[CAUT] Digest, Vol 1103, Issue 85 Moving Wippen Rail

[Richard Brekne]

Hi Keith

Ok, now I see where you are comming from.  You simply say the output arm 
is the jack pin and therefore a fixed length, and further the jacks 
angle supporting whatever load is on it doesnt really figure into the 
equation. 

I think its fair to say the huge majority of things written up to now on 
the subject of the whippen disagrees. Fair enough...they may in the end 
be wrong and you right. I believe tho there are a couple points you are 
overlooking that I dont think you correctly can overlook.  One, the 
position of the output load vs the output arm support point are changed 
relative to each other.  Whether you think in terms of the jack top or 
the jack pin... this still effectively changes the ratio in the sense 
Jon points to... i.e. lengthening the output arm. Its just that you 
transfer the responsibility for the change to the hammer shank.  The 
other is that I am unconvinced you can get away with discounting the 
jacks angle as you do.

Still, its an interesting idea and it will be fun to look at closer with 
action models.  One quick experiment would be to chop off the rep lever 
and fashion the rep spring so that it still works the jack return.  Then 
adjust jack angle and reposition the hammer shank so the knuckle matches 
instead of the usual other way around. That way one could use BW 
measurements to look a bit closer at whether the angle of the jack 
itself actually does make a diff.  Even tho BW measurements are rather 
iffy things ... it might be illustrative.

Cheers
RicB


        On 11/1/07, Richard Brekne <ricb at pianostemmer.no> wrote:
         >
         >   Either way moving
         > the whole whippen 2 mm moves both points 2 mm.




    This is where I think you are missing it. The jack center to wippen
    center
    cannot change in distance. The RA remains the same length. 1 to
    1.477changes to 1 to
    1.430  with a 2mm rail move on the S&S wippen I just measured. It
    can lift
    more weight. Not much but some.

    If you lean the post or the jack from the tangent line of the RA,
    you have
    to use vector analysis and angular momentum formulas to figure the
    output
    transfered to the jack. It is not a distance measurment factored back
    directly against the EA. As the jack leans it is an exponential function
    based on the number of degrees the jack rotates. In other words from
    0* to
    30* there is not much change in force then from 30 to 60* it decreases
    rapidily and from 60* to 90* force is about 0.

    As it is I have a lot more to think about and detail, thank you and
    I will
    get back as soon as I can.

    Keith