Virtual Capstan

[Mark Davidson]

Agree, if you increase dip, work stays the same in my example.
I was assuming constant key dip, or any constant movement - say 1mm.
With VC you don't have to increase dip.  Therefore the work appears
to decrease.  But that's impossible since same work is being done
to lift wippen/hammer (even more to lift magnets).

Where does the extra work/energy come from?

(Maybe if I ask enough times in enough ways...)

-Mark

----- Original Message ----- 
From: "Bill Ballard" <yardbird@vermontel.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: Saturday, June 21, 2003 3:54 PM
Subject: Re: Virtual Capstan


> At 1:52 PM -0400 6/21/03, Mark Davidson wrote:
> >I agree that moving some of the upward force closer to the balance
> >rail increases leverage.  But consider for a moment the example of
> >moving a regular capstan toward the balance rail.  Downward force
> >required to move the key is decreased. Work at front of key = force
> >* distance, which is less because force is less. However the wippen
> >and hammer also do not move as far, so the work at the back of the
> >key is ALSO less.  The changes balance out.
> 
> Keep in mind that when you move a regular capstan towards the balance 
> rail, what's being changed is the leverage of the key. Actually the 
> formula should be, work done at the front of the key should equal the 
> work done at the capstan (less amount of energy lost to friction), 
> for any particular set-up. Because of the leverage change in moving 
> the cap closer to the fulcrum, the capstan's motion is now decreased 
> in relationship to the key front.
> 
> Force at the front of the key needed to overcome the top action 
> weight (BW-FW) is reduced, but the other consequence is that the 
> front of the key has to move further. In this situation as well, work 
> done at the front will equal work done at the capstan.
> 
> What balances out is that you've bought the ability to move a heavier 
> weight, at the expense of how far you can move it.
> 
> >With your idea, however, the wippen and hammer move the SAME 
> >distance with or without magnets (same amount of work at back of 
> >key) but with different amounts of work at the front of the key. 
> >This is actually a huge advantage because you do not have to 
> >re-regulate dip/blow etc.
> 
> The only reason to re-regulate dip/blow would be if you'd hanged the 
> mechanical leverage ratio. Because the capstan is still in place to 
> govern the rotation of parts, and because it hasn't moved, the 
> leverage ratio is unchanged. In this respect, springs and magnets 
> offer the same thing. Let's hope that Antares isn't being too hasty 
> in pulling out the springs out of his own action.
> 
> Bill Ballard RPT
> NH Chapter, P.T.G.
> 
> "Talking about music is like dancing about architecture"
>      ...........Steve Martin
> +++++++++++++++++++++
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