>Why? Is it because it's a Baldwin? Or is it because it's flat? Because it's flat, or more accurately too low impedance. > Or is it because all other pianos have too much bearing? Or is it because there is >some fairy dust that makes them allergic to excess bearing? Maybe the >casters need grease. I want to know. Given a 600mm rib, 19mm high and 24mm wide (for example): 72' (21.95M) = 2.05mm crown (Baldwin) 60' (18.288M) = 2.46mm (Traditional) 50' (15.24M) = 2.95mm 40' (12.19M) = 3.69mm The Baldwin rib in this case only has 83% of the crown of the "usual" 60' radius. Using just the rib, it takes 3.05 pounds to deflect the 60' to the 72' crown height. To deflect these example ribs to 0 crown takes: 72' - 15.2lb 60' - 18.25lb 50' - 21.9lb 40' - 27.4lb A higher crowned rib will support more load and still remain crowned. In the area of the board where you might find this rib, at different bearing angles you would expect to find loads this rib is responsible for to be similar to this: 1.5° = 60lb 1° = 40lb 0.5° = 20lb The panel is under compression too, naturally, and will add stiffness and crown. How much? Depends on how far you dried it down before assembly, how thick it is, how dense it is, and how much bearing load is placed on it. Bearing settings, successful ones anyway, will be determined by rib dimensions, crown height, panel characteristics, and what you expect to get out of the finished produce in sound. That's why comparing bearing settings from one shop to the next isn't too informative. >What does the vertical hitch pins >have to do with it? Nothing. >Does using vertical hitch pins on a non-Baldwin affect the decision on >downbearing? No. Another caveat about pre-loading old boards by feel. Once you have it wedged down where it feels solid and stiff, crawl underneath and check the crown and see if it is already concave under load. The criteria for replacing the soundboard is, or should be, whether or not it is still structurally up to the job. Ron N
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