Terry, Terry wrote; >I am trying to optimize plate height and location in a small grand. I have >no idea where the plate was originally (plate was not in piano when I got >it). If you are building new bridges or recapping, then you will be able to vary the height of the plate to suit other requirements, such as the action geometry, since you will be able to set the new bridge heights to obtain the desired down bearing. If you are retaining the original hammers, the plate (and in particular the strings at their strike point) will need to be located at a distance (height) from the key bed to enable the hammer shanks to pass through an optimum arc of travel during the key stroke. For example, if the plate is set to a lower position than that to which it was originally set (assuming that the original setting was appropriate), then the hammers will contact the strings with the hammer shanks in a lower position than previously. This will place the jack/roller contact further away from the line of centers, resulting in increased action friction. If you are replacing the hammer set also, you might choose to alter the hammer boring distance to set the hammer shanks to an appropriate arc of travel for optimal action function. >The thing was apparently installed originally too high and shifted over >toward the bass end. You may need to determine if the bridges were positioned towards the bass also. If so, it may be simpler to reinstall the plate in the original position, since the string lines from the bridge to the hitch plate may be misaligned if the plate alone is relocated. It may be wise to run a thread through the string lines for the first and last note of each string section with the plate installed in its proposed location, to check the relationship of the bridge string sections to the plate. Of course, if you're fitting new bridges you will be free to relocate them along with the plate. Furthermore, the action stack and strike line may have been installed to suit the original misalignment of the plate also. If this is the case, you may be creating more problems than you will solve by moving the plate across. >The only area I am not sure what is the best comprimize >is up at note 88 (of course!). Having pushed the plate all the way forward >in the case, I have a speaking length of 52 mm and a strike point about 9.5 >mm from the termination point at the capo. A 52 mm speaking length at C88 will work, but the strike point at 9.5 mm from the capo will not allow the note to speak effectively. Our 225 piano has a C88 speaking length of 53 mm. We found that the strike setting which produced the highest sound pressure level was between 2.5 to 3.0 mm from the capo', optimally 2.75 mm. If you position the plate for a 52mm speaking length, you will be unable to move the keyboard enough to correct the strike, since it would run up against the key slip, and there would be excessive clearance between the fall board and the black notes. While alternatively you could reduce the hammer shank length by 6.5 mm to arrive at a satisfactory strike, this is a major change (there may be insufficient space between the hammer moulding and the hammer stop rail). You may find it easier to move the plate away from the stretcher by at least 3 mm to reduce the C88 speaking length to 49 mm which will bring the hammer strike point back to 6.5 mm from the capo' (Steinway Hamburg historically set C88 at 53 mm in the D - the most recent D we measured [circ. 1999 piano] had a C88 length of 49 mm). You may then be able to correct the strike by mounting the hammer 3.5 mm along the shank towards the center (I am assuming that the optimum strike position is 3mm - this will need to be verified by moving the action backwards and forwards as the note is struck). >If needed, I can slide the plate >toward the rear about 5 mm, which would then give me a speaking length of 47 >mm and a hammer strike point about 4.5 mm from the capo. I probably could >move the action a little bit, but I am pretty sure that the action is >sitting where it was supposed to, or at least where it originally did - and >I'm not sure how it would work with the fallboard - I have about a 3 mm gap >between the keyslip and the key front. > >Anyone have any input on whether I should go with a 52 mm or a 47 mm >speaking length? Or best way for me to decide? Be aware that repositioning the plate will also alter the string scale. For some instruments, which might originally have been strung beyond a safe percentage of breaking strain in one or more string sections (anything over 60% is already in the danger zone), further lengthening of the string scale (by moving the plate toward the stretcher) might aggravate a likelihood of string breakage. When considering a possible plate position, it may be good policy to measure the first and last speaking length of each string section, graphing them on a speadsheet to determine the percentage of breaking strain. You might also wish to investigate the inharmonicity effect of any plate reposition on the scaling, although this is getting beyond the scope of a straight repair and into customising - nontheless it is an interesting area to get into. With the setup in your particular piano, it would seem more appropriate to set the C88 speaking length to a lesser length if possible (say 49 mm), to minimise the necessity of major action changes. >If it is likely that the 52 >mm speaking length and 9.5 mm strike point combo is right in the typically >good functioning ballpark, I'd rather stick with that - it will be easiest >for me. As mentioned earlier, I doubt that a 9.5 mm strike will work with a 52 mm speaking length. While you could shift the entire action stack on the key board to retain the 52 mm speaking length, positioning the hammer to the optimum strike point without altering the shank length, this would involve a recalculation of the action geometry between the key and wippen. A new wippen heel depth would be required and the capstan and wippen heel would require relocating to satisfy the action geometry requirements. This work might require more time than a small piano is worth. If you are rebuilding a longer quality piano it may be worth the trouble. On the other hand, if you're keen to learn this stuff without exposing yourself on a high value piano, it may be worth the educational experience. After all, getting half paid for a job while learning a lot may be worth it. I'm doing this very thing at present with a sound board modification on a Yamaha G2. To those of you on the list who are waiting for the pics of the modifications I haven't forgotten you. I expect to be emailing them soon. All the best with the project Terry. Regards, Ron O -- Overs Pianos Sydney Australia ________________________ Web site: http://www.overspianos.com.au Email: mailto:ron@overspianos.com.au ________________________
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