Maintenance Manuals

[Peter Cole]

jim beam wrote:
> Peter Cole wrote:

>> Why do reduced spoke count wheels have much higher spoke tensions?
>
> er, they don't. you check facts, right?

Yes, I've looked at both Shimano and Mavic sites and linked and quoted
the spoke tension specs I've found there. If you have contrary findings
I'm all ears.

 

[Michael Press]

In article
<[email protected]>,
Ozark Bicycle
<[email protected]> wrote:

> On Oct 7, 10:42 pm, Michael Press <[email protected]> wrote:
> > In article
> > <[email protected]>,
> > Ozark Bicycle
> >
> > <[email protected]> wrote:
> > > On Oct 6, 8:28 pm, jobst.brandt, the great and mighty, wrote:
> >
> > > > That many rims today are a poor balance of cross section and
> > > > durability, when reasonably tensioned, is apparent by many that crack
> > > > at spoke eyelets.
> >
> > > If one follows some of your "methods", that much is surely true. OTOH,
> > > using a tensionmeter and following the makers recommendations avoids
> > > this problem in most cases.
> >
> > Building a rim with sockets that can carry a spoke load in
> > excess of the buckling load of the rim avoids the problem
> > without a builder wasting time going to a manufacturer's
> > web site and wasting time searching for the information.
> >
> > Choice:
> >
> > * Search for the data and use a tensiometer to keep
> > spoke tension under the manufacturer's specification.
> >
> > * Build the wheel with spoke tension just under
> > the tension that will buckle the rim.
> >
> > I want the second choice.
> >
>
> I think you should petition the rim makers to make a special line of
> rims for lazy, cheapskate home wheel builders. ;-)

You rang?

--
Michael Press

 

[Michael Press]

In article
<[email protected]>,
Ozark Bicycle
<[email protected]> wrote:

> On Oct 7, 10:42 pm, Michael Press <[email protected]> wrote:
> > In article
> > <[email protected]>,
> > Ozark Bicycle
> >
> > <[email protected]> wrote:
> > > On Oct 6, 8:28 pm, jobst.brandt, the great and mighty, wrote:
> >
> > > > That many rims today are a poor balance of cross section and
> > > > durability, when reasonably tensioned, is apparent by many that crack
> > > > at spoke eyelets.
> >
> > > If one follows some of your "methods", that much is surely true. OTOH,
> > > using a tensionmeter and following the makers recommendations avoids
> > > this problem in most cases.
> >
> > Building a rim with sockets that can carry a spoke load in
> > excess of the buckling load of the rim avoids the problem
> > without a builder wasting time going to a manufacturer's
> > web site and wasting time searching for the information.
> >
> > Choice:
> >
> > * Search for the data and use a tensiometer to keep
> > spoke tension under the manufacturer's specification.
> >
> > * Build the wheel with spoke tension just under
> > the tension that will buckle the rim.
> >
> > I want the second choice.
> >
>
> I think you should petition the rim makers to make a special line of
> rims for lazy, cheapskate home wheel builders. ;-)

You rang?

--
Michael Press

 

[Ozark Bicycle]

On Oct 8, 11:59 am, Michael Press <[email protected]> wrote:
> In article
> <[email protected]>,
> Ozark Bicycle
>
>
>
> <[email protected]> wrote:
> > On Oct 7, 10:42 pm, Michael Press <[email protected]> wrote:
> > > In article
> > > <[email protected]>,
> > > Ozark Bicycle
>
> > > <[email protected]> wrote:
> > > > On Oct 6, 8:28 pm, jobst.brandt, the great and mighty, wrote:
>
> > > > > That many rims today are a poor balance of cross section and
> > > > > durability, when reasonably tensioned, is apparent by many that crack
> > > > > at spoke eyelets.
>
> > > > If one follows some of your "methods", that much is surely true. OTOH,
> > > > using a tensionmeter and following the makers recommendations avoids
> > > > this problem in most cases.
>
> > > Building a rim with sockets that can carry a spoke load in
> > > excess of the buckling load of the rim avoids the problem
> > > without a builder wasting time going to a manufacturer's
> > > web site and wasting time searching for the information.
>
> > > Choice:
>
> > > * Search for the data and use a tensiometer to keep
> > > spoke tension under the manufacturer's specification.
>
> > > * Build the wheel with spoke tension just under
> > > the tension that will buckle the rim.
>
> > > I want the second choice.
>
> > I think you should petition the rim makers to make a special line of
> > rims for lazy, cheapskate home wheel builders. ;-)
>
> You rang?
>
> --
> Michael Press

