a new question: Magnesium



B

Brad Behm

Guest
Hello, I posted the question below about my bent frame. Thank you everyone for your excellent
advice. Anyway I found what looks to be a good deal on a magnesium frame. But I know nothing about
magnesium frames. Apparently it's a little like al. right? but lighter?

This is what I found: Merida magnesium 909 road frame with carbon ahead fork for $250

Is this a pretty good deal? pros and cons of magnesium? Your opinions are greatly appreciated.

Thanks again,

Andrew
 
On Sun, 29 Feb 2004 22:02:36 -0800, "Brad Behm"
<[email protected]> may have said:

>Hello, I posted the question below about my bent frame. Thank you everyone for your excellent
>advice. Anyway I found what looks to be a good deal on a magnesium frame. But I know nothing about
>magnesium frames. Apparently it's a little like al. right? but lighter?
>
>This is what I found: Merida magnesium 909 road frame with carbon ahead fork for $250
>
>Is this a pretty good deal? pros and cons of magnesium? Your opinions are greatly appreciated.

Magnesium is generally more brittle than aluminum. Most items advertised as "magnesium" are actually
an Al/Mg alloy; in my experience, the more aluminum in such an alloy, the better.

I do not affirmatively know of any specific drawback in the Merida 909, but the fact that they're
billing it as magnesium would be enough to put me off. That's just a personal opinion based on
experience in the automotive and industrial lift truck fields combined with cynicism about buzzwords
and hype in general.

--
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.
 
Had a Merida Magnesium 907 that broke at the seat tube after about 1,000km. That's OK cause
Merida replaced it with a carbon frame under warranty so all good in the end as the new frame
seems great so far.

For what it's worth it looked like a design problem with the original frame rather than a material
weakness that caused the break. Re-enforcing tube inside the seat tube was too narrow and offered no
extra strength to the seat tube???? How the hell would I know anyway I just ride it :)

Cheers Gary

"Brad Behm" <[email protected]> wrote in message
news:[email protected]...
> Hello, I posted the question below about my bent frame. Thank you everyone for your excellent
> advice. Anyway I found what looks to be a good deal on
a
> magnesium frame. But I know nothing about magnesium frames. Apparently
it's
> a little like al. right? but lighter?
>
> This is what I found: Merida magnesium 909 road frame with carbon ahead fork for $250
>
> Is this a pretty good deal? pros and cons of magnesium? Your opinions are greatly appreciated.
>
> Thanks again,
>
>
> Andrew
 
> Run away!! Run away!! ;-)

hmm.. Why do you say that? Just curious.

Thanks,

Andrew

>
> Just my opinion,
>
> Scott..
 
Brad Behm wrote:
> Hello,

Hello!

> Anyway I found what looks to be a good deal on a magnesium frame. But I know nothing about
> magnesium frames. Apparently it's a little like al. right? but lighter?

Funny - I was very curious about comparison of a marvellous Magnesium metal properties in theory and
in practice and actually I started quite a similar discussion on a Polish bicycle newsgroup
(pl.rec.rowery) just Yesterday - and it goes on;

Merida seems to be the company that started dealing with this metal as a frames' material for a
relatively large scale.

And it seems that being the first is not always easy; a few opinions that have already emerged from
the discussion mentioned are that the frames made in 2003 (MTB ones actually) were braking
"constantly" on the seat tube/top tube welding, and this was due to a not to the bad material
properties, but to the design. According to frame user (who actually broke a few of them in a few
months, and a company (in Poland) replaced them immediately with no complaints (which is
unfortunately not a rule)) the cause appeared to be a plastic "sleeve" put inside the seat tube to
make a smaller-dimension seat post fit.

That "intelligent" solution seemed to concentrate stress and cause a failure quite soon - so
wasn't working with magnesium at all (as might do with Cro-Mo possibly, although being not a good
idea anyway).

When this "sleeve" was finally gotten rid of everything else with a frame is perfect. The warranty
is given (by Merida) for 3 years (as for aluminium frames), in contrary to carbon ones with only 1
year warranty.

