---------------------- multipart/related attachment --============_-1089258731==_ma============ Michael and all, =46orgive me if this post turns up twice in your=20 mailboxes. I sent it earlier today and it seems=20 not to have come through on my emails. The=20 pianotech server might have blocked the original=20 post on account of the number of images enclosed=20 So I'm sending it again with the extra images=20 included via links to my private webspace (the=20 images are now uploaded for those of you who=20 would like to see them).. At 7:10 PM +0100 31/7/05, Michael Gamble wrote: >This close-up shows a metal shim which fell out=20 >of a place between the "dam" and the underside=20 >"nose" of the plate on my S&S 'A' . I stood it=20 >on the soundboard near its normal location. I=20 >can only hazzard its use as being intended=20 >to convey the pressure of the fully strung piano=20 >from the web to the dam and sound board. Any=20 >other ideas? It is about 1/4" thick. Take a look at the plate strut shown in your=20 image, and note its vertical position relative to=20 the string-plane of the strings. The string plane=20 will run between 35 - 50 mm below the centerline=20 of the plate strut. Clearly, the total string=20 tension ( which will be between 16 - 18 ton for=20 an A) will be trying to bend the struts down at=20 the strut ends and up in the middle. Steinway=20 have chosen to use quite small struts in this=20 design, and this bowing of the struts will be=20 tend to be worse with their instruments than say=20 a B=F6sendorfer, which has much deeper and heavier=20 struts (B=F6sendorfer don't use a horn system). The=20 horn - wedge - tension collector system allows=20 the back beams and case structure to take some of=20 the load on the opposite side of the string=20 plane, relative to that of the struts. This will=20 help to prevent the bowing of the struts, stiffen=20 up the whole assembly, and hopefully, result in=20 better tuning stability and sustaining tonal=20 qualities. A Steinway plate might still survive=20 the string tension if the horn wedge was left=20 out, but I'd be a bit nervous about its long term=20 prospects, if it managed to get to pitch without=20 collapsing. > You can see the gap into which it fits. It was=20 >nor glued in place - should it be? No > I doubt it as the glue would give a deadness and tend to be elastic in= situ. >Now all the strings are off, the soundboard=20 >gives a healthy bass "thwummm" of G# 0 @ A=3D431=20 >when tapped with a fingers on the bass bridge.=20 >Having vacuumed off all the debris of ninety=20 >years I am about to gently wash the plate and=20 >soundboard with a damp cloth from a bowl of=20 >water with washing up liquid in. Now that you've got it unstrung, I presume that=20 you will be lifting the plate to see what's=20 happening with the board. A couple of compression ridges are visible in=20 your image, to the right of the horn wedge. Have a look at the following graphic I've drawn for you. (this graphic represents a sound board, shown is=20 a crowned, then collapsed condition) http://members.optusnet.com.au/ronovers/s.board.graphic.jpg =46or a piano as old the one you're dealing with,=20 there will be no way that the crown remains in a=20 healthy condition. I know that some believe this=20 is possible, but if you make up a plywood=20 straight edge, with a cutout for bridge=20 clearance, you will see immediately what I am=20 referring to. Almost all 90 year old boards will have collapsed=20 to conform to the image graphic above. There will=20 usually be some residual crown either side of the=20 bridge, with a 'valley of collapse' running right=20 along the line of the long bridge. You can=20 usually place a straight edge under the bridge,=20 on the under side of the board, and it will rock,=20 showing that the crown has turned inside-out=20 under the bridge. You can also try this on new=20 pianos on the showroom floor, only to find that=20 there is often an early onset of the syndrome. Older boards in the second top string section=20 will usually collapse as per the lower image in=20 the graphic shown above. Again, using a plywood=20 straight-edge, this is easy to see. Now they'll=20 be some who'll swear and declare that their 100=20 year old 'wonder piano' still sounds as good as=20 the day it was made even though the sound board=20 might have sunken a bit. Well, I doubt that this=20 is possible. While older instruments may still=20 sound somewhat like a piano, they will in almost=20 all cases sound significantly inferior to what=20 they once were. Well there you go Michael. There's a little=20 project for you. Knock up a plywood straight edge=20 during the week, and pull the plate next Sunday. We've currently got a little project of our own=20 going on at the workshop, doing a 'mouth-to-mouth=20 job' on a collapsed sound board for a retired=20 client. The patient in question is a Howard=20 grand, which by the look of it was made by=20 Challen of London. It was a bit short and 'honky'=20 before we de-strung it, so I was already=20 suspicious of the board. It turned out to be dead=20 flat with a few small checks, which got=20 significantly worse once we jacked it to what we=20 judged to be an appropriate crown (I was a bit=20 concerned that we might push the board of the rim=20 altogether, but it held despite the creaking and=20 groaning). While the crown is jacked we're giving=20 it a heavy coating of epoxy on each side to=20 produce of sort of epoxy/floppy-spruce sandwich=20 (you never know, it might sound like a Hamburg D=20 after all that epoxy - though I'll try to keep my=20 expectations somewhat tempered). We'll set it up=20 with just a small amount of positive bearing to=20 see what sort of 'twilight performance' we can=20 get out of it (there was no bearing anywhere at=20 the time of pull-down). I gave David Love a call=20 about the epoxy treatment, since I hadn't done it=20 for over twenty years, and I remembered him=20 talking about the procedure on-list some time=20 back. As usual, David is a wealth of knowledge=20 and was very helpful. We're also gluing a new set=20 of bridge pins into the 'sad' bridges with West=20 System epoxy. Here's a few images of the process under way,=20 with two showing the jacking operation. Note that this piano has a sensible cut-off=20 arrangement, whereby the inner rim and cut-off is=20 bent as one piece. Very nice. The sound board is=20 grossly under-engineered, but its going to have=20 to stay that way. Both the piano and its owner=20 are in retirement. This work might allow to piano=20 to be reasonable company until she, ie. the=20 owner, leaves this mortal coil. The following link shows the arrangement we used=20 for jacking crown back into the Howard grand's=20 soundboard. http://members.optusnet.com.au/ronovers/howard.bd1.jpg This link shows a close-up of a sound board 'jack'. http://members.optusnet.com.au/ronovers/howard.bd2.jpg The 'jack' ends are made from free machining 5/8"=20 hexagonal stock which is tapped with a 3/8"=20 internal thread. Threaded rod (which is cheap to=20 buy) can be cut to the desired length for jacking=20 any piano. Two 5/8" or 16 mm spanners can be used=20 for adjusting the jacks Now I must get to work. I got up at 5 am to leave=20 home around 6.30, and its 7.45 already. Aaaaah -=20 the distractions of life. Now Michael - about=20 that board? Ron O. -- OVERS PIANOS - SYDNEY Grand Piano Manufacturers _______________________ Web http://overspianos.com.au mailto:ron@overspianos.com.au _______________________ --============_-1089258731==_ma============ An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/cb/25/66/b1/attachment.htm --============_-1089258731==_ma============-- ---------------------- multipart/related attachment A non-text attachment was scrubbed... Name: l1010696.jpg Type: image/jpeg Size: 33055 bytes Desc: not available Url : https://www.moypiano.com/ptg/pianotech.php/attachments/81/a4/5a/da/l1010696.jpg ---------------------- multipart/related attachment--
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