Aero wheels for a small light rider

Fukawitribe writes:

Carbon

Fukawitribe writes:

Carbon fibre composite structures can support relatively high degrees of
deflection without failing or inducing permanent deformation.

What structures though? I used the example of a simple tube, assuming the lay
up of the fibres would be in-line with maximal stress.

How about a link to the description of such a structure and it’s mechanical
properties? I know it’s such a hassle to back up baldly stated facts, I seem
to be the only one on here who does.

From what I read on that site, carbon fibre’s mechanical properties are
directional. Whilst you could in theory make a bendy carbon fibre composite by
not using the directional properties of the fibre and instead rely on the
properties of the matrix instead, to quote from the article I gave you a
link to, that wouldn’t make sense (why use a strong material and then not make
use of that property?) and in practice:

Because of the way the crystals of carbon fibre orient in long flat ribbon or narrow sheets of honeycomb crystals, the strength is higher running lengthwise than across the fibre. That is why designers of carbon fibre objects specify the direction the fibre should be laid to maximize strength and rigidity in a specific direction. The fibre being aligned with the direction of greatest stress.

And later under the heading: Carbon Fibers are brittle:

When the fibers bend they fails at very low strain. In other words carbon
fibre does not bend much before failing.

You suspect wrongly.

This is getting tiresome: to the next muppet who doesn’t supply any links,
from now on I wont bother replying.

Frank, I’ve been called many
Frank, I’ve been called many things (quite a few of them by you actually) but never before a mechanical engineer. I am a Civil Engineer, MICE. Amongst other things I have experience of structural design.
I’m not sure the whistle stop tour of the profession was of wide interest :B suffice to say that these days engineering attracts rounded people with soft skills and indeed an increasing number of women – current graduates never cease to impress me with their confidence and communication skills.
Now, for the sake of all our sanity and diminishing reputations lets put this to bed shall we?
N.

…and Frank, how about a

…and Frank, how about a link to the stiffness tests that lead to your conclusion, you naughty engineer?

FYI, I’m not an engineer. I only studied mech/man engineering a long time ago
and I know that I’ve forgotten a lot of it. I didn’t finish my course, for
various reasons, hence I hold no qualifications and haven’t worked as an
engineer. I ended up doing a Dip.Comp. which I got and drifted into IT. I do
however remember enough that I can bone up on it, if I need to.

As for the guys who have posted here who have got qualifications in
engineering. The guy who is chartered, a CEng, IIRC it was Nixster, he will
have gone to university got his BEng/MEng, got a job practising as an engineer
whilst simultaneously working towards his professional examinations with his
Institute. IIRC he’s a mech eng so his institute would be IMechE: the
institute of mechanical engineers. Whilst working towards getting chartered,
he would have been guided by somebody who’s already a CEng. I believe this
takes a few years. Then if he passes his professional exams he becomes
chartered and becomes a full member of IMechE and has every entitlement to
call himself an “engineer”. With becoming a CEng comes considerable
professional prestige but also responsibilities. For instance, if you’re
significantly negligent in anyway, you face getting kicked out of your
institute. Not good, you’re then professionally doomed. For instance, if
you’re a chartered civil engineer and the bridge who’s design and construction
you oversaw was to fall down because you fouled up: that’s the end of your
career.

CEng’s are very much in demand. Because they are chartered they can do stuff
engineers who are not chartered can’t and are consequently paid more. It is not
at all unusual for CEng’s to become directors of their company, like Nixster.

CEng’s and even those who aren’t chartered, are held in more respect in
some countries. I believe that in France, for instance, they are held in high
regard and social status. Not so much in this country. I don’t know why this
is.

The other guy who posted who had a BEng and MSc and worked in aerospace, isn’t
chartered or he didn’t mention that he was. He didn’t get chartered for
whatever reason; possibly because his career path didn’t allow it. If he does
any safety critical work, he would have to be overseen by a CEng and to get
his work “signed-off”. So my comment about not flying anymore was done
with tongue firmly in cheek.

This is how I remember it being many years ago. But things might have changed.

In IT for instance, you get guys who like to call themselves “software
engineers” and such like. They are no more an engineer than my dustman. They
might have a degree in Comp.Sci but not necessarily so, they don’t have a
professional institute and therefore don’t have any professional development.
Because of this, they can range from good to atrocious.