A huge advantages are
- weight
- damping properties (in theory 100 times better then with aluminium - and the rider I mentioned
says the difference (compared to the alu) was really noticeable indeed).

A disadvantage is a low corrosion resistance of magnesium in general, so the surface coating must
cover the frame tight, and possible big scratches don't seem be good for the frame.

Courious about Mg made parts' users pionions too!

Greetz

--
TheYvid I seek You at 49894592
 
Werehatrack wrote:
> Magnesium is generally more brittle than aluminum. Most items advertised as "magnesium" are
> actually an Al/Mg alloy;

What do you mean? In this case all aluminium alloy frames should be called magnesium ones since Mg
is one of the major additives of 6000 and 7000 aluminium series.

> in my experience, the more aluminum in such an alloy, the better.

The typical Mg alloys contain up to 10% aluminium and a 6% Al addition combines optimal strength and
ductility. So for some reason "the more aluminium, the better" doesn't seem to make sense.

Regards,

--
TheYvid I seek You at 49894592
 
"Brad Behm" <[email protected]> wrote in message
news:[email protected]...
> hmm.. Why do you say that? Just curious.
>
> Thanks,

Heehee..I'm sort of a retro-grouch, and a bicycle to me is much like a hammer, not a work of art.
I've seen some Mg parts and they usually corrode very quickly and are quite brittle. Not to say you
can't do it. If it's designed properly around the relative strengths and weaknesses of that
material, you should be OK. But I'm not convinced that Merida frames meet that criteria. I have a
similar dislike for composite frames. This comes from several bad experiences with carbon fibre
frames back in the early '90's. Frames with a thousand k's on them and you could pull the drop-outs
out of the forks with your bare hands. I'm sure some of the newer frames, particularly the Trek
OCLV's, are somewhat better, but even they have plenty of failures. Unfortunately I sound like a
crochity old guy when I say this (I'm only 34!!) but steel is real. If you're not doing Alpe d'Huez
with 195 other guys in July on TV, I'm not sure Mg is the path to get where you want to be. OTOH,
$250 for any good frame is pretty fair deal, especially if it fits you perfectly!

Cheers,

Scott..
 
Originally posted by Brad Behm
Hello, I posted the question below about my bent frame. Thank you everyone for your excellent
advice. Anyway I found what looks to be a good deal on a magnesium frame. But I know nothing about
magnesium frames. Apparently it's a little like al. right? but lighter?

This is what I found: Merida magnesium 909 road frame with carbon ahead fork for $250

Is this a pretty good deal? pros and cons of magnesium? Your opinions are greatly appreciated.

Thanks again,

Andrew
Click to expand...

Wow ... where's that ? Anywhere online ??

Would be interested in magnesium. Would be glad if you can post me a link.

Thanks. ;)
 
maxxevv <[email protected]> wrote in message news:<[email protected]>...
> Brad Behm wrote:
> > Hello, I posted the question below about my bent
> > frame. Thank you everyone for your excellent advice.
> > Anyway I found what looks to be a good deal on a
> > magnesium frame. But I know nothing about magnesium
> > frames. Apparently it's a little like al. right? but
> > lighter? This is what I found: Merida magnesium 909
> > road frame with carbon ahead fork for $250 Is this a
> > pretty good deal? pros and cons of magnesium? Your
> > opinions are greatly appreciated. Thanks again, Andrew
>
>
>
> Wow ... where's that ? Anywhere online ??
>
> Would be interested in magnesium. Would be glad if you can
> post me a link.

http://www.chucksbikes.com/
 
maxxevv wrote:
> Brad Behm wrote:
> > Hello, I posted the question below about my bent
> > frame. Thank you everyone for your excellent advice.
> > Anyway I found what looks to
> be a > good deal on a magnesium frame. But I know
> nothing about magnesium > frames. Apparently it's a
> little like al. right? but lighter? > This is what I
> found: Merida magnesium 909 road frame with carbon ahead
> > fork for $250
> > Is this a pretty good deal? pros and cons of
> > magnesium? Your
> opinions > are greatly appreciated.
> > Thanks again, Andrew
>
>
>
> Wow ... where's that ? Anywhere online ??
>
> Would be interested in magnesium. Would be glad if you can
> post me a link.

