Snaping Spokes

I hope that maybe i could shed a little light on this discussion. I am
a civil engineering student (last semester thank goodness) that has
drawn hundreds of free body diagrams and knows a little about steel
design as well as a ton about statics and strength of materials.
First, the idea that tension being reduced in the bottom spokes
constitutes a reaction of support to the hub is a complete
misunderstanding of basic mechanics. If there is ANY tension left in
the bottom spokes, than the force on the hub can ONLY be in the down
direction!! Period. End of Story.
In Steel Design, we learned that no engineer worth his salt would ever
dream of using a piece of steel that resembles a wire as a compression
member. I'll spare you the formulas, but basically, four spokes would
buckle under FAR less load than a rider. I'm curious as to who did
this finite element analysis and what software they used. We use LS
Dyna at our school. I'll see if i can't get some extra time to put it
in but it is a waste of time. There is NO WAY that a mechanical
engineer would use spokes as compression members.
Sorry, not going to buy it!!!

I think you are overly dichotomizing the situation. The load is
supported by the loss of tension in the lower spokes. That does not
mean that the rest of the spokes are uninvolved, as the FEA clearly
shows. The wheel does not hang from the upper spokes, any more than
it
hangs from the spokes at 90 degrees or from the spokes immediately
outside of the rim's LAZ. What you seem to fail to grasp, in your
rather odd semantic obsession, is the concept of net effects. About
4
spokes are lowered in tension when the wheel is loaded through the
hub;
the remaining spokes (not just the top ones) see a small increase in
tension; this increase is measured to be about 25 times smaller than
the loss of tnesion seen in the spokes attached to the rims LAZ.
Because the force vectors of all the other spokes cancel each other
out, it is accurate to state that "the wheel stands on the bottom
spokes." Or, if you prefer, "the load is supported by the bottom
spokes."

Most of the posters arguing against the concept are not thinking
about
whole wheels but are focusing on small bits that they find
objectionable- mainly because they haven't yet grasped the
whole-wheel
concept nor how pretensioned structures operate.

On 4 Mar 2005 21:27:36 -0800, may have said:

I hope that maybe i could shed a little light on this discussion. I am
a civil engineering student (last semester thank goodness) that has
drawn hundreds of free body diagrams and knows a little about steel
design as well as a ton about statics and strength of materials.

I would refer you back to your books, and to "The Bicycle Wheel", by
Jobst Brandt, for an authoritative discussion of the subject, then.

http://www.sheldonbrown.com/brandt/

I believe that if he were in a particularly charitable mood, Jobst
would say something to the effect of "I'll see your civil engineering
class, and raise you a mechanical engineering degree and a number of
extensive analyses of the issue, including a published treatise on the
subject", but he's likely to be less diplomatic.

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And why on earth are you resurrecting a thread that's been dead for
three years?

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Someone offered anonymously:

I think you are overly dichotomizing the situation. The load is
supported by the loss of tension in the lower spokes. That does
not mean that the rest of the spokes are uninvolved, as the FEA
clearly shows. The wheel does not hang from the upper spokes, any
more than it hangs from the spokes at 90 degrees or from the spokes
immediately outside of the rim's LAZ.

What you seem to fail to grasp, in your rather odd semantic
obsession, is the concept of net effects. About 4 spokes are
lowered in tension when the wheel is loaded through the hub; the
remaining spokes (not just the top ones) see a small increase in
tension; this increase is measured to be about 25 times smaller
than the loss of tension seen in the spokes attached to the rims
LAZ.

Because the force vectors of all the other spokes cancel each other
out, it is accurate to state that "the wheel stands on the bottom
spokes." Or, if you prefer, "the load is supported by the bottom
spokes."

Most of the posters arguing against the concept are not thinking
about whole wheels but are focusing on small bits that they find
objectionable- mainly because they haven't yet grasped the
whole-wheel concept nor how pretensioned structures operate.

I hope that maybe I could shed a little light on this discussion.

On which discussion? I take it you changed the subject line so this
doesn't follow on a previous discussion other then the lines you had
misplaced at the end of your bluster. I suppose you should be aware
of newsgroup protocol, in which the subject of discussion is cited for
the benefit of those who are to understand what is being discussed,
usually in the sequence of occurrence.

I am a civil engineering student (last semester thank goodness) that
has drawn hundreds of free body diagrams and knows a little about
steel design as well as a ton about statics and strength of
materials.

I take it you are studying engineering for other reasons than that the
subject interests you or why else should you make your education sound
so odious. Maybe you were not cut out to be an engineer and should
have pursued a different career.

