In praise of titanium - and Spa Cycles

[jowwy]

I hate using this one because it smacks of call to authority, but if ti was so great why aren't the pro's using it? I'll redeem myself for asking it because I think I have answered that question adequately.

Prof, have you done the design-a-pen mind experiment yet? What is your chosen material?

In 1999 lance armstrong used a titanium time trial bike in the tour de france, it was a litespeed blade, badged up as a trek

 

[Yellow Saddle]

In 1999 lance armstrong used a titanium time trial bike in the tour de france, it was a litespeed blade, badged up as a trek

Present tense Jowwers, present tense.

 

[Profpointy]

Ok, I'll try again. Here goes.

Weak (Alu), Strong (Ti), Very Strong (Steel).
Light (Alu), Mediium light (Ti), Heavy (Steel).

So your original half-as-strong, twice as light thing - wasn't intended to be proper numbers, just stronger / heavier (not quibbling, just trying to be clear)

so, which is strongest for a given weight - surely that's the key thing isn't it

(with strength meaning that combination of strength-related good characteristics for a given purposes)

 

[Smurfy]

I am not sure what your point is but I would not quote a magazine that writes this type of tripe.:

"The Excel quickly picks up speed and takes little encouragement to accelerate to cruising pace, from where it rolls along with ease, responding readily to extra pressure on the pedals."

Or this corker: "
Strength has never been a concern with titanium (it’s tough as nails) but the increased strength and stiffness of 6Al-4V means Enigma have been able ...."

Nails are not tough when talking in engineering terms, so this frame is made from soft stuff. Or they're lying...or, the irony of the metaphor escapes them.
Anyway, bicycle magazines are very poor sources of science education.

My point is that you were incorrect when you said most Ti bikes are made from 6Al-4V. You may not agree with everything that the article I linked to said, but if you were to compile a list of Ti frames, I'm pretty sure you'd find that very few are made from 6Al-4V.

No, can you? Noddy Badge for you then.

No, but I wasn't the one who tried to claim that the use of lugs in steel frames had 'sorted out crack propagation issues'.

Most, if not all, mass produced steel frames are now welded, same as Ti frames. So how do these frames function without cracking?

 

[Pale Rider]

Seems to me the best evidence we have is that, weight for weight, titanium is roughly twice as strong as steel - for a bike frame.

This enables a frame builder to use a bit less of it, although welding and extrusion problems lessen the weight advantage to less than double.

Result is a lighter than steel frame, but one with similar riding properties.

If cost can ever be left aside, titanium looks a good choice to me.

 

[jowwy]

Present tense Jowwers, present tense.

Why present tense, titanium has been used in professional bike racing FACT.......

 

[Yellow Saddle]

So your original half-as-strong, twice as light thing - wasn't intended to be proper numbers, just stronger / heavier (not quibbling, just trying to be clear)

so, which is strongest for a given weight - surely that's the key thing isn't it

(with strength meaning that combination of strength-related good characteristics for a given purposes)

Strength is such a difficult word that I just don't even want to attempt the answer unless you give me a very specific example and a bicycle frame is not a specific example.

Material strength is measured in different ways. Basically, we measure pull strength (tensile), push strength (compression) and shear (hold your two fists together clutching a banana. Now move your right fist forward whilst holding the left fist in its original position. This is shear). A high one in one area doesn't mean a high one elsewhere. Then, we get structural strength that has little to do with the material and more with the shape of the material. A long piece of copper sheet cannot be picked up like a fishing rod. It will flop. A copper pipe make from the exact same piece of sheet, will even work as a fishing rod. Here we say the one structure is stronger than the other.
The same for twisting forces. a pipe transmits twisting forces better than a flat sheet from the same metal. In fact, bang the pipe flat and it transform into a poor twisting force transmitter.
Then we have fatigue properties. An item may be very strong but it can only bend twice before it breaks. High strength, low durability.
Then we have mixed strength properties. A biscuit is stiff but brittle.
Other items are tough, yet another property.
Some items become tougher, the more you bang on them - copper and titanium are two excellent examples of materials that work-harden.
Some materials crack very easily if there are pre-existent flaws in them. Here ti is suspect because it gets flaws from manufacturing which cannot be seen and only surface with use.
Some materials crack and allow the crack to travel very quickly. Think windscreens on your car or the material that potato crisps are made from. If you manage to open the package without nicking the edge, you can be sure that the packet will survive until the crisps are finished. But nick that same packet and it will be torn right to the bottom before you are finished.
Many of these "strengths" depends on how the item was designed and manufactured. Search here for a recent post on Specialized pedal extenders. There the design is at fault by 100%. The gadget was made from CroMo steel (strong stuff) but a schoolboy design error make it lethal.

