jim beam said:Quoted message said:jim beam said:[email hidden] wrote:
Quoted message 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!
Quoted message said:jim beam's behavior is increasingly bizarre!
Quoted message said: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.
Massive, massive weight penalty! In the case of disk caliper mounts,
the front mounted ones might have to be nearly 15 grams heavier than
the rear mount ones. Massive!
Quoted message said:Quoted message said:2) I never claimed handlebars are cast.
yes you did.
Quoted message said:Here's the relevant quote:
Quoted message said:j.b. "handlebars are extruded."
Quoted message said: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...."
Try reading slowly. The word "cast" modifies "aluminum cantilver
brake arms." It does _not_ modify handlebars. As I said, almost all
handlebars are extruded.
Quoted message said:first, there's no "almost" about handlebars. /all/ aluminum bars are
extruded. end of story.
The reason for my "almost" is that there are carbon bars out there,
jim, including some with very complicated shapes. Those are not
extruded.
Quoted message said: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.
I did assert that hubs are sometimes cast. And I provided at least
one link that said that, indeed, they are.
The quote, once again: "These casting techniques are the way many
crank arms, pedal bodies, hub shells, seatpost head pieces, stems, and
some headset parts are commercially made in volume." From http://
www.bikepro.com/products/metals/alum.html
Quoted message said: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.
That's not what I claimed you said. What you _did_ say is this:
"cranks are forged."
When I responded "Some are, some aren't," you said:
"most are forged. only mega-cheap garbage is not. of the forgings,
cold
are best but hot is much more common. "
However, Andrew Muzi let you know 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'.
"
IOW, die cast. But _not_ forged. Campagnolo Centaur. Not mega-cheap
garbage.
Furthermore, he said "Cold forged parts were made in the same
facilities but at a minuscule fraction of the volume of pressure-
molded parts. "
Quoted message said: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.
Right! Which means, apparently, you now agree that tremendous numbers
of bike parts that fight tensile fatigue are not forged! Hallelujia,
we are making progress!
Let's see if we can take another little step:
Now that you understand that there are many castings on bikes that
fight tensile fatigue, do you understand that it is, after all,
possible to successfully design a disk caliper mounting lug on the
front of a fork? IOW, that tensile fatigue can be controlled?
- Frank Krygowski
