Optical illusions, continued ...

In article <[email hidden]>,

Sandy said:

Dans le message de news:[email hidden],
Mark Hickey <[email hidden]> a réfléchi, et puis a déclaré :

Quoted message said:

"Sandy" <[email hidden]> wrote:

A lot of words.

Sandy, I don't know if you just enjoy being obtuse, or reply just to
hear your keyboard click... but the subject at hand is very simple,
and not the psychodrama you're making it out to be.

The question is: "has someone finally found a way to flex a solid
tetrahedron on the back of a bicycle several mm's?".

Let's start with that, for a dumb, non-math, non-engineer.
I look at your words, and I look at the actual bicycle, and I don't see a
tetrahedron.
Tetra - four
Hedron - sides
I am not sure either of them actually pertain.
/Four/ - first, look at the attachment point to the main triangle. It's
distant from the point where the seatstays or the chainstays converge. So,
not being contrarian, but just an observer, I don't see a simple FOUR.
/Side/ - if you mean a regular plane, again, I don't see that except by
connecting the dots of the most outlying points. The surfaces described by
the curved chainstays and seatstays don't develop a "hedron". So, unless
the math actually covers the folds and waves of the projectible surfaces
(yes, of course, there are numerous potential results, unless you can
describe all the dimensions of all the edge components), you don't have the
second element.

You claim to be ignorant about these matters, then prove
it. What is the opposite of irony?

[...]

--
Michael Press

In article <[email hidden]>,

Sandy said:

I was not trying to squirm into a regular tetrahedron or other carbon forms.
You may want corrective lenses at your age. Or admit to being an
impressionist (not cubist) engineer. The only common straight line in this
assembly, lately, seems to be the wheel axle. For us engineering-impaired,
I offer :

"Triangle is a convex polygon with three segments joining three
non-collinear points. Each of the three segments is called a side, and each
of the three non-collinear points is called a vertex"

and, so you don't wonder if French triangles are different :

"En géométrie, un triangle se définit rigoureusement sur une surface comme
une figure fermée à trois côtés, ces trois côtés étant des arcs de
géodésiques de cette surface. "

Since you want to learn about this, try this exercise.
While visualizing an ideal tetrahedron, stare at the seat
stays, chain stays, seat tube, and rear axle of your
bicycle. There is geometry and there is engineering. Note
the points of similarity. Note the points of difference.
Do the points of difference make a real difference? Why or
why not?

--
Michael Press

Dans le message de
news:[email hidden],
Michael Press <[email hidden]> a réfléchi, et puis a déclaré :

Quoted message said:

In article <[email hidden]>,

Sandy said:

Dans le message de news:[email hidden],
Mark Hickey <[email hidden]> a réfléchi, et puis a déclaré :

Quoted message said:

"Sandy" <[email hidden]> wrote:

A lot of words.

Sandy, I don't know if you just enjoy being obtuse, or reply just to
hear your keyboard click... but the subject at hand is very simple,
and not the psychodrama you're making it out to be.

The question is: "has someone finally found a way to flex a solid
tetrahedron on the back of a bicycle several mm's?".

Let's start with that, for a dumb, non-math, non-engineer.
I look at your words, and I look at the actual bicycle, and I don't
see a tetrahedron.
Tetra - four
Hedron - sides
I am not sure either of them actually pertain.
/Four/ - first, look at the attachment point to the main triangle.
It's distant from the point where the seatstays or the chainstays
converge. So, not being contrarian, but just an observer, I don't
see a simple FOUR. /Side/ - if you mean a regular plane, again, I
don't see that except by connecting the dots of the most outlying
points. The surfaces described by the curved chainstays and
seatstays don't develop a "hedron". So, unless the math actually
covers the folds and waves of the projectible surfaces (yes, of
course, there are numerous potential results, unless you can
describe all the dimensions of all the edge components), you don't
have the second element.

You claim to be ignorant about these matters, then prove
it. What is the opposite of irony?

Well, Mr Press, if what I wrote doesn't demonstrate a limited understanding,
then you must be telling me I got it right. I would be doubly surprised.

right? the manufacture hires a PR man to advertize
he looks out at the multitudes waving green $100 bills
and asks
what do we write to steal this $$$ and buy an estate in southern
france?
or less likely make an honest living.
or communicate!!!! here read, we gotta product, buy it!
so you see, like i (who know not about bicycles) probabbbly lie in the
top 95% in bicycle knowledge amung all bike riders
so dig it - what's the ad man gonna say??
here if youn eat shgit you can hit 5 zillion home runs!
so you think - hey this is a good idea!! I'll lay out $5 for the shgit
and ....

