Don, Thanks so much for taking time to respond to my question. This makes sense. Thanks for the clear explanation of what is happening when worn hammers hit the strings. Have a great weekend. Claude Harding _____ From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Don Mannino Sent: Saturday, January 29, 2011 6:14 PM To: pianotech at ptg.org Subject: Re: [pianotech] Worn hammers breaking strings Claude, The short and simple version: Properly shaped hammers push up on the string with a curved profile which (sort of) matches the natural curve that is formed in the wire by the shock. The force of the hammer against the string pulls against the front termination (agraffe / capo) and throws a nice big wave in the string towards the bridge. Within a few microseconds this shock wave settles down into a relatively consistent vibration of the string throughout its length. It is the initial pulling and bending up motion of the string that is most stressful for the wire. A flat topped hammer pushes up on the wire with a flat surface, which in itself is harder on the wire. Plus, the edge of that flat surface is closer to the termination point. This increases the stress on the wire because the transfer of energy into the wire is not as efficient, because it too close to the termination for proper "leverage" if you will. The "yank" on the string is sharper and harder, and from the hammers point of view the string is less yielding. Worn hammers in themselves do not cause string breakage, but tests have shown that they clearly increase the metal fatigue in the wire at the proximal termination. The longer the string grooves are, the higher the stress. Don Mannino From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Claude M. Harding Sent: Saturday, January 29, 2011 10:23 AM To: pianotech at ptg.org Subject: [pianotech] Worn hammers breaking strings Through the years I've heard, and sometimes repeated, the conventional wisdom that says worn hammers are more likely to break strings. I recently refrained from saying it again because I realized that I really don't know why this may be true. I'm not necessarily doubting it, but if it IS true, I would appreciate a "Readers Digest"-version explanation of the physics involved, or the "address" where I could find such an explanation. Help appreciated. Claude Harding _____ No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1204 / Virus Database: 1435/3410 - Release Date: 01/29/11 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20110129/87a3c04b/attachment-0001.htm>
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