Mike Burrows busts a handful of well known bicycle design myths
23rd March 2016
In the summer of 2014 MadeGood.films caught up with Mike Burrows, who to some is the most influential bicycle designer in British history. Famous for designing the revolutionary Lotus bike with Chris Boardman, Mike took some time to talk to us about some commonly held cycling myths.
What’s the best material to make a bike from?
The first bicycles arrived in the early nineteenth century and were built largely of wood. Fast-forward to today and entering a bike shop one will be confronted by a dazzling array of machines, coming in all shapes, sizes, materials and price-tags. In this clip, expert cycle builder Mike Burrows outlines some essentials of understanding frame material, and dispels some of the myths surrounding the subject.
When looking at what a frame is made of a key concern should be the strength of the material in bending and twisting. Bicycle frames with high levels of stiffness provide a more efficient ride, as more of the rider’s energy goes into turning the wheels, and less is lost through the frame flexing.
The majority of the bicycles in the world today have frames made of steel; it’s strength, durability, and affordability mark it out as the obvious choice. The density of the metal allows steel frames to have small sizes of tubing whilst giving decent levels of stiffness. Higher grades of steel with thinner tubing offer an even better ride. Whilst Mike champions steel as a frame material, he states the belief that it absorbs bumps in the road and offers a ‘more forgiving’ ride is unfounded. It has no magic properties, it is just another material.
The late twentieth century saw the introduction of aluminium frames. Aluminium is pound for pound much softer and weaker than steel, so alloy frames require larger sized tubing to cope with the stresses put on them by cycling. Aluminium weighs far less than steel though, so these bigger tubes are still lighter and stiffer than their steel counterparts.
In terms of stiffness and lightness, carbon fibre frames are a another step up from aluminium. A carbon frame with the same strength and stiffness as steel or aluminium will weigh far less. As Mike points out, that is why professional racing cyclists use carbon frames.
However, most people do not regularly race up mountains, and for the everyday cyclist a decent steel frame is perfectly fine. Mike tells us that what really gives a bicycle its structural stiffness is the traditional diamond-shaped format. Despite all the advancements in technology, this is something that has yet to be bettered (gratis gokkasten voor echt geld).
It has been said that there are three golden properties to frame material: high strength, low weight and small price-tag. When buying a new bike you can choose two of these properties, but not all three!
Why are bicycle forks set at an angle?
Mike Burrows is considered by many to be the doyen of British bike designers. Key to his success is a willingness to break the mould and challenge tradition in order to improve his craft. His nonconformist approach has brought a number of innovations which have redefined standards in cycle design. In this film he examines one of the fundamental givens of cycle geometry: fork angles.
The variables which affect the way a bicycle handles include its head angle (the angle the head tube intersects the horizontal) and its fork rake (the horizontal distance between the steering axis and the front axle). These two factors in turn affect a bicycle’s trail, which is the distance between the point the front tire contacts the ground and the steering axis.
In the early days of cycling, a bicycle’s steering axis, and fork, were vertical – look at an image of a penny farthing. The reasons for the evolution towards the titled steering axes of today is something of a mystery, but cycle historian John Allen has suggested the change happened for rather run-of-the-mill reasons: to bring the handlebar closer to the cyclist, and for the front wheel to clear the rider’s feet. Whatever the reason, this standard has stuck for generations, and works perfectly well for upright bikes.
When developing a new recumbent bike though, Mike decided to work out what the best configuration for handling really is. To allow him to test how head angle influences handling, he built a bike with an easily adjustable front set up. He then test-rode each set up to determine which offers the most comfortable and effective steering.
These rides taught Mike that optimum steering in terms of efficiency comes from having a vertical head tube and forks raked slightly back – like casters on a shopping trolley. The reasons are fairly straightforward: a vertical head tube means turning the handlebar will influence the direction of the bike 100% – anything other than vertical compromises steering for up-down movement. Mike’s results tally with research by Tony Foale and Vic Willoughby who, in motorcycle engineering bible Motorcycle Chassis Design, carried out a similar trial using a modified BMW 650.
Despite his findings, Mike acknowledges that bicycle shapes will remain unchanged largely because of the shape we, their riders, are. But it should be noted that forks are angled forward for ergonomic, not handling, reasons.
Do wheels affect bicycle ride comfort?
The big leap forward in bicycle wheel design arrived in the mid-nineteenth century with the introduction of highly tensioned wire spokes. This technology, borrowed from the aviation industry, enabled wheels to be both weight-bearing and light. Since then, whilst wheel design has certainly been advanced, it is fair to say that to the casual cyclist at least, a degree of mystique has crept in and surrounds the practice of wheel building.
Mike Burrows is a leading cycle builder with a reputation for producing ground-breaking bikes. Burrows takes a thoroughly pragmatic approach to designing, so when choosing the right materials for a job he rejects received wisdom in favour of hard facts. Everything is put under the microscope, spoke patterns included.
Spokes on a wheel are arranged either crossed or radial. Crossed spokes leave the hub at a tangent and pass one or more opposing spokes before reaching the rim. Radial spokes go directly from the hub to the rim, without crossing any other spokes. Each style has its merits and uses, but the relative stiffness and ride quality of the various patterns is the subject of some misinformation, which Mike puts to bed in this film.
