Keep on filing...(picture attached)

[Richard Brekne]

Hi Dave

I read what he wrote, and replied as I felt appropriately. (friendly 
tone here just so thats said)  It is not given that you need to change 
the tension of the spring when you change pinning resistance. You dont 
know that until you've actually changed the pin and find out.  I tend 
(try) to keep to the exact subject matter as best I can, and the 
sequence of posts written that he replied to had one specific reference 
to changing the spring tension... and that stated to quote:

        "Whatever friction there is at the lever pin simply restricts
        the amount of movement of the lever for same spring strength"

The subject matter was in other words nicely isolated and I treated it 
thus.  I went on to point out that if you first did decide to imply that 
an increase in pinning resistance bore with it a need to increase spring 
strength... that this was questionable.  It  may... or it may not... 
depends on how strong the thing was... depends also on whether or not 
you need to change the hammer center first... depends on other things 
you need to take care of first as well.... which makes it very 
complicated to comment on unless one keeps each moment isolated bit for bit.

As to your closing claim.. I agree.. you can increase the push on the 
key without making a hammer jumpy by increasing the tension on the 
spring and other appropriate adjustments. But this can be done in 
several ways... and not all of them are equally wise.  The point is, the 
tension of the spring affects jack travel, hammer lift, and key return, 
and all these are in turn affected by the friction of their respective 
centers, and by their individual mass.  And the main point of the whole 
repetition lever is not to help key return speed... but to raise the 
hammer and reset the jack well before the key returns full distance.  
How fast the key returns in all this in the end is more a matter of 
pianist preference to begin with then it is anything else.  Some like to 
feel a bit of a kick from the rep spring... some like none... some like 
30 grams of upweight... some prefer closer to 20.

Cheers... btw... hows the convention going ??

RicB

    Ric:

    You need to read more carefully.  Dean said " If you increase the
    resistance of the pinning, you must also increase the spring tension to
    overcome this resistance for a given hammer lift."

    Of course the spring
    tension doesn't get increased until you increase it.  The point is you
    can increase the tension helping to return the key and hammer without
    making a jumpy hammer.


dp

 

David M. Porritt
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