<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: compression waves</title></head><body> <div>At 1:07 AM -0500 11/21/01, Stephen Birkett wrote:</div> <div><br></div> <blockquote type="cite" cite>As for changing the tension of the wrapping wire what might be happending<br> there to change the long. freq? The continuous wrapping wire [it is coiled<br> around the core of course] can also produce long. standing waves between<br> its two ends, i.e. vibrating co-axial to the wrapping wire (spiral). The<br> length of the wrapping wire is much longer than the core, and this can be<br> expected to produce quite low frequencies. From string makers' experience,<br> can the wrapping parameters mentioned by Del affect the overall length of<br> wrapping wire required? That might explain the different frequencies of</blockquote> <blockquote type="cite" cite>Harold's Mary's lamb.</blockquote> <div><br></div> <div><br></div> <div><br></div> <div align="center"><img src="cid:a05100301b821f828ff93@[195.147.234.72].1.0"></div> <div>The greater the pull on the copper, the greater the reduction in diameter of the cover.  Picture A shows the theoretical covered string often used by theoretical people in their calculations.  Figure B is a truer depiction of the string.  Sufficient tension needs to be applied to the covering wire to lash it tightly at all points to the steel.  The effective 'wrap factor' is a function of the tangential speed of the wire and the brake on the covering wire.  The further the brake from the steel, the more regular the tension on the covering wire.  As the copper is forced to coil round the steel it is flattened considerably at the point of contact and its structure becomes more brittle.  The reduction of the vertical diameter varies, according to the gauge of the copper, between 9% and 6%.  At the same time the frequency of the coils exceeds slightly the nominal diameter of the wire.  A skilled operator will achieve predictable and regular diameters.  When I train a new man, he learns the required pull by reference to target tables and the scale worksheet includes a column for the target diameter for each string.  No amount of automation will ever obviate the need for a skilled operator, though a certain amount of mechanical automation can ensure consistency and take the sweat out of the work.  The results of fully automated stringmaking can easily be judged in any cheap piano shop.</div> <div><br></div> <div>That's only answered a bit of the question, bit I've got to get some sleep!</div> <div><br></div> <div>JD</div> <div><br></div> </body> </html>