Anybody have any idea how much the end of a bass string winding will move towards the agraffe from tuning? How much closer to the agraffe will the winding be, say, over 10 tunings?

Thanks

Just from observation - A new string moves about a quarter inch in the pull-up to working tension. After that it may move, but it's not noticeable.

It wouldn't be too hard to measure if you install a new string, then take measurements with a good caliper.

Thanks David, but I'm most interested in movement over time, after initial installation, PR and tunings.

In observing the Shout House pianos, which are tuned weekly, I really don't see any discernible movement of the windings, once they're up to pitch. I would think, after 50 tunings or so, if they'd move, I'd see it.

There have been a couple of cases where improper replacements had the windings extremely close to the agraffe once it was up to pitch, like less than 1/8", and they never really moved closer.

Hi Eric,

I am stating one experience because this one really stands out.

About 15 years ago, I replaced the bass wires on a 9' Bose. I ordered them direclty from Bose. EXPENSIVE!!! Anyway, when I first put them on the pointed ends of the coils were about 1/4" from the agraffe after it was up to pitch.

Over time, probably the first few years or so, I really didn't keep a record of it, I noticed the windings ever so slowly creeping toward the agraffe. The strings were stretching, I'd raise them up to pitch, stretch them gently, raise them again etc., but even after I finished with the stretching, they continued to go flat for a good 3 or 4 years give or take.. Like I said, I wasn't keeping a record of it.

After about 5-7 years, (I'm guessing) the pointed ends of the wrappings were darn near into the agraffes where they have remained ever since. After they got to that point of being nearly into the agraffes it stopped and that is where they remain. I was surprised at how much they moved over that amount of time. I do worry if they get any closer, they will jam in there and something is bound to give but, it appears they have settled where they are now.

I can't say as if I recall noticing that much movement with other replacement wires or with exsisting ones. But then, I've not paid much attention to it either. It's something we take for granted I think.

The idea of strings stretching has been discussed a lot. As I now understand it, the material itself does not creep. Creeping or permanent stretch would mean that the material has exceeded its yield point or elastic limit. This point is substantially above the string tension at pitch.

What can be seen (or heard as new strings "settle in") is not the strings stretching per se, but rather the wire complying to the bends at the hitch pins, bridge pins, front bearing, tuning pin coils etc. After a few years, this process more or less comes to a halt. Frequent tuning helps. as we all know. In the case of the Bosie bass strings, I would suggest that the hitch pin loop twists were slowly tightening. They were probably a bit on the loose side. This is very difficult to see unless it is very extreme.

Hmmm. Very interesting Jurgen. Something I had not thought of or considered! Excellent thought! I'll be you are right!

Thanks for these responses. I have a client with a new high quality piano on which the windings are, as Jerry referred to, pretty darn near the agraffes. The piano is at pitch and stable and I've never really even thought about such issues before. However as technicians we are usually raising the pitch of a string which means twisting the string clockwise. My understanding has always been that one of the things we do when we tune is to compensate for the slow, gradual stretching of the wire. When the elastic limit is reached, time to replace.

Again, normally I wouldn't give it a thought but in this case I'm trying to decide if this is going to be a problem sometime in the future or not.

If they are doing what Jurgen suggests then possibly, ---probably--- after a given period of time, it will tighten up enough and stop moving like mine did. I don't have any more room for them to move more. So long as they remain where they are, I'm okay and so is the piano and tone of the wires. The piano tunes fine.

The reason I replaced them in the first place was due to wires breaking. None have broken since then knock on wood!

Do you recall if the strings originally broke at the winding?

I agree with Jurgen in regards to the perception of stretching really being a byproduct of the string better conforming to its friction points and attachment at the tuning pin. Years ago on a string replacement, I found continuous drops in pitch for up to a year or so whenever I returned to tune. I now very carefully over bend hitch pin attachments and other points and massage them back to what I consider a very neutral shape when I pull the string up to pitch. I will then work the tuning pin and string back and forth a few times to better form the tiny radius' at these points and lastly, I double check that the coils are extremely snug from below, then tapping down the first coil from the becket to close it up some more. The difference in stability is like night and day. The pianos reach a stable point in a fraction of the time compared to how I used to do it.

Some of them were breaking down at the hitch pins. Others were breaking at the agraffes and some at the tuning pin. I figured it was string fatigue seeing as how there we so many beginning to break and they were breaking in so many different places.

I think that sometimes there are just bad batches of music wire which is not tempered properly, and they will break no matter what. It could even be a bad section in a coil.

This was the common understanding until recently. We all thought so (royal we).
The elastic limit of string wire is somewhere around 125% to 250% of the tension of a string at pitch, depending on where in the scale you measure. In normal use or service a string should not reach that high tension. Below that elastic limit, aka yield point, the material will stretch under tension, but not deform, i.e. when the tension is released the string will shrink back to its original state. It is not a question of a string at pitch slowly creeping for X amount of years until it wears out.

Building on what Keith suggests: Try this - on a newly restrung piano (in your shop because only then do you know what work has been done to "settle" the strings) which you consider ready to go (tuned to pitch etc). Take some smooth jawed duckbill pliers and grab a random coil from the top. Squeeze hard and turn in direction of the coil, as if you were trying to tighten it. (You actually are.) Repeat two or three times. Check the pitch of that string - it will have dropped almost a semi tone! If left undone, this semi-tone of pitch drop will happen slowly, over a few years. The string is not stretching, it is conforming to the bends around the tuning pin.

One more piece of evidence: softer string wires such as Pure Sound etc. stabilize within six months or so. Why? Because that wire doesn't resist bending and conforming to the plate contours as much as the spring steel wire commonly used.

If the crown on the soundboard collapses over time, wouldn't it have the same effect on the apparent length of the string? In which case the change in the string would have nothing to do with the apparent lengthening. Trying to figure out the math on this... I know it involves Tangent. Will get my son on it right away.