Myth Busters:

[indianatrials]

Im sure most of you probably already know this, but i thought id post it up for all the noobs like me. Its comonly assumed that titanium is lighter than aluminum. Titanium is the best strength to weight ratio though. Check out how much heavier titanium is than aluminum: http://mojobob.com/roleplay/weight_chart.html

I alos found somewhere else that carbon is almost half the weight of alu. Interesting stuff =)

[monkeyseemonkeydo]

Im sure most of you probably already know this, but i thought id post it up for all the noobs like me. Its comonly assumed that titanium is lighter than aluminum. Titanium is the best strength to weight ratio though. Check out how much heavier titanium is than aluminum: http://mojobob.com/roleplay/weight_chart.html

I alos found somewhere else that carbon is almost half the weight of alu. Interesting stuff =)

The comparitive density of different materials isn't the whole story by a long way though. Sure aluminium is lighter than steel but to get the same approximate strength in something like a bike frame you have to use far more aluminium and so frame weights start to converge more than you'd think if you just looked at density on its own.

Likewise if you want something made from carbon fibre you need to use a lot more of it than aluminium and also probably need to use some kind of sandwich again adding to the weight in order to obtain acceptable properties.

[Shaun H]

This is the reason "uneducated" (I just mean people who aren't engineers and materials scientists etc) people end up with so many misconceptions.

There's a lot more to it than you think!!! Most people just see the strength and weight of a material and go off that. Plus sometimes they pick up one of the characteristic properties of a material, like the brittle failure mode of CFRP and then whenever the use of carbon fibre comes up loads of people start blurting out "oh you can't use that it's brittle and just snaps"

Materials is a very complex subject (that's why you can do an entire degree pretty much dedicated to them) that requires an understanding of all the different properties of materials and how they affect the performance of a particular function and/or design.

[Greetings]

Pure titanium is never used for manufacturing, it's always an alloy. So the weight of titanium in that chart doesn't say much about how it relates to aluminium parts/frames especially as those are also made of an alloy.

But yes, Ti is much heavier than aluminium, it's comparable to steel.

[monkeyseemonkeydo]

Pure titanium is never used for manufacturing, it's always an alloy. So the weight of titanium in that chart doesn't say much about how it relates to aluminium parts/frames especially as those are also made of an alloy.

That doesn't really hold true... the weight of pure titanium does say something because any titanium alloy will still be ~98% Ti and similarly and aluminium alloy will be ~98% Al (guestimates but probably not far out). The elemental density is therefore going to be fairly close to what you end up with.

[Greetings]

That doesn't really hold true... the weight of pure titanium does say something because any titanium alloy will still be ~98% Ti and similarly and aluminium alloy will be ~98% Al (guestimates but probably not far out). The elemental density is therefore going to be fairly close to what you end up with.

Well if that is true then I stand corrected. Thought it was usually between 70 and 80%.

[chris4stars]

can i throw magnesium alloy into the picture here?!

anyone aware of bike frames made of the stuff...or any other more exotic materials other than carbon/titanium

edit* and with reguards to trials, if any of these materials have been used in any way with frames yet..

Edited January 10, 2010 by chris4stars

[Shaun H]

That doesn't really hold true... the weight of pure titanium does say something because any titanium alloy will still be ~98% Ti and similarly and aluminium alloy will be ~98% Al (guestimates but probably not far out). The elemental density is therefore going to be fairly close to what you end up with.

Well if that is true then I stand corrected. Thought it was usually between 70 and 80%.

I think you're underestimating the variation in alloy density Dave. If alloys were that close to elemental density much of the research into new alloys wouldn't be as useful. In my personal experience (research for materials to use in new projects) Al alloys can have more than 20% variation in densities and I imagine the same is true of other alloys.

can i throw magnesium alloy into the picture here?!

anyone aware of bike frames made of the stuff...or any other more exotic materials other than carbon/titanium

edit* and with reguards to trials, if any of these materials have been used in any way with frames yet..

Magnesium alloy (which is largely Al by volume btw) is already used in pedals (the very popular Welgo MG-1s for example). There have been a few frames that were made from the alloy but in my opinion they've all been made far too light when the material could have just been substituted for a Al alloy on existing designs to give lighter frames at similar strengths/life cycles. Now Mg alloys have a bad reputation in trials for life expectancy.

[monkeyseemonkeydo]

I think you're underestimating the variation in alloy density Dave. If alloys were that close to elemental density much of the research into new alloys wouldn't be as useful. In my personal experience (research for materials to use in new projects) Al alloys can have more than 20% variation in densities and I imagine the same is true of other alloys.

