What could be done to increase rigidity in a keyframe? Besides stressing the keyframe via the glide bolts...I'm thinking structurally... Is it the differences in wood used? David Ilvedson, RPT Pacifica, CA 94044 Original message From: "David Skolnik" To: "Pianotech List" Received: 7/8/2008 2:27:24 PM Subject: Re: Keyframe Bedding Hello Andre, List - Hope you're well. Sorry to likely miss you in Vancouver in July. I'd be glad to buy the DVD. Note: With regard to recent discussion about extraneous material, I left Andre's post intact, for reference. I apologize if it seems unnecessary. There are a few reasons why I don't think the tuning fork analogy applicable to the concept of stressing the frame. For one, the objective in the case of the tuning fork is exactly to transfer energy to the solid surface, in order to magnify its audibility. In the case of the key frame, the objective is to reflect, or minimize the energy transfer. The shock, and thus the transfer of energy, causes the other child to hop up a little into the air. While the shock is certainly perceived, it is inertia that makes the little critter fly up in the air. Whatever the weight of the load, it would seem that the ratio of energy transfer to energy reflection would be determined by the mass and rigidity of the supporting structure - keys, keyframe, keybed. While stressing a keyframe might be a byproduct of assuring a positive interface with the keybed, I don't see how the issues of developing internal stresses, such as has been discussed in relation to soundboards, can apply here, since those stresses would impact upon the way in which the board responds to the energy transfer, whereas we don't want to see such transfer into the key frame. The key frame, supported in the middle by posts, the glide bolts, carries the weight and automatically transfers the energy onto the key bed, which is a part of the 'basic' construction of the 'basis' of the instrument. The weight of the action is supported by the front and back rails, and stabilized by the glide bolt. The bulk of the weight remains on the front and back. The better the construction, the less energy transfers to the frame and bed. So, if the contact between the glide bolts and the key bed is so so... the transfer of energy is 'so so' as well. If however the contact is firm, so will the transfer of energy be, resulting in a louder tone. I certainly agree that a faulty interface between glide bolt and key bed will compromise the energy transfer to the string, but I don't see how putting additional pressure on a well-set glide will improve things. Actually, I can see how stressing the newer, more flexible frame would add to its own rigidity, which, in turn would better reflect the energy. Even if accurately bedded by traditional standards, the floppier construction probably absorbs a considerable amount of energy. I would still be concerned about friction and compromised back rail bedding, but, maybe you persons are correct. David Skolnik Hastings on Hudson, NY At 03:16 PM 7/8/2008, you wrote: On Jul 8, 2008, at 8:10 AM, David Skolnik wrote: I'm not sure that Andre's tuning fork analogy is operational here. I would need to hear a more thorough explanation. Hi David, and list, The principle applied here is the 'transfer of energy', nothing else. I always use the analogy of the sea saw, used by children : two children on a sea saw and they go up and down fast... One child goes down. The sea saw hits the ground (the consistency of the ground is important ... remember the endless pro's and con's about white conical front punching ? brrrr....) and the shock of hitting the ground is transferred along the sea saw to the end of the sea saw and, to the other child going up. The shock, and thus the transfer of energy, causes the other child to hop up a little into the air. The energy is transferred along the balancier (the lever) of the sea saw, but also into the post that supports the lever. The combined weight of the sea saw lever, the children, and the shock of impact of the lever hitting the ground is supported by the post that supports the lever, the balancier. The heavier the weight of the lever and the heavier the weight of the children, the more energy is transferred into the post, and thus into the 'ground'. This is my explanation of what happens to keys and an action, resting on a key frame, which rests on the key bed. The keys (the balancier) and the action (the children sitting on the sea saw) represent the combined weight of the balancier and the children. The key frame, supported in the middle by posts, the glide bolts, carries the weight and automatically transfers the energy onto the key bed, which is a part of the 'basic' construction of the 'basis' of the instrument. The heavier the weight of the lever(s) and action, the more energy is transferred into the ground, the structure of the piano. More energy input will cause the structure to respond (re-sound). So, if the contact between the glide bolts and the key bed is so so... the transfer of energy is 'so so' as well. If however the contact is firm, so will the transfer of energy be, resulting in a louder tone. If you put energy into a tuning fork by hitting it on a solid object and you then bring it into contact with a 'sounding board', the energy of the vibrating tuning fork will be transferred into the board. The quality of the board of course determines the transfer, but the final output it is also determined by the weight (down bearing) of the 'sea saw and the children'. In other words : More wieght/pressure results in this case in a louder tone. We find analogies everywhere. A good example is the shock absorber of, for instance, a car, and, of course, a piano hammer head, or anything that transfers/absorbs energy. friendly greetings from André Oorebeek Antoni van Leeuwenhoekweg 15 1401 VW Bussum the Netherlands tel : 0031 - 35 6975840 gsm : 0031 - 652388008 concertpianoservice at planet.nl www.concertpianoservice.nl "where music is, no harm can be" -- No virus found in this incoming message. Checked by AVG. Version: 7.5.524 / Virus Database: 270.4.6/1540 - Release Date: 7/8/2008 6:33 AM -------------- next part -------------- An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/20080708/f02ac02a/attachment.html
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