I've not experience a case where adding a couple of grams of friction to the flange would be enough to keep the hammer from bobbling if it was inclined to do so in the first place for other reasons. If you add enough friction to inhibit the hammer from moving freely likely you have added too much friction to the flange and can create other problems with hammer return speed. Excess damper spring tension will inhibit (I wouldn't say discourage) completion of the key stroke on light playing by adding excess and ever increasing tension through the stroke. While you can certainly train the player to play "harder" the piano shouldn't require that and taking some tension off the damper springs will take care of the problem if the tension is excessive which can be the cause. I've experience this several times on new uprights and made the correction with immediate results. In those cases the hammers without dampers were not bobbling which clued me in to the problem. I don't know what the problem is in this particular case but the original posting indicated that the regulation had already been refined. Checking the damper spring tension was a suggestion not a diagnosis as not having a chance to examine the piano more carefully leaves me somewhat in the dark. I would certainly check that before engaging in dismantling and repining all the flanges. David Love www.davidlovepianos.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Scott Helms, RPT Sent: Wednesday, August 19, 2009 2:34 PM To: pianotech at ptg.org Subject: Re: [pianotech] double-striking hammers on Chinese uprights David - Repinning flanges to address bobbling in uprights works for the same reason that it does in grands. If the hammers are pinned too loose, there is too much energy in the hammer assembly during aftertouch and it will rebound and double-strike. Note that this typically happens on a blow that isn't strong enough to put the hammer into check, but that IS strong enough to make the hammer return to the string a second time. When you say excessive damper spring tension is the culprit for "exactly the reasons [I] mention", do you mean that it discourages the player from following through the keystroke? If so, how does that explain bobbling in the treble hammers that don't have dampers? And, wouldn't that be a player technique/education issue and not a piano malfunction issue? Scott ------ Scott A. Helms, Registered Piano Technician 480-818-3871 www.helmsmusic.net > Why would repining flanges help with double striking? > > As I mentioned earlier, and as was discussed in a previous thread, excess > tension in the damper springs is a common culprit for double striking > (especially in some new pianos) for exactly the reasons you mention below. > > > David Love > www.davidlovepianos.com > > -----Original Message----- > From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On > Behalf > Of Scott Helms, RPT > Sent: Tuesday, August 18, 2009 8:56 PM > To: pianotech at ptg.org > Subject: Re: [pianotech] double-striking hammers on chinese uprights > > I'm surprised that repinning the flanges didn't help - that always seems > to do the trick for me. Have you tried reducing the blow distance to get > more aftertouch? This was actually a thread on this list about a year ago, > and some suggested that damper springs that are too strong could cause > bobbling, although I've never been able to figure out why that would be > the case (unless it just discourages the player from following through the > entire keystroke) ... > > ------ > Scott A. Helms, Registered Piano Technician > 480-818-3871 > www.helmsmusic.net > > > > > > > > > >
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