First, the idea that tension being reduced in the bottom spokes
constitutes a reaction of support to the hub is a complete
misunderstanding of basic mechanics. If there is ANY tension left
in the bottom spokes, than the force on the hub can ONLY be in the
down direction!! Period. End of Story.

Is it that you don't believe the only spokes in a wheel that
experience a substantial change in tension are the ones in the load
affected zone (LAZ), aka the tire contact with the road? Can you
clarify which spokes you believe are affected vertically loading a
wire spoked bicycle wheel. Did you come across algebra in your
studies in which signed (+-) values are operated on so that negative
and positive numbers can be added.

I think you missed some homework assignments, it couldn't have been
any laboratory sessions, they no longer being part of curricula these
days. Just the same, you must have seen some load superpositions.
Even butchers know how to set their scales to derive net weight from
packages of meat by setting a tare weight (preload)... and that at
times has been called "the butcher's thumb" at times.

In Steel Design, we learned that no engineer worth his salt would
ever dream of using a piece of steel that resembles a wire as a
compression member.

Salt comes at different prices these days that when that phrase was
coined.

Preload and superposition occurs in all sorts of constructions and
has nothing specific to do with "Steel Design". So who is proposing
using wires as compression members? I think you're making this up as
you go. How did your axe get so that you need to find others to
grind. You probably missed this but your approach to prestressed
structures has been aired here regularly for the past twenty years by
disgruntled narrow minded "engineers".

I'll spare you the formulas, but basically, four spokes would buckle
under FAR less load than a rider. I'm curious as to who did this
finite element analysis and what software they used. We use LS Dyna
at our school. I'll see if i can't get some extra time to put it in
but it is a waste of time. There is NO WAY that a mechanical
engineer would use spokes as compression members. Sorry, not going
to buy it!!!

On the other hand, I'm curious how you did your analysis. Please do
one and show what results you get with "LS Dyna". It would not be a
waste of time any more than attending engineering school, but then you
already made clear that the school is wasting your time. (!!!)

By the way, on the net no one can tell whether you are who what you
claim and that you know things others don't. so parading your
association with higher learning doesn't benefit your credibility. In
fact your disdain for it only casts more doubt on what you say.

I assume that you like the others, who appeared here to present the
claims that you do, have not read or even looked into "the Bicycle
Wheel" where these things are thoroughly explained. A Google search
of the archives will readily show some more recent ones that in
retrospect are comically entertaining to most readers.

Don't go away, and by the way, who are you?

Jobst Brandt

On Sat, 05 Mar 2005 00:13:49 -0600, Werehatrack
wrote:

And why on earth are you resurrecting a thread that's been dead for
three years?

Dear Werehatrack,

He probably just began browsing old threads and had a
perfectly normal flat-earth reaction to Jobst's round-earth
theory.

It really is hard for most of us to remember how many eyes
bulged out in anger and disbelief when we first read Jobst's
explanation of how a pre-tensioned wheel works--

Stands on the lower spokes? Fer chrissakes, cut a lower
spoke on a bare wheel and it falls out!

--because unlike Jobst, most of us haven't really thought
about it and need to hear "pre-tensioned" about a hundred
times before we stop boggling at the notion that a wheel
could effectively stand on its lower spokes with no
significant increase in the upper spokes, even if they were
all made of kevlar string--

Stand on a string? What have you been smoking?

--with enough pre-tension.

If anything, I'm pleased to see such a post because it
reminds me of how I felt when I first looked at "The Bicycle
Wheel" and wasn't bright enough to follow his first few
pages.

Carl Fogel

On Sat, 05 Mar 2005 00:13:49 -0600, Werehatrack
wrote:

And why on earth are you resurrecting a thread that's been dead for
three years?

Dear Werehatrack,

He probably just began browsing old threads and had a
perfectly normal flat-earth reaction to Jobst's round-earth
theory.

It really is hard for most of us to remember how many eyes
bulged out in anger and disbelief when we first read Jobst's
explanation of how a pre-tensioned wheel works--

Stands on the lower spokes? Fer chrissakes, cut a lower
spoke on a bare wheel and it falls out!

--because unlike Jobst, most of us haven't really thought
about it and need to hear "pre-tensioned" about a hundred
times before we stop boggling at the notion that a wheel
could effectively stand on its lower spokes with no
significant increase in the upper spokes, even if they were
all made of kevlar string--

Stand on a string? What have you been smoking?

