Original Message:
Sent: 06-28-2025 13:47
From: Roger Gable
Subject: Repeated String Breakage Yamaha C7X
- A number of years back (1970's) I owned a Yamaha C7 (7'4") where the capo/string buzz was becoming intolerable. Being mildly educated in metallurgy I knew that heating the capo to the temperature needed to re-format the hardness would be extremely risky. Heating cast iron is susceptible to breakage, due to the fact that heating in one area causes the metal to expansion disproportionately as a whole -- hence cracking. It is common knowledge that as metals cool, the outer surfaces cool faster. The faster the cooling process the harder the surface area. I remember visiting a manufacturing company that made large gears in transmissions used in cargo ships propulsion systems. As I was watching the gears being removed from the casting, a worker used a gas torch to apply heat to the outer edges of the teeth to slow down the cooling process. That prevented the teeth from becoming too hard and brittle. That is the case with piano plates. The rate of cooling of the capo will determine the hardness of the surface. Fortunately, in our case with capo hardness, as with any metal, that hardness is "skin" deep. The better, and safer, alternative is to grind the capo down past the outer hard surface with a die grinder. That process poses its own problems as the depth can be difficult to control resulting in different hardnesses throughout the capo. I'm not advocating anyone approach this process impetuously as there are many variables. Fortunately, using a die grinder on Yamaha pianos is relatively easy as you can remove the keybed and approach your work without much physical hinderance.
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Roger Gable RPT
Gable Piano
Everett WA
(425) 252-5000
Original Message:
Sent: 06-28-2025 12:30
From: Garret Traylor
Subject: Repeated String Breakage Yamaha C7X
So heating the area to a "dull red" in daylight would be conceivable?
I wonder if the iron can be aneled at a lower temperature or would it have to be at around this 800°
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Garret Traylor
Trinity NC
(336) 887-4266
Original Message:
Sent: 06-27-2025 19:30
From: Parker Leigh
Subject: Repeated String Breakage Yamaha C7X
You would need to pre-heat the plate to 800 degrees F and cool very slowly. Otherwise you risk cracking the plate.
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Parker Leigh RPT
Winchester VA
(540) 722-3865
Original Message:
Sent: 06-27-2025 16:37
From: Garret Traylor
Subject: Repeated String Breakage Yamaha C7X
Quite some time age when Ron Overs first brought his piano to convention, I seem to remember that there was a recipe for heat treating the capo bar to alleviate work hardening. Has this concept been able to be tested out? I surmise that this would have to be performed while the plate is out of the piano and before finishing. The process would require a series of torch tips ove the area at one time to bring up the temperature to a light cherry red and allowed to cool ... by air, by quenching I have not been able to determine.
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Garret Traylor
Trinity NC
(336) 887-4266
Original Message:
Sent: 06-27-2025 10:59
From: Don Mannino
Subject: Repeated String Breakage Yamaha C7X
The contact surface should be shaped something like a half round rod. If the width of a half round is 4mm, that equals a radius of 2mm
2mm to 3mm is considered a good size from treble string contact, but for me smaller is better - unless the iron is super hardened.
Don Mannino
Original Message:
Sent: 6/27/2025 10:49:00 AM
From: John Pope
Subject: RE: Repeated String Breakage Yamaha C7X
"If the width of the V is around 4mm, that is a 2mm radius which is good."
Don, by "width of the V", do you mean the width of the surface of the V that contacts the string?
Thanks much,
John Pope
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John Pope
University of Kentucky School of Music
Lexington, KY
Original Message:
Sent: 06-25-2025 23:56
From: Don Mannino
Subject: Repeated String Breakage Yamaha C7X
Teri,
A few thoughts:
-
Yamaha capo bars are sometimes VERY hard. They heat treat them to the point where they are hard to file them! So the in those pianos the strings don't dig into the V, but the hardness can contribute to the wire weakening.
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A smaller radius on the contact area actually encourages the pivoting action of the wire during hard playing. This slightly reduces metal fatigue. So if you are replacing the wire in the affected area, check the radius of the V-bar underneath. If the width of the V is around 4mm, that is a 2mm radius which is good. If it seems larger, see if you are able to file it smaller. If there are deep grooves in the iron from the wires, then the capo is not too hard - file it front and back first, then smooth the bottom to get rid of the grooves. Those grooves become 'saddles' that actually grab the wire, making it harder to tune and also forcing the wire to flex on the speaking side instead of pivoting as it should.
-
I have had excellent luck with Paulello 'XM' wire. You can order it online from France and they will ship it direct. It really is stronger. Of course, just having fresh wire in the entire section combined with shaping the hammers nicely usually completely stops the string breaking for a while anyway, but with the Paulello wire it will hold up longer.
-
One last minor tip I have used in some pianos: I raise up the balance rail glide that is closest to the breaking wire. Screw the glide bolt up as high as they can go so that they don't knock. This really takes away a lot of the attack - and it will weaken the tone of course and the pianist might complain about the feeling. Don't do multiple glides - just the closest one. And of course, never do this on a performance instrument!
I've worked through this issue quite a few times with multiple piano brands - good luck!
Don Mannino
Original Message:
Sent: 6/25/2025 8:48:00 PM
From: Teri Meredyth
Subject: Repeated String Breakage Yamaha C7X
Hi Everyone,
I'm looking for your advice regarding string breakage in a several note section in the lower treble section of a Yamaha C7X. There were no issues the first couple years. then strings began breaking in the several note section just after the tenor/lower treble break. Strings are not breaking anywhere else on this piano. In my view this is not a warranty issue, as I see nothing unusual or abnormal about the capo, string rests, etc. in this section. My client is a faculty member, and this is her personal piano at home. She truly is a "monster" pianist (as in hugely talented and wonderful), and she performs contemporary works as part of her concert schedule. I have lovingly told her "just don't play like that" (kidding), but that hasn't gotten us very far. She loves her piano, and would really like to keep it. But this problem is annoying (to us all!).
I have already made sure the hammers are filed and well-voiced in that section, and I have altered the regulation in the two treble sections to reduce power. She is ok with this. What else might you suggest I do? I am primarily interested in any suggested alterations of the capo itself in this several-note section, and the possibility of raising or lowering the counterbearing angle to the string rest. Does a broader capo surface promote string breakage? Does a sharper counterbearing angle help prevent it or aggravate it? Thank you for sharing your thoughts! Please feel free to refer me to articles about this, or to reply privately.
Teri
email: teri22ns@att.net
cell: 310-702-2389
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Teri Meredyth RPT
Harbor City CA
(310) 702-2389
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