Rivnut success
Lindsay Rowlands
I've just had my first encounter with rivnuts and finally won. I needed
to fit water bottle mounts on a frame I've set up as a fixed wheeler.
In this small town, the places you'd expect a chance of buying a couple
of 5mm rivnuts were disappointing. I may as well have been speaking
Urdu or Fon. Rivnut is a great trigger for 'Huh?'.
I finally located some at the local aircraft maintenance hanger for $1
each. For all intents and purposes aircraft bits and pieces are AF or
non-metric. I wasn't deterred and as it turns out 3/16 fine thread is
so close to 5mm x .8 (most water bottle screws) that they're as good as
interchangeable.
After carefully measuring and drilling the frame, it was time to wrangle
with the rivnuts. I'd assumed it was just a matter of putting the rivnut
in the hole and then tightening a water bottle bolt to expand the 'riv'
part of the device. Nope. It took a bit of fussing around to locate a
longer 5mm bolt, nut and a piece of flat plate with a hole the right size.
The device went: bolt, 8mm spanner, nut, washer, flat plate, rivnut. Then
it was down to carefully tightening the nut with the rivnut inserted in
the frame. I made a point of greasing the washer under the nut so that it
could spin easily. It was then a matter of feeling when the resistance
slightly increased then stopping. The rivnuts are aluminium so it would be
very easy to strip the threads.
In my searching earlier I came across a rivnut kit with assorted sizes and
a pop rivet plyers - $160! Sure the plyers would have made the insertion a
whole lot easier, but without them I had a very intimate learning
experience. And I'm quite chuffed to have water bottle mounts where they
weren't previously and it only cost $2.
So if anyone is thinking about fitting water bottle mounts to a bike I can
vouch that is quite straight forward and they should have the confidence
to take the job on, even without the special tool.
Cheerz,
Lynzz
Ronald
> it was down to carefully tightening the nut with the rivnut inserted in
> the frame.
Thanks, i was planning on using the same device to fit some rivnuts and
wundered if it would work.
"Lindsay Rowlands" <lrow...@metz.une.edu.au> wrote in message
news:b9b1vo$3k1$1...@gruvel.une.edu.au...
jobst....@stanfordalumni.org
> This may not be a big deal for the 'old man and the bicycle' types,
> but I've just had my first encounter with rivnuts and finally won. I
> needed to fit water bottle mounts on a frame I've set up as a fixed
> wheeler.
> I finally located some at the local aircraft maintenance hanger for
> $1 each. For all intents and purposes aircraft bits and pieces are
> AF or non-metric. I wasn't deterred and as it turns out 3/16 fine
> thread is so close to 5mm x .8 (most water bottle screws) that
> they're as good as interchangeable.
> After carefully measuring and drilling the frame, it was time to
> wrangle with the rivnuts. I'd assumed it was just a matter of
> putting the rivnut in the hole and then tightening a water bottle
> bolt to expand the 'riv' part of the device.
Not a good idea! I don't know many riders who believe that drilling a
hole in a frame tube is a reasonable concept. I assume the rivnut was
securely tightened and painted to prevent motion, corrosion and water
intrusion. Normally a water bottle thread is brazed or welded into
the tube, thereby becoming a structural reinforcement for the hole in
the tube. A rivnut is not doing anything for strength and is not part
of the tube and I suspect it will loosen with time, having no preload.
Jobst Brandt
jobst....@stanfordalumni.org
Palo Alto CA
Mike Jacoubowsky
> hole in a frame tube is a reasonable concept. I assume the rivnut was
> securely tightened and painted to prevent motion, corrosion and water
> intrusion. Normally a water bottle thread is brazed or welded into
> the tube, thereby becoming a structural reinforcement for the hole in
> the tube. A rivnut is not doing anything for strength and is not part
> of the tube and I suspect it will loosen with time, having no preload.
Jobst: These days, water bottle bosses are not "normally" brazed or welded
into place. Even Reynolds is suggesting rivnuts for 853, which is
amazingly-thin tubing. If you look at modern bikes, you'll find virtually
all of them sporting rivnuts these days, with no more incidence of failure
that what you'd find from the brazed variety (which would sometimes be the
point of tube failure, just as the rivnut style are). The use of rivnuts
cuts across all lines... materials (steel, aluminum, carbon, titanium),
pricing (mass produced & custom) and origin (Italian, Chinese, domestic).
--Mike-- Chain Reaction Bicycles
http://www.ChainReactionBicycles.com
John Everett
<ronaldvt_re...@hotmail.com> wrote:
>> The device went: bolt, 8mm spanner, nut, washer, flat plate, rivnut. Then
>> it was down to carefully tightening the nut with the rivnut inserted in
>> the frame.
>
>Thanks, i was planning on using the same device to fit some rivnuts and
>wundered if it would work.
