Renner Wippens Straight Heel vs Angled on Stys

[Phillip Ford]

>I'm curious what any of you have found/prefer/come to any conclusions about
>when it comes to choosing between the two different Renner wippens on older
>Steinways.  Since I amd often changing the capstan, most of the time
>relocating it anyway, the existing angle of the capstan isn't an issue.
>I'm more wondering about general performance characteristics associated
>with the difference between the regulated height of the capstan on each
>(the straight heel usually ends up with a lower capstan profile) and
>whether the straight heel offers any advantage due to it's relationship to
>the arc scribed by the capstan in comparison with the angled heel.  While I
>have stretched strings to look at magic lines and such, the results of
>these methods are inconclusive to me in terms of differences.
>
>
>David Love

David,

      I haven't done anything scientific, but I have done some playing 
around with this.  My conclusion (if that's not too strong a term) is that 
what seems to matter is the magic line and the actual location of the 
capstan-wippen heel contact point on the key lever, and that straight or 
angled doesn't really matter.  This conclusion is based on measuring DW and 
friction for various configurations.
      Part of the problem is that it's difficult to compare apples to 
apples.  For a given action setup, if you put on a new Renner angled heel 
wippen and take some measurements, and then take that wippen off and put on 
a new straight heel wippen and take measurements, there will likely be 
differences in the numbers.  But as you point out, the capstan will have to 
be a different height to accomodate the different wippens, which is 
changing the contact point relative to the magic line.  Also, the 
capstan-wippen heel contact point distance from the key balance point is 
probably not the same for the two wippens because the angled heel ends up 
laying on a slightly different spot on the capstan than the straight heel 
does, so that leverage is going to be slightly different.
     I have to say that I find it difficult to look at installed parts and 
accurately determine the capstan-wippen heel contact point and to tell with 
any confidence whether it's on the magic line at half stroke.  I have tried 
putting on a new wippen, checking the magic line, having it look like it's 
right on at half stroke, and then taking some measurements.  Then cut the 
heel off that wippen, put on an identical heel that's been sanded down so 
that it's markedly shorter than the original, put it in the same spot on 
the wippen, adjust capstan for blow distance, and take measurements.  Then 
gradually build up the height of the wippen heel with 1 mm shims, taking 
measurements at every increase in wippen heel ht.  The point where I get 
the min friction I'm assuming is the point that's truly on the magic 
line.  That height doesn't necessarily end up being the same height as the 
original wippen heel, which appeared to me to be on the magic line when 
checked with a string.
      I've also tried putting on both a straight heel and an angled heel 
and moving them back and forth along the wippen and taking 
measurements.  In theory, the leverage should be determined by the location 
of the capstan.  However, since the wippen cushion is not flat on the 
bottom, as you move it along the wippen the position of the 'hump' relative 
to the capstan changes, altering the contact point slightly, which is 
changing the leverage slightly, which will affect at least the starting DW.
      For a given capstan location and angle (I've tried straight up, 
angled a bit, and angled a lot - but no so much that the corner of the 
capstan is digging into the cushion) I've found that by playing with heel 
height and location I can get the numbers to come out the same for an 
angled heel or a straight heel (call the configurations where the numbers 
are the same the 'optimized' configuration).  However, that's not to say 
that the straight heel optimized configuration I end up with in terms of 
heel location and height, or the angled heel optimized configuration I end 
up with in terms of heel location and height, look like their respective 
standard wippen right out of the box.
      I think either standard wippen (straight heel or angled) will rarely 
match this optimized wippen.  Which one will come closer I think will just 
depend on how those wippens interact with the particular capstan location 
and height you end up with, in terms of contact point and magic line, and I 
don't really think you can predict that beforehand.  It's also not always 
the case that an angled wippen heel will work better with an angled 
capstan, and a straight heel with a vertical capstan, although that usually 
seems to be the case in my experience.  I think you just have to try a 
sample of each one and see.

Phil



Phillip Ford
Piano Service and Restoration
San Francisco, CA