Disk brakes?

Gary Young said:

frkrygow said:

The process Andrew described sounds exactly like classic die casting.
That's exactly how it's done - although for most common commercial
products, the flouroscope inspection would be skipped. The essence is
that the molds (or dies) are expensive, complex, precise tool steel
devices, liquid cooled for quick freezing of parts. They are held
closed by large hydraulic forces, and the molten metal is injected
very rapidly and under high pressure, not gravity poured. The result
is strong, accurate parts with excellent surface finishes, with
tolerances generally held to a few thousandths of an inch. And to
increase production, all but the largest die-cast parts are made on a
"tree" with several parts produced in one shot.

"Die casting" sounds like what I've always pictured "hot forging" to be.
Is "hot forging" a misnomer or is that an entirely different process?

Hot forging is an entirely different processes.

Hot forging consists of taking a solid piece of metal and shaping it
by pounding it (or sometimes by squeezing it more slowly).

To visualize a common forging process, think of the pounding that a
blacksmith does. Of course, that's artisan work. The shape of the
part is determined mostly by the skill of the operator; that is, it's
not controlled by any sophisticated shape of the tooling.

This "open die" forging is done on very low production parts, but some
of those parts are huge. I've seen shafts over 30 feet long and over
3 feet in diameter being forged this way. In that case, it was slowly
squeezed by a huge hydraulic press, instead of being pounded.

Forged parts that need precise, repeatable shapes (as in mass
production) are done "closed die" - that is, pounded using dies that
have cavities hollowed out to produce the required shape. It's
usually a multi-step process, where a series of cavities gradually
produce the shape as the part is transferred from cavity to cavity.

Steel is (almost?) always hot forged - done at a high temperature to
make the metal much easier to move around. Forged aluminum bike parts
are cold forged. I don't know the exact temperatures involved - it
could be anywhere from room temperature to, oh, maybe 300 degrees
Fahrenheit, yet still be considered metallurgically "cold".

With aluminum, cold forging doesn't require nearly the amount of force
that would be required for steel, and it can enhance the part's
strength.

- Frank Krygowski

Quoted message said:

A Muzi said:

Quoted message said:

> On Fri, 02 Feb 2007 08:56:46 -0800, jim beam lied:
> krygowski's blanket assertion that all cranks, brakes, etc
> are cast is pure ignorance.

-snip much-
I have not followed this thread closely but I can tell you, having spent
a lot of time with SR-Sakae on the Prizm precision cast lug frame
system, and having visited Shimano's Shin-Osaka plant, that the bulk of
bike parts are 'melt-formed'.

In that process, (think Campagnolo Centaur arms for example), parts are
pressure-molded from molten aluminum in a 'tree'. They come out joined
like model car parts from a tree with quick-change heated molds. The
material flows in heated tubes under pressure to the tree. Pressures are
well below cold forging values as the material is already flowing from
the heat. The tooling crew can make a tree with three right cranks,
five stem blanks, six left cranks and two pedal bodies, then change the
molds easily to balance against orders.

After being popped out of the mold, parts go through a heat treatment
[also called 'rapid aging' for aluminum]. Before finish work [at
SR-Sakae - didn't see one at Shimano -?] 100% were inspected for voids
in a fluoroscope with a very small reject rate. The operators watched a
screen outside the room with the belt-driven fluoroscope, positions on
the belt were numbered.

Cold forged parts were made in the same facilities but at a minuscule
fraction of the volume of pressure-molded parts.

So, when we speak of "cast", please don't picture some 60 year old
French abortion of a sand-casting waiting to crack. The industry is way
beyond that - and my report is from the middle eighties. I'm sure, from
looking at things like Frank's brake arms, the process has advanced even
further, blurring the line between 'forged' and 'cast'. Most stuff we
ride is neither, in the classic sense.

What Andrew describes sounds absolutely accurate. But to expand on
the final paragraph, in case anyone is confused by it:

The word "cast" does not imply molten metal poured by hand into a sand
mold. All that it implies is that liquid metal flows into a mold
where it freezes solid. There are many, many types of casting
processes, and many are advanced and highly automated. At one
extreme, sand casting is generally most economical for low production
parts that are not needed to be as precise or as strong. At the other
extreme, die casting (with its high initial cost) is best for high
production parts that need more precision and strength. Like bike
parts.

