Call for scaling spreadsheets

[Farrell]

I've asked Del about the need/logic of moving the agraffes toward the belly 
rail to maintain an optimal strike point when adding a transition bridge to 
a former hockey-stick long bridge. His response has been exactly what you 
state Ron - that it doesn't seem to make too much difference and doesn't 
seem to be worth the trouble of trying to move them.

One of these days though, and of course every piano plate is different, but 
I'm going to do just that - move the agraffes rearward for optimal strike 
point. I've stared at a few plate and did some figuring and it just doesn't 
seem like it would be all that difficult to take a piece of 1/4-inch plate 
steel (or whatever thickness would work best), cut to size, epoxy in place 
on top of the cast iron shelf that most pianos have toward the belly rail 
from the original agraffes, and then locate, drill and tap.

One of these days.....

Project: # 3,792

Terry Farrell

----- Original Message ----- 
SNIP
>> Suppose you now redraw your bridge to produce a tension on this note 
>> (assuming for argument's sake the same gauge of wire) of about 160lbs, 
>> then you will need to reduce the length of the string by 11 cm to 65 cm. 
>> You will thereby achieve, nay even over-achieve, your desired 
>> back-length, but what of the strike point?  This will have moved nearly 
>> 14 mm. nearer the front bridge.  Surely the only ideal solution then is 
>> to move the whole string back 14 mm in order to bring the strike point 
>> back to the strike line.  In other words you need to reposition the stud 
>> (agraffe) in the metal frame unless the hammer is to strike the string at 
>> a less than ideal point and produce less than ideal harmonics.
>
> It's unlikely that I'd make that drastic a change that high in the scale, 
> but if I did, that whole section would have been similarly changed and it 
> would all sound much alike, so it wouldn't likely be a problem.  The 
> biggest concern with strike points in the lower half of the scale is at a 
> discontinuity from one note to the next. This does happen at the 
> bass/tenor break where I've put a transition bridge on the low tenor, with 
> considerably shorter speaking lengths to improve the crossover. Yes, in 
> principal you would want to move the agraffes to get whatever you might 
> deem to be the ideal strike point, or at the very least to eliminate the 
> discontinuity. I'd love to have the luxury of doing so, but I don't when 
> I'm working around an existing plate, so there will be a strike point 
> discontinuity there. The reality is, however, that I have yet to do one of 
> these without significantly improving the original crossover, even with 
> the strike point in a not quite ideal spot, and discontinuous at the 
> transition between wrapped bichords and plain trichords. It just hasn't 
> proved to be a problem in practice that low in the scale.
>
> Ron N