Virtual Capstan

[Bill Ballard]

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
+++++++++++++++++++++