The process Andrew described sounds exactly like classic die casting.
That's exactly how it's done - although for most common commercial
products, the flouroscope inspection would be skipped. The essence is
that the molds (or dies) are expensive, complex, precise tool steel
devices, liquid cooled for quick freezing of parts. They are held
closed by large hydraulic forces, and the molten metal is injected
very rapidly and under high pressure, not gravity poured. The result
is strong, accurate parts with excellent surface finishes, with
tolerances generally held to a few thousandths of an inch. And to
increase production, all but the largest die-cast parts are made on a
"tree" with several parts produced in one shot.

jim beam's assertion - "it's not 'casting' in the traditional sense,
it's more
'thixo-forming' "- sounds like another typical beamish evasion, to
avoid admitting to a proven mistake.

First, it's _certainly_ not a forging process - and if you read
upthread, jim beam was claiming that the bike parts that fight tensile
fatigue are forged, _not_ cast. Here's a quote: "cranks are forged.
hubs are forged or machined from bar stock, not cast." So even if it
is thixoforming, he was still off-base.

Secondly, there's nothing in Andrew's description that indicates those
parts were thixoformed. "Pressure-molded from molten aluminum in a
'tree' " is die casting. Had he said "pressure-molded from a slurry
of semi-liquid aluminum" then I would have assumed the parts were
thixoformed.

And anyway, thixoforming is generally considered a variation on die
casting, not an entirely separate process.

Again, it's _certainly_ not considered a forging process!

- Frank Krygowski

translation:
krygowski, having now realized that tensile fatigue stress on true
castings like fork sliders is a bad thing and trying to gloss over the
[censored] of claiming that things like handlebars are cast, is now trying
to claim ownership of thixoforming with some bizarre claim that it's
merely a variant of die casting. all while not understanding the vastly
different metallurgical distinctions!

now the interesting thing will be watching to see if can do sufficient
homework quickly enough on what those distinctions are and whether he'll
try to claim ownership of that too....

jim beam said:

[email hidden] wrote:

[snip]

Quoted message said:

Quoted message said:

Secondly, there's nothing in Andrew's description that indicates those
parts were thixoformed. "Pressure-molded from molten aluminum in a
'tree' " is die casting. Had he said "pressure-molded from a slurry
of semi-liquid aluminum" then I would have assumed the parts were
thixoformed.

And anyway, thixoforming is generally considered a variation on die
casting, not an entirely separate process.

[snip]

Quoted message said:

krygowski, having now realized that tensile fatigue stress on true
castings like fork sliders is a bad thing and trying to gloss over the
[censored] of claiming that things like handlebars are cast, is now trying
to claim ownership of thixoforming with some bizarre claim that it's
merely a variant of die casting. all while not understanding the vastly
different metallurgical distinctions!

What is thixoforming? It seems to be missing from Wikipedia.

A thixotropic material is one that gets less viscous when you stir it
(is paint like that? Custard?). So is the basic idea that if you have an
alloy with this property, you stir it up before squirting it into the
mould which means you don't have to have it as hot?

Ben C said:

jim beam said:

[email hidden] wrote:

[snip]

Quoted message said:

Quoted message said:

Secondly, there's nothing in Andrew's description that indicates those
parts were thixoformed. "Pressure-molded from molten aluminum in a
'tree' " is die casting. Had he said "pressure-molded from a slurry
of semi-liquid aluminum" then I would have assumed the parts were
thixoformed.

And anyway, thixoforming is generally considered a variation on die
casting, not an entirely separate process.

[snip]

Quoted message said:

krygowski, having now realized that tensile fatigue stress on true
castings like fork sliders is a bad thing and trying to gloss over the
[censored] of claiming that things like handlebars are cast, is now trying
to claim ownership of thixoforming with some bizarre claim that it's
merely a variant of die casting. all while not understanding the vastly
different metallurgical distinctions!

What is thixoforming? It seems to be missing from Wikipedia.

A thixotropic material is one that gets less viscous when you stir it
(is paint like that? Custard?).

basically, it's like a slurpee - lots of small solid particles with
liquid between them, which left still will coalesce, but agitated, keep
fluid. there's different degrees of this depending on temperature and
composition.

Quoted message said:

So is the basic idea that if you have an
alloy with this property, you stir it up before squirting it into the
mould which means you don't have to have it as hot?

that's part of it but the main thing is the resulting microstructure vs.
economics. in a single shot, you get something well formed, often with
only minimal subsequent re-machining required, and with much improved
microstructure compared to a traditional casting. with a fully liquid
casting, solidification starts at the shell and crystals grow inwards.
this leads to undesirable crystallization forms for this application,
and often, internal voids. with thixoforming, since it's already
substantially solid on forming, voids are minimal if at all, and the
grain structure is much more even throughout.

jim beam said:

Quoted message said:

First, it's _certainly_ not a forging process - and if you read
upthread, jim beam was claiming that the bike parts that fight tensile
fatigue are forged, _not_ cast. Here's a quote: "cranks are forged.
hubs are forged or machined from bar stock, not cast." So even if it
is thixoforming, he was still off-base.

