Bolt strength

[Farrell]

I agree with Clyde. I usually put a pipe clamp on either side of the bolt I
am installing - yes, that may mean up to 10 pipe clamps - argueably
overkill, but especially with a large separation its pretty close to
necessary). Then tighten a little here, little there, and so on down the
line. I did a Baldwin Hamilton a while back with a 1/2" to 1" separation
across the entire back. It was a lot of work bringing it back together with
the ten clamps - and that was with tension down two full steps, and I did
not quite get it completely back together - but at least the damper were
rising from the strings (that was the original complaint from the customer -
the plate was so bent over, the dampers were not able to lift from the
strings!).

Terry Farrell

----- Original Message -----
From: "Clyde Hollinger" <cedel@supernet.com>
To: <pianotech@ptg.org>
Sent: Thursday, September 20, 2001 10:31 PM
Subject: Re: Bolt strength


> Bob,
>
> I don't know the answers to all of your questions, but I have repaired two
or
> three separated Everett backs, using 5/16" carriage bolts and epoxy.  No
further
> problems.  You understand, I presume, that the back is pulled together
with
> clamps first, not just with the bolt.  I think that wouldn't work.
>
> Regards, Clyde
>
> BobDavis88@AOL.COM wrote:
>
> > Subject: Everett studio, pinblock separating from back
> >
> > I need to bolt this sucker back together. I have done this repair twice
> > before with half-inch bolts (w/long-term success), and I know others
have,
> > but I would like to take a fresh look at this from the perspective of
the
> > engineers out there.
> > 1) I chose bolts empirically, and they worked. However, is there anyone
out
> > there who knows the tensile strength of various diameters of bolts? Of
> > hardened bolts?
> > 2) How much strength do I actually need to resist breaking or bending of
the
> > bolts?
> > 3) Is there an advantage or disadvantage to hardened bolts in this
> > application?
> > 4) Is the separating force the only one I need to worry about, or should
I be
> > worrying about the shearing force tending to collapse the plate?
> > 5) In re: above, I have always assumed the bolts did all the work, and
that
> > the glue line was contaminated/dirty enough it wouldn't cinch up
completely.
> > Is there a glue better than Titebond for resisting creep in a glue line
which
> > is both dirty and not as thin as it should be? Weldwood? Polyurethane
> > (Gorilla) glue? Are both the adhesive and cohesive strengths of epoxy
> > sufficient?
> > Thanks, engineers,
> > Bob Davis
>
>