Rivnut success

Andy Dingley said:

Quoted message said:

The Rivnut was designed for it, but the bicycle frame was not designed for it. They can be
installed in older steel frames.

Quoted message said:

Anyone got any evidence of a frame that failed at the water bottle mounts, Rivnut or not ?

Quoted message said:

It's like the way that thin swaged spokes don't cause wheel failures. Yes, they're obviously less
strong at that point. But that's not where the _structure_ fails.

Quoted message said:

Never ask a metallurgist to do a structural engineer's job.

I think there is a lot of conjecture surrounding this subject and I think it may arise from
different frame tubes and different demands put on the bicycle. I know many riders who rode and some
who still do Cinelli frames with the Cinelli sloping fork crowns. These are not only heavy (solid
steel) but are failure prone at the abrupt transition from fork blade to the internal lug of the
crown that cannot be feathered to a gradual transition as an external lug can.

I broke two forks before I insisted to no longer have an internally lugged fork crown. That they
don't break for many riders is fortunate but the evidence is obvious when investigated. The same is
true for a thin walled frame tube with a hole in its side. Under torsion the hole distorts
elliptically at 45 degrees to the long axis of the tube, the angle reversing with torque reversals
somewhat like what one can do with ones lips (upper left-lower right and reverse).

The best example would be to have a frame builder braze an "H" with the drilled frame tube as the
crossbar of the "H". Then manually torque the uprights of the "H" goal posts back and forth. The
hole distortion is obvious and the cracks that result in time also. No doubt, many users might never
achieve that condition but I certainly did, consistent with how many of these things that "never
happen" have happened on my bicycle. It may have a lot to do with where I ride.

Jobst Brandt [email hidden] Palo Alto CA

In article said:

I think there is a lot of conjecture surrounding this subject and I think it may arise from
different frame tubes and different demands put on the bicycle. I know many riders who rode and
some who still do Cinelli frames with the Cinelli sloping fork crowns. These are not only heavy
(solid steel) but are failure prone at the abrupt transition from fork blade to the internal lug
of the crown that cannot be feathered to a gradual transition as an external lug can.

I broke two forks before I insisted to no longer have an internally lugged fork crown. That they
don't break for many riders is fortunate but the evidence is obvious when investigated.

Hmmm. My Ritchey has an internally lugged fork- not Cinelli but Ritchey's own unicrown-looking fork.
I'll have to keep an eye on that.

Quoted message said:

The same is true for a thin walled frame tube with a hole in its side. Under torsion the hole
distorts elliptically at 45 degrees to the long axis of the tube, the angle reversing with torque
reversals somewhat like what one can do with ones lips (upper left-lower right and reverse).

The best example would be to have a frame builder braze an "H" with the drilled frame tube as the
crossbar of the "H". Then manually torque the uprights of the "H" goal posts back and forth. The
hole distortion is obvious and the cracks that result in time also. No doubt, many users might
never achieve that condition but I certainly did, consistent with how many of these things that
"never happen" have happened on my bicycle. It may have a lot to do with where I ride.

Since you ride a lot and are a tall guy, on and off road and in mountainous terrain, you
probably load the equipment more than most riders. And you (as far as I can tell from the
photographic evidence) don't buy the latest and greatest equipment every year. I've noticed from
the photos that your bike doesn't appear to have water bottle bosses (nor water bottles for that
matter). Is this why?

I've seen, in person and photos, cracks in bike frames that appear to propagate from a notch or
corner. I haven't seen one start at a round hole, and the lore of bike frame building seems to
suggest that round shapes and holes are OK. I've always wondered about that, but I've never seen a
crack develop at, for example, a brazing vent hole or a hole for internal cable routing. Sounds like
you're saying, however, that none are good and that all can result in tubing failure (at least in
tubes loaded in torque).

Tim McNamara said:

Quoted message said:

I think there is a lot of conjecture surrounding this subject and I think it may arise from
different frame tubes and different demands put on the bicycle. I know many riders who rode and
some who still do Cinelli frames with the Cinelli sloping fork crowns. These are not only heavy
(solid steel) but are failure prone at the abrupt transition from fork blade to the internal lug
of the crown that cannot be feathered to a gradual transition as an external lug can.

Quoted message said:

Quoted message said:

I broke two forks before I insisted to no longer have an internally lugged fork crown. That they
don't break for many riders is fortunate but the evidence is obvious when investigated.

Quoted message said:

Hmmm. My Ritchey has an internally lugged fork- not Cinelli but Ritchey's own unicrown-looking
fork. I'll have to keep an eye on that.