Quoted message said:

Secondly, there's nothing in Andrew's description that indicates those
parts were thixoformed. "Pressure-molded from molten aluminum in a
'tree' " is die casting. Had he said "pressure-molded from a slurry
of semi-liquid aluminum" then I would have assumed the parts were
thixoformed.

Quoted message said:

And anyway, thixoforming is generally considered a variation on die
casting, not an entirely separate process.

Quoted message said:

Again, it's _certainly_ not considered a forging process!

translation:
krygowski, having now realized that tensile fatigue stress on true
castings like fork sliders is a bad thing and trying to gloss over the
[censored] of claiming that things like handlebars are cast, is now trying
to claim ownership of thixoforming with some bizarre claim that it's
merely a variant of die casting. all while not understanding the vastly
different metallurgical distinctions!

jim beam's behavior is increasingly bizarre!

1) Again, tensile fatigue stress on true castings can easily be
handled by any competent design engineer. It's done every day. Many
examples have been given.

2) I never claimed handlebars are cast. Here's the relevant quote:

j.b. "handlebars are extruded."

F.K. "Yes, almost all are. That's almost always the best way to make
aluminum shapes of constant cross section."

3) There are certainly metallurgical differences between thixoforming
and ordinary die casting, and I never claimed there were not.
Similarly, there are metallurgical differences between hot forging and
cold forging. But nonetheless, cold forging is still considered a
variant of hot forging, and thixoforming is usually considered a
variant of die casting. See http://www.pcc-aft.com/thixo.htm for an
example.

4) While jim beam seems to accept Andrew's evidence that high quality
cranks are produced by _some_ metal injection process (whether die
casting or thixoforming), he is certainly glossing over the fact that
neither is considered a forging process! That fact was emphasized
when Andrew said, "Cold forged parts were made in the same facilities
but at a minuscule fraction of the volume of pressure-molded parts."

Obviously, properly designed cast parts can stand up to tensile
fatigue stresses. It can obviously be done with disk brake mounting
lugs, contrary to jb's assertions.

And again, it's bizarre to attribute fabricated statements to me,
especially when the thread shows I said the opposite! I can only
wonder at the tortured state of mind that would produce that behavior.

- Frank Krygowski

Quoted message said:

On 3 Feb 2007 11:01:01 -0800, "[email hidden]"

Quoted message said:

On Jan 31, 4:20 am, dabac <dabac.2l9...@no-

mx.forums.cyclingforums.com said:

Michael Press Wrote:

Quoted message said:

Quoted message said:

> ...The manufacturers have their
> reasons not to acknowledge that the current
> configuration exerts a force in the axle ejection
> direction.

Quoted message said:

Quoted message said:

Are they saying:
A)There is *no* force acting in the ejection direction present?

Quoted message said:

Quoted message said:

or are they saying:
B)There is *no significant * force acting in the ejection direction
present?

Quoted message said:

Quoted message said:

The existence or not of a force acting in the ejection direction should
be easy to determine. If it IS there then moving to a front caliper
configuration would cancel this cause for concern completely.

Quoted message said:

Quoted message said:

But I have the feeling that by now the trenches are so deeply dug that
the manufacturers would be very unwilling to consider such a change
even if it there was sound reason for it.

Quoted message said:

Quoted message said:

--
dabac

Quoted message said:

The only thing I have to say on this subject is that I want my bike to
look and work like a bike, not a motorcycle. Disk brakes are the only
instance I can think of where the bicycle industry has been influenced
from the automotive/motorcycle industry. Strange, most of the time
it's the other way around. On a philosophical level it seems a step
backward, no longer influancing but rather following along. However if
you like to carry too much gear, ride in the mud, need to get the heat
off the rim, and or drop off cliffs, then you need to ride a bike that
works more like a motorcycle.

Dear Othy,

Rumor has it that modern bicycle suspension developed from modern
motorcycle suspension.

