I will do Science to it

It takes a big person to use a power meter, which isn't to say that you need to have legs like Sir Chris Hoy to benefit from training with one. Rather, it is a reflection of yourself that is too true to be beautiful. Whatever ambitions and dreams you may have about your potential are leadenly anchored by numbers on a screen, often lower than you would hope.

I am borrowing a powertap wheel from a friend, and using it has been both informative and slightly disappointing, though its use as a training tool can hardly be overstated. I would be curious to compare the difference in times over time-trials from riders with power meters compared with aerodynamic wheels, because I suspect that simple knowledge of your effort would allow you to outperform even your best unmetered attempts.

As well as the training benefits, using a power meter has allowed me to check something that I had been wondering about for a long time - the accuracy of Strava power estimate. With the wheel on, I rode my standard loop and compared the measured power over segments with the two bracketing calculated values. Here's what I found:

Speed (low)	Power	%diff	Speed (measured)	Power	Speed (high)	Power	%diff
Climbs
34.5	280	-14.6	34.8	328	35.1	299	-8.8
28.3	263	-12.6	28.3	301	28.4	259	-14.0
Flats/rolling
34.4	206	-12.7	35	236	35	228	-3.4
34.1	196	-31.2	34.6	285	34.6	203	-28.8
34.9	215	-23.8	35.3	282	35.3	197	-30.1
35.6	242	-18.0	35.9	295	37.6	286	-3.1
Overall
32.4	214	-24.4	32.9	283	34.3	227	-19.8

Huh. So, basically, on climbs, Strava underestimates power, usually on the order of 10%. On the flats, though, it can be anywhere from 3% to 30%! The overall estimation was low by more than 20%.

Ok, so this isn't exactly science - more evidence is required. Nevertheless, I think I have showed 2 things:

1) You can't train with Strava

2) Strava tends to underestimate power.

Good trails!

On Adjusting Expectations

Reporting from here in Scotland, I can relay, to the surprise of precisely no-one, that the winter is long.

It's getting to that stage now where I'm starting to feel like we should be out of it already. On the weekends, almost unbidden, I am finding my pedals mysteriously attached to my race bike. My legs scream for light and air, and so endure being smeared with embro' for the merest semblance of summer riding. I push hard - not just for training, but because I am barely wearing enough layers to stay warm for ten minutes stationary.

It seems mad, sometimes. The work; the time; the effort put in over the off-season. For five months of the year we prepare for the next seven - the "good" seven. All of these non-rides - the city-centre commuting, the long nights of base training, the quick blasts to test out the bike - don't seem to count towards the legendary "good days", where the miles tick by under a warming sun, or where you're tooth by jowl with a jostling pack of enthusiastic racers, or where you can stop and sit out in the sun and feel without looking which panels of your kit are black and which are white.

If there are any blessings to a long winter, it is that it encourages you to stay true to a training plan. When the options for training are unstructured hill repeats up and down a pitch black hillside versus sitting for an hour in a temperature-controlled room with a heart rate monitor and a laptop stuck on an online stopwatch, the scientific approach seems most appealing to me.

Which isn't to say that it's easy. I have been following a back-to-back interval day plan by Chris Carmichael, and whilst I cannot yet give results to vouch for its efficacy, it certainly does the job of making me utterly, pathetically knackered.

The short duration of intervals makes starting easy - there are hardly any excuses not to do them if you are only going to be on the turbo for an hour - but the intensity also makes those durations the longest possible time you can imagine.

Earplugs in both sides to drown out the drone of the turbo trainer are the only distraction from the task at hand. At the end of the fourth of seven sprints, my eyes are squeezed shut, my brain searching through my legs for a single patch of muscle fibres not screaming from the effort, then switching my position slightly to force them to fire. In left and right ear it's Bad Religion:

I look for inner wealth,
By punishing myself.

It's gut-wrenching, vicious stuff. Every time I open my eyes and glance at the clock, there are fractions in my mind.

Fifteen more seconds. Three-quarters of the way there on the fourth sprint of seven. Once I'm done I'll be over half way through this block. And there's only three blocks. So I'm already over one sixth done.

