Carbon vs. Aluminum vs. Titanium

[Bikelyst]

I just found this vid on Googs and I am not saying that I support the "strength" of titanium at all...I just thought it was an interesting video. Most likely it is just a couple of guys trying to sell their titanium bikes because demand has fallen. (I think its Litespeed bikes)

http://video.google.com/videoplay?docid=3741362681682291899&hl=en

Post your thoughts.

 

[alienator]

Stupid. Exactly how often are bicycle tubes loaded like that? Uhm, never.

It might be a good pitch to feed to suckers, though.

 

[Bikelyst]

Stupid. Exactly how often are bicycle tubes loaded like that? Uhm, never.

It might be a good pitch to feed to suckers, though.

I 100% agree dude.

 

[sogood]

Where did I see this exact video being discussed? Essentially, you are a dope if that makes you want to buy Ti.

 

[hd reynolds]

Stupid. Exactly how often are bicycle tubes loaded like that? Uhm, never.

It might be a good pitch to feed to suckers, though.

U picked the words right out of my mouth alienator.

Ti frames are 60% heavier than Aluminum or Carbon because they cant be butted, shaped or reinforced in areas where it matters.

 

[LeDomestique]

May I suggest the reading of this very insightful series of articles on the frame building materials. It covers everything from Steel, Ti, Alum, Carbon and others.

Also explains basic concepts of frame building such as stiffness, elongation, fatigue, etc.

http://www.63xc.com/scotn/metal.htm

cheers

 

[John M]

Stupid. Exactly how often are bicycle tubes loaded like that? Uhm, never.

It might be a good pitch to feed to suckers, though.

If me and my carbon bike get subjected to that type of loading, I suspect that I will have bigger problems than flattening of the downtube.

 

[ScienceIsCool]

Actually, I think that was an interesting demonstration. It showed, for a given load, what the relative strengths and failure modes are. You typically won't get run over by a very slow moving vehicle, but most of us who race crash once a season give or take.

What I saw is that a carbon tube will splinter, fracture and lose structural integrity when overloaded. I also saw that aluminum will crumple and fold with a slight chance that it will not completely lose structural integrity. You couldn't learn very much about titanium from the video other than perhaps when comparing normally dimensioned bicycle tubes, titanium is the toughest (least susceptible to localized impacts).

In a crash, I would suspect that the frame/fork will recieve high impulse (lots of energy over a small time), localized impacts. So based on the video, I'd say titanium has the best chances of surviving a crash. You could expect aluminum to bend and dent. And carbon might turn to splinters.

Note that this is all different from the material strength which is based on very low impulse loading over a large area...

John Swanson
www.bikephysics.com

 

[Walrus]

Whoppdeedoo. How irrelevant.

It's like demonstrating the strength of a helmet by seeing how long it lasts inside a volcano.

 

[alienator]

Actually, I think that was an interesting demonstration. It showed, for a given load, what the relative strengths and failure modes are. You typically won't get run over by a very slow moving vehicle, but most of us who race crash once a season give or take.

What I saw is that a carbon tube will splinter, fracture and lose structural integrity when overloaded. I also saw that aluminum will crumple and fold with a slight chance that it will not completely lose structural integrity. You couldn't learn very much about titanium from the video other than perhaps when comparing normally dimensioned bicycle tubes, titanium is the toughest (least susceptible to localized impacts).

No, no, no. The range of loads to which a frame can be subjected aren't even of the same type demonstrated in the video, let alone are even within several magnitudes of order of that load.

The video is solely for its shock value.

 

[dhk2]

Interesting video, but anyone notice that steel wasn't included? If they had included a steel tube with decent wall thickness, bet that would have survived just fine too. Of course, someone promoting ti wouldn't want to show the "strength" of good old cheap steel in their demo. If "crush resistance" was really an important characteristic, we'd all still be riding old-school 6 lb steel frames.

The demo suggests to me that for a frame that was going to see rough handling, eg to be crashed against rocks, or thrown in the back of an SUV and then have camping or climbing gear thrown on top of it, ti is a better choice than al or cf. If I was buying a frame that would see this kind of abuse, I'd pick steel over ti just for the cost factor.

 

[Bikelyst]

Again, I want everyone to know that I am not in favor of Ti bikes and did not post this video in favor of that. I thought it would cause some discussion...but I think everyone should take a look at Le Domestique's link, it answered all of my questions about the video and left me feeling smarter (although a little long).



Cheers!

 

[ScienceIsCool]

No, no, no. The range of loads to which a frame can be subjected aren't even of the same type demonstrated in the video, let alone are even within several magnitudes of order of that load.

The video is solely for its shock value.

I know. I just felt like taking the contrary position and seeing if I could back it up. Still, it does give some info on toughness and failure modes.

John Swanson
www.bikephysics.com

 

[metrovelo]

Ti frames are 60% heavier than Aluminum or Carbon because they cant be butted, shaped or reinforced in areas where it matters.

???

You are kidding, right? My Merlin CR6/4 says otherwise, grasshopper.

And it will never moan and creak like all those mid-range carbon bikes out there that are starting to show their age after 2 years.

 

[alienator]

I know. I just felt like taking the contrary position and seeing if I could back it up. Still, it does give some info on toughness and failure modes.

John Swanson
www.bikephysics.com

I know. I was pickin' up what you were layin' down.

I wish there was a place that catalogued bad or stupid marketing vids, vids in which truthiness was applied to science and engineering.

This video actually made me think of the latest Litespeed ad in Velonews...you know, the one w/ the Carbonello stickers. Not only does that ad display a fine sense of sarcasm, but it does what ads are supposed to do without raping scientific sensibilities. Also, nowhere does the ad mention nano anything!

Still, the vid with the truck running over the tubes of various materials does do one valuable thing: it serves to remind visitors (pay attention, here, riders flying to the US to race in the Tour of California.) to the US of the special dangers associated with riding on roads in the US....

 

[vadiver]

I think I got this link from this forum a while ago. Maybe not, but it is interesting.

http://www.damonrinard.com/EFBe/frame_fatigue_test.htm

The vid in this thread does nothing for me. I already knew the CF will splinter. Watching enough motor racing shows that. I would be more interested in seeing built up bikes going through normal stess tests.

Although one thing for sure. When I get to the point of wanting to lay my bike in my driveway and drive over it with my SUV, I will buy a TI bike.