Cheers,

Carl Fogel

Dear Mr. Fogel, I'm going to just quote Mr. Archibald Sharp. From his
book Bicycles&Tricycles (originally printed by Longmans, Green & Co.
London and New York, 1896), Chapter XXII, section 224 titled Spring-
frames. "In the days of solid tyres (sic) many attempts were made to
support the frame of a bicycle or tricycle on springs, so that the
joltings (sic) due to the inequalities of the road might not be
transmitted to the frame. The universal adoption of pneumatic tyres
(sic) has led to the almost total abandonment of spring-frames." I
believe that motorcycles didn't have shocks until much latter.

email hidden said:

Quoted message said:

On 3 Feb 2007 11:01:01 -0800, "[email hidden]"

Quoted message said:

On Jan 31, 4:20 am, dabac <dabac.2l9...@no-
mx.forums.cyclingforums.com> wrote:
> Michael Press Wrote:

Quoted message said:

> > ...The manufacturers have their
> > reasons not to acknowledge that the current
> > configuration exerts a force in the axle ejection
> > direction.

Quoted message said:

> Are they saying:
> A)There is *no* force acting in the ejection direction present?

Quoted message said:

> or are they saying:
> B)There is *no significant * force acting in the ejection direction
> present?

Quoted message said:

> The existence or not of a force acting in the ejection direction should
> be easy to determine. If it IS there then moving to a front caliper
> configuration would cancel this cause for concern completely.

Quoted message said:

> But I have the feeling that by now the trenches are so deeply dug that
> the manufacturers would be very unwilling to consider such a change
> even if it there was sound reason for it.

Quoted message said:

> --
> dabac

Quoted message said:

The only thing I have to say on this subject is that I want my bike to
look and work like a bike, not a motorcycle. Disk brakes are the only
instance I can think of where the bicycle industry has been influenced
from the automotive/motorcycle industry. Strange, most of the time
it's the other way around. On a philosophical level it seems a step
backward, no longer influancing but rather following along. However if
you like to carry too much gear, ride in the mud, need to get the heat
off the rim, and or drop off cliffs, then you need to ride a bike that
works more like a motorcycle.

Dear Othy,

Rumor has it that modern bicycle suspension developed from modern
motorcycle suspension.

Cheers,

Carl Fogel

Dear Mr. Fogel, I'm going to just quote Mr. Archibald Sharp. From his
book Bicycles&Tricycles (originally printed by Longmans, Green & Co.
London and New York, 1896), Chapter XXII, section 224 titled Spring-
frames. "In the days of solid tyres (sic) many attempts were made to
support the frame of a bicycle or tricycle on springs, so that the
joltings (sic) due to the inequalities of the road might not be
transmitted to the frame. The universal adoption of pneumatic tyres
(sic) has led to the almost total abandonment of spring-frames." I
believe that motorcycles didn't have shocks until much latter.

Dear Othy,

True.

Figure 275 of my copy of Sharp shows what could arguably be called a
rear monoshock, though it's just a coil spring with no damping.

Figure 276 bears a faint resemblance to a rear twin-shock system, but
uses undamped springs at 90 degrees to modern twin shock motorcycle
systems.

Figures 277 and 278 defy easy description, but involve stretching
springs in the middle of frames.

But none of these odd designs were popular, and none of them used
damping. Bicycles, as Sharp points out, abandoned spring frames.

Arguably the Moulton revived bicycle suspension in 1962 with its
eccentric hydroelastic system, but the Moulton is scarcely a
mainstream bicycle.

Meanwhile, motorcycles steadily developed twin-shock rear suspension
using coil springs and hydraulic damping. I don't know of any bicycles
that used hydraulic damping.

Then in the early 1970's motorcycles began the switch to monoshock
rear suspension without, as far as I know, recourse to Sharp's quaint
illustration of undamped springs. Indeed, the Dover reprint of Sharp's
long out-of-print book wasn't available until 1977

Mountain bikes later adapted the rear monoshock technology, pretty
much copying off-road motorcycle technology.

Apart from complications of the articulation, the chief development of
bicycle monoshock suspension has been automatic lock-out valving to
reduce unwanted movement caused by pedal action:

http://groups.google.com/group/rec.bicycles.tech/msg/f04281837795b2fb

As for hydraulically-damped telescopic front fork suspension, the
history is much simpler. There are no telescopic forks in Sharp's book
because they were developed for motorcycles and only later adapted to
mountain bikes.

Cheers,

Carl Fogel

True. After the idea was implemented, and abandoned, in bicycles it
was greatly improved upon in motorcycles and later jumped back into
bicycles. But the fact is motorcycles got it from bicycles, the
evolution of modern equipment was not what I was talking about. Disk
brakes came from the automotive/motorcycle industry. No bicycle
influence. That was my origional point. As pointless as it was. I
also like to argue about the history/influences of modern music. I
can never find anyone to argue with about music, maybe music nuts just
aren't as tightly wound as bike nuts.

