Might have been weakened when the rib was still a tree. Consider the stress when the bridge pins were pounded in. I believe Steinway likes to bottom out the bridge pins. Perhaps enough shock to split a rib made of shake-damaged wood. (Were other ribs made from the same stock?) Meanwhile, we don't know if the mid-range noise Kent reported has anything to do with this rib. Ed Sutton -----Original Message----- >From: David Love <davidlovepianos at comcast.net> >Sent: Dec 10, 2010 11:06 AM >To: caut at ptg.org >Subject: Re: [CAUT] strange rib damage > >And, yes the board is more heavily loaded at the upper end and the bridge >does some work to distribute the load. Were you to plot the stiffness >coefficient of the ribs themselves it might look something like this. X >axis are the rib #s and the y axis represents stiffness. Number 1 rib is >the bass end, of course. Even though the #14 rib is smaller in cross >section than, say #6 rib, it is much shorter and so therefore is much >stiffer. > > > >In terms of the question at hand, in order for the board to deflect enough >to crack the rib as it was pictured you likely wouldn't be able to achieve >that level of deflection without doing some serious damage to the panel >itself in the treble end. Even if the panel wasn't dried down enough (one >suggestion) the amount of change in the crown radius that might take place >seems hardly enough to crack that rib like that. Thus my guess that the rib >was already damaged when installed. > > > > > > > > > >David Love > >www.davidlovepianos.com > > > >From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of David >Love >Sent: Friday, December 10, 2010 7:51 AM >To: caut at ptg.org >Subject: Re: [CAUT] strange rib damage > > > >That would be correct. It depends, of course, on how you set bearing and >that may depend on the type of board and/or its condition. I often try and >set bearing at the low end of the bass bridge at near zero with only >slightly more pressure at the upper end of the bass bridge. Some set even >more bearing at the upper end of the treble bridge than I have indicated. >This is an average setting for me on the new boards that I'm doing (rib >crowned with minimal compression) and I find it unnecessary, even >counterproductive, to load the board more than this. In practice, at the >very top of the treble bridge (last half of the upper section) I actually >back off the bearing some down to more like 1 degree. The board is usually >stiff enough up there without trying to achieve it by adding load and more >problems come from too much stiffness or a restricting movement (jangles) >than the opposite, I find. > > > >David Love > >www.davidlovepianos.com > > > >From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of >Laurence Libin >Sent: Friday, December 10, 2010 7:23 AM >To: caut at ptg.org >Subject: Re: [CAUT] strange rib damage > > > >Just to be sure I'm interpreting this correctly, each string of trichord >Note 88 exerts a downbearing of 4.423 lbs (1/3 of 13.27 lbs), roughly 3.6 >times more pressure than the single string of Note 1, right? And pressure is >not evenly distributed across the bridge and soundboard but much more >heavily loaded at the treble. > >Laurence Libin > > > >----- Original Message ----- > >From: David Love <mailto:davidlovepianos at comcast.net> > >To: caut at ptg.org > >Sent: Friday, December 10, 2010 9:47 AM > >Subject: Re: [CAUT] strange rib damage > > > >Here's a typical Steinway B scale and resulting lbs. This totals out to 694 >lbs. The lbs on each note takes into consideration the number of unisons. >Using an average setting of 1 degree for every string would produce a total >of 698 lbs. HTML probably helps to keep the chart organized. > > > > > >Note# / bearing deg/ lbs > > > > >1 > >0.25 > >1.22 > > >2 > >0.25 > >1.21 > > >3 > >0.25 > >1.19 > > >4 > >0.25 > >1.19 > > >5 > >0.25 > >1.16 > > >6 > >0.25 > >1.15 > > >7 > >0.25 > >1.11 > > >8 > >0.25 > >1.11 > > >9 > >0.25 > >1.78 > > >10 > >0.25 > >1.74 > > >11 > >0.5 > >3.43 > > >12 > >0.5 > >3.41 > > >13 > >0.5 > >3.36 > > >14 > >0.5 > >3.31 > > >15 > >0.5 > >3.24 > > >16 > >0.5 > >3.20 > > >17 > >0.5 > >3.19 > > >18 > >0.5 > >3.13 > > >19 > >0.5 > >3.04 > > >20 > >0.5 > >2.99 > > >21 > >0.75 > >4.99 > > >22 > >0.75 > >5.29 > > >23 > >0.75 > >5.41 > > >24 > >0.75 > >5.74 > > >25 > >0.75 > >5.85 > > >26 > >0.75 > >6.28 > > >27 > >0.75 > >6.32 > > >28 > >0.75 > >6.37 > > >29 > >0.75 > >6.62 > > >30 > >0.75 > >6.49 > > >31 > >0.75 > >6.65 > > >32 > >0.75 > >6.44 > > >33 > >0.75 > >6.53 > > >34 > >0.75 > >6.56 > > >35 > >0.75 > >6.54 > > >36 > >0.75 > >6.55 > > >37 > >0.75 > >6.52 > > >38 > >0.75 > >6.55 > > >39 > >1 > >8.84 > > >40 > >1 > >8.35 > > >41 > >1 > >8.43 > > >42 > >1 > >8.54 > > >43 > >1 > >8.57 > > >44 > >1 > >8.55 > > >45 > >1 > >8.67 > > >46 > >1 > >8.60 > > >47 > >1 > >8.65 > > >48 > >1 > >8.33 > > >49 > >1 > >8.45 > > >50 > >1 > >8.47 > > >51 > >1 > >8.73 > > >52 > >1 > >8.45 > > >53 > >1 > >8.31 > > >54 > >1 > >8.49 > > >55 > >1 > >8.63 > > >56 > >1 > >8.72 > > >57 > >1 > >8.77 > > >58 > >1 > >8.90 > > >59 > >1 > >8.72 > > >60 > >1 > >8.84 > > >61 > >1 > >8.84 > > >62 > >1 > >8.77 > > >63 > >1 > >8.81 > > >64 > >1 > >8.89 > > >65 > >1.5 > >13.23 > > >66 > >1.5 > >13.06 > > >67 > >1.5 > >13.12 > > >68 > >1.5 > >13.26 > > >69 > >1.5 > >12.79 > > >70 > >1.5 > >12.94 > > >71 > >1.5 > >13.09 > > >72 > >1.5 > >13.24 > > >73 > >1.5 > >13.40 > > >74 > >1.5 > >13.55 > > >75 > >1.5 > >12.92 > > >76 > >1.5 > >13.07 > > >77 > >1.5 > >13.22 > > >78 > >1.5 > >13.38 > > >79 > >1.5 > >12.73 > > >80 > >1.5 > >12.88 > > >81 > >1.5 > >13.03 > > >82 > >1.5 > >13.18 > > >83 > >1.5 > >12.51 > > >84 > >1.5 > >12.66 > > >85 > >1.5 > >12.81 > > >86 > >1.5 > >12.96 > > >87 > >1.5 > >13.11 > > >88 > >1.5 > >13.27 > > > > > >David Love > >www.davidlovepianos.com > > >
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