<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: [CAUT] Keydip--how deep</title></head><body> <div>Hi Mike and all,</div> <div><br></div> <div>There have been some good posts on this thread.</div> <div><br></div> <blockquote type="cite" cite><font face="Verdana">. . .  I don't think any hard-fast rule is going to suffice.</font></blockquote> <blockquote type="cite" cite><font face="Verdana">-Mike Jorgensen</font></blockquote> <div><br></div> <div>With the exception of the final jack position relative to the roller, I agree.</div> <div><br></div> <div>The jack position (relative to the roller) at full key dip (with the hammer in check) is probably the only hard-fast rule when it comes to key dip/hammer blow considerations. Since the hammer/key ratio varies so widely, as others have also mentioned, even within the one brand/model of instrument, there will need to be an adjustment from the standard spec of dip and/or blow in many situations. Increasing the blow distance on a high-ratio action will tend to place the already ordinary-relationship of the jack roller contact even further away from its line of centers. Reducing the blow distance in the case of a low ratio action will tend to improve it.</div> <div><br></div> <div>If the dip is insufficient for a given action ratio, the lack of jack/roller clearance at check may cause the action to blubber at let-off, particular when played softly. If the dip is set so deep as to cause considerable clearance between the jack and roller at check it will slow repetition.</div> <div><br></div> <div>The much mentioned problem of the hammer/key ratio varying so much with the US S&S pianos got me thinking about the problem again recently when retro-fitting one of my actions to another factory piano (the instrument in question seemed to have a plate position problem which was accommodated in the original action by fitting the hammers 3 mm short of 130 mm. When I fitted my action I followed suit and hung the hammers short also, since I wanted to keep my action stack at the correct position with respect to the keyboard (to preserve the action ratio I wanted - 5.7:1). The shorter hammer position will reduce the hammer/key ratio, but only by a small amount.</div> <div><br></div> <div>In the factory situation, if the plate is not positioned according to the standard specification, I believe it is inappropriate to shift the action stack relative to the keyboard, in an attempt to shift the strike position (line). If a piano is built with the plate out of position, it should be a simple matter to tolerate a small adjustment in the hammer position along the hammer shank. A 3 mm + or - adjustment of a hammer from say a standard 130 mm standard distance from the hammer center pin will allow for an out-of-position plate to be accommodated without turning the action geometry into a disaster.</div> <div><br></div> <div>If an action stack is moved only 2 mm relative to the keyboard it will have a major influence on the hammer/key ratio, which will cause major headaches at regulation time (if the regulator is aiming to obtain a workable regulation with standard specifications). The truth is we often need to bend the specs somewhere, to get real-world actions working at their optimum level.</div> <div><br></div> <div>Ron O.</div> <x-sigsep><pre>-- </pre></x-sigsep> <div><font face="Times New Roman" size="+1" color="#0000FF"><b>OVERS PIANOS - SYDNEY</b></font></div> <div><font color="#000000"><i>   </i></font><font color="#0000FF"><i>Grand Piano Manufacturers</i></font><font color="#000000"><br> _______________________</font></div> <div><font size="-2" color="#000000"><br> </font><font color="#000000">Web http://overspianos.com.au</font></div> <div><font color="#000000">mailto:ron@overspianos.com.au<br> _______________________</font></div> </body> </html>