So yes, I did not quote proper numbers and even warned that "strength" is an illusive concept.

If you force me into a corner and hit me on the nose until I give you a single answer, then it has to be carbon.

 

[PhilDawson8270]

I have seen a test done by Jobst Brandt with various tyres rolling on a steel drum and the test confirmed that for a given tyre casing design, wider has less rolling resistance. The test also showed that inflating a tyre harder does reduce rolling resistance (we knew that) but that it is a case of diminishing returns. At 10 Bar you may as well chew rocks, the tyre is so hard that it is uncomfortable but it doesn't improve RR.

BTW, it is not so much the deformation from inflation that produces the rolling resistance but the hysteresis in the casing. For the same deformation but different casing design you will get different RR values. I just wanted to define "deformation". It is the deformation in the rubber and flex in casing material that matters. .

Here is a good source on Rolling Friction.

http://rstl.royalsocietypublishing.org/content/166/155.full.pdf

It includes a good example of leading edge deformation, and other factors. Though with rollers and belts, the same principles apply, especially from page 5 onwards.

 

[Yellow Saddle]

My point is that you were incorrect when you said most Ti bikes are made from 6Al-4V. You may not agree with everything that the article I linked to said, but if you were to compile a list of Ti frames, I'm pretty sure you'd find that very few are made from 6Al-4V.


No, but I wasn't the one who tried to claim that the use of lugs in steel frames had 'sorted out crack propagation issues'.

Most, if not all, mass produced steel frames are now welded, same as Ti frames. So how do these frames function without cracking?

Why should I believe the article? Why do you believe it? Do you see a source quoted anywhere? My argument is based on the fact that most structural titanium is of a specific type. It is the industry's bread-and-butter alloy.

Further, who said that welded steel frames do not suffer from cracks? I certainly didn't, but I do understand the role of lugs and how they are fitted to frame tubes and how working with them avoids exceeding the heat limits of CroMo steel.

But I guess for every answer you'll have another question, like a child of certain age.

 

[Citius]

Wow - this is like two or three different threads all rolled into one

Litespeed and Merlin Ti frames have been used for signature mountain stages in the TdF (and probably other tours too) on a few occasions during the 90s - but these have always been painted up in whatever colours the team was sponsored by. As I understand it, Ti was used mainly for its weight advantage over the lugged steel frames of the day - but because in those days Ti frames were bendy as hell, I don't think they were considered as options for anything other than climbing.

Most teams went from steel frames, to MMC frames and then on to carbon. Literally a handful of riders have used Ti over the years.

 

[Yellow Saddle]

Here is a good source on Rolling Friction.

http://rstl.royalsocietypublishing.org/content/166/155.full.pdf

It includes a good example of leading edge deformation, and other factors. Though with rollers and belts, the same principles apply, especially from page 5 onwards.

Thanks, I'll have a look. the document doesn't want to open on my computer. I think BT Internet is dedicating neighbouhood bandwidth to iPlayer at present. The is a very good simulation on leading edge formation on Youtube. I saw it just a few weeks ago but can't remember who/what/where.

 

[jowwy]

Magnus Backstedt won Paris Roubaix in 2004 on a Ti frame and was riding a Ti frame at least as late as 2006.

At his height, Bianchi didn't have a CF frame that he liked and worked form him.

It was cheaper for Bianchi to custom build a Ti bike for him than make a new mold for a one off CF bike.

 

[Yellow Saddle]

Ti is more emotive than wheels, it seems.

I recently wrote about my perspective of the mystic allure of Ti here: https://www.cyclechat.net/threads/environmental-impact-of-frame-materials.182803/#post-3770333

I would like some fleshing out on my take of the rise of Ti as a consumer metal of choice. Can you list other events that glorified titanium?

 

[PhilDawson8270]

Thanks, I'll have a look. the document doesn't want to open on my computer. I think BT Internet is dedicating neighbouhood bandwidth to iPlayer at present. The is a very good simulation on leading edge formation on Youtube. I saw it just a few weeks ago but can't remember who/what/where.

It was a little slow to open for me.

A heavy, but interesting read. Rolling resistance is quite complicated, and more than likely beyond the scope of a cycling forum for discussion

 

[Yellow Saddle]

Here is a good source on Rolling Friction.

http://rstl.royalsocietypublishing.org/content/166/155.full.pdf

It includes a good example of leading edge deformation, and other factors. Though with rollers and belts, the same principles apply, especially from page 5 onwards.

Thanks, got it. I started reading and the found some old-fashioned words like India Rubber. I scrolled back up and saw 1875. Now I am super-intrigued but will look at it in the morning. Thanks.