Virtual Capstan

[Bill Ballard]

At 7:15 PM -0500 6/22/03, Ron Nossaman wrote:
>>20 grams x (WC,WMag / WC,Cap) yeilds the net lift on the casptan by 
>>the magnet
>>force upwards at the whippen magnet. This is a negative number because we are
>>lightening the load on the capstan.
>
>Unless I missed something, yes.
>>A very neat way of viewing all net effects of this extra <<virtual capstan>>
>>through the eyes of the real capstan and corresponding key ratio.
>
>It's the simplest approach I came up with.

It also makes the decision that the leverage doesn't change. By 
translating the uplift at the magnets to their actual force applied 
at the capstan, we simplify things considerably. Nothing like making 
measuring points a constant instead of a variable. But we have to 
uphold the correlary of this situation, which is that the leverage is 
not changed by the installation and operation of the magnets.

It keeps things simple.

Two things I see the magnets doing here: reducing friction at the 
capstan, and reducing the load at the capstan. The former is a result 
of the latter, and the latter actually means reducing the balance 
weight (how much heavier the back half of the key is than the front).

This thread on "Virtual Capstans" might seem like an off-shoot of its 
immediate predecessor, "Key Leads and Inertia", in a search for an 
action which is easier to play (whatever that means). So far we've 
concentrated on how it lightens the DW (BW, really). That's a matter 
of the static balance of the force of gravity on either side of the 
key. Ric, you had said that the ability to adjust BW was far less 
important than being able to measure the action's moment of inertia, 
and from that, begin to find empirically a proper level of inertia 
for a piano action.

At 3:25 PM -0500 6/22/03, Ron Nossaman wrote:
>>I wonder if a magnet is not exactly acting in the most optimum way
>>against inertia lessening it far better than a spring because of its
>>permanence.
>
>It won't lessen inertia. It will increase it. The question is how it 
>feels in play.

Ron, are you saying that the installation and operation of these 
magnets affects inertia simply by the addition of their mass to the 
rotating parts? Or do they affect inertia in other ways?

At 12:11 PM -0500 6/22/03, Ron Nossaman wrote:
>So far, it looks like I am the only one who has actually taken a 
>little time to try and work out the leverages involved. Forget 
>action terminology for a moment (pun intended), and go back to basic 
>mechanics.

We got maybe a hundred monkeys on this thing, and that's what you're 
working on.

Thanks to you and Ric for carrying this thing so far.

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

"I'll play it and tell you what it is later...."
     ...........Miles Davis
+++++++++++++++++++++