Joe: 1. Since the long bridge and the transition bridge attach to the soundboard in somewhat different places which can create differences in tonal quality, the connecter tends to unify the assembly and mitigate tendencies toward unwanted resonances or tonal differences that can (and do) occur. I’ve since changed my approach (see attached picture from a more recent Steinway B). Now the transition extends directly off the end of the long bridge but angles away from the bass bridge. While that doesn’t produce the optimum scale numbers I find that it creates a slightly better tonal transition due to the lessening of the differences between the SB response of the two bridges. There are other methods of connecting the two bridges, btw, which Ron N and Del both use which involve a larger wooden platform (maybe 5-10 mm thick) that spans the bottom end of the long bridge and the entire transition bridge. I’ve done that as well, this is more a traditional style of connecting bridge (look at some old Steinway As). All are choosing between the best compromises. They are all improvements (in my opinion) over the original precipitous drop in tensions at the tenor bass crossover but have their own quirks. Since I can't make a new plate for these pianos I have to choose the next best thing. 2. The extension off the transition bridge is to control the end of the bridge effect (similar to the extension off the top of the bass bridge, though it's usually of inadequate length on most pianos). The length of the extension in this case corresponds to the position of the first rib underneath but it doesn't have to. The bridge connector on larger Steinways that you are referring to is the ring bridge and I'm not sure of the reason for that one. As you can see from the attached photo I've removed it. It functions well for the end of the bridge effect on the tenor bridge but it also ties down the bottom of the bass bridge which isn't necessarily desirable. Since any benefit of that part of the bridge extension goes relatively unnoticed in view of the poor scale numbers at the bottom of the tenor bridge on the B I find it better to install a transition and remove the ring. The ring bridge probably does help in production as only one bridge needs to be made and located. The effect of the extension is not calculated I just push it out there a ways. Far enough to stiffen the panel beyond the last note but not so far as to get too close to the edge of the panel. In this case, as I mentioned it does correspond to the location of the first rib underneath the end of the extension. On a piano with a new rib layout the extension may not correspond to a rib position but its function is still the same, to stiffen the panel beyond the point of the last note on the bridge. 3. The bottom of the bass bridge is undercut so that the bridge connection to the soundboard doesn't extend beyond the first rib. So the bass bridge is cut back to that point. Otherwise, the extension beyond the rib stiffens the lower end of the panel which has been thinned in order to make it more flexible. Those two things would function at cross purposes. You want the low end of the panel more flexible. 4. In the high treble the bridge is usually undercut back to about the position of the front row of bridge pins, or slightly more depending on the layout. Enough to move the bridge to soundboard contact point away from the belly rail a bit. When I'm using original Steinway bridge roots I don't usually change what they've done finding the amount of undercutting to be adequate. David Love www.davidlovepianos.com Original message..... Hi David, Thanks for posting these pictures, and for sharing your insights and experience with us so frequently. I have a few questions about this one, if you don't mind.... (1) what is the purpose of the connector between the long bridge and the transition bridge? (2) what is the purpose of the transition bride extension? Are either of these calculated and/or proven to produce a specific result, or are they empirically derived (try some out and see)? (I've never known the true value of the bridge connector on a larger Steinway; I've been tempted to hack one off just to find out, but that's an expensive gamble!!!) (3) Are my eyes playing tricks on me, or is the low end of the bass bridge undercut significantly (hard to tell with shadows)? Speaking of which, what degree of undercutting is employed in the treble portion of the long bridge, and where? How do you decide what and how much to undercut? Don't mean to pester you, but the picture got me thinking (always dangerous). Thanks, Joe DeFazio Pittsburgh -------------- next part -------------- A non-text attachment was scrubbed... Name: P3140050.jpg Type: image/jpeg Size: 27754 bytes Desc: not available URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100219/b554d630/attachment-0001.jpg>
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