[pianotech] key leveling with a curve

[Mark Schecter]

Hi, Roger.

Your description implicitly assumes constant bore length, thus pushing string height anomalies down through the entire action. If you compensate by varying the bore length to result in constant shank height, you maintain blow distance but allow the rest of the action to regulate in straight lines as designed, no?

-- Mark Schecter



On Oct 17, 2010, at 11:43 AM, "Roger Gable" <roger at gablepiano.com> wrote:

> Et al,
> Try this theory:
>  
> Given the string height is curved &
> Given the let-off matches the string height curve &
> Given the hammer height is curved to maintain constant hammer travel.
> The wippen heel to capstan line will be curved to reflect the hammer line curve.
> Now, the bottom of the key at the balance rail hole line must be curved to maintain a constant leverage arm length,
> and to maintain a constant angle of attack.
>  
> If you think this theory is sheep-dip try placing a .007" balance punching under a key and notice
> how far the hammer rises and how much increased aftertouch is felt. You can compensate for the increased key dip by
> simply adding front rail punchings, but you also will have to back down the capstan to restore hammer height, thus demonstrating
> that you now have a shorter lever arm.
>  
> Roger Gable
>  
> ----- Original Message -----
> From: PAULREVENKOJONES at aol.com
> To: pianotech at ptg.org
> Sent: Tuesday, October 12, 2010 2:01 PM
> Subject: Re: [pianotech] key leveling with a curve
> 
>  
>  
> In a message dated 10/12/2010 2:16:57 P.M. Central Daylight Time, nelsong at intune88.com writes:
> Are there other reasons for curve leveling that I am missing?
>  
> Correct me if I'm wrong (there's a dependable hope), but the most general argument I've heard is that it is to compensate for the greater playing of the piano in the middle and the compression over time of parts and underkey felts, etc. I can see the argument for mimicking the string plane curve (maybe), but the former argument strikes me as uncompelling.
>  
> P
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