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Posted: Mon Oct 13, 2003 1:43 am
by popawheelie
Relax superlite, You'r way too wrapped up in your product. Don't take it so personaly, O.K.? Whenever you make something and hang it out there some people are going to not like it or question why or how it was made. That's just part of hanging it out there. That's part of the risk. No big deal.

Posted: Mon Oct 13, 2003 2:04 am
by Superlite
Yeah, I did kind of got uptight about that, but I didn't do it because of my part, i was pissed cause 7075 didn't know what he was talking about. when someone trys to tell you something that they have no clue about and that something is part of your life its just very offensive. I'm sure you know what I mean. But true, I was "a little" caught up in it. :wink:

Posted: Mon Oct 13, 2003 2:04 am
by Weenie

7075 alloy anodized

Posted: Mon Oct 13, 2003 10:13 am
by 7075
This was not meant to be personaly - I was actually trying to help superlite
Your insert will loose strenght immediate when anodized - the B-T-P will loose strenght over time because of SCC - maybe the B-T-P will wear out before this happens - and therefor it is not a problem...
It is actually a little scary that you are designing products that people thrust while doing a sprint with 80 km/h - You have of course done a proper fattigue test of your product... right ??
And yes - I am designing products - why do you think I know these things... Instead of being such a stupid moron you should try to learn something.

"Oh year" - Sorry for the spelling - this is not my main language (Child !)

Posted: Mon Oct 13, 2003 1:03 pm
by popawheelie
Now your doing it 7075! I won't get inbetween you two.
Have at it!

Posted: Mon Oct 13, 2003 3:28 pm
by Superlite
What ever you say cheif. :lol:

Posted: Mon Oct 13, 2003 3:33 pm
by ras11
Calm down folks.. you guys are making me nuts here.. We are talking about a pedal incert, it's going to fail due to mechanical deformations by the cleat, not surface treatments. It's not like this thing is going to rust away. Right!

Ok, so I did the leg work for you guys. Here's the jist of it.

7075 is correct in some points. Anodizing does increase the surface hardness, and thus more prone to cracking and stress induced cracking.

But under normal tensile mode, not bending or twisting to induce cracks, anodizing positively affects the tensile strength of the 7075-T6 alloy.

Here's the referance..

Singh, Vakil; Rao, Vinnakota K.; Rao, Palle R. Zeitschrift fuer Metallkunde (1976), 67(4), 235-40. (journal is in english)

Now, Superlite, is also correct. Improper treatment will cause a decrease in fatigue life. Especially with the wrong acid treatment (cleaning). That should be obvious, but here's the referance.

Stickley, G. W.; Lyst, J. O. Alcoa Res. Labs., New Kensington, PA, Journal of Materials (1966), 1(1), 19-33.

So what does all this mean. It means for 7075-T6 alloys are improved with anodizing when the parts are strucural. Why, because A) it looks better B) it prevents further unwanted oxidation which leads to premature failure. To be honest, for the part in question, you could leave off the anodizing or put in on, it won't matter. The part will fail due to mechanical deformation by the cleat, long before a oxidation mechanism will cause failure. That's providing you don't soak these things in warm salt water, in which case anodizing will help.

To make 7075 feel better, stress induced cracking is likely why spokes aren't made of Al. Twisting and bending of Al is a bad thing, especially when anodized.

Nothing like a little argument to get the off-season blood moving. :wink:

7075 alloy anodized

Posted: Tue Oct 14, 2003 7:58 pm
by 7075
OK - Glad to see that somebody knows about this issue...
I have alot of studies that I could show (if I knew how to upload this...) where anodized 7075 alloy fails before unanodized.
And Yes ras11 - you are right - but what if the insert is "close to the limit" of failure - then when anodized you come even closer / To close
As you say: This will first be an issue after years (of oxidation / SCC) with the B-T-P insert....

And btw is some of mavic's spokes made from aluminium alloy :wink:

Re: 7075 alloy anodized

Posted: Tue Oct 14, 2003 9:20 pm
by Joel
And btw is some of mavic's spokes made from aluminium alloy :wink:

Those Zycral spokes are aero spokes, so they can't bend as possible as a normal thin round spoke. And in the Ksyrium and Crossmax wheels they go straight from the hub to the rim without any bend (special nipple construction)

Posted: Tue Oct 14, 2003 10:35 pm
by ras11
I guess I left out something that will help make this all clear... stress cracking is only a problem for structral Al like 7075-T6 if continuted oxidateion occures. As Superlite points out, only the very outer surface is hardened (mostly to prevent scratches and wear). If the crack is only a micron thick it's not going to influance the fatigue life of the part.

I'm done. I'm not going to add any more to this subject. I just did some reading, and summarized what I've learned. That's all. I hope to contribute some more ideas to the subject.

I hope readers do take care to learn and think about the real issues when part lifetimes are considered. In this case, I feel Superlite has the wiser vantage, buildings don't fall down because of the color of their paint.

Posted: Tue Oct 14, 2003 11:47 pm
by Superlite
That was good, I laughed when I read that last sentence. :lol: