̽��ֱ�� of Cambridge - cycling

Opinion: How does a bike stay upright? Surprisingly, it’s all in the mind

Anonymous — Tue, 24 May 2016 15:23:54 +0000

It’s as easy as riding a bike … or so the saying goes. But how do we manage to stay upright on a bicycle? If anyone ventures an answer they most often say that it’s because of the “gyroscopic effect” – but this can’t be true.

Put simply, the gyroscopic effect occurs because a spinning wheel wants to stay spinning about its axis, just as a spinning top or even planet Earth stay aligned to their spin axes. While motorcyclists with their big, heavy, fast-spinning wheels may notice the gyro effect, a modest everyday cyclist won’t because the wheels are much lighter and at a leisurely riding speed they don’t spin quickly enough.

If a pedal bicycle did stay upright because of the gyroscopic effect then any novice getting on a bike could just push off and the bike – and the effect – would do the rest. ̽��ֱ��simple truth is that you have to learn how to ride, just as you must learn how to walk. Riding a bike is all in the mind.

Imagine you had to ride along a perfectly straight line on a perfectly flat path. Easy, surely. Well, no. It’s virtually impossible to ride along a narrow straight line just as it’s really hard to walk perfectly along a straight line, even when you’re not drunk. Try it.

Now attempt this little experiment: stand on the ball of one foot, using your arms to balance. It’s quite hard. But now try hopping from one foot to the other. It is much easier to keep your balance. It’s called running. What your brain has learned to do is to make a little correction every time you take off so that if, say, you’re falling to the right, then you’ll hop a bit to the left with the next step.

It’s the same with pedalling a bike. When riding, you’re always making tiny corrections. If you are falling to the right, then you subconsciously steer a bit to the right so that your wheels move underneath you. Then, without thinking, you steer back again to stay on the path.

This “wobbling” is perfectly normal. It is more obvious among beginners (mostly children) who wobble around quite a lot, but it may be almost imperceptible in an expert cyclist. Nevertheless, these little wobbles are all part of the process and explain why walking – or riding – on a dead straight line is so hard because you can’t make those essential little side-to-side corrections.

Grand designs

There are some really clever bits in bicycle design to make riding a bike easier, too. Most important is the fact that the steering column (the “head tube”) is tilted so that the front wheel makes contact with the ground at a point that lies behind where the steering axis intersects with the ground. ̽��ֱ��distance between these two points is called “the trail”.

Bicycle dimensions. By Rishiyur1, own work

̽��ֱ��trail really helps to stabilise a bike when you’re riding with no hands because when you lean to the right, say, the force at the contact point on the pavement will turn the front wheel to the right. This helps you to steer effortlessly and it allows for hands-free steering by leaning slightly left or right.

But people have built bikes with vertical head tubes and they are perfectly rideable, too. In fact, it’s quite hard to make a bike you can’t ride, and many have tried.

That’s because keeping a bike upright is largely to do with you and your brain – something that’s easy to prove. Try crossing your hands over, for example. You will not even be able to get started, and if you switch hands while you’re riding, be warned, you will fall off instantaneously – something that wouldn’t happen if it were the gyroscopic effect keeping you upright.

Clowns and street performers ride bikes with reverse-geared steering. It takes months of practice to learn how to ride a bike like this, and it’s all about unlearning how to ride a normal bike. It’s amazing how the brain works.

̽��ֱ��gyroscopic effect

But what about the gyroscopic effect I referred to earlier? Surely it helps a bit? Well, no it doesn’t … unless you’re going pretty fast. There is a well-known demonstration that seems to show how a bike wheel is really affected by the gyroscopic effect but if you do the sums you can show that the effect is nowhere near strong enough to hold you up when you’re riding a bike.

To prove that the gyro effect is unimportant I built a bike with a second, counter-rotating front wheel. I’m not the first to have done this – David Jones built one in 1970. We both had the same idea. Essentially, the backward spinning wheel cancels out the gyroscopic effect of the front wheel, proving that it doesn’t matter and that the only thing keeping you upright is your brain. It’s also a really fun experiment that anyone can do.

So what’s the best way to learn to ride? Well, watching children learning to ride with trainer wheels distresses me because every time one of the stabilisers touches the ground it is an unlearning experience. To cycle, your brain has to learn to wobble, so take off the trainer wheels – and the more you wobble the quicker you’ll learn. Cycling really is all in the mind.

Hugh Hunt, Reader in Engineering Dynamics and Vibration, ̽��ֱ�� of Cambridge

This article was originally published on ̽��ֱ��Conversation. Read the original article.

̽��ֱ��opinions expressed in this article are those of the individual author(s) and do not represent the views of the ̽��ֱ�� of Cambridge.

Hugh Hunt (Department of Engineering) discusses how we manage to stay upright on a bicycle.