I don't know what shape his internal lugs have. He is aware of such things and may have designed his
lugs with a better transition. Cinelli ignored them, they being out of sight. All those fancy
curlicues and shapes on the outside of most fork crowns are there in lieu of a feathered transition.

Quoted message said:

Quoted message said:

The same is true for a thin walled frame tube with a hole in its side. Under torsion the hole
distorts elliptically at 45 degrees to the long axis of the tube, the angle reversing with torque
reversals somewhat like what one can do with ones lips (upper left-lower right and reverse).

Quoted message said:

Quoted message said:

The best example would be to have a frame builder braze an "H" with the drilled frame tube as the
crossbar of the "H". Then manually torque the uprights of the "H" goal posts back and forth. The
hole distortion is obvious and the cracks that result in time also. No doubt, many users might
never achieve that condition but I certainly did, consistent with how many of these things that
"never happen" have happened on my bicycle. It may have a lot to do with where I ride.

Quoted message said:

Since you ride a lot and are a tall guy, on and off road and in mountainous terrain, you probably
load the equipment more than most riders. And you (as far as I can tell from the photographic
evidence) don't buy the latest and greatest equipment every year. I've noticed from the photos
that your bike doesn't appear to have water bottle bosses (nor water bottles for that matter). Is
this why?

No. I used to have a bottle on there on former bicycles (brazed in blind threads) but found that
plastic water didn't taste nearly as good as chilled drinks in grocery stores and restaurants.
Not being a racer, I allow myself to stop for refreshments. It seems my body conserves water
fairly well. On hot days I stick a bottle in my jersey pocket if it looks like to far to the next
fuel stop.

Quoted message said:

I've seen, in person and photos, cracks in bike frames that appear to propagate from a notch or
corner. I haven't seen one start at a round hole, and the lore of bike frame building seems to
suggest that round shapes and holes are OK. I've always wondered about that, but I've never seen a
crack develop at, for example, a brazing vent hole or a hole for internal cable routing. Sounds
like you're saying, however, that none are good and that all can result in tubing failure (at
least in tubes loaded in torque).

Vent holes are far smaller than a 1/4" hole for a Rivnut and they are generally locate in a no
torque zone like at the fork end or in the "rear triangle" that is made of thin tubes because there
is no significant torque there. The "rear triangle" is a tetrahedron that is stressed in tension and
compression.

Pedersen made a bicycle in which all tubes were loaded only in tension and compression. He had a
fetish against torque and bending... dirty stresses. Most people who see his design do not recognize
it for that fetish that he pursued without compromise. That is why the bicycle looks so odd and of
course is ungainly enough to remain a collectors oddity.

dursley-pedersen.netdursley-pedersen.netOpen ↗

Jobst Brandt [email hidden] Palo Alto CA

<[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

Pedersen made a bicycle in which all tubes were loaded

only in tension

Quoted message said:

and compression. He had a fetish against torque and

bending... dirty

Quoted message said:

stresses. Most people who see his design do not recognize

it for that

Quoted message said:

fetish that he pursued without compromise. That is why

the bicycle

Quoted message said:

looks so odd and of course is ungainly enough to remain a

collectors

Quoted message said:

oddity.

dursley-pedersen.netdursley-pedersen.netOpen ↗

Interesting.

I've seen a couple of these bikes, and wondered what they were. I didn't know the design anything to
do with structural design fetishes. I always assumed the main feature was the riding position --
like standing normally -- for people with really bad backs or whatever. I used to see an old guy
riding one of these around town a lot. He could barely walk when he got off, but rode the bike OK.

Matt O.

In article said:

Tim McNamara said:

Since you ride a lot and are a tall guy, on and off road and in mountainous terrain, you
probably load the equipment more than most riders. And you (as far as I can tell from the
photographic evidence) don't buy the latest and greatest equipment every year. I've noticed from
the photos that your bike doesn't appear to have water bottle bosses (nor water bottles for that
matter). Is this why?

No. I used to have a bottle on there on former bicycles (brazed in blind threads) but found that
plastic water didn't taste nearly as good as chilled drinks in grocery stores and restaurants.

That is certainly true. Nor does it taste anywhere near as refreshing as the water pouring out of
fountains all over the Alps. An odd thing about the US is that publicly available drinking water and
bathrooms are rarely readily available.

Quoted message said:

Quoted message said:

I've seen, in person and photos, cracks in bike frames that appear to propagate from a notch or
corner. I haven't seen one start at a round hole, and the lore of bike frame building seems to
suggest that round shapes and holes are OK. I've always wondered about that, but I've never seen
a crack develop at, for example, a brazing vent hole or a hole for internal cable routing.
Sounds like you're saying, however, that none are good and that all can result in tubing failure
(at least in tubes loaded in torque).