Quoted message said:

right? the manufacture hires a PR man to advertize
he looks out at the multitudes waving green $100 bills
and asks
what do we write to steal this $$$ and buy an estate in southern
france?
or less likely make an honest living.
or communicate!!!! here read, we gotta product, buy it!
so you see, like i (who know not about bicycles) probabbbly lie in the
top 95% in bicycle knowledge amung all bike riders
so dig it - what's the ad man gonna say??
here if youn eat shgit you can hit 5 zillion home runs!
so you think - hey this is a good idea!! I'll lay out $5 for the shgit
and ....

I'd say that probably sums it up nicely.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

In article <[email hidden]>,

Sandy said:

Dans le message de
news:[email hidden],
Michael Press <[email hidden]> a réfléchi, et puis a déclaré :

Quoted message said:

In article <[email hidden]>,

Sandy said:

Dans le message de news:[email hidden],
Mark Hickey <[email hidden]> a réfléchi, et puis a déclaré :
> "Sandy" <[email hidden]> wrote:
>
> A lot of words.
>
> Sandy, I don't know if you just enjoy being obtuse, or reply just to
> hear your keyboard click... but the subject at hand is very simple,
> and not the psychodrama you're making it out to be.
>
> The question is: "has someone finally found a way to flex a solid
> tetrahedron on the back of a bicycle several mm's?".

Let's start with that, for a dumb, non-math, non-engineer.
I look at your words, and I look at the actual bicycle, and I don't
see a tetrahedron.
Tetra - four
Hedron - sides
I am not sure either of them actually pertain.
/Four/ - first, look at the attachment point to the main triangle.
It's distant from the point where the seatstays or the chainstays
converge. So, not being contrarian, but just an observer, I don't
see a simple FOUR. /Side/ - if you mean a regular plane, again, I
don't see that except by connecting the dots of the most outlying
points. The surfaces described by the curved chainstays and
seatstays don't develop a "hedron". So, unless the math actually
covers the folds and waves of the projectible surfaces (yes, of
course, there are numerous potential results, unless you can
describe all the dimensions of all the edge components), you don't
have the second element.

You claim to be ignorant about these matters, then prove
it. What is the opposite of irony?

Well, Mr Press, if what I wrote doesn't demonstrate a limited understanding,
then you must be telling me I got it right. I would be doubly surprised.

No, I am not. You proved that you are indeed ignorant of
the matters of which you claim to be ignorant. The actual
facts of the matter have been delineated in other articles
in this thread.

--
Michael Press

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

Quoted message said:

In article
<[email hidden]>,

Phil Holman' piholmanc@yourservice said:

They bend because the force on the end of the rod is normal to the
rod.
The seat and chain stays are axially loaded in compression and
tension
only. If they bent any appreciable amount (to allow 3mm of vertical
compliance) the whole rear triangle would fail in buckling. Even
curved
seat stays are a gimmick.
If they were soft enough to allow for that kind of deflection they
would
also deflect laterally and would be
almost unrideable. Look up Johnson and Euler for elastic instability.

Gabby Johnson and who? Leonhard or Houston?

Yes, very funny. How's your slenderness ratio?

Phil H

Sandy said:

You don't have a tetrahedron, so what do you have, and how can it behave
differently, and how can materials contribute to changing the kind of
behavior obtained ?

Whatever you have, any appreciable motion between the rear wheel and
the main frame of the bike would require one or more of the rear frame
members to *buckle*! If the chainstay is compliant enough to allow
vertical motion of the rear wheel, then what must the seatstay do to
allow this motion? Either compress in length (not possible without a
sliding member) or buckle... and if it buckles, then what will keep it
from buckling further... until it breaks? Nothing...

The "correct" way to do this is to design the chainstays with enough
vertical compliance for ~.5 to 1 inch of rear wheel travel (5 to 10
times "a few mm"😉, and put a sliding joint with an elastomer where the
seatstays meet the frame. This has been done with some success for at
least 15 years now. Hincapie rode a Trek with this feature over the
cobbles last year.

Sandy said:

Dans le message de news:[email hidden],
Mark Hickey <[email hidden]> a réfléchi, et puis a déclaré :

Quoted message said:

"Sandy" <[email hidden]> wrote:

A lot of words.

