Pianotech

Hi,

I had a customer in Seattle when I lived there with a Bozey with the same problem. Yes, the capo bar is the issue.  Fortunately, the capo bars on Boseys are removable.  I, with  a new lesson from my mentor, Steve Brady, found the termination points on the capo were too wide causing all the string breakage.  Re shaping the bar is the best way to go.  It's tough to do unless you're restringing the piano and can take the plate out, flip in on its' back and get the proper termination points. About 1.5 mm crest or less.  Too sharp, they'll break again; too wide like 2-3m and they'll continue to break.

Steve and I reshaped the bar and I restrung the section. Never in 10 more years did a string break! Then I moved, so don't know any more history.

I've heard of a diamond  abrasive capo bar grinder is available somewhere, but don't know where to get it.  A tech at Oberlin had one and I asked where to get it but never heard back, so I know it's there somewhere.

I want one too. We have lot of practice grands where the broken strings are almost always in the capo section.

Yes, some fairly fine grit emery cloth can help, but it may only be temporary until you can get a real correct termination point.

Best of luck.

Paul

Robert,

Before looking at the capo bar, look at the hammer condition.

Treble strings breaking is almost always caused by a serious pianist practicing difficult music combined with the string grooves getting long on the hammers.  The long string marks effectively turn the hammer into a flat surface that is trying to drive the string into a sort of square wave shape.  Plus the longer the string marks become, the closer to the capo bar the impact becomes.  This causes metal fatigue and starts the strings breaking.

If the customer will have you reshape the hammers, touch up the regulation, and replace all of the weakened wire (it's usually just one or 2 sizes, like 14 ½ and 15) in the area, then they will stop breaking strings.  At least, until the hammers begin to get worn again!

The iron is much softer than the steel of the wire on most pianos (very few exceptions) so a rough surface has no impact on the wire's strength – the wire just creates a groove.

From your picture, it actually looks like the radius of the capo is too broad also.  This cause a long contact area, which inhibits the string from "rocking" at the capo.  So honestly, with softer iron plates it's better to have a more pointed V under there, and let the string settle into a short saddle area so that it can move better into the duplex scale area.

Don Mannino