>
>"Lindsay Rowlands" <lrow...@metz.une.edu.au> wrote in message
>news:b9b1vo$3k1$1...@gruvel.une.edu.au...
>> This may not be a big deal for the 'old man and the bicycle' types, but
>> I've just had my first encounter with rivnuts and finally won. I needed
>> to fit water bottle mounts on a frame I've set up as a fixed wheeler.
>>
>> In this small town, the places you'd expect a chance of buying a couple
>> of 5mm rivnuts were disappointing. I may as well have been speaking
>> Urdu or Fon. Rivnut is a great trigger for 'Huh?'.
>>
>> I finally located some at the local aircraft maintenance hanger for $1
>> each.
Last time I needed a Rivnut inserted the guy at the local aircraft
maintenance hangar did it with the proper tool, gratis. :-)
jeverett3<AT>earthlink<DOT>net http://home.earthlink.net/~jeverett3
Matt O'Toole
<jobst....@stanfordalumni.org> wrote in message
news:xL9ua.12045$JX2.7...@typhoon.sonic.net...
> Not a good idea! I don't know many riders who believe
that drilling a
> hole in a frame tube is a reasonable concept. I assume
the rivnut was
> securely tightened and painted to prevent motion,
corrosion and water
> intrusion. Normally a water bottle thread is brazed or
welded into
> the tube, thereby becoming a structural reinforcement for
the hole in
> the tube. A rivnut is not doing anything for strength and
is not part
> of the tube and I suspect it will loosen with time, having
no preload.
I've been using stainless steel pop rivets and rivnuts for
nearly 30 years with no problems. They do have to be
installed tightly. A dab of silicone keeps corrosion at
bay.
However, as Mike mentioned, I wouldn't be surprised if some
modern bicycle tubes are too thin to support a water bottle
with a rivet.
Matt O.
Lindsay Rowlands
: Lindsay Rowlands writes:
: Not a good idea! I don't know many riders who believe that drilling a
: hole in a frame tube is a reasonable concept. I assume the rivnut was
: securely tightened and painted to prevent motion, corrosion and water
: intrusion. Normally a water bottle thread is brazed or welded into
: the tube, thereby becoming a structural reinforcement for the hole in
: the tube. A rivnut is not doing anything for strength and is not part
: of the tube and I suspect it will loosen with time, having no preload.
The strength issue certainly occurred to me and I'll keep an eye on
things, though the frame in question is a nothing-exotic steel number
with no intrinsic value other than being an appropriate receptacle
to attach other bike components.
I may be mistaken but I've seen what are suspiciously rivnut-like fittings
in late model aluminium frames. If they're OK for frame makers then
I don't feel reckless about taking the risk with a 20 year old steel frame.
Cheerz,
Lynzz
Lindsay Rowlands
:> The device went: bolt, 8mm spanner, nut, washer, flat plate, rivnut. Then
:> it was down to carefully tightening the nut with the rivnut inserted in
:> the frame.
: Thanks, i was planning on using the same device to fit some rivnuts and
: wundered if it would work.
Some of the details I left out were that I drilled the holes so that the
rivnuts were close fitting and I also deburred them.
The flat plate is to stop the rivnut turning as you tighten up the nut, so
anything that is long enough and with an appropriate close fitting hole will
do.
I should point out too that the thread on the bolt I used for inserting the rivnut
stripped probably because the load on the tightening nut distorted it so be prepared
to sacrifice a bolt or two. I used a couple from a kit of nuts and bolts bought in
the local supermarket.
In hindsight, I should have painted some metal etching primer on the bare steel of
the hole and lathered some silicone sealant on the rivnut to keep water out. I'll
do that next time.
Lots of luck.
Cheerz,
Lynzz
hillbiker
BFGoodrich (1987-1989.) They won't do anything for the strength of the tube.
However, they expand radially into interference with the hole BEFORE they
form a bulge on the back side of the work, so they won't come loose, and
they are "splash-proof" if not fully water-tight.
At one time they made a special which was actually headless, and which held
in the workpiece JUST by the interference with the walls of the hole. In
fact, the interference with the hole will actually keep the head of the
Rivnut from drawing down against the workpiece -- if it isn't down when you
start your pull, it may not GO down at all!
Doug Goncz
and 1/4-20, and inserts, $14.99.
The full deluxe kit goes to 3/8-16, and does the nutserts, too, which are
flush, not head, and expand into the hole in thicker materials.
Yours,
Doug Goncz, Replikon Research, Seven Corners, VA
http://users.aol.com/DGoncz
If a computer won't do what needs to be done, lie to it.
Don't try this trick on people.
Doug Goncz
>a pop rivet plyers - $160!
Where?
That's way too much!
A Muzi
and
> >a pop rivet plyers - $160!
