<html><div style='background-color:'><DIV class=RTE>
<P>An attempt at mathematics...</P>
<P>If the distance hammer to knuckle is 114mmm, and knuckle to flange pin is 16mm, then 114/16=7.125. If hammer weighs 5gr it should weigh 5X7.125=35.625gr at knuckle.<BR>Distance of contact point of knuckle on lever to lever pin is 40mm, and spring contact point to lever point is 30mm, then ratio is 40/30=1.33. By spring contact point the hammer should then weigh 35.625X1.33=47.38gr. Distance of lever drop pad to lever pin is 60mm, and spring contact to lever pin is 30mm, then 60/30=2. So 8gr at drop pad would be 16gr for the spring to carry.</P>
<P>Conclusion is that if friction is zero at lever pin, the spring needs appr 50gr to lift hammer, and for a measured 8gr friction at drop pad, the spring needs 47.38+16=63.38, appr 66gr to lift hammer. A difference of 16gr.</P>
<P>I don't know what the hammer weighs, and some other friction and weight figures are of course omitted, and someone more clever should correct any mistakes above! Is it otherwise on target?<BR><BR>Danilo</P></DIV>
<DIV></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #a0c6e5 2px solid; MARGIN-RIGHT: 0px"><FONT style="FONT-SIZE: 11px; FONT-FAMILY: tahoma,sans-serif">
<HR color=#a0c6e5 SIZE=1>
<DIV></DIV>From: <I>"Dean May" <deanmay@pianorebuilders.com></I><BR>Reply-To: <I>Pianotech List <pianotech@ptg.org></I><BR>To: <I>"'Pianotech List'" <pianotech@ptg.org></I><BR>Subject: <I>RE: Keep on filing...(picture attached)</I><BR>Date: <I>Fri, 22 Jun 2007 08:46:01 -0400</I><BR>>Ric wrote: After all.. the spring tension is not actually increased.<BR>><BR>>Seems to me it is. If you increase the resistance of the pinning, you must<BR>>also increase the spring tension to overcome this resistance for a given<BR>>hammer lift.<BR>><BR>>Dean<BR>><BR>>Dean May cell 812.239.3359<BR>><BR>>PianoRebuilders.com 812.235.5272<BR>><BR>>Terre Haute IN 47802<BR>><BR>><BR>>-----Original
Message-----<BR>>From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf<BR>>Of Richard Brekne<BR>>Sent: Friday, June 22, 2007 4:22 AM<BR>>To: pianotech@ptg.org<BR>>Subject: Keep on filing...(picture attached)<BR>><BR>>I agree with this view, but I have to admit I have never actually<BR>>checked to see whether or not increased rep center pin friction directs<BR>>more of the springs strength towards jack return. It may end up being<BR>>that if actually measured it does not. After all.. the spring tension<BR>>is not actually increased. One could easily think along the lines that<BR>>the spring must use more of its strength to overcome the increased<BR>>friction... and thats it. Might be fun to actually check this out.<BR>>Could be done with strain measuring devices placed on both levers
I<BR>>would think.<BR>><BR>>My main point however goes to this idea about that surfaces from time to<BR>>time about the rep spring/levers' relationship to key return speed.<BR>>This is a by product of the device and not its purpose, tho some will<BR>>have it otherwise. It is true that the rep spring does execute a force<BR>>downwards as well as upwards...increasing key return speed in the same<BR>>proportion to increase in spring strength that this same increases<BR>>hammer lift. But the purpose of the mechanism is to reset the action<BR>>into firing position at the earliest possible moment so that the key<BR>>need not travel full return in order to be replayed. Too strong a<BR>>spring effect creates uncomfortable touch and ill seeming noises among<BR>>other
things.<BR>><BR>>Cheers<BR>>RicB<BR>><BR>><BR>> David Love comments :<BR>><BR>> Pinning the rep lever tighter allows for speedier jack return as well as<BR>> more positive hammer rise since the spring doesn't need to be set so<BR>> close<BR>> to the fail point. Most of the benefit, in my view, comes from the<BR>> speedier<BR>> jack return and thus faster repetition.<BR>><BR>><BR>> David Love<BR>> davidlovepianos at comcast.net<BR>> www.davidlovepianos.com<BR>><BR>><BR>> Ric B writes in response to David Porritt
below<BR>><BR>> I dont think I understand the logic behind this claim. Whatever<BR>> friction<BR>> there is at the lever pin simply restricts the amount of<BR>> movement of the<BR>> lever for same spring strength. I suppose more of the springs<BR>> energy might<BR>> be directed to jack return... not really sure about this either<BR>> when it<BR>> comes to
it.<BR>><BR>> The rep lever springs upwards and downwards with equal strength<BR>> regardless<BR>> of the tightness of the pinning. The only thing that can change<BR>> the relative<BR>> pressure between up and down would be a repositioning of the<BR>> pin... i.e.<BR>> changing its leverage moment.<BR>><BR>> I would suspect, that 8-10 grams works well because it fits well<BR>> with
the<BR>> multi-tasking between the rep spring and other related parts...<BR>> ie jack<BR>> return, hammer lift, appropriate friction levels for centers<BR>> belonging to<BR>> these...etc.<BR>><BR>> Cheers<BR>> RicB<BR>><BR>><BR>><BR>> Pinning the repetition lever to 8 grams restricts the<BR>> jumpiness of
the<BR>> hammer on key release and directs more of the spring's<BR>> energy into<BR>> returning the key. When I'm doing a very careful regulation<BR>> of a<BR>> performance piano (where "it's so even" is the compliment I<BR>> want to<BR>> hear) I use an 8-gram weight I have that has a hole in
the<BR>> middle. If I<BR>> put that weight on the screw that regulates the rep. lever's<BR>> height (the<BR>> short end of the rep. lever) I want the pinning tight enough<BR>> that it<BR>> holds the weight. When I place it on the drop screw pad<BR>> (the longer end<BR>> of the
rep. lever) I want the lever to gently fall.<BR>><BR>> dp<BR>><BR>><BR></FONT></BLOCKQUOTE></div><br clear=all><hr>Vårens klädmode <a href="http://g.msn.com/8HMBSVSE/2752??PS=47575" target="_top">De senaste tipsen på MSN</a> </html>