Virtual Capstan

[Richard Brekne]

Bill Ballard wrote:

> >An interesting idea.  I'm not sure that I see how the effects of
> >this device differ from those of a whippen assist spring.
>
> The big issue here is coupling between the key and the weight on the
> capstan. I imagine it would be pretty good as long as the return
> stroke is faster than that which would occur by gravity alone. That
> way, the key having one reason greater than gravity for which to do
> the return stroke, magnetic repulsion of what is the driving lever(s)
> in this situation, the wippen, carrying a hammer and shank.
>
> If you're looking for a force to make the key return faster than
> gravity, this magnetic repulsion is it. The two magnets are coupled
> together in that, should the key move too fast in relation to the
> wippen, it will move out of the wippen magnet's influence, and lose
> speed (until the wippen catches up again). When magnets are the
> dominant forces in the return stroke of the parts, there is no reason
> for the key (the driven lever) to go any faster than the wippen/shank
> (driving levers). That is, unless of course somebody then lowered the
> FWs, so that the key's now-lower moment of inertia would cause it to
> accelerate faster under the wippen/shank's first kick back into the
> return stroke.
>

Some nice comments, and I will look out for the affect on the actions backstroke
in motion. I had rather thought of lowering FWs no more a small amount. I havent
visioned this as a key leads replacement scheme, but more a way of providing a
range of about 5 grams or so BW while at the same time allowing more freedom
(with respect to weight concerns) in positioning the standard capstan.

>
> How this coupling would be different with springs is not clear. At
> anyrate, have at it, Ric! This might just be the way to get an action
> optimized for both soft and hard play.
>

Any input or experimentation by yourself or anyone else is really cool as well.
Might be kinda neat if this is ended up a collective Pianotech invention for
everyones use. That would really be a feather in our hat eh ?

>
> >I've been playing with the basic concept of spliting the weight and
> >distance components of the action ratio into two seperatly
> >adjustable quantities for about 8 months now. Tried some pretty
> >weird things.
>
> Care to confess?

Grin.. the first try was with upright jack return springs. Actually worked quite
well once in place... but impossible to regulate and you could forget about
getting to the capstan. A few other spring solutions included  tried contriving
a double headed capstan on a rocker arm.....:). The convex headed capstan also
seemed usable... but had minimal affect... but at least you could regulate the
darn thing easy enough.  Lots of dinking around.


> >But the main problem has always been finding something
> >that didnt get in the way of regulating the standard capstan. This
> >solves that problem.
>
> Again, congratulations.

Thanks, nifty idea me thinks. But again... I'd like to see any and all get in on
the further development of the idea. We have a lot of good thinking heads here
with lots of creativity. Between us...we can perhaps put out a solution that
does all that we really need it to do (relative to touchweight adjustments and
key leads reduction) for minimal cost and effort.


> Bill Ballard RPT
> NH Chapter, P.T.G.

Cheers

RicB

--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html
http://www.hf.uib.no/grieg/personer/cv_RB.html