Herrburger Action

[John Delacour]

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At 08:48 26/09/01 +1000, Overs Pianos wrote:

Is this the action. Thanks for sending this to the list Clarke.

I did say, in the message you quote, that this is of course NOT the =
action.

This is the one:




               J

         L R    C
             H

In the Herrburger lever JL is 70, LC is 69, LR is 9.5 and R is almost in =
line with LC.
JC is 50.  LH is 47, CH is 30.  The jack tender makes contact 26 mm from =
C, 4 mm
above the line LC produced.

John, would you mind explaining the letter diagram you have used above, =
just to avoid confusion. Thanks.

J =3D Jack corner (=3Dknife cut on rep lever)
L =3D Intermediate lever centre
R =3D Repetition lever centre
C =3D Jack centre
H =3D Mid-point of lever heel

supposing it is 8, then reducing LC to 75, as you have done, will =
diminish this
figure and reducing it to 69 as Herrburger did will diminish it further

How?

You wrote "...the roller/knuckle contact scrubs badly since the contact =
is around 8 mm below the line of centers at the rest position."

Have I not understood you?  You are talking of the line from hammer =
centre to lever centre I understood.  If we take a hypothetical set-up =
with a 50 mm jack at a given angle, a horizontal line from lever centre =
to jack centre (whether 99 or 75 or 69)  and a given vertical distance =
from this line to the hammer centre, and a line AB from hammer centre to =
lever centre, then

a) the closer the lever centre approaches to the jack centre, the =
shorter the distance of the contact point below the line AB.

b) the smaller the roller , the shorter the distance of the contact =
point below the line AB.

That's all I'm saying.

In practice the line from lever centre to jack centre at rest is rarely =
horizontal.

What I am saying is that you have reduced the length of this line to 75 =
and Herrburger reduced it to 69; both you and Herrburger use the older 9 =
mm roller rather than the current 10 mm roller and there are good =
reasons for these choices.  I have not yet investigated the geometry of =
your action and it's probably 20 years since I investigated the =
Herrburger action, but there is no doubt that either is preferable to =
any currently used version of the Erard-Herz action.  I do doubt though =
whether your version is significantly better than Herrburger's if at =
all.  When I have time, I'd like to make drawings to make a proper =
comparison.

I have a question about your angled lever heel/capstan block, which =
looks that same as an arrangement patented by Grotrian in 1905.  I see =
no rationale for this and Pfeiffer says of it "..the point of view on =
which the patent was based is not to be upheld."  It looks to me also as =
if this arrangement makes even more fiddly the process of adjusting the =
capstan screw.

JD




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