It's a collect call! ;-)

 

[Ozark Bicycle]

On Oct 8, 11:59 am, Michael Press <[email protected]> wrote:
> In article
> <[email protected]>,
> Ozark Bicycle
>
>
>
> <[email protected]> wrote:
> > On Oct 7, 10:42 pm, Michael Press <[email protected]> wrote:
> > > In article
> > > <[email protected]>,
> > > Ozark Bicycle
>
> > > <[email protected]> wrote:
> > > > On Oct 6, 8:28 pm, jobst.brandt, the great and mighty, wrote:
>
> > > > > That many rims today are a poor balance of cross section and
> > > > > durability, when reasonably tensioned, is apparent by many that crack
> > > > > at spoke eyelets.
>
> > > > If one follows some of your "methods", that much is surely true. OTOH,
> > > > using a tensionmeter and following the makers recommendations avoids
> > > > this problem in most cases.
>
> > > Building a rim with sockets that can carry a spoke load in
> > > excess of the buckling load of the rim avoids the problem
> > > without a builder wasting time going to a manufacturer's
> > > web site and wasting time searching for the information.
>
> > > Choice:
>
> > > * Search for the data and use a tensiometer to keep
> > > spoke tension under the manufacturer's specification.
>
> > > * Build the wheel with spoke tension just under
> > > the tension that will buckle the rim.
>
> > > I want the second choice.
>
> > I think you should petition the rim makers to make a special line of
> > rims for lazy, cheapskate home wheel builders. ;-)
>
> You rang?
>
> --
> Michael Press

It's a collect call! ;-)

 

[[email protected]]

On Mon, 08 Oct 2007 09:58:47 -0400, Peter Cole
<[email protected]> wrote:

>[email protected] wrote:
>> On Sat, 06 Oct 2007 16:29:52 -0400, Peter Cole
>> <[email protected]> wrote:
>
>>> I have no doubt that spokes could be tensioned to 175kg, just that it's
>>> unlikely that Jobst's method would get you there -- for all the reasons
>>> I previously mentioned.
>>
>> Dear Peter,
>>
>> If the spoke is at 175 kgf with a presumably inflated and constricting
>> tire in place, then it was presumably close to 190 kgf when built bare
>> on a truing stand.
>>
>> The rim looks fairly ordinary, neither deep section nor low spoke
>> count:
>>
>> http://www.flickr.com/photos/38636024@N00/1498602218/
>>
>> If the spokes are indeed all tensioned to about 175~190 kgf, why
>> wouldn't Jobst's practical method for determining the highest
>> practical tension work?
>>
>> Raise tension until the wheel goes out of true when spoke pairs are
>> squeezed, then back off half a turn and re-true.
>>
>> If you raise the tension well beyond that level, the wheel is
>> presumably going to pop out of true shortly after you start riding it.
>
>I don't know what final tension Jobst's method would give for that rim.
>
>My only point is that I am skeptical that his method was followed
>accurately, since the final tension would have to be much lower than the
>peak tension (1/2 turn off all nipples) and the combination of peak
>tension and the stress relief "squeeze" should have raised the tension
>in the squeezed spokes well above failure. Something doesn't add up.

Dear Peter,

How much does a half turn reduction, followed by re-truing change what
tension?

What do you think is the "peak" tension and how do you calculate it
for the wheel in the photograph, since you say that you don't know
what final tension Jobst's method would give for that rim?

