Archive for the ‘Physics’ Category

Higher education on two wheels


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

Don’t tell the fat old man

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

Anti-Gravity Cycling


Why does a moving bicycle stay upright? It seems a simple question but, as yet, nobody has been able to answer it exactly.

Scientists are getting closer but mystery still surrounds the precise way geometry, mass, gravity, velocity and gyroscopic forces combine to keep an articulated two-wheeler coasting along, even when there’s no rider.

Now one expert of bike stability, Professor Andy Ruina of Cornell University in Ithaca, New York, has been discussing a curious finding that adds a little more to our knowledge. Last year he presented it to a quiet meeting in Japan. This month he repeated it in the US. If you weren’t at either, here’s the gist.

First, his students built a tricycle, with one wheel at the front and three at the back.Bricycle static

Like most tricycles, the front wheel steers. Unlike most tricycles, there is an adjustable suspension spring for the rear set of wheels.

It’s not a suspension spring to absorb vibration. Instead, it can be adjusted to allow the tricycle’s rear wheels to lean into the corner, in the same way that the rear wheel of a bicycle leans in.

Pushing the bricycleWhen the suspension spring is given complete flexibility, the rear wheels tilt as the rider leans into the corner, exactly like a bicycle.

When the suspension is locked to rigid, the rear wheels are locked upright and the tricycle corners exactly like a tricycle.

That’s why Ruina has nicknamed this hybrid machine as a “bricycle” (not to be confused with the energetic Bricycles cycling pressure group in Brighton UK).

The weirdest thing happens, though, when the suspension is adjusted somewhere in between being being totally flexible and being locked rigid, at a critical point where it counterbalances the forces created for steering.

Leaning in anti-gravity

Suspension adjusted to eliminate the effect of gravity

At this setting, the suspension eliminates the effects of gravity.

It becomes an anti-gravity bricycle.

When the bricyclist tries to corner, by turning the front wheel and/or leaning towards the centre of the curve, the bricycle does not respond. It will not change direction. It just keeps on going straight on.

So, by switching off gravity, it’s impossible to alter course.

What does this clever experiment reveal?

Well, now we know that, as cyclists, without gravity we would be fated to riding forever in one direction. If we wanted to change course we’d have to stop, dismount, pick up our bicycle, turn it and start off again. Our bicycle would be as manoeuverable as a train that’s gone off the rails.

We may curse gravity when we’re riding uphill but, from now on, we should give gravity due praise every time we steer.

*I first stumbled across an abstract of Professor Ruina’s paper and tweeted it in January 2014, later that month he kindly engaged in a Skype conversation. Since then, he and his team have posted an explanatory video of the bricycle in action, with a full explanation of the physics at work. It’s well worth watching – several times!

"Shall we just cycle home?"

“Shall we just cycle home?”

The Lessons of 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

Cycling and the fourth state of matter


The ionised gas stuff, not the bloody stuff

One of the most surprising things I stumbled across when researching Cycling Science was the potential application of plasma to cycling. As has been frequent in recent year, I have to thank Bob Jones (names changed to protect the innocent) for not only pointing me in the right direction but also giving me a good shove to get me there sooner.

Plasma is the fourth state of matter. Most of our bikes are made of solid matter and our riding would be very uncomfortable without being able to put gaseous matter into our tyres. Liquid matter is becoming more common on bikes as hydraulic brakes are being fitted to off-road, commuter and road bikes.

But plasma, well, I’d thought that was only for oversized TV sets or blood transfusions (which, incidentally, are mentioned elsewhere in the book). Then I went for a ride along the seafront with Bob.

I’d known Bob for 25 years. Well, I’d known him for about six years, when he was a keen young racer. He stayed in the sport and I didn’t so I lost contact. Some 15 years later he tracked me down and hauled me back into writing about bikes once more. Yes, the book is his fault.

But this is a no-blame blog and Bob’s idea that day on the seafront was to lend me a small-wheeled e-bike that gave me the acceleration and speed of a sleeping donkey.

Then he mentioned plasma. He said he didn’t understand it. He said it sounded quite fantastic.

He gave me a name and a number. I rang it and asked about plasma. The man explained. I understood it. It was fantastic.

The explanation is in the book. Plasma could make you ride faster.

Of course, it’s still a concept and hasn’t even been taken to the prototype stage.

But the theory’s good and the technology is part-way there.

So it’ll only be a matter of time before the UCI bans it.