For the longer-durations, it gets more and more complex, as I set out the minute markers that signal the end of one phase and the start of another. For all the dullness and repetition, I cannot afford to let my mind wander, or else my efforts will follow it. The furthest I can go is to a race, or a dream. To holding more than 450 Watts towards Hampton Court Palace. To jumping up on the pedals and dancing to the top of the Angliru.

The delusions sink in, somewhat. The winter has been long - I believe I may have mentioned that - and it has been even longer since I raced. I want to believe that a metamorphosis is being undertaken, that these long hours will result in something wholly unrecognisable once I get back onto the road.

I should stop asking for miracles.

The plan suggests that Saturdays can be used for crit'-pace rides, which I tend to take as liberty to time-trial or climb or otherwise test myself. Every time, I go out with the idea in my head that I will now, somehow, be unbeatable. That I will have trained myself into a state better than I ever have been, fitter and lighter than the best of my best. It is, of course, a wholly preposterous idea.

Looking at things logically, I am still midway through my first real training block of the year - I have put barely six weeks of true, race-preparation effort in. I still haven't done any real climbing work, and I have a kilogram or two to lose to get to race weight. The idea that I would, at this stage, be better than my best last year, after all the work I had put in then, is an unintentional slight on my past self, and completely unreasonable. Benefits come after training, after all, rather than during.

Yet still, I desire for my performance to saltate. Looking back on how I have developed over the last two years (as this blog very handily allows me to do), I can see the massive steps that I have taken.

But this is just time being compressed by paucity of information and uninteresting memory. At least I have the time stamps to confirm what I know - that between those posts, days, weeks and months went by where I worked, and worked hard, at becoming a better rider. Not all of it was fitness work - some of it was very necessary rest and kidding around - but it was all part of building up who I am and making me proud of what I have achieved.

So I'll carry on, and I won't take my disappointments too seriously. It's a long winter, but there'll be days, soon. Good days.

Stealth Cycling

It may surprise some reading this, but I wasn't always happy being a cyclist. I loved cycling, but appearing as one of those (as I saw) aloof, self-regarding masochists - a road cyclist - was something I made every effort to avoid. This was made easier by my starting out in mountain biking, where the lycra tends to be hidden underneath more durable layers and the shoes remain useful when you get to where you're going.

Say what you like about road cycling, full race kit makes it difficult to actually ride anywhere. You can't carry enough layers to keep you warm when you stop; wearing nothing but a layer of tight-fitting fabric around your nether regions doesn't present a view you want to share too much; and, most importantly, the shoes are lethal. Before I had any interest in cycling as a fitness tool and recreational activity, and surely long after, I saw (see) cycling as a method to get from place to place. When I got to my destination, I would then want to do whatever I came there to do without looking or feeling like a cyclist. I still cycle to work every day, and I wear normal clothes.

The point that I am slowly coming to is that I've felt, from the beginning, that most cycling should not require "looking" like a cyclist - especially not once you get to your destination. Thus, "dual-mode" clothing has always interested me.

High vis is good on a bike. It's not great - it's not attractive, and that's a reasonable consideration. I work in an industry that clashes with people's aesthetic tastes daily, and to dismiss the desire for the world to look pleasing is to give up any attempt to engage with one of our most important stakeholders. Intuitively, making things beautiful is worthwhile because it provides "free" pleasure. Despite this, high-visibility clothing is a useful enough an "attention-grabber" to be worthwhile using on a bicycle on public roads. Today, anyway.

As soon as you're off the bike, though, it looks daft.

With this in mind, I made a few "modifications" to some of my kit. Whilst I'd only be the last word in fashion if my appearance actively drove away the audience, I think they work quite well.

Pedal reflectors work well, because they're dynamically moving lights. The more dynamic lights you can have, the better off you are. Hence reflective trouser clips.

But these are naff.