Cheers,

Carl Fogel

 

[[email protected]]

On Mon, 08 Oct 2007 09:35:41 -0400, Peter Cole
<[email protected]> wrote:

>jim beam wrote:
>> Peter Cole wrote:
>>> [email protected] wrote:
>>>
>>>> Dear Peter,
>>>>
>>>> Whatever you two are arguing about, the numbers on the Park tension
>>>> gauge read in increments of 5.
>>>> Though fuzzy, the inset shows the needle pointing to about 26, which
>>>> is the extreme high end of the Park table calibration for a round
>>>> steel 1.8 mm spoke, about 175 kgf, or ~385 pounds of tension.
>>>
>>> OK, thanks Carl.
>>>
>>> I have no doubt that spokes could be tensioned to 175kg,
>>
>> ridiculous. that wasn't the case when you declared it "impossible".
>
>No, I said that to end up with ">175", you had to tension to at least
>210 (because you back off all nipples 1/2 turn), and that at 210, the
>50% increase in spoke tension caused by squeezing the spokes together
>would take you to plastic, if not ultimate, yield for those spokes.
>
>175 isn't impossible, getting there with Jobst's method is.
>
>>> just that it's unlikely that Jobst's method would get you there -- for
>>> all the reasons I previously mentioned.
>>
>> hypocritical bullshitter.
>
>Whatever. Your explanation still doesn't hold water.

Dear Peter,

How do you determine that a half turn on all spokes will raise tension
from 175 kgf to 210 kgf?

It may be in the thread, but it's far too large to hunt through.

Incidentally, should I tension a spoke in my pipe vise rig to 175 kgf,
squeeze it and see if it takes things to plastic yield?

Have you ever managed to squeeze a spoke to plastic yield in an actual
wheel, whose rim deforms noticeably when you squeeze spoke pairs?

You can check the rim deformation quite easily by taping a spoke flat
to the brake surface so that it sticks out at a tangent to the wheel.
When you squeeze the spoke pairs, the end of the spoke wiggles.

Cheers,

Carl Fogel

 

[[email protected]]

On Mon, 08 Oct 2007 07:09:08 -0700, [email protected] wrote:

>On Oct 7, 4:12 pm, [email protected] wrote:
>> ...Big Snip...
>>
>> ********.
>>
>> You wrote this, accusing Jim Beam of fraud, with as much evidence as
>> claims that NASA faked moon landing pictures. You couldn't have been
>> clearer:
>>
>> "You tightened down the tension spring adjustment screw of your Park
>> Tool TM-1 Tensiometer to give about double actual values."
>>
>> You have no evidence, no credibility, and not enough character to be
>> ashamed.
>>
>> Stop emailing me with duplicates and excuses.
>>
>> Carl Fogel

Stop emailing me duplicate of your excuses. This is the third one.

 

[[email protected]]

On Mon, 08 Oct 2007 05:01:33 -0000, "[email protected]"
<[email protected]> wrote:

>On Oct 7, 7:57 pm, [email protected] wrote:
>
>> >Dear Carl,
>>
>> >I don't care one way or another about jim beam's
>> >photograph and see no reason to doubt its veracity, but:
>>
>> >http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/5c...
>>
>> >You're in a fine position to lecture people about
>> >the rudeness of disbelieving photographic evidence
>> >on RBT.
>>
>> >Ben
>>
>> Dear Ben,
>>
>> Are you still to dumb to read the original post and notice the smiley?
>>
>
>Dear Carl,
>
>Language, dear boy, language. Calling me "dumb" is
>discourteous. You could accuse me of having no
>sense of humor and achieve the same effect without
>rudeness.
>
>Smileys are common on Usenet - I didn't realize then
>that the smiley was a clue you were no longer interested
>in a serious discussion, but wished to play a joke on
>your audience. Judging from the other people who posted
>in that thread, I wasn't alone. But that is all water
>under the bridge. The point is that you can't always
>trust everything you see on Usenet or the poster's motives,
>even in a technical discussion on RBT, and that's why
>I brought it up today. That is all.
>
>Ben
>
>

Dear Ben,

You're probably right.

