Archive for the ‘Aerodynamics’ Category

Higher education on two wheels

27/04/2015

If you’ve not heard of the Faculty of Science and Engineering at the University of Chester, you have now. It’s new, fast-moving and extremely welcoming.

What’s it got to do with cycling science? Well, the powers that be at the Faculty have their fingers on the pulse and recognise that cycling is blossoming.

So they invited me to lead a cycling science ride at the weekend, an initiative generously supported by CWAC/iTravel.Under the railway bridge

That’s why a group of people could be found in a back lane near the River Dee, discussing the functions, materials and dimensions of that most under-rated component, the spoke.

Tangential, radial, three-cross, four-cross, bladed, steel, aluminium, carbon – all the little niceties were discussed vigorously.

One of the cyclists realised for the first time that the front wheel he’d been using for more than a year has lovely radial spokes – and why his rear wheel doesn’t.

To cap it all, another rider, an information systems expert of course, had a tuning app on her smartphone so we could demonstrate to any doubters that it’s the tension in the wire spoke that keeps the wheel together.

Fact: knowledge keeps the legs warm

Fact: knowledge keeps the legs warm

The weight of a general practitioner, who volunteered innocently, bearing down on the axle was then shown to be enough to reduce the frequency of the lowermost spoke by half a tone.

Elsewhere on the ride, along Chester’s glorious Greenway, the effects of rolling resistance were demonstrated by putting some air in the tyres on which an esteemed chemical engineer usually rides almost totally flat.

Human balance, steering, the self-stable dynamics of a bicycle, aerodynamics and how to hover simply by pedalling hard (and building an enormous lightweight helicopter) were all covered.

So, if you’re looking to study science or engineering, you could do worse than to consider Chester University. Not only do they know HOW a bicycle works, they also know WHY.

Photos: Garfield Southall

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Don’t tell the fat old man

02/07/2014
Screen shot 2014-07-02 at 14.50.42

That’s not me at the front and that’s not a fat old man behind.

It’s been a tough few weeks, trying to ride as much as possible in between work. It was made tougher by the appearance of a ‘fat old man’ on the track each morning, arriving earlier than me and leaving later. It got tougher still when I learned that he’s not fat and he’s younger than me.

Then he had the nerve on Monday to sit on my wheel for 20 minutes while I pushed the air aside as fast as I could. Afterwards, as I ‘warmed down’, he slid past and thanked me for providing shelter from the wind. Polite, yes, but somewhat galling. I could’ve done with some aerodynamic help myself, I thought.

The next day I got a copy of new research into just how beneficial wheelsucking can be. It contained the most dramatic figures I’ve yet seen. OK, they were obtained from experiments with dummies in a wind tunnel and shouldn’t be confused with the real world, but they blew me away.

Under ideal conditions, say the Australian researchers, a rider tucked in behind a leader can reduce their drag by 49%. That’s huge. I’m not saying we were in the ideal conditions on Monday morning but it did, then, seem even more unfair if the ‘thin young man’ might have almost halved his drag by tucking in behind me.

Mind you, the same research confirmed that by riding close to my rear wheel, he would also have smoothed my wake, reducing my own drag by a useful 5%. So maybe that’s why I did achieve my fastest average speed yet this year.

Whoosh! The truck pushes more air right in your way

Whoosh! The truck pushes more air right in your way

The scientists did some neat research into what happens to the aerodynamics when two cyclists are riding bit and bit, taking turns at the front. You know that feeling you get when a truck overtakes, of being shoved backwards by an invisible maw? Well, the same happens when a rider comes out of the slipstream and draws level with their mate. The drag on both riders increases.

Not that I’m going to tell any of this to the ‘thin young man’. Why should I help him any more? It’s about time he took his turn at the front.

For more info, see The effect of spatial position on the aerodynamic interactions between cyclists by Nathan Barry, John Sheridan, David Burton and Nicholas A.T. Brown

The Lessons of 2013

28/12/2013

Every week I scan the abstracts of about 25 new papers published in peer reviewed journals and by universities. Sometimes I have access to complete papers.

They are all relevant to cycling and I try to stick to the one that have some basis in, or relevance to, science. Considering I read only those written in English, ones that cross my radar and ones that I have any hope of understanding, clearly there’s a lot out there that I miss. Nevertheless, the pickings are rich and diverse.

While I tweet nearly everything I find (@cyclingscience1), here’s a summary of  a little of what I’ve learned this year from those thousands of diligent researchers who continue to add to our understanding of cycling.

I don’t necessarily agree with any of them.

• Yoga stresses the heart and respiratory system less than cycling
• The weaves of skinsuit materials affect your aerodynamics
• Bike reviews criticising comfort are largely untrustworthy
• Regenerative braking for e-bikes is going to blossom
• Cycling in London is either more dangerous or the safety models were wrong
• The Mayor of London is more worried about commerce than road safety
• Mountain bikers suffer the worst injuries in the first third of an endurance race
• French riders in the Tour de France live longer than mere French mortals
• Traffic calming and separate cycle paths make cycling safer in Netherlands
• Medics worldwide believe that bicycle helmets are fantastic
• The health benefits to US society of cycling outweigh the costs
• Caffeine definitely helps if you drink it, but not as a mouth rinse
• Cars don’t pass helmeted cyclists any closer than they pass bare-headed riders
• Steer by wire is on its way for e-bikes
• Support for, and research into, safety in numbers is growing
• Male cyclists have bigger thighs than triathletes
• The secrets of bicycle stability and steering remain enigmatic
• The best time to ride along Oxford Street in London is 10:07 on 25th DecemberOxford St cycling 25 Dec

To stay ahead of the bunch in 2014, buy a copy of Cycling Science and follow the tweets @cyclingscience1

Read on, online, dear reader

29/05/2013

Cycling Science by Max GlaskinWith your shelves now groaning under the burden of all the editions of Cycling Science (in at least five languages if you count US English and UK English as different flavors), then you will be pushed for space to store any more books. So here’s the first round-up of websites that you might find useful to further your interest in science related to cycling.

For aerodynamic drag force formulas (formulae?) there’s Rainer Pivit’s explanation – try not be put off by the symbols. They only want to be your friend.

The dynamics of the peloton aren’t as clear as they might appear in those sweeping shots from the helicopter during the Grand Tours. In fact, it’s a dynamic of transient mathematical beauty and it is being explained in all it’s glory by Hugh Trenchard.

Hugh Trenchard's peloton modelIf you want to cut to the chase, Hugh has built a great model online that you can actually play with – choosing rider numbers, speed, drafting distance etc. It mimics the real thing convincingly and is just as entrancing. (Personally I like the way the whole page looks. Somehow it reminds me of the early online scientific animations of the mid-’90s, although it is far more sophisticated and driven by powerful algorithms.)

What else? Ah yes, how about a short diversion into physiology. How on earth do your bulging leg muscles work? Don’t ask me, ask the experts. There is everything you need to know and more at the ExRx site for exercise professionals.

Me and my muscles before I put on my Lycra

Me and my muscles before I put on my Lycra

And just how much extraordinary power are your muscles producing? Well, you could buy some power cranks or one of the many other devices you can fit to a bike or you could simply enter some data into the site created by Walter Zorn and watch it calculate the answer in a jiffy. Walter Zorn died in 2009 but his family and friends maintain it in his memory.

That’s it for now. More soon.