[CAUT] Nordiska; feedback and design flaw

[Fred S Sturm]

Hi Jim,
Moving (bending) the dowel capstans back mostly affected 
the wipp ratio (the key ratio to a much lesser extent), by 
moving the contact closer to the wipp center. The same 
effect would come from either shimming the wipp rail 
forward or moving the action bracket supports forward. 
Either of those actions also would change the angle of the 
action relative to the strings (or I guess I should say 
relative to vertical) so that the shape/angle of the butt 
leather at check would be more upright and the jack could 
clear more easily (not sure if that wording is clear).

On the couple early Nordiska uprights I have seen, they 
looked like they were, shall we say, not put together 
carefully, so even assuming action geometry was a 
reasonable design (probably fairly safe assumption), 
exactly how they placed the keybed, the keyframe, and the 
bottom action bracket supports could easily vary enough to 
cause problems. I have found this to be the case with 
action models, including those created for the PTG upright 
regulation test. A shift of the placement of the keys and 
the bottom of the brackets, even a small one, can have a 
big effect.
Regards,
Fred Sturm
University of New Mexico
On Tue, 16 Oct 2007 18:31:20 -0600
  Jim Busby <jim_busby at byu.edu> wrote:
> List,
> 
> 
> 
> 
> 
>Feedback on the short term solution;
> 
> 
> 
> On the Nordiska in question I found that bending the 
>(wire) capstans
> backward so they hit further back on the wippen cushion 
>indeed solved
> MOST of the problem with bobbling hammers. On hammers 
>that continued
> multiple hitting; weakening the damper spring also 
>helped with that
> problem.
> 
> 
> 
> IOW, since most of the bobbling came from the butt 
>hitting on top of the
> jack moving the capstan increased the distance the 
>wippen traveled and
> this extra movement allowed the jack to get out from 
>under the butt.
> However, on soft blows the but/jack wasn't the issue. 
>The springs were.
> So, it now works to the lady's satisfaction, but not to 
>mine! Why? It's
> still .450 dip, about 75 DW and blow is about 41mm. But 
>hey, I'm keeping
> my mouth shut...
> 
> 
> 
> Since we're talking a poor execution of design I guess 
>the "design flaw"
> and possible correct "fix" should be;
> 
> 
> 
> 1.	Move capstans back
> 2.	Move wippen cushion to the right spot
> 3.	Remove lead (4 leads on the back of each key) to 
>obtain a better
> DW
> 4.	???? (Change action post location?)
> 
> 
> 
> Does this seem like a proper correction in design? Not 
>that I'll mess
> with it this time, but it's good to know IMO.
> 
> 
> 
> All these years I've been tweaking grands and have never 
>really
> considered uprights. I've never been to or seen a class 
>on them except
> Jack Wyatt's "Turbo charging the Upright" class. 
> 
> 
> 
> Thanks to all who contributed! 
> 
> 
> 
> Jim Busby BYU
> 
> 
>