But you missed the smiley, missed what the text said, speed-read past
it all (as Frank Krygowski's excuse put it), failed to notice that the
_single-butted_ spoke lying across a 4.5" gap in a vise in the picture
was obviously about half the length of a bicycle spoke--

And unwittingly illustrated the point that I was making in that post:

RBT has plenty of posters who insist that they can't be mistaken and
there can't be any little details (like a 168 mm motorcycle spoke
lying loose on a vise giving measurements indicating a 19 pound
"squeeze" has raised its tension almost 200 pounds.

You went off in a great hurry and calculated that it was just
impossible.

Then it finally dawned on you what was going on, so you wrote another
furious post, still without re-reading the opening of my post and
seeing the dripping sarcasm and smiley:

"Wait a minute, looking at your picture the spoke is unusually short
and thick. Goddamnit, Fogel, that is a 3mm or 3.5mm motorcycle spoke,
isn't it? No wonder it doesn't bend much. I know you were trying to
be cute with this demonstration, but that is perilously close to
scientific fraud, or at least ********."

Incidentally, as Jim Beam has repeatedly pointed out about that
bending effect, in a _real_ bicycle spoke in a _real_ tension gauge,
there are _three_ bends, not the _single_ bend_ whose effect so many
posters dismiss without testing--the thickness of the spoke does
indeed affect the delicate effect of the small force.

Cheers,

Carl Fogel

 

[Chalo]

Ozark Bicycle wrote:
>
> Reid wrote:
>
> > Just out of curiosity, are rim walls weaker or are rims constructed in a
> > way that they are tougher to buckle?
>
> Compared to an older, "box section" rim (e.g., the Mavic MA-2), most
> newer rims are "tougher to buckle", making the "Brandt methodology"
> obsolete, even dangerous to the life of the rim.

In my observation, most of them are weaker too, especially but not
exclusively in their ability to support the point loads of spoke
tension. Mavics have seriously declined in that regard, and their
welded seams are now less able to resist hoop compression from high
spoke counts. At one time they were my rims of choice, but then their
quality deteriorated and their prices soared. I no longer have any
use for Mavics.

Aero rims constitute another "innovation" that doesn't generally work
for me. Their increased section height almost always comes at the
expense of width, which makes them less than satisfactory for mounting
wide tires. If more aero rims were both tall and moderately wide like
the Velocity Deep-V ATB rim, or if Velocity made that extrusion in the
700c size, I'd probably use them sometimes. But no such luck.

Chalo

 

[[email protected]]

On Mon, 08 Oct 2007 02:54:55 -0500, Ben C <[email protected]> wrote:

>On 2007-10-08, [email protected] <[email protected]> wrote:
>[...]
>> I certainly wasn't presenting an excuse to you. You seemed to be
>> embarrassed by your own seven sequential duplicate RBT replies to my
>> post.
>
>FWIW I saw several duplicates of the original post, each one with a
>single duplicate of the follow-up from Carl. I wasn't sure whether to
>adjust my set.

Dear Ben,

With that many duplicates, who knew which would be deleted on some
servers, and where things would end up in this huge thread? Some
appeared on my newsreader _after_ I posted my first reply.

Cheers,

Carl Fogel

 

[[email protected]]

On Mon, 08 Oct 2007 09:18:49 -0400, Peter Cole
<[email protected]> wrote:

>Rim deformation is related to spoke slackness.
>
>If you consider the tables that accompany the FEA in Jobst's book,
>you'll see that the nominal 50kg load causes a ~0.15mm deflection in the
>bottommost spoke and about half that in the two adjacent spokes.

[snip]

Dear Peter,

For what it's worth, Ian's load is twice as much, 102 kgf on a
36-spoke rim where the same bottom 5 spokes lose tension. The spokes
are 2mm, but the wheel may differ in other ways from Jobst's
model--diameter, width, cross-section.

Ian calculates that the maxiumum deflection on his rim is 0.1803 mm:

http://www.astounding.org.uk/ian/wheel/index.html

It's just below "Results" on that long page, not in the huge table of
calculations.

I'm still wondering whether all wheels lose tension over the same arc
(about 40 degrees), or the same number of spokes (5)?