--with enough pre-tension.

If anything, I'm pleased to see such a post because it
reminds me of how I felt when I first looked at "The Bicycle
Wheel" and wasn't bright enough to follow his first few
pages.

Carl Fogel

wrote in part in message
ups.com...
There is NO WAY that a mechanical
engineer would use spokes as compression members.
Sorry, not going to buy it!!!


I would guess that tensioned wheels evolved, likely from compression wheels,
rather than springing forth fully developed.

On Sat, 05 Mar 2005 00:25:05 -0700, may have
said:

On Sat, 05 Mar 2005 00:13:49 -0600, Werehatrack
wrote:

And why on earth are you resurrecting a thread that's been dead for
three years?

Dear Werehatrack,

He probably just began browsing old threads and had a
perfectly normal flat-earth reaction to Jobst's round-earth
theory.

It might have been a good idea for him to have read enough of it to
get a little more of a clue about the subjects before presenting
himself as a target for a game of whack-a-mole though.

(I will note that Jobst did not disappoint me with *his* response,
though I was a bit surprised that like me, he didn't check the
reference line in the headers and backtrack to discover the staleness
of the thread before posting the initial reply. Beyond that, however,
he was in fine form.)

If anything, I'm pleased to see such a post because it
reminds me of how I felt when I first looked at "The Bicycle
Wheel" and wasn't bright enough to follow his first few
pages.

As long as we don't end up with Yet Another Endless Rantfest about a
subject whose corpse was cremated and ashes scattered long ago, yes,
it's instructive to have such things brought up now and then...and for
those of us who are not presented with the opportunity to shred a
target often enough, it can provide some vicarious gratification to
see a master at work at that task.

(I will relate in passing that a different person with superficially
similar predilections was briefly the topic of conversation over
dinner recently, and it was posted that the term which most succintly
describes Harlan Ellison in social situations is "egoterrorist".
Jobst, however, has more reason for his responses, so I do not believe
the term is applicable in his case.)




--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

HE the SF author? Will you explain, by e-mail if you wish?


"Werehatrack" wrote in message
...
On Sat, 05 Mar 2005 00:25:05 -0700, may have
said:

On Sat, 05 Mar 2005 00:13:49 -0600, Werehatrack
wrote:

And why on earth are you resurrecting a thread that's been dead for
three years?

Dear Werehatrack,

He probably just began browsing old threads and had a
perfectly normal flat-earth reaction to Jobst's round-earth
theory.

It might have been a good idea for him to have read enough of it to
get a little more of a clue about the subjects before presenting
himself as a target for a game of whack-a-mole though.

(I will note that Jobst did not disappoint me with *his* response,
though I was a bit surprised that like me, he didn't check the
reference line in the headers and backtrack to discover the staleness
of the thread before posting the initial reply. Beyond that, however,
he was in fine form.)

If anything, I'm pleased to see such a post because it
reminds me of how I felt when I first looked at "The Bicycle
Wheel" and wasn't bright enough to follow his first few
pages.

As long as we don't end up with Yet Another Endless Rantfest about a
subject whose corpse was cremated and ashes scattered long ago, yes,
it's instructive to have such things brought up now and then...and for
those of us who are not presented with the opportunity to shred a
target often enough, it can provide some vicarious gratification to
see a master at work at that task.

(I will relate in passing that a different person with superficially
similar predilections was briefly the topic of conversation over
dinner recently, and it was posted that the term which most succintly
describes Harlan Ellison in social situations is "egoterrorist".
Jobst, however, has more reason for his responses, so I do not believe
the term is applicable in his case.)




--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

On Sat, 5 Mar 2005 11:39:32 -0500, "Doug Huffman"
may have said:

"Werehatrack" wrote in message
.. .

(I will relate in passing that a different person with superficially
similar predilections was briefly the topic of conversation over
dinner recently, and it was posited that the term which most succintly
describes Harlan Ellison in social situations is "egoterrorist".
Jobst, however, has more reason for his responses, so I do not believe
the term is applicable in his case.)

HE the SF author? Will you explain, by e-mail if you wish?

Harlan Ellison, if you've never met him, is not one to mince words or
to let the opportunity to aggrandize himself of belittle others pass
unused. It has been said, by those who have had to spend more time
than they would like in his presence, that it is a miracle that he has
survived this long...or perhaps it's proof of the perversity of the
universe.

Jobst Brandt, for all that he can be insulting, does not do it without
reason, however tenuous the rationale might be. Ellison does.




--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.