Explainer: how to win a Tour de France sprint

By Bryce Dyer, Senior Lecturer in Product Design

The final dash to the line in a Tour de France sprint finish may appear to the bystander to be a mess of bodies trying to cram into the width of a road, but there is a high degree of strategy involved. It takes tactics, positioning and, ultimately, power.

The perfect sprint

In a perfect race, the best execution of a sprint win does not always come down to one rider. It is often the result of the work of teammates too. The back story to a winning sprint may have started hours before the finish line is in sight.

Jack Bauer in tears after the agonising stage 15 finish
Yoan Valat/EPA

During the stage, riders who have little chance in the finale will try their luck to beat the pack by being part of a “breakaway” – they jump clear of the peloton and then hope to outrun the others to the line. But if any team wants the stage to end in a mass sprint, it will check the speed of this breakaway and typically calculate how quickly the riders in it could be reeled in. Catch them too soon and new attacks may go clear (meaning more work for the interested teams to chase down), leave it too late and the breakaway wins. In stage 15, this approach got tested when New Zealand rider Jack Bauer spent all day in the breakaway. He finally was caught just 20 metres from the finish line by the sprinters. The sport can sometimes be very cruel.

Commentators typically suggest that on flat terrain, the ideal controllable gap is roughly one minute per 10 kilometres between a breakaway and the chasing pack. Towards the end of a stage, the interested teams supply riders to power into the wind and slowly close this gap down. The breakaway should then hopefully be caught with a handful of kilometres left to go.

At this point, the sprint-orientated teams deploy what is known as a leadout “train”. This train is made up of as many riders as possible from the same team. Each team member on the front then rides at a maximum effort before peeling off. The team’s designated sprinter is at the back of this train and is intentionally sheltered by the efforts of those riding in front to save his energy. It has been demonstrated that with four cyclists riding in a line, a rider positioned four men back only has to produce 64% of the power of the rider at the very front.

Mark Cavendish and Mark Renshaw execute the perfect lead out and sprint on the Champs Elysee in 2009
Guillaume Horcajuelo/EPA

If the leadout pace is high, the racing will be fast enough to discourage any late attacks from other riders. When viewing overhead TV footage, if the speed is high, the head of the main pack will have a pointed arrowhead-like shape to it. If the speed is at its highest though, you’ll see the peloton instead strung out into a very long, thin line. This is hard work for everyone but actually provides a safer and more controllable path for the riders through the final kilometres.

The penultimate rider in a sprint train is referred to as the leadout. This person puts in the last effort to position the sprinter sheltering behind. Ideally, the sprinter is then finally only exposed at the front with around 200 metres to go. When this happens, a winning sprinter like Mark Cavendish will cover this final portion in around 11 seconds.

Freelancing

If a sprinter doesn’t have the use of a leadout train – which does happen – he can “freelance”. This makes the opposition teams do the work before the sprinter leapfrogs around the group, hopefully ending up directly behind another sprinter with enough time to beat him to the finish line. In this case, a sprinter from one team effectively becomes the leadout for another.

On some occasions, no single team is able to control the final run to the line at all. From the air, the shape of the peleton in this case becomes broad at the front and spread across the full width of the road. When this happens, the chances of crashes are higher as rival leadout trains jostle for position and riders leap from wheel to wheel looking for shelter.

First week desperation

The first stage of this year’s Tour de France was unusual as it was likely going to result in a bunch sprint. The first rider past the post would not only get a stage win for their team but would also get to wear the yellow jersey as overall leader. With such a prestigious prize on the line, this meant more riders were involved and willing to take the risks, ramping up the chances for a crash.

Crashes normally occur when riders touch the wheels of other riders around them or lose control of their bicycles. In stage one this year, aggression played a part as Mark Cavendish and Australian Simon Gerrans battled to follow the wheel of Slovakian sprinter Peter Sagan. Sometimes riders realise they have nowhere to go and have to delay their sprint or wait for a gap to open up. Some opt for more punchy tactics though, using shoulders, elbows or heads to force gaps to open up between them and other riders. In stage one, Cavendish was boxed in, tried to force his way out and took both men down.