Quoted message said:

Quoted message said:

jim beam said:

[email hidden] wrote:

[snip]

Quoted message said:

> Secondly, there's nothing in Andrew's description that indicates those
> parts were thixoformed. "Pressure-molded from molten aluminum in a
> 'tree' " is die casting. Had he said "pressure-molded from a slurry
> of semi-liquid aluminum" then I would have assumed the parts were
> thixoformed.
>
> And anyway, thixoforming is generally considered a variation on die
> casting, not an entirely separate process.

[snip]

jim beam said:

Quoted message said:

Quoted message said:

krygowski, having now realized that tensile fatigue stress on true
castings like fork sliders is a bad thing and trying to gloss over
the [censored] of claiming that things like handlebars are cast, is now
trying to claim ownership of thixoforming with some bizarre claim
that it's merely a variant of die casting. all while not
understanding the vastly different metallurgical distinctions!

Quoted message said:

Ben C said:

What is thixoforming? It seems to be missing from Wikipedia.
A thixotropic material is one that gets less viscous when you stir it
(is paint like that? Custard?).

jim beam said:

basically, it's like a slurpee - lots of small solid particles with
liquid between them, which left still will coalesce, but agitated, keep
fluid. there's different degrees of this depending on temperature and
composition.

Quoted message said:

Ben C said:

So is the basic idea that if you have an
alloy with this property, you stir it up before squirting it into the
mould which means you don't have to have it as hot?

jim beam said:

that's part of it but the main thing is the resulting microstructure vs.
economics. in a single shot, you get something well formed, often with
only minimal subsequent re-machining required, and with much improved
microstructure compared to a traditional casting. with a fully liquid
casting, solidification starts at the shell and crystals grow inwards.
this leads to undesirable crystallization forms for this application,
and often, internal voids. with thixoforming, since it's already
substantially solid on forming, voids are minimal if at all, and the
grain structure is much more even throughout.

maybe this from a thixoform house would help:

" ThixoFormingâ„¢ technology continues to grow in popularity as a method
of creating high density, injection molded products that are precisely
formed, exceptionally strong yet lightweight. ThixoFormingâ„¢ combines the
shape making capabilities of plastic injection molding along with
conventional die-casting technology."

http://www.provensystems.com/aft/0408/news.html

i.e., casting, not forging

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

Ed Pirrero said:

On Jan 31, 2:20 am, dabac <dabac.2l9...@no-

mx.forums.cyclingforums.com said:

The existence or not of a force acting in the ejection direction should
be easy to determine.

This has been hashed over repeatedly. DAGS on this subject..

Well, I've read a couple of threads debating the possibility of ejection due to braking or not. Conclusions are far from unanimous, and I have no interest of reviving THAT part of the discussion.

Ed Pirrero said:

On Jan 31, 2:20 am, dabac <dabac.2l9...@no-
mx.forums.cyclingforums.com> wrote:> If it IS there then moving to a front caliper

Quoted message said:

configuration would cancel this cause for concern completely.

Probably. It may raise other concerns, however. This has also been
discussed.

E.P.

I must have missed that part, hence my curiosity.

Quoted message said:

jim beam said:

Quoted message said:

First, it's _certainly_ not a forging process - and if you read
upthread, jim beam was claiming that the bike parts that fight tensile
fatigue are forged, _not_ cast. Here's a quote: "cranks are forged.
hubs are forged or machined from bar stock, not cast." So even if it
is thixoforming, he was still off-base.
Secondly, there's nothing in Andrew's description that indicates those
parts were thixoformed. "Pressure-molded from molten aluminum in a
'tree' " is die casting. Had he said "pressure-molded from a slurry
of semi-liquid aluminum" then I would have assumed the parts were
thixoformed.
And anyway, thixoforming is generally considered a variation on die
casting, not an entirely separate process.
Again, it's _certainly_ not considered a forging process!

translation:
krygowski, having now realized that tensile fatigue stress on true
castings like fork sliders is a bad thing and trying to gloss over the
[censored] of claiming that things like handlebars are cast, is now trying
to claim ownership of thixoforming with some bizarre claim that it's
merely a variant of die casting. all while not understanding the vastly
different metallurgical distinctions!

jim beam's behavior is increasingly bizarre!

1) Again, tensile fatigue stress on true castings can easily be
handled by any competent design engineer. It's done every day. Many
examples have been given.

with a massive weight penalty. we've discussed this before, just in
case you weren't paying attention.

