Shanks parallel to strings

[Phillip Ford]

>Phil Ford wrote:
>
> >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?
>
>Wouldn't the distance from strike point to hammer center be
>greater? (assuming you're going above horizontal, and hammer
>is perpendicular to string when it strikes - therefore angle
>between shank and hammer is > 90)  So hammer would
>not take  quite the same path.

The tip of the hammer is moving in a circle about the hammer flange 
center.  The radius of that circle is the distance of the hammer tip from the 
flange center.  The angle the shank makes to the hammer molding doesn't 
affect that distance.

>   A slightly larger radius, I
>would think.  Now whether it would matter...well it does
>increase your moment of inertia <G>.

I think you're right about that.  If the shank is not at 90 degrees to the 
hammer molding the shank will have to be slightly longer, increasing moment 
of inertia of the assembly slightly.

>   More practically,
>if you're measuring SWs, it would be a pain with the
>hammers not at 90 degrees to the shanks.

If you look back at Stanwood's original article, the way he measured SW was 
to turn the hammer upside down and let the tip of the hammer rest on the 
scale.  I suppose you would have to decide if you want the shank to be 
level to the scale or the hammer to be square to the scale.


> >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.
>
>Not weaker, but if it's not 90 degrees, that would put a
>twisting force on the joint at impact that's not there
>otherwise.

Do you mean a bending force (as opposed to a twisting force on the shank 
caused by an off-center hammer)?  If the load is not straight down the 
molding I can see that a slight moment will be induced at the joint.  I 
don't know if this is significant either to the glue joint or to the 
shank.  Could be.


> >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.
>
>Funny you should mention that.  The piano I am
>working on with the too-long bore distance has
>drop screws all the way up (already posted about
>that) but I just figured out that it's also causing the
>hammers to be way too far off the rest cushions
>(Steinway - so there's no rail to adjust).
>
>-Mark

Right.  For an action that was designed to have a certain bore distance 
with shanks parallel to strings then that needs to be maintained in order 
for things to work properly.  But if an action were designed to have that 
same bore distance with shanks above parallel at strike would it have 
degraded performance as compared to the action with the parallel 
shanks?  Perhaps it would have improved performance.  That's what I'm 
pondering.

Phil