Or does the number of spokes (or the arc) where tension is lost vary
with the number of spokes--do a 72-spoke highwheeer, a 36-spoke MA2,
and an 18-spoke modern deep rim all lose tension over the same arc or
same number of spokes?

And does the load matter? That is, would Jobst's model show the same 5
spokes losing tension whether the load was 5, 50, or 100 kgf?

With a theoretical 3-spoke wheel, I wouldn't be surprised if _no_
spokes lost tension with the wheel loaded in this position:

|
/ \

After all, there's a 120 degree arc with no spokes.

The question really isn't as theoretical as it may seem.

If we don't even know _which_ spokes lose tension on anything other
than a 36-spoke theoretical model, then we don't know how _much_
tension they lose--and the reverse is true for the other spokes.

How much tension do how many other spokes _gain_ on a modern deep rim
18 spoke wheel? That gain is probably more for any individual spoke on
an 18-spoke wheel than the gain on the theoretical 36-spoke models, so
it may help explain the rim cracking.

Cheers,

Carl Fogel

 

[Jay Beattie]

On Oct 7, 9:12 am, [email protected] wrote:
> On Oct 7, 11:38 am, jim beam <[email protected]> wrote:

<snip>

> Should wheel building _require_ the use of a $60 single purpose tool
> to prevent unrepairable rim damage? Absolutely not.

But regrettably it does. My 1970's-standard optimum tension by "feel"
will crack modern rims. I have recalibrated my feel but now check it
with a tensiometer. That tension represents a compromise between
cracking and the wheel going out of true. I never had to make that
compromise back in the old ModE days, since the tension necessary to
crack the rim would cause it to taco during build. Over-tension was
easy to avoid. Now it is not so easy without a tool. C'est la vie. I
like tools (except ones for propreitary parts that you use twice
before the part breaks/goes out of production). -- Jay Beattie.

 

[[email protected]]

On Mon, 08 Oct 2007 14:13:30 -0000, [email protected] wrote:

>On Oct 7, 11:12 pm, [email protected] wrote:
>> On Sun, 07 Oct 2007 19:04:49 -0700, [email protected] wrote:
>> >
>>
>> >I don't feel the need to buy every special tool for every possible
>> >process. My success proves to my satisfaction that I don't need every
>> >such tool.
>>
>> Dear Frank,
>>
>> Off-topic, but I'm curious.
>>
>> Plenty of people build wheels without tension gauges, and even more
>> people ride without tire gauges.
>>
>> I've been looking, but I can't get any handle on when tire gauges came
>> into wide use for bicycles for pros or for commuters.
>>
>> Do you have any idea when tire gauges came into use? Or suggestions
>> about who to ask or where to look?
>>
>
>For "wide use"... I don't know, I suppose you'd have to define
>"wide." I imagine that most cyclists today don't use them very much.
>But I assume they came into use as soon as pneumatic tires were
>invented!
>
>That was a period that produced an immense number of mechanical
>inventions for bicycles, and there's certainly nothing complicated
>about inventing a pressure gage.
>
>Have you examined the reprinted Sears catalogs from the late 1800s?
>
>- Frank Krygowski

Dear Frank,

Thanks, I'll try to find some old Sears catalogs.

I've been looking in the scanned-lit section at www.nostalgic.net (and
getting wildly side-tracked from this side-track, of course), but so
far no tool catalogs show anything.

The oldest tire pressure gauges seem to be all schrader--I can't find
_any_ old presta and now wonder how old presta is.

(Another thread a while ago failed to find even what the hell the
origin of "presta" is.) means)and generally imply truck and car use.

Anyway, the old gauges are patented from at least as early as the
1890's and are split into "balloon" (10-50 psi) and presumably
non-balloon (20-120 psi), judging by what I've found on eBay.

I'll probably start a thread with some pictures after I wade through
the rest of today's chores.

