Del, Tony et al, >. . . Early writers spoke of >a SPR at C-88 of between 1/12th up to 1/20th of the speaking length. If >memory serves, Wolfenden mentioned a SPR of 1/16th in the first edition of >his book. Yes, I am starting to suspect that the radius and the hardness of the bar may have an influence over the ideal SPR. We have done quite careful checks to arrive at the optimum SPR at C88 for the three 225 we've built so far. It's turned out for all three instruments that with a speaking length of 53 mm, the ideal strike point from the capo was 2.5 to 2.75 mm (1/19 - 1/21). Now I realise that this seems to be rediculously close, but I suspect that the small radius hard bars we use just might allow for more flexibility of the string at the termination point - hence the requirement for the hammer to come closer to the bar. It's just a hunch, but I suspect that a larger radius bar might in some way limit the ability of the string to be excited. What do you think Del? > >From there the SPR will slide down toward 1/8th (+/-) and get there >somewhere about the middle of the scale. I say 'about' because I've measured >enough old (and new) scales now to realize many pianos don't come all that >close to this so-called ideal. Agreed Del. When we set up our own scale in the 225, the agraffe for G#24 (the lowest note on the long bridge) ended up about 3 mm further away from the stretcher rail than on a standard Samick 225, yet our piano has the same speaking length at G#24 of 154 cm (it's the only speaking length which is the same on our piano as for a Samick 225), obviously the strike ratios on the Samick over the cross are not uniform (further more, I know they are not, because I've measured a standard Samick 225 piano). Our jig for locating the plate in the case is set up with a cut away along the strike line at C88. This allows us to set up a light with a mirror on the keybed, enabling us to position the plate such that the bar is right where we want it for that critical SPR at C88. It's quite satisfying setting the plate with this jig, since you don't have to wonder if the piano will work as planned when finally put together. How's your new piano coming along Del? I'll get back to you soon Ron N. Regards to all, Ron O -- ______________________________ Website: http://www.overspianos.com.au Email: mailto:ron@overspianos.com.au ______________________________
This PTG archive page provided courtesy of Moy Piano Service, LLC