Frame Material
 

Ok, I was about to post in the other thread, but it got closed. I'd like to respond to that OP and have Hank and the other guy NOT FIGHT in this thread. Just be helpful so people have the straight facts.

First, I'd like to resort to the Periodic table as for weights of the metals. I'm not sure about density's here, but the elemental weights do help to convey the idea.



http://wps.prenhall.com/wps/media/ob...ols/period.jpg




Correct me if I'm wrong on the next few things:

Carbon frames : (C) Very light and not a metal. It's a series of fibers. Excellent use for bikes that need to be very light and see little abuse and no crashing.

Aluminum frames: (Al) Also light, but not as light as Carbon. Used for a variety of bikes. Can be very strong, but not as strong as Steel frames. I've seen quite a few Aluminum frames break, and I actually saw a bigfoot frame snap today (read more about it in my other thread).

Steel frames : Made mainly of Iron(Fe) and can go by many names. Cromoly and reynolds are a few common names for the variences of steel frames. Stronger than Carbon or Aluminum. I've never seen a broken steel frame. More Malleable than aluminum, and hangers can often be a part of the frame, because they can be bent back into place.

I don't know enough about Titanium(Ti) frames because they don't get as much attention. As far as I know, it's stronger than Aluminum but heavier.


Please feel free to correct any of this if it is incorrect.

I've seen broken carbon frames, broken aluminum frames, and broken steel frames.. haven't seen a broken ti frame, but I'm sure they break. titanium is denser than aluminum, but much stronger, so you don't have to use as much. reynolds is not a common name, its a tubing maker, like true temper or columbus.

Yes, but reynolds makes their own variety of steel. Steel isn't just Fe, it's a mixture of it and other substances. Reynolds is relatively thin I believe, it's what the Norco Moment frames are made of, and they're pretty light.

There's a bunch of different reynolds tubing too...

The problem with Titanium is that it's got quite a bit of flex in it, which means even though it's lighter than steel, you have to use thicker tubing to get acceptable stiffness, which diminishes its weight advantage. Titanium is also not cheap, and more difficult to machine and weld compared to steel or aluminum. I guess those reasons are why Ti frames are not very commonplace.

kim jong il's bike is made out of uranium (U)
stable, but it causes chain reaction when it crash

Good post LongIslandTom.


I know this is a joke, but it's not possible. When he crashed, the U would have to be shot with a neutron to cause a nuclear reaction :rolleyes:

Paper!

It's still CARBON! :eek:

lol

Actually it's a gigantic mixture. You could actually live off of paper for a while, because it's got carbohydrates in it since it's made from trees :rolleyes:

ok... Carbboard!!!!

I give up.

Jason, this sounds like an excellent set of questions for Falanx, our resident materials scientist. He'll give you the facts, as opposed to our opinions. You may find out more than you want to know, but you will find out.

There is so much that is incorrect that it's not worth my time.

Thank you for the chuckles though.

Yes I win. Just for the heak of it... Wicker!

Sorry only if you are a cow. It's got carbs in it but humans don't have the enzymes to break it down.

50cent's bike is made out of silver gold platinum and diamond!

i'll stop here

4130 Cromoly CrMo
.283 lb/in(cubed)
tensel strength=179000psi
-dense, stiff, inexpensive, readily avaliable
-high endurance strength
-excellent fatigue strength

6061 Al
.098 lb/in(cubed)
tensel strength=43000
-no fatigue or endurance strength
-inexpensive
-loses strength during welding, requires artificial aging

3/25 Ti
.160lb/in(cubed)
tensel strength=125000psi
-highest corrosion resistance
-very high strength to weight ratio
-infinite fatigue strength
-acid etch process

Thats all I know...

Atomic weights do not equate to densities of metals. What controls the density of metal is valence in a pure crystal and crystal structure, neither of which appear on the periodic table. While it is correct to assume Lead is denser than Magnesium, Zinc is less dense than Iron, Cerium is much less dense than Gold, rather than a little....


Right:

Carbon: Close enough for an entry level understanding. Some newer thermoplastic matrix composites are demonstrating far superior fracture toughnesses to the older epoxy systems, but still essentially brittle and stiff for their density.

Aluminium: Pure aluminium has moderate fracture toughness and poor mechanical strength. It's work hardening rate is low. Aluminium alloys fall into two camps. The only ones that cyclists are likely to see have to be two-stage heat treated. They can be readily joined by fusion wedling techniques in the majority. Their primary benefit is their low density, which enables the contruction of larger diameter tubes at the same mass and wall thickness, leading to greater longitudinal and rotational stiffness in the tube. Aluminium frame is likely to be more rigid (not stiffer - stiffness is a material parameter, not a geometrical parameter). This has given aluminium alloys a reputation for harsh rides.
Aluminium alloys also do not rust. This does not mean that they do not corrode. Indeed, their corrosion rate in salt water is higher than steels. This performs both an aesthetic and structural function in aluminium frames.

Steels: Two thousand years of development cannot be addressed in a paragraph. Highest stiffness, highest toughness, highest strength of all the alloy families used in frames. Downsides - rusts, just under three times as dense as aluminium alloys, so frames of equal stiffness are heavier than aluminium. Can be joined by conventional and esoteric fusion welding, filler-metal soldering and thermal bonding processes. Metallurgy is still contantly being evolved as levels of impurities have least effect on steels, so ever-superior refining techniques lead to ever-greater mechanical properties. Almost all manufacturers of steels for bicycle frame tubing use the same ranges of alloys, contrary to some beliefs. They are either based on the iron-carbon-chromium-molybdenum system or the iron-carbon-manganese-molybdenum system. With the exception of stainless steels, all alloys are derived from either one or the other.

I have seen frames in all three break. There is no such thing as an indestructible frame, but the severity of the failure and the warning you get before it varies between materials.

No such thing. Fatigue life is rated at a stress, and as such varies above that stress. And titanium alloys do not have higher fatigue lives than steels.


As simple as I could make it

Well then if you didn't want to take the time to correct it, why even bother taking the time telling us?


Okay, here's a big question:

If welding Aluminum frames weakens it, would this be pointless?

Thanks for the read Falanx.

Because thanking you for the chuckles takes practically no time at all, especially when compared to the time that it would take to correct all of the glaring errors in your OP.

In a practical scenario, what does this mean? An alu bike exposed to too much salt will become brittle and snap? What about fresh water?

Nice post btw.

Alminum frames dont have as long as a fatigue life as the other types of material.. Typical life of an aluminum frame would probally be like what? 6 -8 years of hard riding? Thats what Ive heard anyways I could be worng.

I think it depends on the style of riding. Aluminum XC frames generally last longer than Aluminum freeride frames.

I'd say the average life for an aluminum freeride frame is around 1-6 years.

after breaking 2 aluminum frames from powering up hills and countless chains, cranks and pedals I looked into Titanium but was told by a trusted source that I would break it at the bottom bracket area. I guess at the welds, I didnt ask
nothing sucks more than having a frame break, getting hurt in the cajonas from the sudden slip and then having to hike a broken bike out of the woods.
thats why I went with my Devinci Guzzler. its got lots of gussets in the right places on the frame and came with tougher components. I also havent destroyed the carbon pedals yet either, though I have broken my chain twice , destroyed the mid gear on the crank and broken a bottom bracket bearing