Vent holes are far smaller than a 1/4" hole for a Rivnut and they are generally locate in a no
torque zone like at the fork end or in the "rear triangle" that is made of thin tubes because
there is no significant torque there. The "rear triangle" is a tetrahedron that is stressed in
tension and compression.

Pedersen made a bicycle in which all tubes were loaded only in tension and compression. He had a
fetish against torque and bending... dirty stresses. Most people who see his design do not
recognize it for that fetish that he pursued without compromise. That is why the bicycle looks so
odd and of course is ungainly enough to remain a collectors oddity.

dursley-pedersen.netdursley-pedersen.netOpen ↗

My wife- of Danish extraction- has wanted a Pedersen for years. I seem to recall that his design was
inspired by bridge design.

Quoted message said:

I think there is a lot of conjecture surrounding this subject and I think it may arise from
different frame tubes and different demands put on the bicycle. I know many riders who rode and
some who still do Cinelli frames with the Cinelli sloping fork crowns. These are not only heavy
(solid steel) but are failure prone at the abrupt transition from fork blade to the internal lug
of the crown that cannot be feathered to a gradual transition as an external lug can.

I can attest to the potential for internal crown forks breaking, as I just had one break.

The fork has a semi-sloping internal crown, had somewhere between 20,000 and 25,000 miles on it, and
came with my Nobilette SLX frame bought new in 1991. Mid-ride a few weeks ago, the bike suddenly
developed an odd creaking, and when braking to a stop to check it out, I noticed that the fork
seemed to bend backward much more than it should under brake force (and more than I thought possible
for an intact fork). Upon closer inspection I found that one fork blade had a crack running almost
all the way around just below the crown, and was hanging on only by a sliver of metal. The crack was
just at the lower edge of the crown/leg brazing bond.

Mark McMaster [email hidden]

Mark McMaster said:

Quoted message said:

I think there is a lot of conjecture surrounding this subject and I think it may arise from
different frame tubes and different demands put on the bicycle. I know many riders who rode and
some who still do Cinelli frames with the Cinelli sloping fork crowns. These are not only heavy
(solid steel) but are failure prone at the abrupt transition from fork blade to the internal lug
of the crown that cannot be feathered to a gradual transition as an external lug can.

Quoted message said:

I can attest to the potential for internal crown forks breaking, as I just had one break.

Quoted message said:

The fork has a semi-sloping internal crown, had somewhere between 20,000 and 25,000 miles on it,
and came with my Nobilette SLX frame bought new in 1991. Mid-ride a few weeks ago, the bike
suddenly developed an odd creaking, and when braking to a stop to check it out, I noticed that the
fork seemed to bend backward much more than it should under brake force (and more than I thought
possible for an intact fork). Upon closer inspection I found that one fork blade had a crack
running almost all the way around just below the crown, and was hanging on only by a sliver of
metal. The crack was just at the lower edge of the crown/leg brazing bond.

Not to worry, the non-scientific community of riders will tell you it doesn't happen and when it
does, it's your fault. I'm sure with your grasp of engineering that you can understand why it occurs
and that it is likely. As I said, I have had to such failures, both with the crack at the place you
describe, the remaining "hinge" being at the front on both my occurrences. I found this interesting,
because it explains why the fork has about a 15 degree rake. The idea being to put the fork mainly
in compression for the road roughness impact rather than for braking loads as is often suggested.

Jobst Brandt [email hidden] Palo Alto CA

In article said:

The same is true for a thin walled frame tube with a hole in its side. Under torsion the hole
distorts elliptically at 45 degrees to the long axis of the tube, the angle reversing with torque
reversals somewhat like what one can do with ones lips (upper left-lower right and reverse).

I think that the torsion problem, while certainly an element of things, is not the only problem.
Even for the case of pure bending, which imparts tensile stresses at the hole location, or for axial
loading, there is the potential for significant stress concentrations near holes.

Both this and your torsion scenario are discussed explicitly in the "Theory of Elasticity", 3rd Ed,
Timoschenko and Goodier (both with a Stanford lineage to boot <g>😉, pp 90 and 307, respectively.

cheers, john

Quoted message said:

I've seen a couple of these bikes, and wondered what they were. I didn't know the design anything
to do with structural design fetishes. I always assumed the main feature was the riding position
-- like standing normally -- for people with really bad backs or whatever. I used to see an old
guy riding one of these around town a lot. He could barely walk when he got off, but rode the
bike OK.

Matt O.

