Delwin and others, Have you ever considered using high pressure inflatable air tubes for the soundboard spring idea? -Mike Jorgensen Delwin D Fandrich wrote: > Richard, > > I have not actually attempted this procedure myself, but I have run across > it from time to time -- see, there really is very little new under the sun. > Usually these things are in the form of wedges stuck in at various > intervals. In no case have I found it to be particularly effective. Not > even in an 1890's Steinway D. The usual giveaway is the lack of fundamental > energy in the tone coupled with the lack of power. > > Those ribs are tapered (feathered) at their ends for a reason. You really > do need to have a somewhat moveable diaphragm to produce sound energy. > > If you are still curious, I can only suggest that you do what I would do if > I were curious about such a thing -- try it. Buy an old piano with a flat > soundboard. That shouldn't be very hard or very expensive. Stare at it for > a while, then cut some dowels -- or whatever -- and stick them in where it > seems appropriate. > > Once you've determined that this isn't working you can take them back out > and try the soundboard spring idea. These go directly behind the bridge. > My most successful procedure -- and the least complicated, overall -- was to > install a few blocks to the sides of the backposts centered right over the > bridge. You'll want about 4 to 6 of them spaced along the length of the > tenor bridge and one or two behind the bass bridge. Before these blocks go > on there is a hole drilled through them with a T-nut pressed in from the > soundboard side. A long bolt is run through with the head toward the > outside. Double nut the ends of the bolts with large fender washers between > the two nuts. This makes the spring adjustable. Felt the end of the bolt > and washer assembly so the spring does not buzz. You will probably also > want to fill the spring with some loose wool felt so it doesn't ring. You > will want to choose springs that will exert about 50 to 100 lbs (22.5 to 45 > kg) of force against the soundboard when they are compressed from about 1/4 > to 1/3 of their maximum height. As I recall, the springs that I normally > used were about 35 to 40 mm long (uncompressed). Put a small wood block on > the soundboard for the spring to rest against along with a piece of hard > felt or leather to cushion it. Bolt the blocks against the backposts and > crank away. > > Start by compressing the springs -- all of them -- to about 90% of their > uncompressed height and go for a listen. Then try some more, and listen > again. Soon you'll get the idea if this is what you want and if they are > doing any good. Or just making the thing less bad. > > I'm sure I've forgotten a few details in the above description, but I hope > you get the idea. > > After you've played with them for a while you'll know if they are doing what > you want. If they do, leave them. If you don't like them, you can always > take them off and replace the soundboard, which is probably what you should > have done in the first place. But you will have learned something in the > process. > > Regards, > > Del > Delwin D Fandrich > Piano Designer & Builder > Hoquiam, Washington USA > E.mail: pianobuilders@olynet.com > Web Site: http://pianobuilders.olynet.com/ > > ------------------------------------------------------------------- > > ----- Original Message ----- > From: Richard Brekne <richardb@c2i.net> > To: <pianotech@ptg.org> > Sent: Thursday, December 02, 1999 12:19 PM > Subject: Re: Soundboard backposts ?? > > > Del... As usual you are up to your informative best.. many thanks indeed. > I had > > no idea that anything like this had ever been serioiusly considered. Food > for > > thought as far as it goes. > > > > I am wondering about one thing tho.. You mention that solid posts would > mean > > that the strings would be required to move the back posts (beams) as well > as the > > sound board to produce any energy (sound). Just how big an effect would a > few > > square inches over the whole of the soundboard have ?? Wouldnt the rest of > the > > board be free to vibrate.... and wouldnt energy take the path of least > > resistance ?? > > > > These are at least the jist of the arguments presented to me by my > counterpart > > in this discussion we had, (are still having..grin) And I am not > informed...well > > enough read, nor experienced to authoritivly counter these. If you have > the > > time... grin.. > > > > Thanks again Del.. > > > > Richard Brekne > > I.C.P.T.G. N.P.T.F. > > Grin.. Now Head Technician for the University of Bergen (patting myself on > the > > shoulder a bit) > > Bergen, Norway > > > > > > > > Delwin D Fandrich wrote: > > > > > ----- Original Message ----- > > > From: Richard Brekne <richardb@c2i.net> > > > To: <pianotech@ptg.org> > > > Sent: Wednesday, December 01, 1999 2:04 PM > > > Subject: Soundboard backposts ?? > > > > > > > Hi list.. > > > > > > > > Got into a discussion today with another piano tech which prompted me > to > > > > put the following question to you experts out there. > > > > > > > > Given an old beater with a flat soundboard, perhaps a bit of negative > > > > crown... What would the effect be of glueing in wood pieces between > the > > > > ribs and the back frame beams to force and hold the soundboard into a > > > > artificial crown ?? > > > > > > > > sounds off the wall, I know... but I am curious to hear your > responses. > > > > > > > > Richard Brekne > > > > I.C.P.T.G. N.P.T.F. > > > > Bergen, Norway > > > > > > > ------------------------------------------------------------------------- > > > > > > Richard, > > > > > > Crown, by itself, is not the issue. It is the relationship between the > > > strings and the soundboard. To function as a transducer, the soundboard > > > must be able to move in response to the vibrating energy in the string. > > > Putting a solid coupler between the backpost and the soundboard would > > > (could) force a curve into the soundboard, but I'd hardly call it crown. > > > Now the string will have to move both the soundboard and the backpost to > > > create any sound energy. Backposts are often fairly difficult to move. > > > > > > Garold Beyer has replied with a reference to the old practice of > installing > > > springs between the backposts and the soundboard at strategic spots. > This > > > was a bit of a fad back in the mid 1960's and the early 1970's. Several > > > rebuilders, myself included, had been experimenting with this notion > from > > > time to time. I installed these devices -- the best were 1957 Corvette > > > progressively wound valve springs -- on several old upright and grand > pianos > > > with varying degrees of success. (Actually, there was nothing magic > about > > > 1957 Corvette valve springs. I had owned one and at one time had > replaced > > > the heads. I had a few of the old springs floating around.) > > > > > > The practice was eventually ridiculed out of existence by the more > > > traditional and more "respected" members of the trade as being a > > > non-professional repair, but I have come back to the idea several times > over > > > the years. I guess I am non-professional enough to wonder just what the > > > dynamics of the process are. And to not worry overly much about what > > > tradition thinks of some of my strange ideas. Were I doing the same > type of > > > rebuilding today that I did then I would probably still be experimenting > > > with them. > > > > > > As for not being "professional," well, I put soundboard springs into the > > > same category as all of the CA pinblock repairs I read about. And the > same > > > principle applies: Yes, the piano needs a new pinblock (soundboard), but > for > > > a nominal amount of money -- compared to a new pinblock (soundboard) -- > this > > > repair will effect some improvement and possibly postpone the inevitable > for > > > a few more years. It will not tune (sound) as well (good) as a properly > > > remanufactured instrument, but it will be better than it was. And for a > lot > > > less money. > > > > > > Regards, > > > > > > Del > > > Delwin D Fandrich > > > Piano Designer & Builder > > > Hoquiam, Washington USA > > > E.mail: pianobuilders@olynet.com > > > Web Site: http://pianobuilders.olynet.com/ > > > > > > > >
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