Well you pretty much agreed with the original arguement I was making, which was Making complex shapes out oif Ti isn't impossible, just that C is easier.


As far as Al vs Ti for a custom builder it comes down to welding al isn't any easier than Ti, Ti frames aren't heat treated after building, Aluminum frames must be heat treated (with few exceptions), and heat treating Al frames is very difficult without warping occuring. Also you have to paint Aluminum or anodize it if you want any kind of life out of it.

I'm not sure of your background but I've consulted with well over 200 metalworking plants. A lot of this is outside my area of expertise but I've got lots of exposure to the various operations.

Styrrell

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Styrrell

Cracked a TTX frame after 1 year and told myself I would not go through that again with carbon - so I Ebay'd the replacement frame and bought a Guru Merus Ti frame for $3k (discontinued in 2010) and have put 3 years of heavy miles on it - still good as new - and it is unique when I roll up on it... which I like.

Same here. I have owned Alum, Titanium, Steel and Carbon bikes - all made by the same manufacturer (Colnago) and all in the same size (56) and with the same components. Hence I was able to do a controlled experience with only the frame being the variable. I did this for many years over many types of roads, races and various conditions.

The sweetest, bestest, finest frame I had amongst all of them was the Master Extra Light steel frame. That thing rode like a dream. It was the heaviest but the ride quality was excellent.


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Was the Ti frame the double down tube one? I've heard those were very nice, unfortunately they had a cracking problem. I knew a guy that bought one, got it right before winter, didn't ride it much until summer, then had it crack about 5 days and 500 miles after the warrantee ran out. Colnago didn't replace it.

Styrrell

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Styrrell

As far as the actual welding, Ti is actually easier to weld than Al -- the low thermal conductivity and high melting point means it's easy to get the heat just where you want it and you don't have to adjust so much as the piece warms up while laying a bead. Where it's tricky is that the backside of Ti welds should purged continuously with inert gas at the very minimum and ideally done in a complete argon atmosphere inside a glove box. Sure, you don't have to heat-treat it afterwards, but there are alloys used for Al frames (7005, for instance) that don't require post-weld heat treatment either.

Asad

Yeah I never got the welding arguement. Steel for a high perfromance bike wouldn't be a real treat to weld either just cause its so thin, but really steel should be brazed with nice lugs ;-)

Styrrell

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Styrrell

So for instance would you say a bike that looked like this would be impossble to make out of Ti?



Styrrell

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Styrrell

I am hearing lots of ill informed opinions here. Would love to hear how exactly a scratch weakens carbon fibre... Also don't tell me a scratch is a few mm deep as that isn't a scratch. You don't need 8 stiches in your arm if you scratch it do you??

Rocky M obviously knows about metal fab. Ti is not easy to weld and the welds are the weak point and around the wlelds in they over heat it.

I'll ping back on this one, once having worked in an aerospace shop that did a lot of Ti fabrication and welding a long time ago. Yeah, that would be a pretty hard shape to make. If you look at the aero tubes that Litespeed makes, they're either "smooshed" round tubes, or flat simple curves that can be made in a press brake. My understanding is that the high strength to Youngs modulus of ti makes it very hard to press complex compound curved shapes in dies - the amount you have to "overbend" it is not practical, or often geometrically possible, in a conventional die. A more common method of forming Ti parts in a die is "superplastic forming," where sheet titanium is heated up to high, but below melting, temperatures and pushed by inert gas pressure into a die. It's a slow process, though, sometimes taking hours (low utilization rates in expensive dies), and the dies have to be made of materials that can withstand 4-digit temperatures. So, you could make a bike similar to the one photographed with superplastically formed parts, but your tooling and production costs would be higher than CF.

As mentioned by others, Ti's big welding challenge is its sensitivity to oxygen or other contaminants, and maintaining a continuous purge, or welding in a glovebox, without contamination, is what makes Ti hard to weld. That, however, seems to be an issue that the cycling industry has already addressed successfully - it's a skill, not an insurmountable roadblock.

I have a hunch that the bike pictured below IS made of titanium.

but of course nothing is impossible.

the question is what does it cost, and how heavy is it? (weight is a low order consideration, but if its 25lbs...)

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If it is, it's made in the manner I described above, and is frightfully expensive. I'd guess that it is carbon, though.

Another consideration is that, with superplastic forming, you can't always control where the material thins out during the stretching. You may be able to predict it, but you can't necessarily control it, unless you machine the thickness of the sheet prior to its formation (and that gets even more frightfully expensive). You may end up using a sheet that is thick enough so the most stretched out area is sufficiently thick, but the rest of it is overbuilt.

That was made from carbon.

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Titanium all the way! I even have one of these in my aerodrinky thing!

http://www.thinkgeek.com/...office/kitchen/e59c/

Ti is an expensive raw material. More importantly it's a bitch to weld compared with steel or ali. This drives up the skill requirement (and therefore price) and also takes longer (drives up the price) and this gets it above a threshold which limits the numbers made, making it more expensive (development costs get spread over less bikes). Also, it can't easily (read cheaply) be made into complex (ie aero) shapes.

As for longevity, I'm not so sure. Cameron Brown used to ride LIghtspeed Ti frames and cracked them relatively regularly according to scuttle butt around these parts.

I used to Covet a 650C lightspeed Tachyon back in the day....but that was the same time a a "Slingshot" was on the list as well. Oh yeah, and a Softride........ Now I just want a P2 (Carbon, not the original P2) to replace my now aging ali P2K

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TriDork

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