To scientifically test how the different spoke patterns affect the ‘stiffness’ of a wheel – i.e. how much force is required to deform it – Mike built a test-rig. By putting load onto a wheel and gauging how much it flexed, the rig measured the effect tire deflection (where the bike contacts the road) has on rim deflection (something the rider may feel).
On the first wheel Mike tested, tire deflection of 16mm caused just 0.4mm of flex at the rim. In other words, on this wheel a bump in the road would impact the rim only ever so slightly, and would have a negligible effect on the comfort of the ride. In fact, such a tiny deflection would only be picked up by a sensitive measuring tool, not a rider’s backside.
The test was repeated on different wheels, and Mike found that rim deflection under load was essentially the same with any spoke pattern, radial or crossed. So, it would be a mistake to say one particular spoke pattern is stiffer than another.
Mike Burrows points out that what can be felt by the rider is a wheel’s lateral (sideways) stiffness. When sprinting, a wheel is put under side-load from the force put on the cranks. As wheels are thin structures, they will inevitably yield to these loads. Asymmetrical rear wheels with a cassette are particularly susceptible to this.
Mike Burrows also observes that people sometimes have a tendency to assume something is wrong if they are not used to it. For example, a solid disc wheel (one without spokes) might produce a noise going over a pothole. This does not mean the wheel is any less stiff or weaker than a spoked wheel, it is simply that the spoked wheel would not have made the noise.
Can you climb hills on a laid back bicycle?
As the man responsible for such notable machines as the Windcheetah ‘Speedy’ trike, the Ratcatcher and the Ratracer, Mike Burrows is something of a trailblazer in the world of recumbent cycle design. Being a founder member of the British Human Power Club , he is strong advocate of laid-back cycling – for racing and recreation – and is eager to dispel any myths surrounding the mode.
Riding recumbent holds several advantages over regular upright cycling. Compared with traditional frames, their more streamlined profile and lower centre of gravity give recumbents reduced aerodynamic resistance and more efficient braking. But owing to the fixed laid-back riding position – you cannot jump on the pedals when tackling a steep hill – some people have suggested they do not climb as well as their diamond-framed cousins.
Mike makes three points to counter this claim:
It is people climb hills – bicycles descend.
In cycling there are no such things as hills, only resistance to motion. Bradley Wiggins illustrates this point well, being able to sustain a high power output regardless of the obstacle, be it a head wind or an Alpine ascent.
It is scientifically not always true.
To demonstrate the third point Mike timed himself riding up the same hill on either a recumbent or a regular bike. He repeated the climb several times, each time upping his intensity level. The tests revealed that at certain heart-rates the laid-back bike was actually able to climb quicker than the upright. Only when riding flat out did he find the regular bike was able to catch up.
To give a fuller answer to the question Mike also draws on research carried out by doctors at the former pro-team ONCE, which compared riding on the saddle with riding out of the saddle when climbing. Their research found that, for some cyclists at least, riding out of the saddle can make sense because it uses muscles other than the main leg muscles – e.g. the upper body. Using these other muscles can offer relief to the legs which would allow the body to recycle lactates and achieve a higher overall power output.
Out of the saddle climbing is clearly not possible when riding recumbent, but you will use and develop different muscles and techniques when riding this way. The point to take from this is that different bikes will suit different riders and riding styles.
Does shaving your legs make you cycle faster?
Victory and defeat in cycle sport can be decided by seconds, so even the most minor of adjustments to your setup can give critical marginal gains. Being both a racer and an engineer, bike designer Mike Burrows is famed for his rigorous approach to the physics of cycling. Air resistance is one of the biggest barriers to speed, so to give his creations the edge over the competition he pays particular attention to aerodynamics. Mike will modify anything to boost a bike’s speed, including the hair on its rider’s legs.
Cyclists have traditionally shaved their legs – it gives comfort during massages and can reduce the risk of wounds becoming infected. But do smooth legs really have an effect on performance?
Mike points out that the human leg is not a very aerodynamic form to start with. Conventional wisdom might suggest that removing its fuzzy coating will increase speed by reducing air friction and giving a slightly more streamlined shape. In his typically maverick style though, Mike rejects convention and recommends we look at golf balls for a better understanding of aerodynamics.
A golf ball is dimpled, and as it spins through the air these dimples create turbulence on its surface. This turbulence has the effect of reducing drag and increasing the ball’s velocity and flight. Some cyclists wear dimpled helmets to achieve the same benefit. But Mike points out that as helmets do not spin or fly, it makes more sense to equip them with a single wire across the top. This wire would trip up the air and create a thin layer of turbulence which oncoming air could flow over, cutting down on drag.
This principle can be applied to the leg. Instead of a trip wire though, Mike says you could shave your legs but leave thin strips at each side – in other words, give each leg a Mohican. The rough surface would create a turbulent layer of air and allow better flow around the smooth skin online roulette geld. Adopting this look would help you go marginally faster, but beware: to the untrained eye you may appear slightly ridiculous.
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