springs

After a number of attempts (resulting in a sizable "graveyard" of scraggly wire bits), I think I finally have the springs working, for the machine-pedal aspect of the stops mechanism.  It was difficult to find the right strength for the springs, to overcome the considerable (intentional) friction in the stops motions, without presenting so much force as to make pedal operation unpleasant -- or simply, so much force that my simple wooden mechanism would self-destruct.  And, it was difficult to fit the necessary springs into the cramped and irregular volume of space available for this part of the mechanism.  Here, then, is what I came up with...

First, I made models using thinner wire (#18 steel).  This is a crucial point; trying to work and re-work an already crooked and kinked-up piece of #12 steel wire, to snake around all the obstacles and fit into the right place, was an exercise in frustration which I repeated several times in previous attempts (I have already mentioned the "graveyard").  Once I realized I needed to fit a *pair* of springs into the same space, for each of the four ends of rails which needs a spring, I knew I had to get serious with the modeling.

Here are two of the four final pieces, in #12 steel wire.  You can see that I have marked left and right (one or two bands), because they are not interchangeable.  They're *roughly* mirror images, but each is shaped to fit into its exact situation.

Here you can see how the pairs of springs interlace, in-vitro.

You can see how limited the clearance is, between the nameboard and the wrestplank (it's about 3").  I've had to substantially refine the design to fit into such a space: the original idea would have required more like 12" of clearance behind the panel (so it obviously would have had to be placed in a very different way on the instrument, not on the nameboard).