Hi David: I am very aware of the isssues you bring up. I've been rebuilding for 35 years, and every teardown of a new piano in the shop tells the tale of what they did well in the factory and what they did badly, who drank their lunch on Friday, etc.. But ME? make a mistake, that's NEVER happened... J You must be talking about setting note 88's speaking length exactly to Steinway's factory standard, right? J I'm sure I could keep it within their spec... Actually, I already have the scale. I took all the speaking lengths, wire diameters, back scale lengths, etc. etc. at teardown, as I had Jude Reveley calculate the rib scale, loading and deflection, and so on for this new board. I don't intend to change much in the plain wire; the bass will be rescaled along the lines discussed in the Steinway A thread on the forum. This being only my second board, I live with a healthy and ongoing paranoia about the mistakes I can make at every step, and I will take great pains to put the plate back where it was (and yes, the factory position on this one is fine). I appreciate your further elucidation. Will From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of David Love Sent: Tuesday, June 02, 2009 11:38 PM To: pianotech at ptg.org Subject: Re: [pianotech] Repairing Bridge Consider having someone reexamine the scale before you lay it out if you can't or don't want to do this yourself. One of the reasons to lay it out from scratch is that when you make a template of the existing bridge the final layout is too far removed from the original and small mistakes can be compounded. Each stage has the possibility for mistakes: first the original scale is laid out by someone in the factory; second the scale is copied by you; third it's placed on the new bridge cap; fourth the pattern is actually transferred. If a one mm mistake is made at each step the tensions can be quite dramatically off and the tone can really suffer in some sections--especially at the upper end. Also, since we don't really know exactly what was intended out of the factory (they range quite a bit at note 88 you may notice when you examine lots of similar models) it's better to recalculate and lay it out fresh with a particular scale idea in mind. A couple of mm's down in the tenor doesn't make much difference but in the capo section it does. As I mentioned, the pattern can be useful for alignment and spacing (though not always) and is worth making as an insurance policy. David Love www.davidlovepianos.com From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of William Truitt Sent: Tuesday, June 02, 2009 5:17 PM To: pianotech at ptg.org Subject: Re: [pianotech] Repairing Bridge And I am contemplating doing what you do for the first time on my present Steinway project. In the past, I have simply gone from the pattern of clear mylar and an awl to punch the markings for the bridge pins. I have made a pattern for the present piano, and will use it to help me reference the questionable notes. I have had a set of the Mazzaglia punches for a number of years, and they are very nice indeed. Much thanks for the additional info. Will From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of David Love Sent: Tuesday, June 02, 2009 7:10 PM To: pianotech at ptg.org Subject: Re: [pianotech] Repairing Bridge I do the same thing with the trichords in that case the line drawn represents the middle string. Check the spacing carefully in the high treble as the notes can get very close up there. Take lots of pictures of the bridge near the struts before teardown so you have a reference near the struts. On many pianos where the struts flair a lot the strings can travel under the strut a bit. You just need to be sure that on those notes adjacent to the bridge you don't run into a problem with damper clearance from the strut. A small deviation is not likely to cause trouble with side bearing. I have not had to make a new damper guide rail (though I have for different reasons) or put new wire on the damper heads laying out a new bridge though making a new guide rail is not difficult if you need to. When adding a transition bridge I have had to plug a few holes at the end of the tenor bridge and relocate them slightly. Not hard. The dampers, recall are relatively much nearer to the agraffes and capo than the bridge through most of the piano so a small change at the bridge is not likely to reposition the string that much at the dampers. Still, you want to look at the long bridge carefully before teardown to see if there are any anomalous places. Run a string if in doubt and make lots of notes. I don't know how complete my list is, I'm sure I forgot some things but that was as quick an outline as I could come up with on short notice. At this point I always lay out the bridge from scratch on all recapping projects. I do try and remove the old cap in one piece for a reference and that's a good idea in general. David Love www.davidlovepianos.com From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of William Truitt Sent: Tuesday, June 02, 2009 3:15 PM To: pianotech at ptg.org Subject: Re: [pianotech] Repairing Bridge Hi David: Thanks for the great detail with which you have laid out bridge pin holes without using a pattern. How do you vary this when laying out the trichords on the treble bridge? And how do you accommodate those notes in the treble where the position the bridge pins cannot follow a straight line from agraffe to hitch pin (most typically adjacent to the struts at the breaks)? Do you find that you need to either make a new damper guide rail and/or put new wire on the damper heads when you use this methodology, since the position of at least some of the notes will vary from a carefully located pattern? Will Truitt From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of David Love Sent: Monday, June 01, 2009 1:44 AM To: pianotech at ptg.org