Sandy, I don't know if you just enjoy being obtuse, or reply just to
hear your keyboard click... but the subject at hand is very simple,
and not the psychodrama you're making it out to be.

The question is: "has someone finally found a way to flex a solid
tetrahedron on the back of a bicycle several mm's?".

Let's start with that, for a dumb, non-math, non-engineer.
I look at your words, and I look at the actual bicycle, and I don't see a
tetrahedron.

Sigh. You DO reply just to hear that keyboard click, don't you?

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

Ron Ruff said:

Whatever you have, any appreciable motion between the rear wheel and
the main frame of the bike would require one or more of the rear frame
members to *buckle*! If the chainstay is compliant enough to allow
vertical motion of the rear wheel, then what must the seatstay do to
allow this motion? Either compress in length (not possible without a
sliding member) or buckle... and if it buckles, then what will keep it
from buckling further... until it breaks? Nothing...

Heh-heh. He said sliding member. Heh-heh.

Bill "lightening the moo...aw, screw it" S.

Quoted message said:

Quoted message said:

Quoted message said:

Mike Reed <[email hidden]> wrote:

-snip-

Quoted message said:

Quoted message said:

Quoted message said:

>http://forum.bikemag.com/photopost/data/504/2990Optical_illusion.JPG

Quoted message said:

Quoted message said:

"Luke" <[email hidden]> wrote in message

Quoted message said:

I still don't see the boat.

Quoted message said:

G.T. said:

What boat?

Sorni said:

I'm pretty sure there's a little man in the boat, but it's covered.

Family newsgroup, buddy.

(OK, Addams family newsgroup, maybe)

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

A Muzi said:

Quoted message said:

Quoted message said:

> Mike Reed <[email hidden]> wrote:

-snip-

Quoted message said:

Quoted message said:

>> http://forum.bikemag.com/photopost/data/504/2990Optical_illusion.JPG

Quoted message said:

Quoted message said:

"Luke" <[email hidden]> wrote in message
> I still don't see the boat.

Quoted message said:

G.T. said:

What boat?

Sorni said:

I'm pretty sure there's a little man in the boat, but it's covered.

Family newsgroup, buddy.

Touche' (dern it).

Quoted message said:

(OK, Addams family newsgroup, maybe)

It does kinda /Fester/, doesn't /It/?

Bill "almost /Wednesday/ (oy)" S.

Ron Ruff said:

The "correct" way to do this is to design the chainstays with enough
vertical compliance for ~.5 to 1 inch of rear wheel travel (5 to 10
times "a few mm"😉, and put a sliding joint with an elastomer where the
seatstays meet the frame. This has been done with some success for at
least 15 years now. Hincapie rode a Trek with this feature over the
cobbles last year.

What happens 10 years from now when you need a new elastomer?

Sandy said:

I'm stuck with simple concepts and words. Not meaning to inject the subject
of shock-absorption, but as I understand cars, the shock absorber enters the
suspension to moderate the oscillations of springs. Perhaps there are less
complex systems to do that. I recall my Mini, with rubber springs and
lever-arm shock absorbers, was a different approach that may or may not have
been a good one. So, the bicycle system has multiple parts that attenuate
shock, and perhaps it is only in combination that specifically desired
effects can be achieved. Admittedly, there may not be great degrees of
difference, and you can't avoid real shock with big bumps.

The simple concept/words of "shock absorber" are a mismatch. A shock
absorber doesn't absorb shocks, at least not in the way most people
would interpret it.

A spring is a spring. The various compliances between the road & your
seat are like a series of springs. What happens when you stack a hard
spring (frame) on a softer one (tire)? Pretty much nothing.

Peter Cole said:

Ron Ruff said:

The "correct" way to do this is to design the chainstays with enough
vertical compliance for ~.5 to 1 inch of rear wheel travel (5 to 10
times "a few mm"😉, and put a sliding joint with an elastomer where the
seatstays meet the frame. This has been done with some success for at
least 15 years now. Hincapie rode a Trek with this feature over the
cobbles last year.

What happens 10 years from now when you need a new elastomer?

Are you familiar with the term "SOL"?