I thought I’d post about engineering as a profession even though it’s OT
because it’s poorly understood by those who aren’t in the profession. I’m sure
Nixster for instance, has had occasions where people have asked him what he
does and when he’s told them “mechanical engineer” they’ve thought he carries
a spanner and works fixing car engines.

freebsd_frank wrote:Carbon

freebsd_frank wrote:

Carbon fibre composite whilst strong, with the caveats above, is brittle.
It will fail before it has deflected to any extent, like glass.

Those are some of the properties of carbon fibre composites.

Carbon fibre composite structures can support relatively high degrees of deflection without failing or inducing permanent deformation.

freebsd_frank wrote:

There are various grades of carbon fibre composite. I suspect (although I
don’t know) is that the only important property that differs is that some
grades are stronger (ie. have higher UTS and E) than others and they use the
stronger (and probably) more expensive grades for more expensive frames.

You suspect wrongly.

Firstly, not that it really

Firstly, not that it really matters, but I’m a she not a he.

My apologies, it didn’t occur to me that you are of the fairer sex.
I thought when you posted: “Crikey, he’s bit of a weed; better not refer to it,
he’s bound to have issues with it”!

As you say, your sex doesn’t matter but I’m glad you, as a woman, have taken
up the sport/hobby: not enough have, IMO. You’ll act as an example which
hopefully your girlfriends will follow.

Secondly, I did not acknowledge his help because I am a brown-noser and a
lickspittle, whatever that is.

I’m sorry, I mistakenly thought you were a regular poster and if I’d known you
were a woman, I wouldn’t have abused you in the way that I did. I know that
probably doesn’t make any sense to you and it’s a poor justification but I’m of an age where such behaviour
was beyond the pale. Men on the other hand, I consider fair game. Sexist
nonsense but there it is. We are what we are.

You can take this however you want but I do triathlon and a small part of the appeal is all the shiny new bits of gear you can get, wheels included. I completely appreciate your view that I shouldn’t waste money on something that will not benefit me. I also take on board your comment of “I’m sorry, you’re just going to have to train harder”. I am not expecting any wheels to do the work for me. But – and this could be a complete coincidence – as mentioned, at the weekend I had aero wheels on my bike and I felt faster and it felt easier. I have a bit of spare money that I had set aside for an upgrade on my bike and this is where I have chosen to spend it.

I completely understand where you’re coming from, cycling is much more than
dry facts and figures and technical details. A large part of it is psychology:
I know, though I’ve never raced, that some days I fly and others I can barely
turn over the cranks.

As you will have noticed, I tend to come from things from an engineering
perspective and you kindly thanked me for my views. If you think that your
wheels will make you faster and you can afford the money: go for it. I can’t
give any opinions whether brand x is better than brand y; I’d guess that for
the amount you’re spending, you’re likely to get yourself a decent set of
wheels whichever reputable brand you go for. I would, like I think I said, use
a cheaper more robust pair for training; so if you trash them you’re not so
much out of pocket.

You’ve mentioned a few times that buying into carbon wheels seems to be some kind of fashion choice. Maybe it is. I’m pretty sure buying a helmet that matches the colour scheme of my bike isn’t going to improve my performance but it does look better.

A large part of my original post’s purpose was to save you money. I don’t want
people reading this forum to think that they need expensive gear. You don’t
and it’s not as easy as equating “more expensive” equals “better”. Often it is
but it’s not always true.

BTW, the person who first posted a reply, IIRC, gave an informative link to the
opinions of an aerodynamics engineer with regards to aero gear which will make
you faster. He listed a variety of things: aero helmets, skinsuits etc. but he
didn’t mention aero wheels. That suggests to me that he thinks the gear he
lists gives you a greater advantage than aero wheels.

Maybe you could buy some of the gear he suggests with your next purchase.

All the best, happy cycling and I hope you win your next triathlon (with your
new go-faster wheels)!

Very stiff and Planet X Pro
Very stiff and Planet X Pro Carbon are not often seen in the same sentence. Lovely bikes, but not renowned for their stiffness…

…and Frank, how about a link to the stiffness tests that lead to your conclusion, you naughty engineer?

Meh, working tomorrow…
Meh, working tomorrow…