[pianotech] Hammer strike line

[Clayton Bean's Piano Biz]

Bravo!  well said. Fini
----- Original Message ----- 
From: "John Delacour" <JD at Pianomaker.co.uk>
To: <pianotech at ptg.org>
Sent: Monday, February 08, 2010 6:41 PM
Subject: Re: [pianotech] Hammer strike line


> 
> Before the discussion goes completely off-topic I'll give my take on 
> the question of the strike line.
> 
> My definition of the strike line is the first (straight) line that is 
> made on the drawing board in the designing of a piano and is the line 
> that crosses the strings at the point where the hammers are 
> _intended_ to strike the string, with the hammer-heads at a right 
> angle to the strings.
> 
> From this line, the line of the string to the top bridge (agraffe 
> etc) and the line to the first bridge pin are drawn in a certain 
> proportion one to the other, this proportion having been determined 
> by the piano maker, through his own experience and that of his 
> predecessors and masters, to be the very best proportion for the 
> piano in question and similar pianos.
> 
> In a piano of reputable manufacture it is unlikely that the choice of 
> these proportions is anything but the best, and no matter what the 
> condition of the soundboard is, it is unlikely that the tone of the 
> piano can be improved by striking the string at any other proportion 
> of its length than that set by the maker.
> 
> A bird's eye view of the strike line will show it as straight.  Gross 
> errors in the placement of the agraffes and the bridges will 
> frustrate the designer's plans.  Lesser errors will make very little 
> difference except in the extreme treble.
> 
> A view of the strike line from the front (ie. a line joining the 
> points that represent the strike height at the strike line) will 
> occasionally be straight but more often than not it will have steps 
> (at the breaks), slopes and curves.  In addition to this, 
> particularly on pianos with agraffes all the way up, the angle of the 
> strings to the horizontal (going at an upward slope to the bridge) 
> will increase in the top section towards the top.  This also needs to 
> be taken into account.
> 
> If the hammers are correctly bored as regards bore length and bore 
> angle, by taking into account the above factors and calculating the 
> bore given a straight hammer rail at a constant height above the 
> key-bottom (and this must be most carefully verified and adjusted as 
> necessary having regard to the total geometry of the action, which is 
> a whole nother story) then each hammer will strike its string at a 
> right angle and at the strike line, and the best possible performance 
> will be had from the instrument.
> 
> If I buy standard bore hammers for a Steinway my chances of getting 
> things wrong are roughly 100%.  I worked on a very fine 1970s Hamburg 
> model B a couple of months ago that had the original hammers and 
> these had been certainly been refaced once or twice but this would 
> have accounted for the removal of say 3mm from the nose of the hammer 
> at the maximum.  It was obviously a great piano but performers were 
> complaining of weaknesses.  I had Abel make me a set of raw hammers 
> and bored them according to my calculations from the careful 
> measurements I had taken.  The bore of my hammers differed from the 
> originals by up to 8 millimetres! and, since they were, for the first 
> time ever, hitting the strings in the right place at the right angle, 
> the piano has a purity and power that it never had before.
> 
> One of my current jobs is a 1927 Model O.  If I had ordered standard 
> bore hammers with a bore length of 45 mm, again I would be wrong.  At 
> places in the scale I need a bore length of 49 mm because the string 
> heights are not what they should be for the given action and 45mm 
> hammers.
> 
> The alternative to doing things properly is to take no measurements, 
> make no calculations, buy standard hammers and make the best of a bad 
> job by shifting things backwards and forwards until they sound OK.
> 
> JD
> 
> 
> 
> 
> 
> 
> -- 
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