One of the most dramatic examples of a sprint crash is the first stage in the 1994 event when a policeman who was manning the finish straight barriers decided to lean out to take a photo of the finish.

Video The 1994 crash

But he underestimated both how fast and how close the riders were to him. Belgian Wilfried Nelissen (who had his head down) crashed into him and was thrown nearly 50 metres down the road with multiple broken bones. Another competitor, Frenchman Laurent Jalabert took the crash full-force in the face and his bicycle was destroyed in the impact.

Ultimately the perfect sprinter is a rider who expends as little energy as possible on the day, is deposited by others in the right place at the right time and has the ability to make fast judgement calls as the shape of the peloton changes around them. Marcel Kittel and his Giant Shimano team have shown everyone else how it’s done so far in 2014, but the prestige sprint stage on the Champs Élysées this weekend will give his rivals (Cavendish excepted) a final chance to put the theory into practice.

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Bryce Dyer does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

This article was originally published on The Conversation.
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From one man and his bike to the hi-tech peleton: the changing face of the Tour de France

By Bryce Dyer, Senior Lecturer in Product Design, Faculty of Science & Technology

The Tour de France is one of the most iconic and physically demanding sporting events in the world. Held annually since 1903, it has evolved from a simple test of endurance and speed to a festival of technology and innovation as teams fight to find the edge that will take them over mountains, high speed straights and cobbled roads ahead of their rivals.

The basic premise of the tour has generally remained the same since 1913 – the rider who covers the route in the least accumulated time across all of the stages wins. But the route is changed by the organisers every year, which means that unique demands are placed on the riders, the teams and their resources.

This year’s tour is divided into 21 stages covering a total of 3,656km. There are nine flat stages, five hilly stages, six mountain stages, one 54km time trial and two rest days. As a result of all these different conditions, an awful lot of specialised equipment is needed. In early tours, the same bike was used for the whole race but these days, a different one is chosen based on the different demands of the stage, its gearing and wheels tailored to the terrain.

Cobble horror

Perhaps the most intriguing test for the teams this year will come on stage five when the riders face some perilous sections of cobbled roads. The tour riders, who generally weigh between 60kg and 80kg, will be subjected to massive levels of impact and vibrations as they pass over these surfaces.

To add to their misery, these cobbled roads have been in place for decades so they are not flat. Wear, breakage and subsidence makes them uneven, to put it mildly. To maximise speed and control, the best riders often ride in the middle or “crown” of these sections. With space at a premium though, experienced riders might also choose to ride in the dirt gutter between the cobbles and the grass banks at the sides of the road which has often been worn smooth.

This decision becomes critical in wet weather in particular, when riding on even the slightest camber can be extremely dangerous at these speeds. Punctures, loss of control and crashes are common and injuries can be severe.

Many of the riders looking to do well in a race like the tour will not typically ride on these kind of surfaces in other events because they are suited to heavier, stronger riders rather than those built for mountainous terrain. There are a small number of early season races in the spring that do feature these kind of surfaces such as the notorious Paris-Roubaix – known as the “Hell of the North” – which give a flavour of what riders can expect.

Paris-Roubaix

To ride these cobbled stages, bicycle frames may use a different geometry when compared to those used on tarmac or asphalt. These bikes may be longer in length to help smooth the ride. Riders will also often use extra padded bar tape and wider tyres to absorb the vibrations and sometimes extra brake levers are added to help them stop quickly in the peloton.

Higher ground

During the hilly and mountain stages, when the race passes through both the Alps and the Pyrenees, the teams will send their riders out on the lightest bikes possible. The lighter a bike is, the faster it will go uphill. A professional rider may be able to generate and sustain 6.4 watts of power per kilogram on a typical alpine climb whereas a recreational rider may only be able to achieve half of that ratio. As a result, the bike’s weight will be as close to the regulation minimum of 6.8kg as possible and lightweight wheels will be used to minimise the impact of rotating mass which could slow a bike’s acceleration when a rider wishes to attack others when on a climb.