Quoted message said:

2) I never claimed handlebars are cast.

yes you did.

Quoted message said:

Here's the relevant quote:

j.b. "handlebars are extruded."

F.K. "Yes, almost all are. That's almost always the best way to make
aluminum shapes of constant cross section."

funny. yet again, let's return to the original krygowski foot-shooting:

"Neither are cast aluminum cantilever brake arms. Nor their mounts.
Nor crank arms. Nor hub flanges. Nor handlebars. Nor stems...."

first, there's no "almost" about handlebars. /all/ aluminum bars are
extruded. end of story. steel ones are pipe, but that's not casting
either.

in sort, you're changing your story as you go along. you made no
qualifications regarding die casting. you made no qualifications
regarding thixoforming. but you did incorrectly assert that hubs and
handlebars are "cast" - they never are.

Quoted message said:

3) There are certainly metallurgical differences between thixoforming
and ordinary die casting, and I never claimed there were not.

no, you pig-ignorantly misused a blanket term "cast" to describe a
forming process you were merely guessing at.

Quoted message said:

Similarly, there are metallurgical differences between hot forging and
cold forging. But nonetheless, cold forging is still considered a
variant of hot forging,

cold forging is a variant of hot forging??? utter bollocks.

Quoted message said:

and thixoforming is usually considered a
variant of die casting. See http://www.pcc-aft.com/thixo.htm for an
example.

in marketingspeak, that appears unfortunately to be the case. but in
terms of metallurgy and mechanical properties, no freakin' way.

Quoted message said:

4) While jim beam seems to accept Andrew's evidence that high quality
cranks are produced by _some_ metal injection process (whether die
casting or thixoforming), he is certainly glossing over the fact that
neither is considered a forging process!

don't put words in my mouth krygowski. i never even /vaguely/ hinted
that casting, die casting or thixoforming were any form of forging.

Quoted message said:

That fact was emphasized
when Andrew said, "Cold forged parts were made in the same facilities
but at a minuscule fraction of the volume of pressure-molded parts."

which is a weak straw-clutching exercise, even for you. the equipment
for thixoforming and die casting is utterly different to that of
forging. professor.

Quoted message said:

Obviously, properly designed cast parts can stand up to tensile
fatigue stresses. It can obviously be done with disk brake mounting
lugs, contrary to jb's assertions.

don't put words in my mouth, particularly when you evidently can't be
bothered to read what i write. /all/ disk brake mounting tabs are cast
- i pointed that out to you right at the beginning. the point is that
they're rear mounted for a reason - to ensure compressive loading, not
tensile BECAUSE TENSILE CASTINGS DO NOT PERFORM AS WELL IN FATIGUE!!!

Quoted message said:

And again, it's bizarre to attribute fabricated statements to me,
especially when the thread shows I said the opposite! I can only
wonder at the tortured state of mind that would produce that behavior.

read the thread will you? idiot.

Quoted message said:

True. After the idea was implemented, and abandoned, in bicycles it
was greatly improved upon in motorcycles and later jumped back into
bicycles. But the fact is motorcycles got it from bicycles, the
evolution of modern equipment was not what I was talking about. Disk
brakes came from the automotive/motorcycle industry. No bicycle
influence. That was my origional point. As pointless as it was. I
also like to argue about the history/influences of modern music. I
can never find anyone to argue with about music, maybe music nuts just
aren't as tightly wound as bike nuts.

"tightly wound"? wow, that's the most masterful understatement yet this
year! 10 points.

A Muzi said:

Quoted message said:

Quoted message said:

On 2007-02-04, jim beam <[email hidden]> wrote:
> [email hidden] wrote:
[snip]
>> Secondly, there's nothing in Andrew's description that indicates those
>> parts were thixoformed. "Pressure-molded from molten aluminum in a
>> 'tree' " is die casting. Had he said "pressure-molded from a slurry
>> of semi-liquid aluminum" then I would have assumed the parts were
>> thixoformed.
>>
>> And anyway, thixoforming is generally considered a variation on die
>> casting, not an entirely separate process.
[snip]

jim beam said:

Quoted message said:

> krygowski, having now realized that tensile fatigue stress on true
> castings like fork sliders is a bad thing and trying to gloss over
> the [censored] of claiming that things like handlebars are cast, is now
> trying to claim ownership of thixoforming with some bizarre claim
> that it's merely a variant of die casting. all while not
> understanding the vastly different metallurgical distinctions!

