Keep on filing...(picture attached)

[Dean May]

Ric wrote: After all.. the spring tension is not actually increased.  

Seems to me it is. If you increase the resistance of the pinning, you must
also increase the spring tension to overcome this resistance for a given
hammer lift. 

Dean

Dean May             cell 812.239.3359 

PianoRebuilders.com   812.235.5272 

Terre Haute IN  47802


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Richard Brekne
Sent: Friday, June 22, 2007 4:22 AM
To: pianotech at ptg.org
Subject: Keep on filing...(picture attached)

I agree with this view, but I have to admit I have never actually 
checked to see whether or not increased rep center pin friction directs 
more of the springs strength towards jack return. It may end up being 
that if actually measured it does not.  After all.. the spring tension 
is not actually increased.  One could easily think along the lines that 
the spring must use more of its strength to overcome the increased 
friction... and thats it.  Might be fun to actually check this out. 
Could be done with strain measuring devices placed on both levers I 
would think.

My main point however goes to this idea about that surfaces from time to 
time about the rep spring/levers' relationship to key return speed.  
This is a by product of the device and not its purpose, tho some will 
have it otherwise.  It is true that the rep spring does execute a force 
downwards as well as upwards...increasing key return speed in the same 
proportion to increase in spring strength that this same increases 
hammer lift. But the purpose of the mechanism is to reset the action 
into firing position at the earliest possible moment so that the key 
need not travel full return in order to be replayed.  Too strong a 
spring effect creates uncomfortable touch and ill seeming noises among 
other things.

Cheers
RicB


    David Love comments :

    Pinning the rep lever tighter allows for speedier jack return as well as
    more positive hammer rise since the spring doesn't need to be set so
    close
    to the fail point.  Most of the benefit, in my view, comes from the
    speedier
    jack return and thus faster repetition.  
     

    David Love
    davidlovepianos at comcast.net
    www.davidlovepianos.com


        Ric B writes in response to David Porritt below

        I dont think I understand the logic behind this claim.  Whatever
        friction
        there is at the lever pin simply restricts the amount of
        movement of the
        lever for same spring strength.  I suppose more of the springs
        energy might
        be directed to jack return... not really sure about this either
        when it
        comes to it.

        The rep lever springs upwards and downwards with equal strength
        regardless
        of the tightness of the pinning. The only thing that can change
        the relative
        pressure between up and down would be a repositioning of the
        pin... i.e.
        changing its leverage moment.

        I would suspect, that 8-10 grams works well because it fits well
        with the
        multi-tasking between the rep spring and other related parts...
        ie jack
        return, hammer lift, appropriate friction levels for centers
        belonging to
        these...etc.

        Cheers
        RicB



            Pinning the repetition lever to 8 grams restricts the
            jumpiness of the
            hammer on key release and directs more of the spring's
            energy into
            returning the key.  When I'm doing a very careful regulation
            of a
            performance piano (where "it's so even" is the compliment I
            want to
            hear) I use an 8-gram weight I have that has a hole in the
            middle.  If I
            put that weight on the screw that regulates the rep. lever's
            height (the
            short end of the rep. lever) I want the pinning tight enough
            that it
            holds the weight.  When I place it on the drop screw pad
            (the longer end
            of the rep. lever) I want the lever to gently fall.

            dp