Shanks parallel to strings

[Overs Pianos]

Hi Phil,

>>. . . I've suggested that the improvement in the jack/roller 
>>contact relationship is one of the main benefits in setting the 
>>bore distance so the hammer shanks are over-horizontal when the 
>>hammer strikes the string.
>
>I must have missed this in my search of the archives (not an exact science).

The thread might not be titled action geometry or such. Quite often 
we end up discussing unrelated topics within a thread.

>   I remember lots of discussions and I was aware that your action 
>was set up to have the jack / knuckle contact point on the line at 
>half stroke, but I didn't remember that you were advocating short 
>boring the hammers.

I'm not advocating it with our own action, since it is designed for 
the shank to be horizontal at strike. But for conventional 
contemporary actions, over centering really helps.

>   I'll go back and try to find some of that stuff.
>. . . I also think that we are talking about two separate issues 
>here, although in an action of conventional design they are linked.
>
>1.  Is the shank to hammer molding angle significant in and of 
>itself?  The orthodox guideline is that the shank must be 90 degrees 
>to the molding.  I see no reason for this and haven't heard any 
>convincing arguments in its favor.

We see hammers that are angled back on over centered actions. 
However, I don't have a view on what's right or wrong. Our usual 
approach is to over center the shanks by around 2 mm, and set the 
hammer at 90 degrees. Since must strings are angled up by at least a 
couple of degrees, it works out to be a reasonable compromise.

>2.  Does it improve feel or performance of the action to have the 
>jack/knuckle contact point above the magic line at letoff?

It probably would assist let-off slightly, since the surface of the 
roller would tend to be travelling more with the direction of the 
jack surface as it moves towards the let-off position. But that's not 
the reason for setting it up in this manner.

>If so, on an action of conventional design, on which the geometry 
>was laid out with the premise that the shank would be parallel to 
>the string at letoff, then the only way to achieve this is to short 
>bore the hammer.  The shank will end up being above parallel at 
>hammer contact, but that's only a consequence of the setup to get 
>the jack/knuckle contact to be where you want it to be.

As usual, it would be a compromise.

>If you were so inclined, it seems that you could design your action 
>to have both jack/knuckle contact above the line and shanks parallel 
>to strings at hammer contact.

Our action has been designed in this way.

I've been following this thread. But since I have no particular 
opinion on the matter of mass distribution of the hammer/shank 
assembly, and its effect on tone, I'm quite content to read other 
opinions.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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