Quoted message said:

Ben C said:

What is thixoforming? It seems to be missing from Wikipedia.
A thixotropic material is one that gets less viscous when you stir it
(is paint like that? Custard?).

jim beam said:

basically, it's like a slurpee - lots of small solid particles with
liquid between them, which left still will coalesce, but agitated,
keep fluid. there's different degrees of this depending on
temperature and composition.

Quoted message said:

Ben C said:

So is the basic idea that if you have an
alloy with this property, you stir it up before squirting it into the
mould which means you don't have to have it as hot?

jim beam said:

that's part of it but the main thing is the resulting microstructure
vs. economics. in a single shot, you get something well formed, often
with only minimal subsequent re-machining required, and with much
improved microstructure compared to a traditional casting. with a
fully liquid casting, solidification starts at the shell and crystals
grow inwards. this leads to undesirable crystallization forms for this
application, and often, internal voids. with thixoforming, since it's
already substantially solid on forming, voids are minimal if at all,
and the grain structure is much more even throughout.

maybe this from a thixoform house would help:

" ThixoFormingâ„¢ technology continues to grow in popularity as a method
of creating high density, injection molded products that are precisely
formed, exceptionally strong yet lightweight. ThixoFormingâ„¢ combines the
shape making capabilities of plastic injection molding along with
conventional die-casting technology."

http://www.provensystems.com/aft/0408/news.html

i.e., casting, not forging

it's a big improvement over traditional casting, but it's still not as
good as forging for high strength high fatigue applications,
unfortunately. and it's also unfortunate when the marketing people get
involved since they muddy the water with inadequate terminology -
presumably because "thixoforming" is too much of a mouthful.

email hidden said:

True. After the idea was implemented, and abandoned, in bicycles it
was greatly improved upon in motorcycles and later jumped back into
bicycles. But the fact is motorcycles got it from bicycles, the
evolution of modern equipment was not what I was talking about. Disk
brakes came from the automotive/motorcycle industry. No bicycle
influence. That was my origional point. As pointless as it was. I
also like to argue about the history/influences of modern music. I
can never find anyone to argue with about music, maybe music nuts just
aren't as tightly wound as bike nuts.

Dear Othy,

Where did motorcycles get telescopic hyrdraulically damped front forks
from bicycles?

Cheers,

Carl Fogel

<[email hidden]> a écrit:

[snip]

Quoted message said:

Arguably the Moulton revived bicycle suspension in 1962
with its eccentric hydroelastic system

[snip]

1960s Moultons used simple rubber (rear) and rubber-and-steel (front)
springs.

Hydrolastic (capital H, no e) was a Moulton-designed automotive suspension
system using hydraulically-linked displacers:

http://www.chris-longhurst.com/carbibles/suspension_bible.html

The AM New Series bikes (late 1990s to present), and later AM 18s use a
modified Hydrolastic spring for the rear suspension.

James Thomson

Ed Pirrero said:

On Jan 31, 2:36 am, dabac <dabac.2l9...@no-

mx.forums.cyclingforums.com said:

I can think of several reasons for more UK than US bikes being bought
and then actually getting used on a regular basis.

Oh? Why not list them, then?

#1 Living space

Houses are generally smaller in the UK than in the US. With smaller living quarters follows less storage space. Without an easy anwer to the question "Where shall I keep the bikes between rides" maybe buying a bike requires more dedication, which probably leads to more regular riding.

#2 Transportation

Cars in UK are also generally smaller than in the US, so if you need to go somewhere to ride your bike (particularly DH) it's probably more of a hassle to set that up in the UK than in the US. Yet another reason that might keep the not-so-motivated from buying a bike in the UK.

#3 Rights to land
If you're in the UK and has the storage issue sorted they have this time-honoured rights to passage across privately owned land (public paths and green lanes), so if you're happy with XC you'll probably have riding opportunities available quite nearby. If it's easy to get to a riding spot you might see more riding.

#4 Youth culture
Youth culture in the US seems more divided into groups than in the UK, there's much more talk about someone being a jock, a goth, or whatever. With a higher degree of group identification comes a more pronounced desired to acquire the right attributes. So someone who wants to hang with the sporty, outdoorsy crowd is more likely to get the gear even if it isn't that interesting to him.

It's a theory anyhow, but of course the real anwer might be something else entirely. What about reporting error and and faulty assumptions? It might be hard to be certain about sequence of events after a bad fall, so how rare are wheels coming off in the first place? If there was a low rate of wheels coming unstuck immediately before/during bad falls prior to the introduction of disk brakes then maybe we're only seeing a new explanation to an old phenomenon?

[email hidden said:

"]
...However if you like to carry too much gear, ...

