W
Werehatrack
Guest
On Thu, 10 Feb 2005 05:00:46 GMT, "Phil, Squid-in-Training"
<[email protected]> may have said:
>The magnesium lowers of my 2003 Manitou Skareb Comp had begun to crack last
>year, about 6 months before I stopped riding it.
You knew they were cracked, and kept riding it that way?
>I've kept it stashed away
>for a while until today, when I was cleaning my room and found the lowers.
>I gave the legs a light (maybe 2.5-4lb) squeeze, and they snapped.
[mondo snip]
Looking at the pictures, I have just two things to say.
First, the failure looks very typical of what I've seen in alloys
which employed too much magnesium in an application where flexure was
going to be present. High-Mg alloys are *brittle*, as is Mg itself.
In small amounts, it can contribute to making a good, tough alloy, but
if too much is used, it's a bad thing in my experience.
Second, the area of the failure looks like it was poorly engineered in
my estimation. The bridge-to-tube transition forms a natural stress
concentrator which I would have expected to result in failure in
exactly the way that it did.
I'm not familiar with the features of the Skareb; is this one of the
forks which has the damping in one tube and the spring in the other?
If so, that would have hastened the cracking.
>Final word: I'm lucky these didn't totally fail on me while I was riding it.
I can see several possible ways that such a failure could have gone
down; unfortunately, a number of them involve you doing a face plant
in the process. I agree; this was a failure which you are lucky to
have had happen where it did.
--
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.
<[email protected]> may have said:
>The magnesium lowers of my 2003 Manitou Skareb Comp had begun to crack last
>year, about 6 months before I stopped riding it.
You knew they were cracked, and kept riding it that way?
>I've kept it stashed away
>for a while until today, when I was cleaning my room and found the lowers.
>I gave the legs a light (maybe 2.5-4lb) squeeze, and they snapped.
[mondo snip]
Looking at the pictures, I have just two things to say.
First, the failure looks very typical of what I've seen in alloys
which employed too much magnesium in an application where flexure was
going to be present. High-Mg alloys are *brittle*, as is Mg itself.
In small amounts, it can contribute to making a good, tough alloy, but
if too much is used, it's a bad thing in my experience.
Second, the area of the failure looks like it was poorly engineered in
my estimation. The bridge-to-tube transition forms a natural stress
concentrator which I would have expected to result in failure in
exactly the way that it did.
I'm not familiar with the features of the Skareb; is this one of the
forks which has the damping in one tube and the spring in the other?
If so, that would have hastened the cracking.
>Final word: I'm lucky these didn't totally fail on me while I was riding it.
I can see several possible ways that such a failure could have gone
down; unfortunately, a number of them involve you doing a face plant
in the process. I agree; this was a failure which you are lucky to
have had happen where it did.
--
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.
