Schwander inverted center linked action

[John Delacour]

At 6:15 PM +0100 7/3/02, Stéphane Collin wrote:

>Does anyone have information about how to regulate this kind of 
>Schwander inverted center linked action ?  It is from a wonderful 
>Bechstein model II of 1870.  The Factory can't help me, as the 
>archives about this instrument are lost.)
>
>schema : <http://fr.be.msnusers.com/bechsteinlovers> on the 
>mainpage, click on images and then on Herrbruger Schwander.

Stéphane,

I haven't worked on this action but I have looked at it several times 
in Pfeiffer's book and dismissed it as NOT one of Herrburger's 
greatest inspirations.  There is an awful amount of friction in the 
design and I imagine it will be difficult to get it totally reliable 
and feeling nice.

The doeskin at the bottom of the jack must be in good condition with 
the smooth direction clockwise with regard to the drawing; the 
burnishing of the curved end of the key carriage must also be very 
smooth so that the return of the key is as swift as possible.  The 
set-off surface of the jack must also be very smooth and the set-off 
button cloth clean, again to minimize friction.  This sort of sliding 
surface escapement is not too bad in practice.  This was the method 
used in Stodart's 1775 Grand Action patent and was used by Broadwood 
for over 100 years.  I have an 1880 Schiedmayer upright with this 
sort of escapement.

I imagine the keys are slightly back heavy and contain very little 
lead except in the treble.  It is important that the keys should be 
completely free; any stiffness will cause great problems.  The return 
of the key is accelerated by the pressure of the repetition block, 
which also serves to raise the hammer out of check and slightly to 
lighten the touch weight.  Since this sprung block has these three 
roles, it is important to achieve a balance.  Its most critical 
function is to raise the hammer, and the rise of the hammer should be 
"positive but gentle".

I think you will find the hammers need to rest on the hammer rest and 
leve a very small amont of lost motion between key carriage and jack, 
as on an upright.  Once you have established the blow, levelled the 
keys and regulated the set-off, you should set the touch depth for 
minimum after-touch.  The repetition rocker can then be regulated.

The drawing shows the set-off button in contact with the sliding 
surface with the hammer at rest.  This is wrong, of course, since 
contact will not be made until the hammer is at most 20 mm from the 
string, I should guess.

I don't like the look of this action, but perhaps it will work.  I 
think it might feel rather clunky.

JD