Time trial tech

Stage 20 this year will showcase the real importance of cycling aerodynamics. This relatively flat individual time trial will see the riders trying to generate maximum power while minimising aerodynamic drag. Put simply, the more aerodynamic you are, the faster you will go (or the more energy you can save) for the same power.

Bradley Wiggins on a time trial.
Waterboyzoo, CC BY-NC

The bicycles used for this are highly specialised, with filled-in disc rear wheels and low drag frames. The riders themselves will assume a riding style that makes them look a lot like a downhill skier with their arms angled directly in front of their chest and torso to minimise their frontal area. They’ll use aerobars and wear a teardrop shaped helmet to reach speeds that can average 50km an hour.

Staying in touch on level ground

One of the more controversial new technologies in professional cycling has been the use of team radios to relay orders and information during the race. The organisers have even experimented with removing the riders’ earpieces in an effort to add more drama to the racing.

It is true that radio technology is often used to influence the result. Flat terrain typically results in a mass sprint but sometimes a small group of riders will break away at an early point in a stage and try to hold onto the lead until its end. However, these early escapes are rarely successful because the team cars and the riders following the breakaway can calculate the distance between the breakaway group and the “peloton” and then use radio transmitters to determine how fast they need to move to control or close the gap. It’s very hard for the breakaway group, typically containing just a few cyclists, to overcome the horsepower of 200 chasing riders armed with precise knowledge of the wherabouts of their quarry.

Do it yourself

Technology is a major part of the tour these days but that has not always been the case. In the early editions of the event over a hundred years ago, the riders were very much expected to compete alone and be self-sufficient.

Eugène Christophe

When the forks of Eugène Christophe’s bike snapped mid-race in 1913, he had to visit a local blacksmith and then re-weld them himself. It was later discovered that Christophe had enlisted the help of a local boy to pump the bellows for the forge and as a result, he was later penalised for receiving outside assistance.

The use of new developments in cycling technology was frowned upon too. The tour’s organisers didn’t even allow the use of mechanical gear changing systems until 1913. Before this, a rider would have to stop, unbolt their rear wheel and flip it over so they could switch to a single cog mounted on the other side of the hub. In the event of a puncture, they rode with spare tyres looped around their torsos.

Battling bodies and brains

Technology is now, of course, a fundamental part of riding the tour. And it stretches far beyond the bicycles themselves. Preparations for the race will have begun long before the start and the clothing riders wear, the bicycles they ride and the nutrition they take are finely honed products that can take months or even years to develop.

When they’re not actually riding, recovery technology is used to prepare them for the next stage. Riders will have massages, wear compression clothing and take ice baths to help reduce muscle soreness and inflammation. The key principle here is that winners are not always the strongest but those who possibly tire the least over the three weeks.

Each team of riders is supported by doctors, mechanics, physiologists, coaches and operational management. There are multiple team cars and buses which house their equipment and spares. They become, in effect, a mobile business and garage for the duration of the race.

Professional bike racing has been referred to as “chess on wheels” as the smartest rider and team, not the strongest, often win. We’ll find out if this is the case this year from July 5.

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Bryce Dyer does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

This article was originally published on The Conversation.
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Explainer: how do cyclists reach super fast speeds?

By Bryce Dyer, Senior Lecturer in Product Design, Faculty of Science & Technology

Even though spoked wheels and pneumatic tyres were invented in the 1880s, bicycle design hasn’t really changed a great deal in the time since – at least, at face value. However, look closer and around a hundred years of research or development has taken the humble bicycle from boneshaker to a speed machine.

The basics

Karl von Drais in the days before lycra.

A modern bicycle is still made up of a double diamond shaped frame, two wheels with air-inflated tyres and a chain-based drivetrain – the mechanism through which the whole system runs. Though we’ve stuck to the basics, man and his machine have increased in speed from the 14.5 km per hour reportedly achieved by Karl von Drais in 1817 to a mind-blowing 55km in a Tour de France time trial nearly 200 years later.

The ability to improve speed on a bicycle comes down to two fundamental factors: you either increase the power that propels the rider forwards or you decrease the resistant forces that are holding that rider back.

