[pianotech] key position at rest

[erwinspiano at aol.com]

? ?Hi Jon
? Beautiful post. The rear end of things is often neglected....lol
? thanks
? Dale






Sorry I don't quite get it ... but? 1 1/2 inch from where ?? From exactly what point

on the whippen to exactly what point elsewhere does this 1 1/2 inch come from ?




>From the key bed. Generally a S&S will have the key end lifter felt at rest at ~1 3/8"

from the key bed and the underlever at rest is around 1 1/2" from the key bed

which is lifted by the key to around 1 3/4" from the key bed.




As an aside, knowing the height to which the underlever is lifted allows

you to determine if the underlever is situated at an optimum angle.

Measure the height of the end felt with the key depressed. Lift the front

of the underlever to that measurement and notice the lever's angle relative

to the key bed. If it is parallel, that is ideal. If it is still angled down then that

indicates that the lever is scrubbing too much on the felt (increased friction)

and there is probably a trough worn into the felt.

Lifting beyond parallel is counter productive as well.




I think it was in the same class (involute gear) with Chris Robinson

that he drew a chart with an x and y axis. Friction is minimal along each axis

but as you migrate further into each quadrant, the friction increases.




So looking at the underlever as being dropped down from the horizontal x axis

with the center pin on the y axis, it makes sense to lift it to a point of least friction

(x axis) which also happens to be the point of Let Off at the end of the key stroke.




This is why I reset the tray pivot such that the underlever is lifted to parallel

to the key bed or to the x axis. Lifting beyond parallel crushes the corner

of the felt and reintroduces sliding friction (getting into the upper quadrant).







>...capstan angle...why is the standard today then perpendicular to the key ?




Ease of installation. Mark a point under the cushion, drill them straight in;

no need to waste time fiddling around with an angle.

-- 


Regards,

Jon Page

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