On 7/15/2018 11:50 AM, John B. Slocomb wrote:
On Sun, 15 Jul 2018 11:06:37 -0400, Frank Krygowski
wrote:

On 7/14/2018 10:20 PM, David Scheidt wrote:
AMuzi wrote:
:On 7/12/2018 10:59 AM, Frank Krygowski wrote:
: On 7/12/2018 11:39 AM, Jeff Liebermann wrote:
: On Thu, 12 Jul 2018 00:22:57 -0700, John B. Slocomb
:
: wrote:
:
: On Wed, 11 Jul 2018 20:16:33 -0700, Jeff Liebermann
:
: wrote:
: Nope. I'm not trying to measure if the tubing is strong
: enough.
: Assuming identical lengths of tubing, I wanted to see if
: the presence
: of a Rivnut significantly changed the tension required
: to bend or
: break the tubing when compared to the identical tubing
: that did not
: have a Rivnut inserted. If I'm able to pull hard
: enough, I should be
: able to eventually break both tubes. If they break at
: the same
: tension, then I'll declare the Rivnuts are safe to use.
: If there's a
: substantial difference in tension, then I'll declare the
: Rivnuts
: weaken the frame.
:
: I'd think it obvious that any hole drilled laterally into
: a tube would
: have an effect on the bending strength of the tube. The
: question
: wouldn't be whether the rivnut changed the strength of
: the tube but
: whether the tube was strong enough with the rivnut
: installed in the
: tube.
:
: Again, I expect some reinforcing effect from the Rivnut's
: clamping action. For an analogy: Did steel frames fail in
: significant numbers when water bottle bosses were brazed on
: and tapped? I doubt it. While a crimped-on Rivnut wouldn't
: add as much strength (as a guess) I think it may add enough
: to get the strength back up to that of the un-drilled tube.
:
: Also, I'm pretty sure a bike down tube sees little if any
: bending stress, except perhaps in a crash. The stresses of
: concern are torsional.
:
:
: Agreed.
:
: Reading between the lines, what others are apparently
: suggesting is
: that even with a hole drilled into the frame, the tubing
: is still
: sufficiently strong to consider the bicycle rideable. In
: other words,
: if the drilling a hole and installing a Rivnut decreased
: the bending
: strength by 10%, I would agree that the hole and Rivnut
: don't pose a
: risk. However, if it decreased the strength by 50%, I
: would consider
: it a hazardous modification. I'm not too sure what to do
: about
: numbers in between or even if the 10% is realistic.
:
: To complicate matters, there's the problem of the notch
: required by
: Rivnuts to prevent rotation. That's a stress riser by
: anyone's
: definition and will probably be the start of any break
: during testing.
: I'll try to position it where it will do the least damage.
:
: The notch is small enough to be enveloped in the crimped
: portion of the Rivnut. I doubt that it's effective as a
: stress riser. Really, I doubt that it feels any significant
: stress, other than compression from the clamping or crimping
: action.
:

:In practice, crashed frame tubes don't deform at the bottle
:bosses. The general truism is that a brazed joint is as
:strong or stronger than the steel tube so a brazed insert
oses no risk. That may not be exactly correct but we work
:with it.

:Some builders at the cusp of change between 'no brazed bits'
:and 'braze every possible thing' fashions (like Galmozzi)
:brazed bolts on the tube and so nuts secured the bottle
:cage. Odd looking but worked as well as anything.

I got a nasty gash from a frame like that. Just picked it up, and cut
myself on the bolt.

Yet another bicycling injury!

Obviously not wearing a helmet.

I saw a head injury yesterday. After eating lunch on a backyard deck, a
good friend pushed his chair back from the table and tumbled backwards
off the deck. He hit the back of his head pretty hard on the brick
walkway, hard enough that he applied an ice pack for 15 minutes.

He's not a cyclist. Still, too bad he hadn't worn a helmet. If he had,
it _obviously_ would have saved his life.


--
- Frank Krygowski