Cheers,

Carl Fogel

 

[Peter Cole]

[email protected] wrote:
> On Mon, 08 Oct 2007 09:58:47 -0400, Peter Cole
> <[email protected]> wrote:
>
>> [email protected] wrote:
>>> On Sat, 06 Oct 2007 16:29:52 -0400, Peter Cole
>>> <[email protected]> wrote:
>>>> I have no doubt that spokes could be tensioned to 175kg, just that it's
>>>> unlikely that Jobst's method would get you there -- for all the reasons
>>>> I previously mentioned.
>>> Dear Peter,
>>>
>>> If the spoke is at 175 kgf with a presumably inflated and constricting
>>> tire in place, then it was presumably close to 190 kgf when built bare
>>> on a truing stand.
>>>
>>> The rim looks fairly ordinary, neither deep section nor low spoke
>>> count:
>>>
>>> http://www.flickr.com/photos/38636024@N00/1498602218/
>>>
>>> If the spokes are indeed all tensioned to about 175~190 kgf, why
>>> wouldn't Jobst's practical method for determining the highest
>>> practical tension work?
>>>
>>> Raise tension until the wheel goes out of true when spoke pairs are
>>> squeezed, then back off half a turn and re-true.
>>>
>>> If you raise the tension well beyond that level, the wheel is
>>> presumably going to pop out of true shortly after you start riding it.
>> I don't know what final tension Jobst's method would give for that rim.
>>
>> My only point is that I am skeptical that his method was followed
>> accurately, since the final tension would have to be much lower than the
>> peak tension (1/2 turn off all nipples) and the combination of peak
>> tension and the stress relief "squeeze" should have raised the tension
>> in the squeezed spokes well above failure. Something doesn't add up.
>
> Dear Peter,
>
> How much does a half turn reduction, followed by re-truing change what
> tension?

A half turn is about 30kg.


> What do you think is the "peak" tension and how do you calculate it
> for the wheel in the photograph, since you say that you don't know
> what final tension Jobst's method would give for that rim?

If the final tension is >175kg, + 1/2 turn = >205kg, plus whatever the
inflated tire is dropping, perhaps 10kg anyway, so >215kg. According to
Jobst's book, 1.8mm spokes let go at 250, I'd think a big guy like jb
could easily squeeze another 35kg.

 

[Peter Cole]

[email protected] wrote:
> On Mon, 08 Oct 2007 09:35:41 -0400, Peter Cole
> <[email protected]> wrote:
>
>> jim beam wrote:
>>> Peter Cole wrote:
>>>> [email protected] wrote:
>>>>
>>>>> Dear Peter,
>>>>>
>>>>> Whatever you two are arguing about, the numbers on the Park tension
>>>>> gauge read in increments of 5.
>>>>> Though fuzzy, the inset shows the needle pointing to about 26, which
>>>>> is the extreme high end of the Park table calibration for a round
>>>>> steel 1.8 mm spoke, about 175 kgf, or ~385 pounds of tension.
>>>> OK, thanks Carl.
>>>>
>>>> I have no doubt that spokes could be tensioned to 175kg,
>>> ridiculous. that wasn't the case when you declared it "impossible".
>> No, I said that to end up with ">175", you had to tension to at least
>> 210 (because you back off all nipples 1/2 turn), and that at 210, the
>> 50% increase in spoke tension caused by squeezing the spokes together
>> would take you to plastic, if not ultimate, yield for those spokes.
>>
>> 175 isn't impossible, getting there with Jobst's method is.
>>
>>>> just that it's unlikely that Jobst's method would get you there -- for
>>>> all the reasons I previously mentioned.
>>> hypocritical bullshitter.
>> Whatever. Your explanation still doesn't hold water.
>
> Dear Peter,
>
> How do you determine that a half turn on all spokes will raise tension
> from 175 kgf to 210 kgf?

Pitch of spoke thread, spoke elasticity.

>
> It may be in the thread, but it's far too large to hunt through.
>
> Incidentally, should I tension a spoke in my pipe vise rig to 175 kgf,
> squeeze it and see if it takes things to plastic yield?

Knock yourself out.


> Have you ever managed to squeeze a spoke to plastic yield in an actual
> wheel, whose rim deforms noticeably when you squeeze spoke pairs?

Nope, never tried.


> You can check the rim deformation quite easily by taping a spoke flat
> to the brake surface so that it sticks out at a tangent to the wheel.
> When you squeeze the spoke pairs, the end of the spoke wiggles.

