Richard Moody and list, Richard wrote of the Overs action drawings >Very interesting pictures, drawings rather. BTW how are they done? >Scanned or CAD, or some other computer drawing program? Converted to jpeg using Photoshop, from the final CAD drawings prior to building the prototypes. The CAD drawings were completed last December, but weren't released to anyone until the patent application was lodged in March 2000. > >It is an interesting (to me at least) short repitition lever and position of >the spring. This design was not a styling exercise - the whole CAD design took three months pretty much full time. The spring design is part of our pending patent. This spring has the lower spring arm positioned on the line of centres from the repetition lever to the jack centre. This minimises spring friction and noise (which can be considerable with the double-wing spring wippens). The Wippen Helper Springs Furthermore, the shorter rep' lever allows for easy access to the helper spring adjustment screw. The first production piano has been set up with the helper spring pressure evenly graded from 18 gm (measured at the face of the jack) at note A1, to zero at note A#50 (51 - 88 have no springs). Keyleads were inserted subsequently to achieve the downweight figures of 52 gram at note A1 to 48 gm at note C88. This action has different size wippen heels for the black and white notes - to optimise friction (ie minimise) and to ensure a constant hammer/key leverage ratio. Obviously, the black notes required more lead to acheive the specified downweight figure, since the black-note weight in front of the balance pin is less than that of the whites. The hammers were carefully graded for weight prior to setting up the keyboard. We were intent on achieving an even grading of the key inertia between the blacks and whites. To acheive this end, the wippen assist springs must exert an even pressure prior to inserting key leads. I am convinced that assist springs (if used) must be accompanied by a means of adjustment. I know that you can adjust them manually, but who goes to the trouble of grading the pressure when there is no screw adjustment? Rep' spring jack-hole The spring hole in the jack is also located on the line of centres (also part of the patent pend.) for the same reason as the positioning of the lower rep' spring arm. >I had to look at action diagrams and a whippen here (Kawai, >Schwander also I suppose) to see why the RL needs a "tail". But now that >you have shortened it, it can no longer be called a "lever" ; ) . I don't see why not! It still performs as a lever which supports the hammer shank to facilitate repetition. The only difference being that the rep' lever height adjustment on our action is via a scew (pulling - as it does on the older Schwander types), rather than an adjustment button (pushing) on the other side of the rep' lever centre. > Now if >you could just figure out how to get the jack regulating screw in the >balance lever. Why would anyone want to ? Explain! >I sure a simple felt spacing pad in the window has been >tried before. Oh yes you're correct! But I would presume that most of us are interested in evolving our craft in a forward direction. Repetition lever centre position The position of the repetition lever centre height is also part of our patent claim. The centre has been located to minimise friction between the roller and the repetition lever during the hammer's rise out of check. Note the line (of centres) between the rep' lever centre and the hammer centre in the lower drawing. This condition is only satisfied when the hammer is in the check position. The jack tail The jack tail design (ie. radius and angle) has been specified according to a mathematical formula (which is also part of our patent claim). This design reduces the friction at the jack tail almost to zero, since the jack tail (in this design only) actually rolls on the surface of the let off button. Both the prototypes and the first production action perform with an upweight measurement which is 10 gm less than the downweight, ie. if the downweight is 50 gm, the upweight is 40. The hammer rest sitting so close to the hammer shanks is not accidental. There remains considerable energy in the leverage system when the shank returns to rest following the keystroke (in this design). The close hammer rest reduces the propensity of the hammer to bounce when it returns to the rest position. Sorry about the length folks. I got a bit carried away. Its 1.10 am here in Sydney, and our first grand piano (with the above mentioned action) is on display today as part of an Olympics business promotion put on by our State government. I'd better get some sleep. Regards, Ron Overs -- _________________________ Website: www.overspianos.com.au Email: ron@overspianos.com.au _________________________
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