So where to draw the line? Should we all be riding fixies, or are SS OK? Maybe turn them into gravity racers and get rid of chain and crank entirely?
Very few of us actually need to ride our bikes, it's a hobby. And finding a solid argument why one way of doing something that doesn't need to be done is somehow better than another way of doing the same something that doesn't need to be done seems like a challenge indeed.

[email hidden said:

"]
...However if you like to ... ride in the mud, need to get the heat
off the rim...then you need to ride a bike that works more like a motorcycle .

That's been known to happen 🙂

[email hidden said:

"]
...However if you like to ..drop off cliffs, then you need to ride a bike that
works more like a motorcycle.

Not me, but to each his own I guess. Spectacular to watch though.

James Thomson said:

<[email hidden]> a écrit:

[snip]

Quoted message said:

Arguably the Moulton revived bicycle suspension in 1962
with its eccentric hydroelastic system

[snip]

1960s Moultons used simple rubber (rear) and rubber-and-steel (front)
springs.

Hydrolastic (capital H, no e) was a Moulton-designed automotive suspension
system using hydraulically-linked displacers:

http://www.chris-longhurst.com/carbibles/suspension_bible.html

The AM New Series bikes (late 1990s to present), and later AM 18s use a
modified Hydrolastic spring for the rear suspension.

James Thomson

Dear James,

I'll take your word for it.

Some idea of the Moulton mindset can be gleaned by browsing the "AM
Booklet" option here: http://www.alexmoulton.co.uk/index.html

(Heroic self-control prevents the familiar comments.)

***

"My requirement was for the bicycle to have a normal riding position,
and:

--be open for ease of access
--be unisex and of universal adult size
--have proper provision for carrying things"

***

"In contrast to large bicycle wheels, the smaller Moulton wheels are
immensely strong."

***

"Their lower moment of inertia allows faster acceleration and more
responsive steering."

***

"Smaller wheels also reduce the overall length of the bicycle, making
it compact and easier to transport."

***

"Although suspension is spreading to other bicycles, it is often in
the form of 'landing gear' for shock reduction on jumping, as opposed
to the continuous benefit of comfort and road holding of the Moulton."

***

"Carrying bikes on the roof or rear of cars is not only vulnerable and
energy consuming, but potentially dangerous to other road users."

***

"The unisex step-through design also avoids the dangerous top tube of
a diamond frame, which can ensnare the rider in an accident."

***

"The low weight and extreme stiffness of the Moulton frame produces a
ride that is lively and amazingly efficient."

***

"There are five types of Moulton Bicycle in production:"

Double Pylon 20-21 lb (2004)
Single Pylon 21-22 lb (2004)
New Series Moulton 21-22 lb 1998
AM 18 24-25 lb (1982)
Bridgestone Moulton 26 lb (2003)
Pashley Moulton 26-27 lb (1992)

***

Cheers,

Carl Fogel

On 2007-02-06, [email hidden] <[email hidden]> wrote:
[snip]

Quoted message said:

Some idea of the Moulton mindset can be gleaned by browsing the "AM
Booklet" option here: http://www.alexmoulton.co.uk/index.html

On the subject of the Moulton mindset, Moulton's suspension designs in
conjunction with small wheels were an important part of the Mini.

The Mini started off with rubber cone springs similar to those found on
the bikes. Then they used Hydrolastic, then they went back to the cone
springs. Both designs were extremely compact, and together with the
small wheels contributed to the large interior and luggage space of such
a small car.

The small-wheeled bikes look to me like a commitment to the same idea,
which dies hard.

Dr Moulton is still developing the Mini in his spare time (I mean the
real Mini, not that BMW abortion). This is an extraordinary article I
read that I've found on the web:

http://www.telegraph.co.uk/motoring/main.jhtml?xml=/motoring/2005/05/07/mfwhit07.xml

or http://tinyurl.com/2k3c3w

This is the best bit:

Alex chauffeured me at some speed around the local country lanes in
his 1966 Mini Cooper S, which was not as it appeared. It had a
single luxurious passenger seat set spaciously well back from the
driver, but it was the calmness of the ride that blew my mind. When
I closed my eyes, it felt like a big car, with barely any pitching
or road vibration.

Alex said that no single modification had made the difference but
rather a constant evolution of ideas and minor changes carried out
by his small and dedicated team.

[email hidden] wrote:
<snip>

Quoted message said:

"Carrying bikes on the roof or rear of cars is not only vulnerable and
energy consuming, but potentially dangerous to other road users."

to heck with the energy or other users - i don't want the bike mangled!