Whatever turns you on.

 

[A Muzi]

>>> [email protected] wrote:
>>>> I don't feel the need to buy every special tool for every possible
>>>> process. My success proves to my satisfaction that I don't need every
>>>> such tool.

>> [email protected] wrote:
>>> Off-topic, but I'm curious.
>>> Plenty of people build wheels without tension gauges, and even more
>>> people ride without tire gauges.
>>> I've been looking, but I can't get any handle on when tire gauges came
>>> into wide use for bicycles for pros or for commuters.
>>> Do you have any idea when tire gauges came into use? Or suggestions
>>> about who to ask or where to look?

> [email protected] wrote:
>> For "wide use"... I don't know, I suppose you'd have to define
>> "wide." I imagine that most cyclists today don't use them very much.
>> But I assume they came into use as soon as pneumatic tires were
>> invented!
>> That was a period that produced an immense number of mechanical
>> inventions for bicycles, and there's certainly nothing complicated
>> about inventing a pressure gage.
>> Have you examined the reprinted Sears catalogs from the late 1800s?

[email protected] wrote:
> Thanks, I'll try to find some old Sears catalogs.
> I've been looking in the scanned-lit section at www.nostalgic.net (and
> getting wildly side-tracked from this side-track, of course), but so
> far no tool catalogs show anything.
> The oldest tire pressure gauges seem to be all schrader--I can't find
> _any_ old presta and now wonder how old presta is.
> (Another thread a while ago failed to find even what the hell the
> origin of "presta" is.) means)and generally imply truck and car use.
> Anyway, the old gauges are patented from at least as early as the
> 1890's and are split into "balloon" (10-50 psi) and presumably
> non-balloon (20-120 psi), judging by what I've found on eBay.
> I'll probably start a thread with some pictures after I wade through
> the rest of today's chores.

This was sorta researched and reported by one Carl Fogel on RBT about
four months ago, albeit inconclusively:
http://groups.google.com/group/rec....read/thread/410dc66cb28cf998/92f81d1b7ed843cf
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[Peter Cole]

[email protected] wrote:
> On Mon, 08 Oct 2007 09:18:49 -0400, Peter Cole
> <[email protected]> wrote:
>
>> Rim deformation is related to spoke slackness.
>>
>> If you consider the tables that accompany the FEA in Jobst's book,
>> you'll see that the nominal 50kg load causes a ~0.15mm deflection in the
>> bottommost spoke and about half that in the two adjacent spokes.
>
> [snip]
>
> Dear Peter,
>
> For what it's worth, Ian's load is twice as much, 102 kgf on a
> 36-spoke rim where the same bottom 5 spokes lose tension. The spokes
> are 2mm, but the wheel may differ in other ways from Jobst's
> model--diameter, width, cross-section.
>
> Ian calculates that the maxiumum deflection on his rim is 0.1803 mm:
>
> http://www.astounding.org.uk/ian/wheel/index.html

Yes, he does.

He also uses much stiffer spokes, (3.16mm^2 vs. 2.0mm^2), and
distributes the load over 3 points, 250N, 500N, 250N at 3 adjacent
spokes vs. just 1 in Jobst's model. Both models use similar rim
stiffnesses, which happen to be much stiffer than Gavin's (apparently
measured from an actual rim), (~1200mm^4 vs. ~800mm^4).

The apparent difference in peak rim deflection is a combination of
stiffer spokes and more distributed load.


> It's just below "Results" on that long page, not in the huge table of
> calculations.
>
> I'm still wondering whether all wheels lose tension over the same arc
> (about 40 degrees), or the same number of spokes (5)?
>
> Or does the number of spokes (or the arc) where tension is lost vary
> with the number of spokes--do a 72-spoke highwheeer, a 36-spoke MA2,
> and an 18-spoke modern deep rim all lose tension over the same arc or
> same number of spokes?
>
> And does the load matter? That is, would Jobst's model show the same 5
> spokes losing tension whether the load was 5, 50, or 100 kgf?
>
> With a theoretical 3-spoke wheel, I wouldn't be surprised if _no_
> spokes lost tension with the wheel loaded in this position:
>
> |
> / \
>
> After all, there's a 120 degree arc with no spokes.