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Cycling to victory

th288 — Tue, 14 Jul 2015 10:36:02 +0000

On the 5th July the Gonville and Caius College student, who is doing a PhD in Inorganic Chemistry, won the RTTC 100 mile time trial championship in Wales, but the race that got everyone talking happened on the 25th June, when she produced a superb ride to become British Cycling National Road Time Trial Champion 2015.

In the race Hayley, who moved from rowing in 2009, took the lead from early pacesetter Ciara Horne over the 33.6-kilometre course, and no one could come close to her winning time of 51:39:89. Liv Plantur's Molly Weaver finished in 52:58:18 to win the Silver medal, and multiple Paralympic champion Dame Sarah Storey stopped the clock at 53:00:61 for the Bronze, meaning Hayley finished more than a minute ahead of her nearest rival.

Both this and the 100 mile time trial are the latest in a long line of wins for Hayley, who was the 2014 10-mile and 50-mile time-trial champion, and is CUCC’s most successful female cyclist in the club’s history. Hayley has also been President of the Women’s Blues during her time at the ̽��ֱ��, and won an astonishing 8 gold and 2 silver medals during the 2014/15 BUCS season.

"It's completely overwhelming - I've worked really hard for this," she said. "I hoped it was going to be really close and I just went out and did the ride that I thought I could, did the effort I thought I could and obviously it paid off.”

"I was just trying to focus on getting out the ride that I was capable of and not necessarily concentrating on the other big names that were starting after me."

"After I finished and I was half collapsing over my bike I could just hear the commentator say my time and then say 'will anyone go under 50 minutes'. Dame Sarah and Katie Archibald are both capable of going under 50 and at that point I wasn't even sure that I was in the lead, let alone that I was going to win by a minute."

̽��ֱ��win has vindicated the massive amount of work that Hayley has put in, as well as the hard work of her coach Mark Holt, who Hayley credits with helping her and Edmund achieve their many cycling successes.

"Cycling has just changed my life to be honest," she said. "I'm so glad that I'm good at it! It's completely changed my life - I've lost loads of weight and I've pushed really hard to drop those extra few kilos, ready for this, ready for that climb on the course and the climb on here.

"It's really paid off - it's been a really hard road but it's paid off."

Cambridge ̽��ֱ�� Cycling Club’s Hayley Simmonds has had an incredible year of sport that reached a pinnacle this summer.

It's really paid off - it's been a really hard road but it's paid off

Hayley Simmonds

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High-quality traffic-free routes encourage more walking and cycling

jfp40 — Thu, 17 Jul 2014 20:03:01 +0000

̽��ֱ��provision of new, high-quality, traffic-free cycling and walking routes in local communities has encouraged more people to get about by foot and by bike, according to a new study published today in the American Journal of Public Health.

Two years after new routes were developed by charity Sustrans with local authority partners, people living nearby increased their total levels of physical activity, compared to those living further away.

People living 1km (0.6 miles) from the new routes had increased their time spent walking and cycling by an average of 45 minutes per week more than those living 4km (2.5 miles) away.

This could make a substantial contribution to helping people achieve the two and a half hours of physical activity per week recommended by health experts.

Independent research led by the MRC Epidemiology Unit at the ̽��ֱ�� of Cambridge, on behalf of the iConnect consortium, surveyed adults living in three communities before and after they benefited from a national initiative led by the sustainable transport charity Sustrans, and funded by the Big Lottery Fund, to build or improve walking and cycling routes at 84 towns, cities and villages around the UK.

Crucially, there was no evidence that the gains in walking and cycling were offset by reductions in other forms of physical activity. This suggests that the new routes have encouraged local people to become more active overall. ̽��ֱ��benefits were equally spread between men and women and between adults of different ages and social groups. However, people without access to a car were more likely to increase their activity levels than those who had a car.

Dr Anna Goodman, lecturer at the London School of Hygiene and Tropical Medicine and lead author of the paper, said: “These findings support the case for changing the environment to promote physical activity by making walking and cycling safer, more convenient and more attractive. ̽��ֱ��fact that we showed an increase in overall levels of physical activity is very important, and shows that interventions of this sort can play a part in wider public health efforts to prevent diabetes, heart disease and other chronic conditions.”

Dr David Ogilvie of the MRC Epidemiology Unit at the ̽��ֱ�� of Cambridge, who led the study, added: “Although it may seem intuitive that improving facilities for walking and cycling will help make the population more active, this has rarely been tested in practice, and most of the existing studies have been done in other parts of the world. This is one of the first studies to show that changing the environment to support walking and cycling in the UK can have measurable benefits for public health. It is also notable that we did not see a significant effect on activity until two-year follow-up. It can take time for the benefits of this sort of investment to be fully realised.”

Malcolm Shepherd, Chief Executive of charity Sustrans who implemented the three projects with support from the Big Lottery Fund, said: “It’s clear that when good quality infrastructure exists people use it. Our experience from co-ordinating the National Cycle Network, which saw an amazing three quarters of a billion (748 million) journeys in 2013, 7% more than the year before, has shown us this over and over again.

