the hammer and further to the strings from 22mm and making the dampers raise to the slightest touch.
The clamp worked greatly for that 3 adjustments. After all, we want to regulate not looking at the hammers only, but at the key dip. Everything should behave the same way when pressed down to 4mm, 5mm and so on until the dip (10mm).

I am very happy with the results and the piano is very well regulated.
The only thing that could be further perfected are backchecks and damper spoons, since they are not on screws and are difficult to adjust.

P.S. when will piano makers make life easier and come up with backchecks and damper spoons that can be regulated with screws?

And what about aftertouch?


Never of course.

Forgot to mention that. This has been also regulated, clamp all the way down. A further press on the key gave a slight raise to the hammer. This was adjusted by touch.
Hey, what about your project?

I read your post again and probably I don't understand what you are doing. If you are regulating hammer distance from strings using capstans at some predetermined key depth, how your lost motion is regulated?

And for my project I right now building something like this for lifting and lowering the plate https://imgur.com/a/C1M1xZj with manual wormgear winch, probably overkill
I also want to practice my damper regulating skill before that a little.

Capstans are regulated when the keys are halfway in their travel, let's say 5mm into the key. I do not leave any lost motion.
Capstans are first regulated in straight line, so that there is no lost motion. Then they are micro-regulated when they are pressed together, that did not affect the lost motion at all because the adjustments required where very tiny.

Oh wow, that's a project within the project

Damper regulation in upright is very difficult, bending the spoons just the right amount is very difficult. Have not tried it on a grand.

Another idea that I have for damper regulation for an upright to get them perfect (but have not bothered to do it):
you place a weight on the key, let's say 50g. The key only goes down until it meets a damper spoon, can not get past that without you pushing the pedal. Than you regulate the damper spoon, until that weight gets your hammer at desired distance from the string (say 22mm). Than you repeat this for all the keys. I would have done it, but every key needed multiple attempts, plus taking an action out every time to access the spoon and I did not bother that much.

But how it comes that when keys are at rest and hammers are at rest (rail ) lost motion is correct? Lets say that for correct lost motion you need hammers to be exactly 20mm from string when key is at exactly 5mm depth, if you would set hammers to 19mm which can happen by mistake, there wil be zero lost motion and hammer will be sitting on jack instead on rest rail, and all of this is assuming exac same action ratio for all keys which isn't true most of the time.



It is constantly like that, I constantly making new tools to make work easier and better, I think many techs can relate.
It's projectception.

This is correct way to regulate dampers, you just need a tool for regulating spoons with action inside the piano



Damper regulation in grands is a different animal, but similarly frustrating.

I can not explain that well or I might be doing it wrong.
I took out the rail first and regulated some hammer capstans, just a bit longer that when they are at rest rail. Let's say, hammers at rail where 45.6mm from the string. I regulated the capstans so the hammers were 46mm from the strings (they were resting on the jack). Than I regulated all capstans (still without the rail) in one straight line. Then the rail is attached back and everything is pushed 0.4mm (so almost not at all) - there is a very slight lost motion. Than I reregulate the capstan when the keys are pressed (5 at times). And when they are pressed let's say to the half, I do not reregulate all capstans by measuring their distance (I do not measure at all), I just reregulate the ones that are out of line a bit. In other words, in the travel any tiny imperfection of capstan regulation that I had during initial regulation is multiplied, so I can see better and regulate more perfectly. This adjustments are so tiny, that they do not almost change the hammer position at rest, at least its not perceptible by touch. However, now the keys travel exactly the same way, they all hit the strings the same time.

I do have that: the only instrument I bought with the tuning lever. But could not make it work easily - too clumsy. I preferred to remove the action and adjust them with small pliers from the back side.

I have never gotten a damper regulator tool to work. So I adjust the spoons so the dampers lift early, and then press on the top of the lever as I press the key so that the spoon bends and the damper lifts at the proper time.

I have the same piano since last year, I am actually quite satisfied in general except the motion is a little bit weak. maybe I will follow your regulations one day. Thank you very much for sharing!

It works if all bend and slot angles and slot width match particular piano, but I agree it isn't a great tool.

Thanks!

what do you mean by motion?

Try it, but in my particular upright (calisia) it wouldn't work, spoons are too stiff, probably because they are very short, so don't break anything

95% of the time, same here

I mean the keys are ok for trills but they don’t go back fast enough.....
I mean compared to more recent pianos.

Tried and did not work for me. Probably the spoons are too strong and short.

You have to push hard, and hold the damper lever firmly.

I will often swivel the action back a few inches and hold the bottom of the lever if the spoons are short and stiff.