Well the usually used Ti6Al-4Vn is 90% Ti so I was a touch off but most of the research is chasing superior properties rather than reducing density I'd have thought. Titanium is an excellent base but by adding alloying elements you can tune the properties to improve how the material reacts in high temperature/stress etc environments but you wouldn't expect any titanium alloy to be 50% lighter than pure Ti...

[Shaun H]

Well the usually used Ti6Al-4Vn is 90% Ti so I was a touch off but most of the research is chasing superior properties rather than reducing density I'd have thought. Titanium is an excellent base but by adding alloying elements you can tune the properties to improve how the material reacts in high temperature/stress etc environments but you wouldn't expect any titanium alloy to be 50% lighter than pure Ti...

You're absolutely right the primary purpose of research is enhanced properties however reduced densities are desirable particularly in aerospace materials. Of course, you won't get an alloy 50% lighter than the pure element, however, the density of an alloy can't be calculated by simply adding the densities of each element in their respective proportions. Adding different constituents changes the microstructure and therefore influences the alloy's density.

[rupintart]

You're absolutely right the primary purpose of research is enhanced properties however reduced densities are desirable particularly in aerospace materials. Of course, you won't get an alloy 50% lighter than the pure element, however, the density of an alloy can't be calculated by simply adding the densities of each element in their respective proportions. Adding different constituents changes the microstructure and therefore influences the alloy's density.

In all reality, without somebody wanting to dump a ton of money in finding out what works BEST for BICYCLES, and for which application, it's all pretty moot. Unless of course, you're the one doing the research and going to make the change, there really isn't any way we can expect a company to produce a tubeset based solely on hypothesis without a solid example or prototype. So basically, it's all nice info to know, but is pretty worthless at the same time.

[Mod-out]

Oh please, listening to all these poor folk talk about their wussy titanium-this, aluminum that. Don't you know the real pros ride beryllium frames? They're just careful not to scratch them, and ride in well-ventilated areas. When I don't feel like pulling out my beryllium comp bike, I practice on my junky old maraging steel frame with Aermet axles and bottom bracket.

The point is, there are materials out there that make titanium look like junk you'd find on a Target bike. But I don't understand why people argue about these things. Don't worry about material choice until you are designing your own bike. Until then, just look at which frames last the longest and weigh the least. Those are the frames you want. Because a broken frame is a broken frame, whether it be aluminum, aermet, 6al-4v titanium, lead, 4340 steel, or play-doh... And the same thing goes for a light frame.

http://en.wikipedia.org/wiki/Maraging_steel

http://en.wikipedia.org/wiki/Aermet

http://en.wikipedia.org/wiki/Beryllium

[Jason222]

My god, anyone who's taken high school chemistry could tell you that Carbon is lighter than aluminum, or that titanium is heavier than aluminum. It's the amount of material used that matters more. Titanium is often considered in lightweight parts because you don't need to use as much of it to produce the same result. Titanium is much stronger than aluminum, so a much thinner tubing can be used, and lighter components can be made, even if base titanium is heavier than aluminum.

Edited January 11, 2010 by Jason222

[monkeyseemonkeydo]

Oh please, listening to all these poor folk talk about their wussy titanium-this, aluminum that. Don't you know the real pros ride beryllium frames? They're just careful not to scratch them, and ride in well-ventilated areas. When I don't feel like pulling out my beryllium comp bike, I practice on my junky old maraging steel frame with Aermet axles and bottom bracket.

Pah! You can keep your beryllium comp bike. I had Pete Wright make me a frame from Unobtainium a couple of years back which was filled with helium...

[aener]

f**k you all.

I got mine made in adamantium.

[Matt Burrows]

f**k you all.

I got mine made in adamantium.

Haha I was thinking of adding ium to my Adamant, I'm sure it is actually indestructable as far as trials use is concerned. I once cracked an old Echo pure (the really strong ones with seats) in half the time I rode my Adamant for

[Dr.scratchensniff]

Pah! You can keep your beryllium comp bike. I had Pete Wright make me a frame from Unobtainium a couple of years back which was filled with helium...

Was it mined from a forest moon called Pandora?

[Monty99]

F:

We have only one hope, Mr. President.

We must encase the entire planet in a protective sphere

of my patented ultra hard Dimondium!

W:

Dimondium? Fe! I can gum through through that with my dentures behind my back.

My trademark Dimondilium is twice as hard!

F:

Twice as hard is your head.

Which makes it still fairly soft.