Virtual Capstan

[Bill Ballard]

At 2:40 PM -0700 6/19/03, Phillip Ford wrote:
>  >The virtual capstan is comprised of two adjustable opposing magnets, one
>>on the underside of the whippen forward of the whippen cushion (heel),
>>the other just forward of the capstan on the key and directly under the
>>whippen magnet.
>>
>>The effect and purpose....
>>
>>Richard Brekne
>  >19 June 2003
>
>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.

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.

>I agree with your point about the friction at the knuckle. Its a 
>good thing... in reasonable amounts.

In slow playing, it's the pianist's final guage as to their speed. As 
their fngers push ther way through ts suddenly elevated friction, 
they can tell by how quickly they slow down whether their actual 
speed is what they were calculating it to be.

>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?

>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.

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

Visit Bhod Ankur, the underwater monument to yesterday's civilisation.
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