The rider’s ability to produce power is generally down to their physiology and biomechanics. The resistant forces that slow a cyclist are mainly air resistance, total mass and any frictional losses, such as the drivetrain or the rolling resistance of the wheels against the ground. If every athlete has an equal chance of winning the challenge for engineers and scientists then is to focus on the technology the cyclist uses to obtain a competitive advantage.

The trouble with air

It has been demonstrated that once a cyclist travelling outdoors gets past speeds of 25 miles per hour, around 90% of the force holding them back will be air resistance. But the relationship between speed and air resistance is not a linear one. It can, for example, take twice as much human power to ride a bicycle at 30 miles an hour as it does at 20 miles an hour.

As a result, reducing air resistance has become a top priority in professional cycling technology in recent times. At the London 2012 Olympic Games, Team GB’s track riders were using bikes, helmets and clothing solely designed to help contribute to the optimisation of each rider’s aerodynamics. Team principal, David Brailsford, has referred to this process as the “aggregation of marginal gains”.

To achieve this, wind tunnels are now used by both professional and amateur athletes to analyse the aerodynamic drag, then work out how to get the rider and machine working together optimally. There is a complication in this process, though, in that the best aerodynamic solution is typically specific to every rider, so each needs to make individual choices about their helmet and bicycle and especially their riding position.

The second problem is that wind tunnels are few and far between and are by no means cheap to access. Thankfully, alternatives for those without an Olympic-sized budget are emerging. You can now use computational fluid dynamic software which can be, in essence, a virtual wind tunnel. This software allows an engineer to simulate a variety of air flow conditions on a new bicycle design, therefore cutting down the time and costs of prototyping and testing. There is now also published research which allows riders to assess their aerodynamics out in the field rather than in a wind tunnel.

Ermargerd! I love this helmet!
EPA/Ian Langsdon

Mark Cavendish famously won his Tour de France stages and world title in 2011 wearing a skin suit and an aerodynamic helmet while the majority of his competitors were still wearing baggier jerseys and heavily vented helmets. Team GB had realised that even though a rider may be sheltered by 200 others during a road stage, when Cavendish sprints for the finish line, he is alone in undisturbed air for around 200 metres at speeds well above 40 miles an hour. Every small advantage at this point converts into winning millimetres.

Tinkering with the tech

Racing bicycles themselves have been subject to a tremendous amount of aerodynamic refinement over the last five years. Braking systems have been positioned so as to be sheltered from the main airflow and gear cables are now run on the inside of the frame. Wheel designs have not only improved in reducing aerodynamic drag, but are now being optimised to provide benefits such as increased rider stability from crosswinds. Innovations like these have traditionally been directed towards making better bikes for either time trials or triathlons but is now spreading towards the road bikes used in mass start racing.

The mechanical properties of the racing bicycle have also evolved. Like computational fluid dynamic software, finite element analysis allows us to optimise the design of bike components to simulate the stresses and strains that they will face when in use. This has allowed us to develop composite frames that weigh as little as 800g but are still stiff enough to sprint for a stage win and comfortable enough to be ridden for five hours or more, day after day.

Even the humble gear derailleur, relatively unchanged in principle since its original invention in 1951 has lately begun to shape shift. The most advanced systems are now electronically powered and triggered. This has allowed for smooth gear changes requiring only thin wires and a small battery as opposed to having a frame design compromised by the limitations of needing cable runs for mechanically actuated gears.

All these improvements have enabled us to morph the humble bicycle into a speed machine without tampering with its basic design. So where does this all lead next? In competitive sport, the technology is typically regulated by its governing body. In the case of cycling, this means that the equipment is currently limited in both its size, nature and weight, so we are more likely to see more incremental improvements than a radical shift away from the bikes we use now.

The average leisure cyclist is not limited by such constraints allowing us to benefit from any level of innovation. For example, if you look at bicycle land-speed records, recumbent cycles – which are unique in the way they position the rider lying down – can move at far higher speeds than a conventional bicycle. And for enthusiastic amateurs, new bicycle designs are continuing to become lighter, faster and ultimately more efficient. Anything could happen.

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Bryce Dyer does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

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