Subject: Re: [pianotech] Repairing Bridge The problem is that if you don't understand what it is you are trying to accomplish with placing bridge pin holes and spacings you can end up making a bad copy of possibly a bad layout to begin with. I see a lot of bad bridge layouts mostly from trying to make copies of old bridge pin placements and then just missing by a millimeter or two front or rear and ending up with either way to much side bearing or none at all. Layout it out from scratch isn't difficult. You can mess up making a pattern just as easy as you can mess up doing it from scratch. For those not familiar with the process it goes something like this: 1. Choose a reference hole on the agraffe, right or left it doesn't matter, I use the treble side hole. Stretch a string through your reference hole an pull it tight toward its hitch pin. 2. Where the string crosses the bridge draw a line along side of it (heavy fishing line works fine). That's your reference line for that note. Go to the next note (not unison) one and do the same until you have all the lines drawn for each note 3. Check the spacing to see that it's equal between the lines. Remember that there's another line to go next to it for the other bichord and notice that the spacing between where the bichords and the monochords begin will be a bit different. 4. Measure the spacing between (right to left not front to back yet) the old set of bichord holes. 5. Using a clear ruler draw a line parallel to the first one you drew for the other string in the bichord pair. 6. Visually check the spacing again and correct if necessary. Look at the old bridge cap and see if it roughly matches the spacing there. 7. Measure the front to back spacing on the original and duplicate it roughly or just use 18 mm. Drawing a line connecting the bichord lines (looks kind of like a tic-tac-toe diagram now except for the monochords). Center the front to back spacing on the bridge body. Check it visually. 8. Where those line cross each other is where the bridge pins will go angled appropriately. One note of caution before you set the holes, be sure that there isn't a set of adjacent strings where the front holes of one note will be exactly adjacent to the rear holes of the adjacent note such that the opposite leaning bridge pins will hit each other. If there are some of those then adjust your rear spacing to accommodate. 9. Using sharp punch or an awl punch small starter holes for the drill to use as a guide. They should by punched exactly on the line representing the string line. You don't need to offset them, the diameter of the bridge pins will do that for you. 10. Drill the holes at 20 degrees. 11. Notch or bevel the bridge as you choose. 12. Coat bridge and notches with clear sealer. 13. When the sealer is dry lightly sand bridge top to smooth out sealer with 400 paper. 14. Insert bridge pins (I use #9 pins in the bass section) 15. Put a single drop of thin CA clue where the pin meets the bridge to seal and tighten the pin. 16. Shoot bridge top (and sides) with a few light coats of clear lacquer. Use an aerosol delivery with a fine mist. You don't want a super heavy coat. Three light applications will do. 17. String her up and you're off to the races. Note: You can skip step 5 if you have one of those two hole set punches from Mazzaglia (if you don't and do bridges they have a lot of excellent tools just for this purpose www.geocities.com/mazzaglia_tools) that give you the spacing without having to draw in the second line although the first time it's probably not a bad idea to draw the line in just so you can visualize the front to back spacing and make sure it's centered on the bridge. Remember that on a curved bridge if you center the left hand string, the right one won't be centered. The trick is as you look down on top of a bichord with four bridge pins, you want to compare the distance to the bridge edge between the top left bridge pin and the bottom right one or the top right and the bottom left. Those distances need to be equal. Measure twice, cut once. Check everything visually and label and number each unison in pencil on the bridge to as you go (you'll sand off the numbers before you put the sealer on the bridge) . Check it again and then one more time before you start punching holes. David Love www.davidlovepianos.com From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Joseph Garrett Sent: Sunday, May 31, 2009 7:11 PM To: pianotech Subject: [pianotech] Repairing Bridge David Said: " Sounds good but I would probably not try and make a pattern from that old cap. Just lay it out from scratch. Not hard." Having capped several hundred bridges in the last 35+ years, I consider that to be bad advice to someone who is attempting their first bridge recap. If one is well versed in bridges, etc. it is fine and can be implimented w/o a pattern. However, that is not the case. A rubbing is adviseable. Use the pencil point to locate all of the bridge pin holes, even on the cracked side this is possible. I usually tape the butcher paper to the bridge while I'm doing the rubbing. W/O a pattern of some sort, all kinds of errors can happen. DAMHIK! The idea is to replicate the original bridge, but hopefully improve on it, if possible. Most Uprights had really crappy wood used in the bass bridges. Why? I have no idea, but such is the case. As for the Airplane Plywood, you could google a search and will come up with a whole bucket of sources. Most Aircraft plywood is made of maple with a poplar core. This is more than adequate for recapping. Using delignet is overkill in my opinion. And, it is harder to work with than the Aircraft ply. Regards, Joe Garrett, R.P.T. (Oregon) Captain, Tool Police Squares R I -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20090603/485b5f1f/attachment-0001.htm>
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