Self lubricating is how my professor in engineering materials class referred
to it. No oil magically appears. In the interest of saving time I’ll just
repost our previous lubricatious exchange of a year and a half ago:
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of PAULREVENKOJONES
Sent: Wednesday, August 08, 2007 5:55 PM
To: Pianotech List
Subject: Re: Counter-bearing drag
It's the mythology to which I referred. Language does strange things as we
both know. Since we, as a group, tend to be technicians and not engineers,
our language tends to be self-lubricating :-).
Paul
"If you want to know the truth, stop having opinions" (Chinese fortune
cookie)
In a message dated 08/08/07 08:55:32 Central Daylight Time,
deanmay at pianorebuilders.com writes:
VERB:Inflected forms: lu·bri·cat·ed, lu·bri·cat·ing, lu·bri·cates
TRANSITIVE VERB:1. To apply a lubricant to. 2. To make slippery or smooth.
It is of course the second definition to which I was referring. On a
molecular level the interaction of some metals against each other produces
an above normal amount of friction, while others, e.g., steel on brass,
produce a friction level below what one would normally expect. Their
interaction is more slippery or smooth than that of other metals, i.e.,
self-lubricating. No oil required.
Dean
Dean May cell 812.239.3359
PianoRebuilders.com 812.235.5272
Terre Haute IN 47802
_____
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of PAULREVENKOJONES
Sent: Tuesday, August 07, 2007 11:39 PM
To: Pianotech List
Subject: Re: Counter-bearing drag
Hey, Dean, another myth rears it head...
Brass, steel, and cast iron have quite different coefficients of friction
because of the way that the surface "galls" or wears down under compression
and the movement of one surface against another. What you're referring to as
"lubricating" is just a way of describing the friction differentials between
the materials. There's no oil, or lubricity, involved.
Paul
"If you want to know the truth, stop having opinions" (Chinese fortune
cookie)
Dean
Dean May cell 812.239.3359
PianoRebuilders.com 812.235.5272
Terre Haute IN 47802
_____
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of PAULREVENKOJONES at aol.com
Sent: Thursday, March 05, 2009 11:07 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Capo Bars
Dean:
There is a mythology here that begs correction. Brass is not
"self-lubricating". There is no "lubricity" to it at all. There is a
significantly lower friction coefficient between brass and steel than
between cast iron and steel particularly because of the different galling
characteristics of them.
Paul
In a message dated 3/5/2009 7:44:29 A.M. Central Standard Time,
deanmay at pianorebuilders.com writes:
Young Chang started doing this in the mid 90s, don't know if they still do.
They used a brass rod instead of steel. Music wire on brass is self
lubricating.
Dean
Dean May cell 812.239.3359
PianoRebuilders.com 812.235.5272
Terre Haute IN 47802
-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Richard Brekne
Sent: Thursday, March 05, 2009 4:30 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Capo Bars
Good question... and I'm looking forward to reading the replies. FTR,
Bohemia pianos, a spinoff of Petrof after the splitup of Czechoslavakia
actually did do this for a while... I'm unsure if they still do. They
used some kind of bronze alloy I believe. Perhaps its a question of
tooling and expense ?
RicB
Why do manufacturers harden capo bars rather than cast (or grind)
the underside of the strut flat, rout out a groove to receive a
steel rod of proper radius, shape and hardness and insert it there
where it could, when it's worn, be easily changed and where the
consistency would be more easily controlled. Is there a compelling
reason not to do it that way?
_____
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