Has anyone noticed how semilog progression bridge pianos are more sensitive to seasonal pitch change than hockey stick bridge pianos, or plain-capped bridges compared with laminated bridges? *Elongation* of the bridge in the tenor area might affect tuning more than say upper treble due to angle of the bridge and space between notes. Tom Cole RicB wrote: > Hi all > > Got to thinking about this previous thread middle/early last month. > Nossaman mentions as he has several times in the past a skepticism > towards soundboard / bridge vertical rise/fall having anything to do > with seasonal pitch change. My own calculations confirm this... and > these are backed up by folks who should have more then adequate > education in physics. > So... since it seems evident that vertical deflection of the string is > not part of this picture.... perhaps to some significant degree string > length is changing... and as a result tension is NOT changing... or > not nearly as much as we take for granted. > > Since the change in pitch is related to seasonal changes... ie > relative humidity changes... we are talking movement in wood. The > width of the bridge is wood and can/will expand contract somewhat. > Instead of the whole assembly pushing upwards more/less in response to > climate change... perhaps the strain causes a slight rolling of the > bridge. Breaks in the bridge would resist as there is no counter > pressure by the strings.... and this resistance could account for some > of the abrubt change in pitch change over the breaks. > My point is that instead of looking in the direction of change in > tension to explain things.... perhaps we should be looking at possible > changes in speaking length segments. Wouldnt take much to make a big > difference... especially in the top. 1 mm change in speaking length > for a 50 mm string with no tension change is around 35 cents... and > for a 1400 mm length about 1.5 cents. > > just some thoughts > > Cheers > RicB > > > > >
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