That would be so cool if it were actually (pure) magnesium.
You could set one portion aflame and it would erupt in a
gigantic fireworks display. You could then say, "I could
have either ridden it or set it on fire... the fire was so
much more fun!"

--
Phil, Squid-in-Training
 
--On Thursday, July 08, 2004 5:51 PM -0400 ZeeExSixAre
<[email protected]> wrote:

> That would be so cool if it were actually (pure)
> magnesium. You could set one portion aflame and it would
> erupt in a gigantic fireworks display. You could then say,
> "I could have either ridden it or set it on fire... the
> fire was so much more fun!"
>
> --
> Phil, Squid-in-Training

Unfortunately for you and the other pyros, this stuff isn't
pure magnesium. I saw some examples of what I assume is
similar stuff at SAE World Congress, and its a
magnesium/aluminum alloy, that has strength properties
similar to magnesium but can be worked and machined like
aluminum. And its
1/3 the weight of aluminum. But, its 3 times the price (per
weight, which isn't how you buy stock). So given those,
the pricing is similar to aluminum as well. Looks like it
might have a future in the automotive industry, so it may
make it into mainstream bikes before too long as well.

Mike Mechanical Engineering 2006, Carnegie Mellon University
Remove nospam to reply.
 
Prometheus wrote:
> --On Thursday, July 08, 2004 5:51 PM -0400 ZeeExSixAre
> <[email protected]> wrote:
>
>> That would be so cool if it were actually (pure)
>> magnesium. You could set one portion aflame and it would
>> erupt in a gigantic fireworks display. You could then
>> say, "I could have either ridden it or set it on fire...
>> the fire was so much more fun!"
>>
>> --
>> Phil, Squid-in-Training
>
> Unfortunately for you and the other pyros, this stuff
> isn't pure magnesium.

Well, of course!

I saw some examples of what I assume is similar stuff at
> SAE World Congress, and its a magnesium/aluminum alloy,
> that has strength properties similar to magnesium but can
> be worked and machined like aluminum. And its 1/3 the
> weight of aluminum. But

Innnnteresting....

> 3 times the price (per weight, which isn't how you buy
> stock). So given those, the pricing is similar to aluminum
> as well. Looks like it might have a future in the
> automotive industry, so it may make it into mainstream
> bikes before too long as well.

But this $240 frame can hardly be the kind of alloy you
speak of. It probably doesn't have anything special in it
other than the regular amount of mag that's alloyed with
aluminum for 6061 and such.

--
Phil, Squid-in-Training
 
"ZeeExSixAre" <[email protected]> wrote:
>
> That would be so cool if it were actually (pure)
> magnesium. You could set one portion aflame and it would
> erupt in a gigantic fireworks display. You could then say,
> "I could have either ridden it or set it on fire... the
> fire was so much more fun!"

Pure magnesium would be useless for a bicycle frame, just
like pure aluminum is useless for that purpose. However,
there are several structural alloys of Mg that have been
used for bike frames in the past, by Kirk Precision and
Litech among others. Merida has been using magnesium alloy
for some time:

http://www.merida.com/s0_global/main_control.php?group0=tec-
h&group1=magnesium&group2=0&

It's only 2/3 as dense as aluminum, and similarly less stiff
and less strong. So most of the benefits, characteristics
and tradeoffs of aluminum frames will also be exhibited in a
magnesium frame.

I am curious as to how well magnesium copes with fatigue.

FWIW, I have machined magnesium structural alloys before,
and their shavings burn similarly to those of pure
magnesium. It would be tough to spot-heat a piece as large
as a bike frame enough to ignite it, without resorting to
something like an oxyacetylene torch, though.

