Two Capstans again

[Overs Pianos]

>Ron Overs wrote:
>
>>  At 9:33 PM +0100 16/1/03, Richard Brekne wrote:
>>
>>  >. . . I dont really know what to think about the ratio in this as it would
>>  >change through the key stroke.
>>
>>  As does a normal grand piano action, ie. one with one capstan, but to
>>  a lesser extent.
>>  Ron O.
>>  --
>
>Yes, but wouldnt this be much more noticeable ?

Yes

>Another thing while I have your
>ear Ron... In taking up and down weight measurements, it's almost always
>apparent that the lower half of the hammer travel needs more weight 
>for DW (and
>less for UW) then the upper half.

This hasn't been our experience. As the jack/roller contact is 
further away from the line of centres at rest. As the key dip 
progresses the contact will move closer to the line of centres 
thereby reducing the difference between up/down weight. However, some 
actions do have problems with the angle of the balance pin relative 
to its balance pin hole. This is a common cause of increased down 
weight at the lower end of the key dip. A higher repetition lever 
tension will also give the player a feeling that the down weight is 
heavier at the bottom of the key stroke.

>But with the increased ratio spread resulting
>from a concave capstan  (or some such idea) wouldnt this tendency be kind of
>reversed... or evened out at least ?

As you say, it would tend to result in a lower ratio at the start of 
dip. A larger diameter capstan will tend to have a similar effect 
also.

>The hammer at the rest position would then see a key leverage that was reduced
>by the diameter of the capstan compared to the the hammer at drop... so it
>would take less weight to get the darn thing moving upwards, and 
>more to finish
>pushing it though the stroke.

Indeed, our action achieves this also to some degree, since the 
hammer/key ratio remains more uniform throughout the key stroke (in 
standard actions the actual ratio is higher at rest, decreasing as 
the key is depressed). While a great majority of pianists approve of 
our action, I have a feeling that the few who don't may be put off by 
the lower than usual ratio at the commencement of the dip, which must 
also be accompanied by a slightly higher ratio at the end of the 
stroke if the overall ratio is to remain at some nominal value (in 
our case we have been setting this nominal value between 5.6 to 5.8:1 
- lower in the later installations).

>Course you dont need so much leverage to handle things after the 
>jack releases.

True. The jack release rate is an interesting consideration with 
regard to let off efficiency. The speed of the jack tip must be 
considered relative to the key movement. A slower jack escapement (in 
cases where 15 or 15.5 mm type hammer shank is used in combination 
with a lower key ratio, but with a higher hammer/key ratio) can make 
an action more prone to 'double hitting' during slow playing.

Ron O.
-- 

        OVERS PIANOS
Grand piano manufacturers
________________________

Web:   http://www.overspianos.com.au
Email: mailto:ron@overspianos.com.au
________________________