“With a physical inactivity crisis and traffic jams clogging our towns and cities the case has never been stronger for governments to guarantee dedicated funding for quality walking and cycling routes for everyone.”

Peter Ainsworth, Chair of the Big Lottery Fund added: “In 2007, Sustrans’ Connect2 project won the public TV vote to bring £50 million from the Big Lottery Fund to communities across the UK to create networks for everyday journeys for people travelling by foot or bike. ̽��ֱ��study released today showcases brilliantly the long lasting benefits that this transformational funding is achieving in creating greener, healthier, fitter and safer communities.”

̽��ֱ��three communities studied were in Cardiff, where the centrepiece of the project was a new traffic-free bridge across Cardiff Bay; Kenilworth in Warwickshire, where a new traffic-free bridge was built across a busy trunk road to link the town to a rural greenway; and Southampton, where a new boardwalk was built along the shore of the tidal River Itchen. All of these new crossings then linked into extensive networks of routes.

New study finds overall physical activity is increased by proximity to routes.

This is one of the first studies to show that changing the environment to support walking and cycling in the UK can have measurable benefits for public health

David Ogilvie

Eifion

Cycle path, Colwyn Bay, Wales

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On yer bike!

sj387 — Wed, 30 Oct 2013 09:58:33 +0000

Motorised transport is the fastest-rising cause of energy-related greenhouse gas emissions and there’s a strong imperative to address this by moving towards a low-carbon transport system. Moreover, as Woodcock, from the Centre for Diet and Activity Research, explained: “It’s possible to benefit public health at the same time.”

But which approaches to achieving a low-carbon transport system would provide the biggest health benefits?

“We can think about the problem in two ways,” he said. “We can evaluate the impacts of an intervention such as new cycling infrastructure, or we can develop scenarios around what a healthy, low-carbon future transport system would look like, and then we think about how to achieve major changes in how people travel. We often see quite small effects from the interventions happening now, whereas potentially large things are possible.”

“Cycling could have a big role to play,” he said. “But to achieve this you’d have to start thinking about changes in land use to reduce trip distances, and cultural and infrastructural changes to make cycling an everyday mass activity for short- and medium-length trips.”

Woodcock has led the development of an Integrated Transport and Health Impact Modelling (ITHIM) tool, which models the health impacts of travel behaviours on both population health and greenhouse gas emissions.

“We’re seeing different effects in different populations,” said Woodcock. “In health terms, switching from driving to cycling consistently shows a net benefit, and the greatest benefit comes from getting older people more active. However, a complicated web of other problems arises. In some contexts, such as inner London, cyclists seem to face notably higher injury risk than users of other travel modes,” he said. “They also breathe harder so are inhaling more air pollution, which is bad for health.But on the other hand, they are not in a car putting other road users at injury risk or producing pollution for everyone else. We need this model to tell us which is the more important effect.”

There are also rebound effects to consider. “If I sell my car and buy a bike, I’ll have money left over, and where do I then spend that money?” he asked. “I may end up causing greenhouse gas emissions somewhere else, and it’s complicated to account for these second-order factors.”

ITHIM has now been taken up in California to evaluate transport plans in the San Francisco Bay area. It showed that a shift from driving to walking and cycling on short trips reduced the burden of cardiovascular disease and diabetes by 14% and reduced emissions by around 14%. By contrast, low-carbon driving reduced emissions by 33.5% but cardiorespiratory disease burden by less than 1%.

̽��ֱ��results are feeding into new policy in which a combination of active transport and low-carbon driving could meet legislative emissions mandates. Meanwhile, working with the Greater London Authority, Woodcock is also evaluating the impact of achieving the Mayor’s cycling targets and has also separately modelled the impacts of the Barclay’s Cycle Hire Scheme.

With funding from the Economic and Social Research Council and the Medical Research Council, Woodcock is leading two additional projects to address the problem of how to achieve the necessary behaviour change. By focusing on the development of cycling cultures through social learning and social influence, and by understanding the unintended outcomes that policies might bring about, these projects are attempting a different approach from those used in traditional transport modelling.

“Our research brings out a potential good news story,” he added. “Health benefits link transport and environment problems, and we need to be sure of the best route to achieving the biggest benefits.”

CEDAR is a partnership between the ̽��ֱ�� of Cambridge, the ̽��ֱ�� of East Anglia and Medical Research Council Units in Cambridge. Visit www.cedar.iph.cam.ac.uk for more information.

With governments around the world under increasing pressure to reduce their greenhouse gas emissions, transport systems are under scrutiny. Dr James Woodcock has introduced another factor into the equation: population health.

Health benefits link transport and environment problems, and we need to be sure of the best route to achieving the biggest benefits

James Woodcock

Amir Kuckovic

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