As I said before, you need to use a FEA program. If you read Ian's site
carefully, you'd at least appreciate the folly of trying to come up
with these numbers by winging it.


> The question really isn't as theoretical as it may seem.
>
> If we don't even know _which_ spokes lose tension on anything other
> than a 36-spoke theoretical model, then we don't know how _much_
> tension they lose--and the reverse is true for the other spokes.

I'm guessing somebody does or else the spoke tension specs I've seen on
16-20 spoke wheels wouldn't be so high.



> How much tension do how many other spokes _gain_ on a modern deep rim
> 18 spoke wheel? That gain is probably more for any individual spoke on
> an 18-spoke wheel than the gain on the theoretical 36-spoke models, so
> it may help explain the rim cracking.

Not the 36 hole cracking, which is what most of the flap has been about.

 

[Ryan Cousineau]

In article <[email protected]>,
Chalo <[email protected]> wrote:

> Ozark Bicycle wrote:
> >
> > Reid wrote:
> >
> > > Just out of curiosity, are rim walls weaker or are rims constructed in a
> > > way that they are tougher to buckle?
> >
> > Compared to an older, "box section" rim (e.g., the Mavic MA-2), most
> > newer rims are "tougher to buckle", making the "Brandt methodology"
> > obsolete, even dangerous to the life of the rim.
>
> In my observation, most of them are weaker too, especially but not
> exclusively in their ability to support the point loads of spoke
> tension. Mavics have seriously declined in that regard, and their
> welded seams are now less able to resist hoop compression from high
> spoke counts. At one time they were my rims of choice, but then their
> quality deteriorated and their prices soared. I no longer have any
> use for Mavics.
>
> Aero rims constitute another "innovation" that doesn't generally work
> for me. Their increased section height almost always comes at the
> expense of width, which makes them less than satisfactory for mounting
> wide tires. If more aero rims were both tall and moderately wide like
> the Velocity Deep-V ATB rim, or if Velocity made that extrusion in the
> 700c size, I'd probably use them sometimes. But no such luck.
>
> Chalo

Are 29ers increasing the quantity of ISO 622 rims that meet your
approval?

--
Ryan Cousineau [email protected] http://www.wiredcola.com/
"I don't want kids who are thinking about going into mathematics
to think that they have to take drugs to succeed." -Paul Erdos

 

[[email protected]]

Bill Sornson writes:

>>>> I find the atmosphere here on wreck.bike to have taken a substantial
>>>> dive in tone of discussions and suspect it may be influenced by the
>>>> insulting manner of the highest offices in the USA, where typically
>>>> department heads accuse the lowest ranking subordinates, or the
>>>> public at large, for their failures and hate mongering they have
>>>> generated ignoring command responsibility... like a CEO saying the
>>>> company went broke because the employees failed him.

>>>> I no longer see "I disagree and believe it is otherwise...". Instead
>>>> insults have replaced accepting opposing comments. We can
>>>> thank the rude ones and then Mr. Fogel, who supports these rude
>>>> people with arguments to support their style.

>>>> In my estimation, we are not making headway, rude responses
>>>> appearing often as anti free speech by intimidation.

>>> Jobst Brandt, sensitive tank! Of course, Mr. Brandt would *never,
>>> ever* behave in a rude, dismissive, insulting, abrasive or
>>> condescending manner, would he? ;-) Note to Jobst: "Physician,
>>> heal thyself!"

>> In any discussion it helps to stay in the present.

>> Don't you just hate it when girlfriend brings up some conversation
>> from a year ago? If Mr Brandt civilly asks for civility today, I'll
>> take that at face value and make an effort myself.

> Ask him to never start another off-topic political thread while
> you're at it. (Maybe he won't flame ride reporters -- in RB-MISC --
> for being OT any more, either.)

An elephant never forgets! except this one forgot that the writer
was asked to post his ride report to RBrides also, not just to RBtech.

What a heinous crime that was... a few years ago.

Jobst Brandt