Bicycle materials

Every bike mag has an article every year on the benefits of the different types of tubing. Something your not taking into account is the ability to contour tubes. No one will ever win this type of debate. Different materials work best for different applicatons. By the way......steel frames will rust from the inside out.

Quoted post said:

Originally posted by hwttdz

Interpretation: All metals can theoretically make the same weight frame with the same stiffness.

Even if the theory is right and I really doubt it, it does not pan out that way in the real workd of framebuilding where I live.

Quoted post said:

Originally posted by hwttdz

Also I'm interested in sparking a debate on bicycle frame materials. So given the above I'm going to say that steel with a good paint job is the best because it is not subjected to rust. It has give, and should last a very long time. Also it can be light because the tube thickness does not need to be as high as Al or Ti.

You are beating a very dead horse.It's pretty well proven that a steel frame to be as stiff as Al or will also be much heavier. For Ti to be as stiff it will also be heavier,but not by as much. Ti may be the best comprimose: NO rust,reasonably light and stiff,and with good durability given proper construction.But, expensive. Don't forget CF. Lots of good properties and maybe the true magic material.

Miamijim's right; it's an interesting subject but most bicycle enthusiasts decided long ago that it's a whack argument to have. There are cost-effective, splendid frames to be made of steel, of aluminum, of Ti, of carbon, and of the infinite combinations, alloys, hybirdizations, and so on out there.

The notion that same weight frames with identical stiffness are a theoretical possibility, I suppose, but that's a supposition born of the stipulation that the 1, 1/3, 1/2 ratios are accurate -- which I doubt. They might provide a general guidline for understanding the stiffness and weight ratios of these base materials, but I seriously doubt they're accurate beyond that... tweak those numbers just a bit (to make them more realistic) and you're bound to impact the end results.

Impact them how much? Ohhh, probably not too much, but then again, between great frames, the stiffness and weight variations are subtle to begin with.

It's all about subtleties when it comes to bike manufacture.

The greatest subtlety of them all, style and preference, is just as important. Some folks just love the feel of steel, and some just love the gentle hum of Ti.

Material: Steel Al Ti
Density (lb/in^3) .283 .098 .160
Stiffness(young's mod, psi x 10^6) 30 10 15.5
relative density 1 .346 .565
relative stiffness 1 1/3 .516

Anyone know of any articles in material science journals addressing the benefits and disadvantages of each?

Personally I prefer Al, mostly a cost consideration.

The revised (and precise) numbers are appreciated, hwttdz; you're definitely doing your homework.

😉

I'm still not sure what we can make of those numbers, though, particularly since few serious frame makers today use anything other than complex designer alloys, each purported to offer a different stiffness/weight ratio than the next tubing material.

I too like Al for its cost efficiency; you can get a great ride with good Al for not too much dough. But it's hard to deny the sweetness of a good Ti frame, which offers lightness, durability, and a more supple ride if well made; steel has its perks as well. And yes, carbon fiber is still hard to beat in most respects...

Screw it; go by paint job.

The stats I gave were from 4130 steel, 6061 Al, and the Ti alloy is Ti3Al-2V. These are all pretty standard in the cycling tubing industry.

Quoted post said:

Originally posted by lokstah

I'm still not sure what we can make of those numbers, though, particularly since few serious frame makers today use anything other than complex designer alloys, each purported to offer a different stiffness/weight ratio than the next tubing material.

Alloys of steel and aluminum are equally stiff. 6/4 Ti is a bit stiffer than 3/25 but that property is usually used to make a lighter frame. For the mostpat,stiffness is a function of diameter ,but thickness and shaping play secondary roles.

Quoted post said:

Originally posted by hwttdz
The stats I gave were from 4130 steel, 6061 Al, and the Ti alloy is Ti3Al-2V. These are all pretty standard in the cycling tubing industry.

4130 is near bottom of the barrel generic Cromo now used only in the cheaper steel frames.It's strength is roughly 1/3 to 1/2 that of more modern heatreated steels and frames made from it are HEAVY.

Quoted post said:

Originally posted by hwttdz

Anyone know of any articles in material science journals addressing the benefits and disadvantages of each?

All of them can be made into excellent frames. Any can be made into a [censored] frame. It's more about how they are designed and built, than with what.