Frame materials - Steel vs CF vs Alu
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Frame materials - Steel vs CF vs Alu
Postby simon.young » Sun Jul 27, 2014 11:59 am
CF look for delamination?
Steel has rust issues, welds etc. Look internal as well.
What about Aluminium? Stress? Cracked welds?
Any tips without going to stress test the frame?
Particularly interested in comment on aluminium, I like some of the 80s/90s cannondales, but their nickname scares me. I've stayed away from CF, but QV has a few, so is 20+ yo carbon ok? I've mainly stuck to steel, I guess I've felt is easier to visually inspect?
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Re: Frame materials - Steel vs CF vs Alu
Postby yugyug » Sun Jul 27, 2014 5:40 pm
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Frame materials - Steel vs CF vs Alu
Postby RonK » Sun Jul 27, 2014 5:48 pm
20 yo alloy - corrosion, fatigue
20 yo carbon - bonding failure at the lugs.
Obviously, these problems may be quite difficult to detect.
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Re: Frame materials - Steel vs CF vs Alu
Postby morini » Sun Jul 27, 2014 6:06 pm
Only buy brand new aluminium and then recycle it when it breaks. There are a number of options for very reasonably priced frames but I wonder how long this situation will last.
Buy carbon if you need to have the latest lightweight technology, a more supple ride (apparently) but I've no idea what you do with it when it snaps in half.
......and buy steel if you want to give it to your grand kids' kids.
I've never had a carbon frame but I know from owning a number of kevlar/carbon honeycomb (Nomex) rowing boats that they're holding up well after 20 years and there seems to be no obvious signs of degradation apart from the gel coat. Kevlar is very forgiving compared to carbon fibre so I wonder how a pure carbon bike frame will go after the same time?
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Re: Frame materials - Steel vs CF vs Alu
Postby simon.young » Sun Jul 27, 2014 7:41 pm
Please feel free to correct me... I've been doing some reading online re alloyRonK wrote:20 yo steel - rust, fatigue
20 yo alloy - corrosion, fatigue
20 yo carbon - bonding failure at the lugs.
Obviously, these problems may be quite difficult to detect.
So rust in steel, orangy in colour, can notice it pretty easily. And the oxidation penetrates the base metal, weakening it. Obviously flaking / bubbling is really bad.
In Alloy, the corrosion is aluminum oxide, a very hard material that actually protects the aluminum from further corrosion. And unlike steel doesn't penetrate the base metal very much at all. Anodizing is "colored" oxidation for aluminum. you actually intentionally oxidize the part to protect it.
If seems that CF unless fractured is ok, its the lugs, the gluing etc that let the frame down
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Re: Frame materials - Steel vs CF vs Alu
Postby simon.young » Sun Jul 27, 2014 7:57 pm
From MTBR
I won't go into the restoration suggestions, but apparently this corrosion isn't anything to worry about. Maybe caused from scratching the clear coat, banging a wrench etc, prolonged exposure to salt spray or more interestingly from dissimilar metal corrosion from chrome plated bolts.
Another post goes into say "Fatigue related to heat treat and weld penetration is a MUCH bigger concern for Aluminum than oxidization."
I guess paint cracking around joints would be sign for alloy? and if so, with steel being more flexible than alloy, would you expect some cracking in joint paintwork and potentially not as much fatigue? just flex?
Both options I'd steer clear of at this stage, but steel is repairable, alloy would be throw away.
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Re: Frame materials - Steel vs CF vs Alu
Postby RonK » Sun Jul 27, 2014 8:06 pm
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Re: Frame materials - Steel vs CF vs Alu
Postby ldrcycles » Sun Jul 27, 2014 8:15 pm
As far as steel frames go, unless you're talking very thin walled Reynolds/Columbus/whatever, rust needs to get to quite an advanced stage to compromise the frame. Just a bit of orange i wouldn't care in the slightest, bubbling/flaking is usually no problem either (although obviously if you were to just leave it to keep going there will eventually be trouble).
EDIT: This is a good example of what can be rescued, rebilda did this one and even managed to salvage the crank arms.
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Re: Frame materials - Steel vs CF vs Alu
Postby Drizt » Sun Jul 27, 2014 8:25 pm
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Re: Frame materials - Steel vs CF vs Alu
Postby bog1953 » Sun Jul 27, 2014 8:56 pm
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Re: Frame materials - Steel vs CF vs Alu
Postby yugyug » Sun Jul 27, 2014 9:14 pm
Sorry off topic but where is the greatest development within the wheel? Hubs mainly? Or is this also true for rims and spokes?bog1953 wrote:The greatest development in bikes in the last 20yrs hasn't been in frames, it's wheels. A modern wheel is light years ahead of those heavy things we put on period correct bikes. A modern wheel seems to spin forever without any effort , and so light.