I've been to Copenhagen, without a bike, and went into various public squares with lots of
pedestrians, plus some bikes that were at least Pedersen-like, and the riders would ride slowly in
the midst of the pedestrians, and be able to easily look over the top of the crowd. It looked like a
good setup for the purpose. The rest of the town seemed totally flat, at least what little i saw, so
the tall position would be at least OK there.

Erik Brooks Seattle

would it be fare to say that if your frame isn't butted, then a couple of holes near the middle
couldn't hurt much? being that the tube there is thicker than it would need to be.

anonymous said:

Would it be fare to say that if your frame isn't butted, then a couple of holes near the middle
couldn't hurt much? Being that the tube there is thicker than it would need to be.

The thicker ends on tubes are for bending. Torsion is the main enemy of holes. Of course the
thicker the tube the safer, but then some thick tubed frames are made of low grade tubing. If it's
a clunker, I wouldn't worry. It's not as though it was going to break in half all at once. Cracks
grow slowly.

Jobst Brandt [email hidden] Palo Alto CA

Quoted message said:

Mark McMaster said:

Quoted message said:

I think there is a lot of conjecture surrounding this subject and I think it may arise from
different frame tubes and different demands put on the bicycle. I know many riders who rode and
some who still do Cinelli frames with the Cinelli sloping fork crowns. These are not only heavy
(solid steel) but are failure prone at the abrupt transition from fork blade to the internal lug
of the crown that cannot be feathered to a gradual transition as an external lug can.

Quoted message said:

I can attest to the potential for internal crown forks breaking, as I just had one break.

Quoted message said:

The fork has a semi-sloping internal crown, had somewhere between 20,000 and 25,000 miles on it,
and came with my Nobilette SLX frame bought new in 1991. Mid-ride a few weeks ago, the bike
suddenly developed an odd creaking, and when braking to a stop to check it out, I noticed that the
fork seemed to bend backward much more than it should under brake force (and more than I thought
possible for an intact fork). Upon closer inspection I found that one fork blade had a crack
running almost all the way around just below the crown, and was hanging on only by a sliver of
metal. The crack was just at the lower edge of the crown/leg brazing bond.

Not to worry, the non-scientific community of riders will tell you it doesn't happen and when it
does, it's your fault. I'm sure with your grasp of engineering that you can understand why it
occurs and that it is likely. As I said, I have had to such failures, both with the crack at the
place you describe, the remaining "hinge" being at the front on both my occurrences. I found this
interesting, because it explains why the fork has about a 15 degree rake. The idea being to put
the fork mainly in compression for the road roughness impact rather than for braking loads as is
often suggested.

In my case, the blade was cracked both front and back, with the remaining "hinge" being in the
middle. The internal crown on this fork was a bit unusual in that it had an additional external
reinforcing point (much like the point on a lug) on the side of the blade closest to the tire. This
reinforcing point extended to about 1/2" below the internal portion of the lug. When I discovered
the crack, it extended around nearly entire circumference of the blade except for the a small
portion at the reinforcing point. The blade remained attached by only a small sliver of the
reinforcing point.

From later examination, it appears the last portion of the blade to go before I discovered it was a
small portion exactly opposite the reinforcing point, at about the center of the face directly away
from the tire. In other words, it appears that there were two cracks, front and back, that grew
until they met at one side of the fork (they were prevented from meeting at the other side by the
reinforcing point).

Mark McMaster [email hidden]

Mark McMaster said:

From later examination, it appears the last portion of the blade to go before I discovered it was
a small portion exactly opposite the reinforcing point, at about the center of the face directly
away from the tire. In other words, it appears that there were two cracks, front and back, that
grew until they met at one side of the fork (they were prevented from meeting at the other side by
the reinforcing point).

It's good to hear that the fork blade was stressed equally by braking and road shock, that is, it
was stressed in tension forward and back effectively the same and failed equilaterally. My forks
also had the long tang on the inside. Now that you mention it, it seems the ancients new something
they didn't talk about. No engineers analyzed these failure back then either.

Jobst Brandt [email hidden] Palo Alto CA

Next thing you know, they'll be switching to a tapered square axle that takes advantage of the
materials commonly used for cranks and bottom bracket axles and has been shown to work for decades.
Oh, never mind.

Quoted message said:

This sound so much like the claims that cranks don't break and that those that do were the result
of any number of unrelated effects, like for instance lubricating the spindle before installation.
The reason that tale got into manufacturer's instruction sheets is because they have a problem.
The results I see are ISIS and that Shimano is still not satisfied with their solution as we see
on the straight spline and pinch bolts on their next generation.

lancearmstrong.com5331302CD9C5EBBA86256D15006FD9B9Open ↗