[CAUT] Leads, Magnets, Springs, etc.

[Ed Sutton]

Jim-

Thank you for your excellent thoughts.

You have expressed what could be the significant difference between the new
Petrof magnetic assist and an adjustable wippen assist spring.

There is a picture of the new Petrof system on p. 20 of the April Journal. 
This is the system I'm referring to here, and no other.

Both the magnetic and spring assist systems will be most effective at the
start of the key stroke, and less effective at the bottom, but the
difference will be greater in the Petrof magnetic assist system.

If this difference is enough to be felt, and whether this is good or not
remains to be seen. One could argue either way.  Springs for Horowitz,
magnets for Rubenstein?

I appreciate your comments on lead.  House paints and art supplies have
changed over the years, in response to many cases of metal poisoning.  Key
leads are near the front where the fingers touch, and will be a fine source
of contamination if there is any oxidation.  This is probably something we
should inspect for in old pianos.  How effective would a lacquer coat be in
sealing this?  Or perhaps an artist's acrylic spirit varnish?

Sincerely,
Ed Sutton

> [Original Message]
> From: James Ellis <claviers@nxs.net>
> To: <caut@ptg.org>
> Date: 3/30/2005 10:39:02 AM
> Subject: [CAUT] Leads, Magnets, Springs, etc.
>
> A few days ago, in the discussion re key leads, magnets, and springs, Ed
> Sutton asked for my opinion.  I can't find his original post now, but I
> remember the general idea.  Sorry to be so long getting back to it, Ed.
>
> Lead weights in piano keys can sometimes be a problem.  I have seen leads
> in keys 100 years old where there was little if any corrosion.  I have
seen
> others half that age where there was very bad corrosion, swelled up leads,
> binding keys, and lots of lead oxide dust in the key bed.  That stuff is
> very toxic - really bad stuff.  I can see why the Germans might want to
ban
> lead in piano keys.  That stuff is extremely toxic, and once you get it in
> your system, your body has no good way of getting rid of it.  It causes
> brain damage big time.  The only thing worse is mercury, but fortunately,
> we don't use mercury in pianos.
>
> As for repelling magners:  There are several different versions out now,
> and each one has it's own pros and cons.  There are some neat ideas here,
> but I would rather wait ans see how they work out in real-life situations
> before commenting on them.
>
> I should also mention that Ron Overs has designed an action that addresses
> the problem of knuckle friction by pure geometry rather than some
> compensating device.
>
> As for springs:  They do not characteristically "wear out", unless there
is
> something to wear them out.  They will distort if subjected to too much
> stress.
>
> Weights have something going for them that springs and magnets do not.  A
> weight will exert the same force on the key, whether it is up, or down.  A
> magnet or spring will not.  With a magnet, you will have the inverse
square
> law that causes the force to decrease as the magnets get farther apart.
> With a spring, you have the spring rate that varies linearly (according to
> Hooke's law) as the spring is compressed or exteded, as the case may be.
> If the spring rate is too much - the spring too stiff - you will feel this
> effect on the key.  If not, you won't.  The same idea carries over to the
> repelling magnets, but for a different reason.
>
> The mass of a certain weight will be the same in Boston as it will in
> Miami, but because of the earth's rotation and centrifugal force, it will
> not weigh the same.  However, that difference will be slight, and you
won't
> see it without a sensitive instrument, or an accurate pendulum clock
> regulated for a specific latitude.  If the clock is regulated at Boston,
ir
> will run slow by a tiny amount at Miami.
>
> However, lead weights in piano keys are for counter-weights - balancing
> weight against weight, so it doesn't matter anyway.  Their balancing
effect
> will be the same at the equator as at the north pole.
>
> The point is, for practical purposes in a piano, these effects are
> negligible.  On the moon, it would be a different matter, but we aren't
> going to play a piano on the moon.
>
> I hope this helps.  Sincerely, Jim Ellis
>
>
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