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Re: Frame materials - Steel vs CF vs Alu
Postby bog1953 » Sun Jul 27, 2014 10:10 pm
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Re: Frame materials - Steel vs CF vs Alu
Postby simon.young » Sun Jul 27, 2014 10:35 pm
Awesome. Exactly what I'm after re alloy and removing corrosion. And the level of rust in steel. Can't believe that pic and even some was recovered..ldrcycles wrote:In my job repairing pool pumps i see extreme aluminium corrosion, to the point where there are whopping great chunks missing. Corrosion such as in that photo is not an indication that the frame is about to snap in two, but it should be made very clear that not removing it WILL lead to trouble, as the corrosion makes it easier for moisture to hang about, accelerating the corrosion.
As far as steel frames go, unless you're talking very thin walled Reynolds/Columbus/whatever, rust needs to get to quite an advanced stage to compromise the frame. Just a bit of orange i wouldn't care in the slightest, bubbling/flaking is usually no problem either (although obviously if you were to just leave it to keep going there will eventually be trouble).
EDIT: This is a good example of what can be rescued, rebilda did this one and even managed to salvage the crank arms.
Another great point, I've heard / seen stuck seat posts, but just moved on. Quickly. Never thought too much about it, but really should check.RonK wrote:The corrosion risk to alloy frames is from electrolysis. Seat posts/seat tubes are prime sites.
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Re: Frame materials - Steel vs CF vs Alu
Postby QuangVuong » Mon Jul 28, 2014 4:47 pm
20 year old carbon is also about 3mm + thick. It is not the coke can thickness of modern carbon. Its unlikely that the carbon will be the one breaking from fatigue, unless it has been struck by something. The lugged frames would fail at the lugs first, mainly due to the galvanic attack between the different materials. The aluminium lug rusts white aluminium oxide powder which essentially expands in size, and the glued joint could crack and not be hold the carbon tube anymore. Some of the newer frames had some sort of sleeve in between the lugs so that debonding was not as great an issue.RonK wrote:20 yo carbon - bonding failure at the lugs.
Obviously, these problems may be quite difficult to detect.
Even the 20 year old monocoque frames were built thick back then. This is a Kestrel 200 chopped in half. Quite thick along the tubes, and even thicker at joints.
Cracks in the carbon are easy to spot. It will be softer in that area, and you should be able to see the crack. Best to watch out for aluminium oxide(whitish powder) around the lugs, and cracks around the lug joints too. If they arent visible, then you should be good.
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Re: Frame materials - Steel vs CF vs Alu
Postby yugyug » Tue Jul 29, 2014 12:44 am
Good info, thanks. I'm guessing that Kestral frame failed in some way before it was bisected?QuangVuong wrote:20 year old carbon is also about 3mm + thick. It is not the coke can thickness of modern carbon. Its unlikely that the carbon will be the one breaking from fatigue, unless it has been struck by something. The lugged frames would fail at the lugs first, mainly due to the galvanic attack between the different materials. The aluminium lug rusts white aluminium oxide powder which essentially expands in size, and the glued joint could crack and not be hold the carbon tube anymore. Some of the newer frames had some sort of sleeve in between the lugs so that debonding was not as great an issue.RonK wrote:20 yo carbon - bonding failure at the lugs.
Obviously, these problems may be quite difficult to detect.
Even the 20 year old monocoque frames were built thick back then. This is a Kestrel 200 chopped in half. Quite thick along the tubes, and even thicker at joints.
Cracks in the carbon are easy to spot. It will be softer in that area, and you should be able to see the crack. Best to watch out for aluminium oxide(whitish powder) around the lugs, and cracks around the lug joints too. If they arent visible, then you should be good.
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Re: Frame materials - Steel vs CF vs Alu
Postby QuangVuong » Tue Jul 29, 2014 9:28 pm
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Re: Frame materials - Steel vs CF vs Alu
Postby singlespeedscott » Wed Jul 30, 2014 2:45 am
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Re: Frame materials - Steel vs CF vs Alu
Postby clackers » Wed Jul 30, 2014 2:16 pm
It may have failed by finishing second in a sprint ... high price for disappointing its owner!yugyug wrote:
Good info, thanks. I'm guessing that Kestral frame failed in some way before it was bisected?
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Re: Frame materials - Steel vs CF vs Alu
Postby rkelsen » Wed Jul 30, 2014 2:34 pm
I guess you can't make mortadella from a bike...
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Re: Frame materials - Steel vs CF vs Alu
Postby simon.young » Wed Jul 30, 2014 6:52 pm
Thanks. really good tips on older carbon frames.QuangVuong wrote:
20 year old carbon is also about 3mm + thick. It is not the coke can thickness of modern carbon. Its unlikely that the carbon will be the one breaking from fatigue, unless it has been struck by something. The lugged frames would fail at the lugs first, mainly due to the galvanic attack between the different materials. The aluminium lug rusts white aluminium oxide powder which essentially expands in size, and the glued joint could crack and not be hold the carbon tube anymore. Some of the newer frames had some sort of sleeve in between the lugs so that debonding was not as great an issue.
Cracks in the carbon are easy to spot. It will be softer in that area, and you should be able to see the crack. Best to watch out for aluminium oxide(whitish powder) around the lugs, and cracks around the lug joints too. If they arent visible, then you should be good.
Been looking at Kestrel MTB's.... maybe I've shouldn't have!
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