Bechstein B hammer rake / more thoughts

[Richard Brekne]

Hi Stéphane / Dean

I'm going to drop the horizontal shank bit for a while, because any 
justification there is for this takes the discussion off in a direction 
all its own, which for the moment hasnt my attention.

Lets just start with this basic formula for bore length thats been 
tossed around here forever namely String height - Hammershank center pin 
height. If that formula is valid, then any hammer bored to the 
resulatant length is going to leave the shank fairly close to horizontal 
unless the rake of the hammer is quite large.  Do we agree on that much 
? Yet the Bechstein I'm doing now has its shanks at the hammer molding 
about 6 mm higher then horizontal at impact. Ok they are old... but no 
way can they have lost 6 mm of total length or anything close to it. 
Lowest bass hammer maybe has lost 1 mm and the highest treble perhaps 2 
mm. This ends up just conflicting too much with the bore length formula 
given.

Indeed.. if you stop to think about it for a second,  any requirement 
for the hammer to be perpendicular to both hammer shank AND string at 
impact puts the hammershank on the string plane, i.e. significantly 
higher then String height - Hammershank center pin would yeild.

So where does that formula come from and why hasnt this been tossed out 
before and replaced with something more close to whats needed ?

We are using the term rake in the same way so thats not a problem 
Stéphane. And yes I understand a hammer that is glued perpendicular to 
the shank and is of appropriate length so that when it touches the 
string the shank is parallel to the string means the hammer is also 
perpendicular to the string. Its just that doing this conflicts with the 
string height formula I've been working with for like ages... and thats 
whats got me scratching my head.

On this Bechstein.. the difference between the two protocols yeilds 
around a 4 mm difference in bore length as far as I can tell.  Thats a 
lot I'm sure you'll agree.  Yes ?

Keep bouncing thoughts here you two... I obviously stumbled on a rather 
large hole in what I thought I had already clear in my mind.

Cheers
RicB


        RicB  wrote :
        I'm not quite sure how you could use that trick to get an
        accurate shank parallel to string plane at impact measurement. 
        At least not one that is any more accurate then the measurement
        above.  One way or another some small degree of error seems
        inevitable I suppose. My main querrie is really this shank at
        horizontal bit. If I drop that requirement, then I'd be able to
        get the hammer perpendicular to both the string and shank at
        impact if the action cavity allows for it I susppose... or at
        least pretty close to it. And that would account for a backwards
        rake yes?


    Here I don't understand.  If the hammer core is perpendicular to the
    string plane and perpendicular to the shank, then the shank is
    obviously parallel to the string plane, not ?  and per definition,
    the hammer perpendicular to the shank means that the rake is 90°,
    not ?  Or do we use different meanings for the word rake ?  I don't
    call this a backwards rake, but rather improperly no rake.  If the
    string plane angles up a little, then the shank will be
    overcentering a little bit, if we agree that overcentering means
    that the shank will be positively angled with the horizontal plane. 
    Did I mix up things ?

    Best regards.

    Stéphane Collin.

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