Materials Science

This morning I serviced my race bike after riding the London 100 yesterday. Checking things over, I noticed that one of the titanium bottle cages had fractured.  I took it off, and ordered up a new one - it was a super-light component, after all.  But my curiosity was piqued, so I had a look to see what the internet had to say about it.  It turns out that the failure, while not common, is not unknown.  It's a stress fracture, caused by the tiny piece of titanium being incorrectly installed.  I know how to do it now, and I'll get it right next time.  But, for a bottle cage ...?

Anyway, this led me to take a look at some other bottle cages.  Here's the titanium one:

It's sitting on my workshop scales, and you can see the broken bit.  You can also see that it weighs 27 grammes, which is light, but significantly more than the 22 grammes that the manufacturer says it weighs.  I find this common enough with race parts - oddly, they rarely weigh less than claimed.

Next, I weighed a carbon fibre one.  The (Californian) manufacturer says that it is the 'strongest available' and that it weighs 28 grammes.  You will see that mine weighs 26 grammes.  I've used these for years and they have never given a problem.  The different construction method is also evident.  The titanium manufacturer has to leave bits off to keep the weight down; but carbon fibre is so light that the manufacturer can use more of it.  The construction method is entirely different, and carbon fibre has its own requirements for successful use.  But, generally, I just screw these on and forget them.

For completeness, I put a stainless steel one on the scales too.  This is genuine bomber kit.  I was recommended to use it for Paris-Roubaix, as most race teams do, and it was perfect.  But, as you see, it's double the weight.  You can only use so much of this level of robustness on your bike.

So, what have I learned from all this?  Well, I know how to fit a piece of titanium without stressing it, which is handy.  And I've learned that carbon fibre is lighter, which is hardly a breakthrough for mankind.  

But, all round, I just though it was kind of interesting, hence the note.

Mark