More off the wall stuff

[Overs Pianos]

At 12:37 AM +0100 18/1/03, Richard Brekne wrote:


>. . . We see very very often that the key ratio between the black and whites
>are significantly different. Sometimes as much as from 0.50 to 0.54.

Indeed, and then folks wonder why the black keys in such pianos 
sometimes have to be buried under the whites or levelled way high to 
get after touch.

>Perhaps more in some exceptional cases. There has been thrown out
>several different ways of approaching handling this. But here is one I
>havent heard and am curious about.
>
>What would bad about staggering the knuckle position ? It wouldnt take
>much to compensate for the difference in key ratio to even out the
>overall ratio....

I agree with David Love's post that it is much better to move the 
capstan line for the black notes. If you were to move the knuckle 
lines you would end up with the 'white' and 'black' wippens moving at 
different speeds relative to the hammer shanks. This whole problem of 
white/black ratio comes about when designers neglect to set an 
appropriate distance between the white and black note balance pin 
hole lines. The practice of spacing them at 18 - 20 mm regardless of 
key stick length is not a good practice.

The Samick 225 specification of 18 mm between the balance pin rows 
resulted in an almost identical ratio between the black and whites, 
whereas a 212 Kluge keyboard I set up recently required the 'black' 
capstan line to be drilled 0.5 mm shorter to achieve an equivalent 
ratio to the the whites.

A couple of days ago I was interested in Roger Jolly's comment about 
the key dip spec' for some Samick grands (of around 11 mm). His 
comments line up very well with my own measurements of some Samick 
key ratios (however we set our hammer/key ratio at 5.6 at present) . 
I have measured 185 cm Samick pianos with around 4.5:1 hammer key 
ratio. No. wonder some of these instruments require 11 mm of dip to 
get after touch.

By the way Richard, a couple of weeks ago when I wasn't paying 
attention, you mentioned some difficulties you were having using the 
hammer/key ratio formula we use. Your comment about the bass hammers 
verses the treble hammers is correct however. The ratio for the bass 
hammers will be a little higher than the treble sections (all other 
things being equal), since the greater boring distance of the bass 
hammers will result in a longer diagonal length from the hammer 
centre to the hammer strike point. However, you will find that most 
modern action installations in which the hammer core is set 130 mm 
from the centre pin will typically have between 138 to 140 to the 
striking point of the treble hammers. I tend to use this a standard 
when calculating the hammer/key ratio. You mentioned in your post 
about the hammer shank ratio being around 7.6:1 if you are measuring 
a 130 mm shank with a 17 mm roller slot. However, the important two 
hammer lever measurements will be the diagonal length from the hammer 
centre to the hammer strike point and the diagonal length to the 
roller jack contact point. If you look at these figures you will get 
typically around 138 to the strike point, and around 20 to 22 mm to 
the roller contact point. This will result in a ratio for these two 
length of around 7.0. At the end of this process, no matter which way 
you measure the ratio, we are all primarily interested in how many mm 
the hammer strike point moves for each mm of key dip. An examination 
of blow distance and dip alone will tell us nothing, since the let 
off and after touch consumes key dip for its execution.

Ron O.
-- 

        OVERS PIANOS
Grand piano manufacturers
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