Chalo Colina
 
"Chalo" <[email protected]> wrote in message
news:[email protected]...
> "ZeeExSixAre" <[email protected]>
> wrote:
> >
> > That would be so cool if it were actually (pure)
> > magnesium. You could
set
> > one portion aflame and it would erupt in a gigantic
> > fireworks display.
You
> > could then say, "I could have either ridden it or set it
> > on fire... the
fire
> > was so much more fun!"
>
> Pure magnesium would be useless for a bicycle frame, just
> like pure aluminum is useless for that purpose. However,
> there are several structural alloys of Mg that have been
> used for bike frames in the past, by Kirk Precision and
> Litech among others. Merida has been using magnesium alloy
> for some time:
>
I would recommend staying far away from the Kirk Precision
Mg frames. JUNK! You never ever see one as just about every
single one broke! This may be the last remaining one alive:

http://www.firstflightbikes.com/KirkPrecision.html
 
[email protected] (Chalo) writes:

> FWIW, I have machined magnesium structural alloys before,
> and their shavings burn similarly to those of pure
> magnesium. It would be tough to spot-heat a piece as large
> as a bike frame enough to ignite it, without resorting to
> something like an oxyacetylene torch, though.
>

I know for a fact that a medium sized camp-type fire will
readily ignite one of those magnesium alloy engine cases
from an old air-cooled volkswagen, with spectacular results.
 
On 8 Jul 2004 19:11:50 -0700, [email protected] (Chalo) wrote:

>I am curious as to how well magnesium copes with fatigue.

In my experience, very poorly.

One stunning example: For their 1970 model, Volkswagen
increased the amount of Mg in the alloy for their engine
block. They'd been having some problems with the blocks for
the 1500 and 1600 engines, and I heard that the expectation
was that the stiffer alloy that they could get by going to
a higher Mg content would reduce the rate of certain
failures. They'd been having a problem with bearing saddles
wallowing out, and with cylinder head studs shearing out
threads in the block It turned out to be a really bad move.
With the stiffer high-Mg alloy, the studs took longer to
pull out, but the blocks were cracking in a dozen places
where they'd never had problems before, including across
the bearing saddles, down the back of the block at the base
of a cylinder, etc. For 1971, they reduced the Mg content
and changed a couple of other things, and the cracking
problem vanished.

I've heard numerous disparaging remarks about Mg as a major
component of Mg-Al alloys from a couple of metallurgists
over the years, one of whom was in R&D with a major fastener
manufacturer for quite a while. He commented that it made
alloys that were really nice to work with, but if you used
too much Mg, the material got very brittle.
--
Typoes are a feature, not a bug. Some gardening required to
reply via email. Surrealism is a pectinated ranzel.
 
Prometheus <[email protected]> wrote:
> --On Thursday, July 08, 2004 5:51 PM -0400 ZeeExSixAre
> <[email protected]> wrote:

>> That would be so cool if it were actually (pure)
>> magnesium. You could set one portion aflame and it would
>> erupt in a gigantic fireworks display. You could then
>> say, "I could have either ridden it or set it on fire...
>> the fire was so much more fun!"
>>
>> --
>> Phil, Squid-in-Training

> Unfortunately for you and the other pyros, this stuff
> isn't pure magnesium.
[snip]

No, but if you put enough energy into it you can
still make it burn. Iron dust, zinc dust, aluminium
filings and even aluminium bodied pencil sharpeners
were all found to burn with a nice bright flame in
our undergraduate labs. Though the bright light had
the downside of causing the imminent arrival of a
grumpy lab technician telling us we were supposed to
be doing chemistry and not playing:)

--
Tim.
 
Jim Smith <[email protected]> wrote:
>
> [email protected] (Chalo) writes:
> >
> > FWIW, I have machined magnesium structural alloys
> > before, and their shavings burn similarly to those of
> > pure magnesium. It would be tough to spot-heat a piece
> > as large as a bike frame enough to ignite it, without
> > resorting to something like an oxyacetylene torch,
> > though.
>
> I know for a fact that a medium sized camp-type fire will
> readily ignite one of those magnesium alloy engine cases
> from an old air-cooled volkswagen, with spectacular
> results.

It takes a little while to ignite, though, because the
case's thermal conductivity requires that the whole case be
brought close to the ignition temperature before any one
part of it can reach that temperature. It's not something
one could do to a bike frame, laptop computer, or crankcase
with just a match or a cigarette lighter (though those means
will ignite shavings nicely).

Chalo Colina
 
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