CA gluing Grand Pinblocks....My take on it/ Richard Brekne

[Farrell]

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Comments below:

Terry Farrell
 =20
----- Original Message -----=20
From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
To: <pianotech@ptg.org>
Sent: Thursday, August 01, 2002 4:52 AM
Subject: Re: CA gluing Grand Pinblocks....My take on it/ Richard Brekne


> > Farrell wrote:
> >=20
> > >
> > > I guess this is where I am getting hung up here... I can
> > > easily accept that there is a shear force exerted on the
> > > bridge pin getting "pinched" as it were between the
> > > string
> > > pushing at it from the one side, and the bridge from the
> > > otherside.
> >=20
> > I believe the above described a compression force of the
> > string toward the pin, and a second compression force
> > between the pin and the wood on the other side of the pin.
> > If the pin had been glued in, then there would also be a
> > tension force between the pin and the bridge wood directly
> > under the string.
> >=20
>=20
> Yes... or said another way... The bridge and string together
> exert a shearing force on the pin (ie the pin is under some
> degree of shear stress). Yet the string and pin share a
> mutual compressive stress as do the pin and bridge hole. And
> tho the relationship between the bridge and pin is much like
> the nailed plate example above... the relationship between
> the string and pin is really just plain compressive force me
> thinks.

Yes, unless it is glued in place, then there would be some other =
forces/stresses.
=20
> All in all,,, this adds up to the only real shear stress
> involved being exerted on the cross section of the bridge
> pin exactly on the plane of the opposite forces created by
> the string pushing the pin against the bridge holding the
> pin.

Hmmmm. I don't like that. But perhaps I do not understand.
=20
> >If the pin had been glued in, then there would also be a tension =
force between the pin and >the bridge wood directly under the string.
>=20
> There would be anyways.. just not exerted on the glue but on
> the two (parallel, lengthwise) surfaces of the pin and
> bridge pin hole. Agreed ?

Hmmmm. Sorry, I just don't follow here.

> Grin.... I still am not sure whether or not we are on track
> with each other here or all mucked up by word usage. Great
> fun eh ?
>=20
> RicB

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