Bechstein B hammer rake / more thoughts

[Richard Brekne]

Hi JD

This is very  much in line with what ended up working out here. Not
quite but pretty close. The bass up to around the break where the capo
bar usually is in other pianos needed about a 1 degree rake back to hit
square with the strings. From there up it was pretty much perpendicular
to the shank. The shank at impact in all cases between between 3 and 4.5
mm over horizontal except in the highest 7-8 notes where it was just a
little less then 3.  The area right around that same break had a rise in
the string height that quickly fell away after the break.

Draconian... not really sure where that begins or ends... but I
registered 3 + degrees in the low bass on the hammers that I removed.
Did a quick very rough check with regulation and clearance with hammers
at a tight dry fit.  Doesn't look to be any problems at all. Quite the
opposite. Looks to be easier to resolve clearance problems in high
treble hammer travel and and the regulation is definitely going to end
up better.

Cheers
RicB


    At 15:32 +0200 22/6/08, ricb at pianostemmer.no wrote:

         >...The design simply calls for the shank to be 3 mm higher at
        the end of the shank then it would be if it was horizontal at
        impact. Nothing
         > like straight forward advice....Following the above advice
        has worked out perfectly. Very easy to get close to a
        perpendicular to string
         > orientation without draconian rakes.


    Well, supposing the strings are horizontal right up to the top,
    which they can be in a Bechstein, and supposing that you make no
    allowance for facing and wear, then 'draconian' or not, the heads
    will need to be raked outwards 1.32 degrees.  If you allow for 1 mm.
    of lost  length between boring and finishing, which is reasonable,
    then you will need to bore for an outward rake of 1.76 degrees.

    JD