" Doug Goncz " <dgo...@aol.com> wrote in message
news:20030508170738...@mb-m28.aol.com...
> Where?
> That's way too much!
Too much for a hundred pieces or too much for twenty thousand pieces? Hard
to tell, isn't it?
--
Andrew Muzi
http://www.yellowjersey.org
Open every day since 1 April 1971
Steven Scharf
> I've just had my first encounter with rivnuts and finally won. I needed
> to fit water bottle mounts on a frame I've set up as a fixed wheeler.
Argh, don't use Rivnuts for this!
Andy Dingley
wrote:
>Argh, don't use Rivnuts for this!
Why ?
>See: "http://www.nordicgroup.us/cageboss.htm"
Why ?
"but it looks tacky and unprofessional" is hardly a compelling
argument.
As it happens, I was looking in the RAF training notes on airframes
tonight. They seem pretty sanguine about using Rivnuts (and a whole
slew of other fastenings, all listed in huge detail). So what's the
problem for downtubes ?
John Everett
wrote:
>Lindsay Rowlands <lrow...@metz.une.edu.au> wrote in message news:<b9b1vo$3k1$1...@gruvel.une.edu.au>...
I checked the link and Scharf's web site (nordicgroup) claim Rivnuts
"look tacky and unprofessional". My Vitus came with Rivnuts and with
the bottle cages in place you can't even see them. How can something
basically invisible look "tacky and unprofessional"?
Meanwhile, Scharf's page touts all kinds of tacky looking methods
requiring straps and/or hose clamp looking things.
Mike DeMicco
jobst....@stanfordalumni.org wrote:
> Lindsay Rowlands writes:
>
> > After carefully measuring and drilling the frame, it was time to
> > wrangle with the rivnuts. I'd assumed it was just a matter of
> > putting the rivnut in the hole and then tightening a water bottle
> > bolt to expand the 'riv' part of the device.
>
> Not a good idea! I don't know many riders who believe that drilling a
> hole in a frame tube is a reasonable concept. I assume the rivnut was
> securely tightened and painted to prevent motion, corrosion and water
> intrusion. Normally a water bottle thread is brazed or welded into
> the tube, thereby becoming a structural reinforcement for the hole in
> the tube. A rivnut is not doing anything for strength and is not part
> of the tube and I suspect it will loosen with time, having no preload.
I concur. Just recently, my Trek 1200 aluminum frame cracked around the
seat tube at a crimped-in (rivnut) threaded insert for the front
derailler mount. Had there been no insert (i.e., had the frame been
built for a clamp-on derailler) I doubt the frame would have failed.
Clamp-on water bottle cage mounts are available and the safer choice.
jobst....@stanfordalumni.org
>>> After carefully measuring and drilling the frame, it was time to
>>> wrangle with the Rivnuts. I'd assumed it was just a matter of
>>> putting the Rivnut in the hole and then tightening a water bottle
>>> bolt to expand the 'riv' part of the device.
>> Not a good idea! I don't know many riders who believe that
>> drilling a hole in a frame tube is a reasonable concept. I assume
>> the Rivnut was securely tightened and painted to prevent motion,
>> corrosion and water intrusion. Normally a water bottle thread is
>> brazed or welded into the tube, thereby becoming a structural
>> reinforcement for the hole in the tube. A Rivnut is not doing
>> anything for strength and is not part of the tube and I suspect it
>> will loosen with time, having no preload.
> I concur. Just recently, my Trek 1200 aluminum frame cracked around
> the seat tube at a crimped-in (Rivnut) threaded insert for the front
> derailleur mount. Had there been no insert (i.e., had the frame been
> built for a clamp-on derailleur) I doubt the frame would have failed.
> Clamp-on water bottle cage mounts are available and the safer
> choice.
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.
http://www.lancearmstrong.com/lance/online2.nsf/Docs/5331302CD9C5EBBA86256D15006FD9B9
I am still waiting to see what they devise for crank failures at the
pedal eye, something far easier to solve than the spindle attachment.
Cranks break and holes in frame tubes, loaded in torsion and/or
bending, causes tube failures. This is nothing new but as often
happens, R&D takes place on the customers shift. If the stresses
around a 1/4" hole in a frame tube were visible, I'm sure few people
would even consider drilling such a hole.
Steven Scharf
> I checked the link and Scharf's web site (nordicgroup) claim Rivnuts
> "look tacky and unprofessional". My Vitus came with Rivnuts and with
> the bottle cages in place you can't even see them. How can something
> basically invisible look "tacky and unprofessional"?
There's a big difference when it comes with Rivnuts from the
manufacturer (for a very good reason in the case of the Vitus),
and doing it yourself by drilling holes after the fact. And even
when factory installed, there are already enough problems with
aluminum tubing to not take any chances with weakening the tubing
even further (see the post in this thread by Mike DeMicco).
