Shanks parallel to strings

[Stéphane Collin]

My try :

The hammer has a rotating movement around the center pin of the shank.  
When hitting the string, we could consider two points : the point of 
first contact between hammer and string, and the point of largest 
excursion of the hammer accompanying the string at it's largest 
deflexion from rest position before rebounding, at loudest playing power 
(this will be very different in the bass than in the trebble).  I 
believe that for maximum power transfer between the hammer and the 
string, the movement of the hammer should be not really perpendicular at 
contact time to the plane of the resting string, but to a plane a bit 
higher (higher of something approaching half the distance between the 
two points defined earlier).  This, because of the cosinus coefficient 
in the vectorial force.  Let us call this third very point the optimal 
quasi tangential point of intersection between hammer arc and quasi 
perpendiculat to largest portion of string plane when at approximately 
1/2 of it's  largest deflection from rest position at loudest power 
playing (OQTPIBHAQPLPSPA1/2LDRPLPP).
The fact is : if you bore your hammer shorter and have the shank run 
beyond parallel to the plane including the OQTPIBHAQPLPSPA1/2LDRPLPP, 
you loose some power because most of the vectorial kinetic energy runs 
in a direction that is not perpendicular to that very plane, thus 
affected by the cosinus coefficient.  Same again when the hammer is 
rebounding : some energy is spent (in frictions and mass direction 
change) affected by the same cosinus coefficient.
Now, talking about power, I am sure that other factors, like soundboard 
desing, impedance matching, hammers desing and voicing, etc. are much 
more important in the end.  And I think that what Bechstein had in mind 
when desinging a rake in their hammers was mainly the thus alowed 
thickness of the pinblock (which proved to be more durable than Pleyel 
pinblocks).

Regards,

Stéphane Collin.

 

 
Phillip Ford a écrit :

>I would like to revisit the idea that shanks should be parallel to strings at hammer contact.  I know we've had some discussion of this before.  I looked back through the archives and also in the back issues of the Journal and couldn't really find what I wanted.  I would like to have some theoretical reasons why having the shank parallel to the string gives better action performance than not having it parallel.  The standard thinking seems to be that the hammer should be perpendicular to the string line at contact and the hammer should be perpendicular to the shank, which results in shanks parallel to strings.  I can see reasons for having the hammer strike perpendicular to the string line.  But I don't see any good reason for having the hammer perpendicular to the shank or the shank parallel to the string.  Reasons given in the archives or the journal for not permitting non-parallel shanks are along the lines of:
>
>1.  It's bad practice.
>2.  It reduces power delivery.
>3.  It won't give as strong a joint at the hammer to shank interface.
>4.  The regulation will get screwed up.
>
>As to these reasons:
>
>1.  If it's bad practice, is there some explanation on offer?
>2.  Why would it reduce power delivery?  The hammer is still traveling in the same path as it was before - the angle of shank to hammer doesn't affect that.  If the hammer is still striking perpendicular to the string why would any reduction in power have occurred?
>3.  I don't see that the joint should be weaker.  If anything, having the shank not perpendicular to the hammer would mean that the hole through the hammer has to be a little longer, which would seem to result in a stronger glue joint.
>4.  I can see that this would be true if the action was designed to work with the shank parallel at contact, and that drastically changing this would cause various things like rest rails and letoff buttons to be in the wrong places for the new shank position.  But I'm talking about an action that was specifically designed to have the shank non-parallel at contact.  In this case everything could be positioned to work properly so that regulation would not be compromised.
>
>Any thoughts?
>
>Phil
>
>
>
>Phillip Ford
>Piano Service and Restoration
>San Francisco, CA
>_______________________________________________
>pianotech list info: https://www.moypiano.com/resources/#archives
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