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Old July 12th 18, 08:31 AM posted to rec.bicycles.tech
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Default drill/tap in frames

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."
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