IMVAIO, the Zefal Gizmo Clamps, the KLICKFix Bottle Fix, and the
Minoura bottle cage holder, are solutions to the problem that
do not have the downside of weakening the frame or allowing water
to get inside the frame. They look no worse that the various
clamps that hold other accessories, such as computers, onto the
bicycle.
Everyone would prefer that their frame has cage bosses from the
factory, be they braze-ons or factoty installed Rivnuts. When
this is not the case, the prudent method for adding bottle mounts
is to use one of the many clamps that are available.
Andy Dingley
wrote:
>There's a big difference when it comes with Rivnuts from the
>manufacturer (for a very good reason in the case of the Vitus),
>and doing it yourself by drilling holes after the fact.
Why ? Why can't a Rivnut be perfectly well installed afterwards ?
It's what they're designed for !
John Everett
Exactly!
Steven M. Scharf
"Andy Dingley" <din...@codesmiths.com> wrote in message
news:lpq1cvo8hoj7qjqk2...@4ax.com...
The Rivnut was designed for it, but the bicycle frame was not designed
for it. They can be installed in older steel frames.
Andy Dingley
<scharf...@linkearth.net> wrote:
>The Rivnut was designed for it, but the bicycle frame was not designed
>for it. They can be installed in older steel frames.
Anyone got any evidence of a frame that failed at the waterbottle
mounts, Rivnut or not ?
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.
Never ask a metallurgist to do a structural engineer's job.
jobst....@stanfordalumni.org
>> The Rivnut was designed for it, but the bicycle frame was not
>> designed for it. They can be installed in older steel frames.
> Anyone got any evidence of a frame that failed at the water bottle
> mounts, Rivnut or not ?
> 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.
> 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.
Tim McNamara
jobst....@stanfordalumni.org wrote:
> 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.
> 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).
jobst....@stanfordalumni.org
>> 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.
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.
>> 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?
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.
> 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.
http://www.dursley-pedersen.net/
Matt O'Toole
<jobst....@stanfordalumni.org> wrote in message
news:7ejwa.14119$JX2.8...@typhoon.sonic.net...
> 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.
>
> http://www.dursley-pedersen.net/
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.
Tim McNamara
jobst....@stanfordalumni.org wrote:
> Tim McNamara writes:
>
> > 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.
> > 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.
>
> http://www.dursley-pedersen.net/
My wife- of Danish extraction- has wanted a Pedersen for years. I
seem to recall that his design was inspired by bridge design.
Dave Kahn
>
> I always assumed the main
> feature was the riding position -- like standing normally --
> for people with really bad backs or whatever.
The riding position doesn't have to be that upright. Racing Pedersens
were also made with quite an aggressive aero position.
--
Dave...
Matt O'Toole
"Tim McNamara" <tim...@bitstream.net> wrote in message
news:timmcn-210F07....@gemini.visi.com...
> An odd thing
> about the US is that publicly available drinking water and
bathrooms
> are rarely readily available.
Sure it is, you just have to pay for it. The bottom line is
the bottom line in the USA. If someone can't make a buck
from it, it's not worth doing. Why have a public drinking
fountain, when you can sell someone a bottle of Evian?
The other problem we have is vandalism. Any unguarded
public restroom gets trashed or filthed within hours.
Matt O.
Dietrich Wiegmann
> 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).
For another data point, the top and downtubes of my Klien broke
simultaneously at the internal cable routing holes. The front of the
bike literally broke off.
The ad copy for the bike said the cable holes made the tubes more
fatigue resistant. Heh heh.
Dietrich Wiegmann
Matt O'Toole
"Dietrich Wiegmann" <dwie...@anteon.com> wrote in message
news:1ee1aae4.03051...@posting.google.com...
I know Klein considers these a design trademark, but they're
awfully stupid and I wish they'd just give them up. Top
tube cable routing makes a lot more sense on mountain bikes
anyway, and threading cables through the frame is a PITA.
I've seen at least two failures like that one, both at MTB
races.
I ride a Klein, but one of the more sensible, Trek-built
ones with normal cable stops on the top tube. It may lack
the smooth welds of the "real" Kleins, and have ugly
chainstays and a lousy paint job, but IMO it's a better
frame.
Matt O.
Mark McMaster
> 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
MMc...@ix.netcom.com
jobst....@stanfordalumni.org
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.
John Red-Horse
>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
Erik Brooks
> 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
stu
holes near the middle couldn't hurt much?
being that the tube there is thicker than it would need to be.
jobst....@stanfordalumni.org
> 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.
Mark McMaster
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
MMc...@ix.netcom.com
jobst....@stanfordalumni.org
> 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.
robert perkins
takes advantage of the materials commonly used for cranks and bottom
bracket axles and has been shown to work for decades. Oh, never mind.