On Thu, 12 Jul 2018 10:05:56 -0500, AMuzi wrote:

On 7/12/2018 2:31 AM, sms wrote:
On 7/11/2018 8:43 PM, Jeff Liebermann wrote:
On Wed, 11 Jul 2018 17:24:40 -0400, Frank Krygowski
wrote:


Exactly. Strong enough is strong enough.

OK, so let's pretend that the tube with the Rivnut bent at
10% less
tension. Is that "strong enough"? There's no way to tell
without the
original design calculations, or reverse engineering the
frame with an
FEA model. Too bad Autodesk killed their online
ForceEffect web app.
http://blogs.autodesk.com/inventor/2017/01/17/autodesk-forceeffect-family-retirement/

I think I could have modeled the problem using the program.

"Rivnuts are great for low stress areas, but they rely on
expanding in addition to crushing to grip the surrounding
material, therefore a rivnut will impose a tensile stress
around the hole which isn't good news since this will add to
any load stresses, not to mention the concentration effect
brucey speaks of.

I'm not sure there is any place on a bike frame that I'd be
happy to use them. Any time I've needed to attach something
it's been with a properly machined alloy 2-bolt clamp around
the tube with a thin [1mm] thick rubber shim between clamp
and tube."


Why then don't more airplanes fall out of the sky?

https://www.skygeek.com/rivnut-tool.html
http://spenceraircraft.com/hardware/...ivet-nuts.html

from that page:
" Our rivet nuts are manufactured to meet the National
Aerospace Standard. " So much for zero tolerance eh?

With a broken bicycle you could walk home!

I might be interesting to know that the "rivnut" apparently was first
developed to hold the deicer boots on the leading edge of an
aircraft's wing in 1930, so we can safely say that they have been
successfully used in the aircraft industry for the past 88 years....
strange how they could have been so successful in one industry while
(apparently) a failure in another.
--

Cheers,

John B.