Peter Cole said:

Sandy said:

I'm stuck with simple concepts and words. Not meaning to inject the subject
of shock-absorption, but as I understand cars, the shock absorber enters the
suspension to moderate the oscillations of springs. Perhaps there are less
complex systems to do that. I recall my Mini, with rubber springs and
lever-arm shock absorbers, was a different approach that may or may not have
been a good one. So, the bicycle system has multiple parts that attenuate
shock, and perhaps it is only in combination that specifically desired
effects can be achieved. Admittedly, there may not be great degrees of
difference, and you can't avoid real shock with big bumps.

The simple concept/words of "shock absorber" are a mismatch. A shock
absorber doesn't absorb shocks, at least not in the way most people
would interpret it.

In the UK, what we call shock absorbers are called dampers. That's a
much better description, but less commercially "interesting".

Quoted message said:

A spring is a spring. The various compliances between the road & your
seat are like a series of springs. What happens when you stack a hard
spring (frame) on a softer one (tire)? Pretty much nothing.

On Wed, 15 Mar 2006 06:36:41 GMT, "Sorni" <[email hidden]>

Quoted message said:

A Muzi said:

Quoted message said:

>> Mike Reed <[email hidden]> wrote:

-snip-

Quoted message said:

>>> http://forum.bikemag.com/photopost/data/504/2990Optical_illusion.JPG

Quoted message said:

> "Luke" <[email hidden]> wrote in message
>> I still don't see the boat.

Quoted message said:

G.T. wrote:
> What boat?

Sorni said:

I'm pretty sure there's a little man in the boat, but it's covered.

Family newsgroup, buddy.

Touche' (dern it).

Bill, that's French, and you're not my type!

Quoted message said:

Quoted message said:

(OK, Addams family newsgroup, maybe)

It does kinda /Fester/, doesn't /It/?

Bill "almost /Wednesday/ (oy)" S.

Not Wednesday enough for me, that's for sure.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Quoted message said:

Ron Ruff said:

The "correct" way to do this is to design the chainstays with enough
vertical compliance for ~.5 to 1 inch of rear wheel travel (5 to 10
times "a few mm"😉, and put a sliding joint with an elastomer where the
seatstays meet the frame. This has been done with some success for at
least 15 years now. Hincapie rode a Trek with this feature over the
cobbles last year.

Peter Cole said:

What happens 10 years from now when you need a new elastomer?

Hang out in a biks shop a while. Every rider with a ten year
old frame will explain to you that he 'wore it out'; that
his frame is now 'noodly' and 'all over the place'.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Quoted message said:

For us engineering-impaired,
I offer :
"Triangle is a convex polygon with three segments joining three
non-collinear points. Each of the three segments is called a side, and each
of the three non-collinear points is called a vertex"

For a physical structure, if the "segment" can transmit force from one
vertex to the other without deforming, then that is as good as a
straight line, from a performance point of view. Wouldn't you agree?
So you could form a functional tetrahedron from straight tubing or bent
ones as long as the physical capacity of the tubes is not exceeded. It
might not be what Euclid had in mind but he'd probably appreciate the
application.

Dans le message de
news:[email hidden],
[email hidden] <[email hidden]> a réfléchi, et puis a déclaré :

Quoted message said:

Quoted message said:

For us engineering-impaired,
I offer :
"Triangle is a convex polygon with three segments joining three
non-collinear points. Each of the three segments is called a side,
and each of the three non-collinear points is called a vertex"

For a physical structure, if the "segment" can transmit force from one
vertex to the other without deforming, then that is as good as a
straight line, from a performance point of view. Wouldn't you agree?

You can win any circular argument, of course you're right. I suspect,
though, that the issue is right there - is there deformation or not. From
the absolute of no deformation to the cooked spaghetti version, it seems
that some manufacturers claim that they construct some sort of controlled
deformation in their frames. After all, there is clear flex in a lateral
plane. The comment has been repeated, often, that a seatstay that
vertically flexes won't do it very long before failure. Yet at the same
attachment point, it is know to flex laterally. I don't know, but I can
recognize a logical gap, even without a micrometer.

Quoted message said:

So you could form a functional tetrahedron from straight tubing or
bent ones as long as the physical capacity of the tubes is not
exceeded. It might not be what Euclid had in mind but he'd probably
appreciate the application.

No argument on this model - to posit it doesn't flex and take that to mean
that you just proved it doesn't flex doesn't move this idea anywhere,
really.
--
Sandy
--
Ce message, issu de l'agriculture biologique, a été rédigé avec des
électrons recyclés. En conséquence, il est possible que des fautes
d'orthographes s'y soient malencontreusement glissées.