As any good urban cyclist - and the good Sir Chris Hoy - will demonstrate, the only appropriate method for keeping one's cuffs out of the drive train when the weather is within your tolerance is to roll up your trouser leg. Rapha is well aware of this, with highlights and branding on the inside of the leg. But you don't need to pay over a hundred pounds to get a pair of cycling-specific jeans.

Hi-vis vests are cheap, commonly available from pound shops, and they have several strips of a certain highly reflective tape on them - probably made by a certain American chemical company that is so large that its only close competitor in the field of tape-backed artificial products is Simon Cowell. 

Pulling this tape off and sewing it onto the outside leg seam on any pair of jeans makes an instant reciprocating reflector that is entirely hidden when the jeans are rolled down. Stealthy!

You may notice that my stitching is, to use the technical term, naff. This is for several reasons:
1) I am lazy
2) I am no good at sewing
3) I forgot to check which side was reflective, so this is actually my second attempt, so I was bored
4) I plan to go over it later with fabric glue, otherwise known as "the friend with a sewing machine for people who don't have any friends with sewing machines."

From the same vest, I made some modifications to my rucksack. Just throwing a vest over your rucksack is effective, but looks unbelievably naff, so I put a bit of thought into this one.

I put a strip of reflective tape onto the back, to shine back whenever I'm sat up at lights. Most of the rest of the vest I sewed onto the bottom of the bag, so that when I'm pedalling with my backside in the air, it's visible, but walking around during the day it's pretty discrete. It's stood up ok over the past year and a bit, but my poor stitching needs replacing now.

Finally, something not for me, but for the bike. As we all know, bike-mounted lock holders are the work of the devil, destroying the lines of the bike, but what are you supposed to do when you need to carry your U-lock, but don't need a bag?

Well, any urban cyclist worth his salt will tell you that you stick it in your belt. But you have to lock it on to be secure, and it stresses the belt loops. What can you do?

Holster.

You can buy these, but what's the need when you can make one yourself? All you need are a few strips of unstretchable fabric.

If you're like me, you'll have a good few pairs of jeans with crotches worn out by saddle time. Even if you're able to fix them, you'll always have one that you're using to take patches from.

Sew the strips around the lock, close enough that it can't slip through, and put a couple of belt loops on the back. Bob's your uncle.

You can buy equivalents of all of these ideas (although I don't know of any rucksacks that limit their high-vis to the underside), but what's the need when you can mod it yourself?

So there you go. Just remember the golden rule: As with single-speeds, it's not hipster if you've Done It Yourself.

Carbon Fibre's Carbon Footprint

I've been meaning to do this one for a while, but I'm afraid that I don't have any real answers for you (or me) yet. I wanted to answer the question: "What is a carbon fibre bicycle's carbon footprint?" under the conditions of me buying a new carbon fibre bicycle and riding it, using similar approximations to my estimates about metal bikes: http://towalestwowheels.blogspot.co.uk/2011/06/low-impact-riding.html

It's not that simple, though.

First of all, I cannot find any data for the lifecycle carbon emissions of carbon fibre composite, even from my old, faithful source, the Bath University Inventory of Carbon & Energy. The best I can do is Glass Reinforced Plastic - GRP - which, at 8.10 kg CO2e/kg of material, is better than virgin aluminium, but carbon fibre cannot come from a recycled source for a large component (frame, fork, wheel, crankset... pretty much anything other than a bottle holder), so I would expect the composite bike to come out worse overall. More importantly, though, working off this number ignores how difficult carbon fibre is to produce compared to glass fibre.

I should probably give a quick explanation about what a fibre composite material is, for those who don't know.

Glasses and ceramics can be pretty strong. Think about the portholes and viewing domes on submersibles - they are under enormous pressures, yet barely compress at all. The downside of that rigidity is that if you do try to bend them, they tend to crack and break, very suddenly.

To overcome this, we can make these brittle glasses and ceramics into fibres. This does several things - primarily, it aligns the crystals of the structure along the fibre (especially with carbon); secondarily, by placing fibres side be side instead of in one homogeneous structure, if there is a defect in one of the fibres, it shall not propagate through the whole structure.

These fibres tend to be very strong in tension, but obviously, when compressed, they buckle. To hold them together, we need to put them in a "matrix" - a bonding material. This is typically something like epoxy resin, and the resulting material is a "composite" of the fibre and matrix. Steel-reinforced concrete is a large-scale fibre composite material.

As mentioned, the fibres tend to be very strong in tension along the axis that they are aligned. To obtain strength in other directions, we bond layers of composite one on top of the other, with the plies of the fibres in different directions.

The balance between the ratio of fibre to matrix, and the diameter of the individual fibres, also affects the mechanical properties of the resulting material, notably affecting the ratio of its tensile, compressive and shear strength, as well as how brittle the overall material is. I'll come back to this later.

Ok, so there's your primer. So how close is glass fibre composite, in manufacturing, to carbon fibre composite?

Glass fibres are made by melting (primarily) silica glass beads (marbles) at approximately 1250 degrees C, which gravity feeds through a sort of strainer and gets pulled into a strand.

So, glass needs to get pretty hot, right?

Not compared to graphite.

There are a few different type of carbon fibres, but one process for structural-grade graphite fibres is the polyacrylonitrile (PAN) process. This starts with a reel of PAN fibres, run it through a controlled oxidisation furnace at 250 degrees C, then into a pyrolysis furnace to drive off any non-carbon atoms at 250 degrees to 1500 degrees, and finally a graphitization furnace to draw out those crystals which warms the strand from 1500 degrees to a whopping 2500 degrees C. Yes, that is considerably more than the melting point of most (if not all?) steels.[1]

So carbon is a totally different animal to glass.

What about the other end of its life, then? What about recycling?

Well, that's actually been pretty well covered in the cycling press. Most large manufacturers offer some form of carbon composite recycling, with Specialized even offering to take in frames from manufacturers who aren't running their own schemes. However, it's not a panacea. Here's a thoughtfully-written piece on the issue:

http://www.redorbit.com/news/science/1112493049/the-dirty-secret-of-carbon-fiber/

I do wish, however, to come up with a slight rejoinder to some of Peter Suciu's closing remarks, where he claims that carbon fibre takes some of the artistry out of design and production.

In my opinion, this is utterly incorrect.

The argument is that 3D CAD design and 3D printing takes humans out of the loop. In reality, we are taking about being out of the loop on things we never really had a say in anyway. How many bike builders cast their own lugs, let alone draw their own tubes? If anything, fibre composites give us more control over the design and feel of our bikes - and it is certainly a lot easier to make a bad one. Invisible things like layout and fibre choice make almost continuous differences, as opposed to the very discrete options of alloy and tube diameter. The laying of "pre-preg" plies or even (as I believe occurs for Look) individual fibre layup is an incredibly taxing job, requiring high dexterity and attention to detail. Manufacturing the moulds alone is a high-precision task, and developing new ways of keeping the internal surfaces of carbon fibre objects "clean" has been one of the major areas of innovation for the bicycle industry over the past few years.

Carbon fibre certainly hasn't taken the human out of the loop. If anything, it is its necessity for hand-layup that has caused so many manufacturers to outsource production to the far east. The design is now more intricate than ever, but based on invisible properties such as durability and stiffness. There will come a day when you can be an artisan carbon-fibre manufacturer - when there is a standard set of lay-ups, moulds and mandrels to iterate on without worrying that your tinkering is going to ruin the ride. Until then, fibre based composites are still an exciting engineering challenge.

I feel I should draw this post back together, as responding to that article has drawn it off-course somewhat.

I cannot guess the carbon impact of a carbon-fibre bicycle, but I have good reason to believe, based off of the GRP values and the relative energy intensity of carbon fibre as well as its inability to be recycled in long strands, that it would be more carbon-intensive than an aluminium bicycle, and therefore than a steel bicycle.

On the other hand, a well-made carbon-fibre bicycle could conceivably outlive an aluminium one, assuming that it is well-sealed. So don't feel too bad.

At least it's not titanium...


[1] Composite Materials for Aircraft Structures (1986); Brian C Hoskin & Alan A. Baker; AIAA Education series,  Washington DC