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September 2015

How do bicycles stay upright?

180915WPHead

Wandering through the supermarket behind a half empty trolley, the mind screams for diversion.

The magazine section is a small oasis in a sea of processed food-like products. It is dangerously close to the chocolate shelves but still worth a visit. There are various titles we like to skim through, and a whole trove of covers to laugh at. Usually we make sure we are up to date with whatever Kim or Wills have been getting up to and move on, but last week the New Scientist stopped us in our tracks.

The cover listed two of a possibly infinite number of questions that physicists have been unable to answer…yet.

One was What Happened before the Big Bang? The other was How Do Bicycles Stay Upright?

We had to buy the issue. It contained the usual mystifying stuff that science enthusiasts get excited about, and these ten big questions to which they have no answer…yet.

Nine of them covered concepts so abstract that our household struggled to stay awake long enough to really grasp the questions, but the bicycle one was immediately digested.

Turns out the mystery is not so much how they stay upright, but how to describe it satisfactorily to other scientists. They think that to adequately explain it mathematically requires about 25 variables. So far they have not been able to. To quote a scientist: “What we don’t know are the simple, necessary or sufficient conditions for a bicycle to be self-stable”.

I have owned several that were stable on ninety nine out of a hundred days, but on that other day they put me in the emergency ward.

I have concluded, without the use of a calculator, that the common factor in the psychotic behaviour of my bikes is myself.

The bikes have all been able to stay upright, but only with me on top. I have tested it, without me they fall over. But sometimes, always with me on board, the laws of physics intersect with whatever we are trying to do and down we go.

The thing that makes a bike stay upright is being ridden. The question I would like answered is what compels us to ride them. Even with a roughly one in a hundred chance of coming out of the exercise scuffed up or actually broken, out we go. Again and again.

We have thousands of people working on it, and so far nobody has been able to describe it mathematically….yet.

 

Things may or may not come in threes

This is thing four This is thing four

Things allegedly come in threes.

Saturday was the day for a road ride, because friends were visiting and the bike rider brought his new bike. It is a beautiful old italian bike to be fair, but it is newly refurbished and needed riding.

I fished out my own version of his bike for a lap of the lake. It is totally unique, it was built in Onehunga by a good friend. Unlike most road bikes, it features enough space in the frame to fit big tyres. It usually wears a pair of a type  my friend tracked down, very light and supple, and about 50% fatter than a racing bike normally has. This makes riding on New Zealand’s primitive coarse chip seal a pleasure, and sliding around on gravel enjoyable too.

The tubes in these tyres on that day were from Italy, a nation that can make the best and possibly the worst of nearly everything. They leak at a rate that means air must be added for every outing, sometimes they can be dead flat when the roadie comes down off the hook. They were. I banged in the 80 psi that is optimal for the tyres, and parked the gleaming machine in the sun so I could admire it while we had our third coffee. The rear tyre let go with a satisfying explosion before I had finished making the brew. While we extracted a tube from the saddle bag the front tyre also went pop. A comical little episode took place, in which both tubes were replaced with german ones. One of them must have been made on a Friday, because just as I put the last 3 psi into the rear one, it exploded with a spectacularly loud bang that caused several dozen birds to leave our property for good.

We checked, it was definitely a dodgy tube.

We used our last spare to sort that out, and headed out for our ride, stage one being a prologue directly to the bike store for five replacements.

The whole threes thing turns out to be a crock of meaningless hokum signifying nothing. We had a very nice ride with more coffee at the halfway point, and threw in a short section of potholed madness on the way home for seasoning. As we parked the bikes we noticed a nasty gash in the sidewall of the almost new rear tyre, probably inflicted by one of the potholes. Dang. That makes four.

C TB Chugs some of Atlanta's finest, before his fourth coffee, in the mistaken belief that it will make him go faster. C TB Chugs some of Atlanta's finest, before his fourth coffee, in the mistaken belief that it will make him go faster.

 

The bicycle you can't buy

The Benson, parked in the middle of the King Country while we stand around eating sugary treats. The Benson, parked in the middle of the King Country while we stand around eating sugary treats.

My friend David Benson could be a professor of cycling. He knows a lot about bikes, and the sport.

Once in a while he builds a bike frame. If you are lucky enough to get one you have a thing which is crafted by hand and is totally unique. But much better than that, it is informed by the experiences of a guy who doesn’t drive a car, and uses a bike for transport as much as anything else.

DB has built full-race track machines, but of late he has been building road bikes that are intended for general riding.

My example is now approaching the end of its second decade of regular use. It is made of steel, I forget what the tubes are but I know they are not a set from one manufacturer. DB chose the tubes to give me a bike that would be comfortable, predictable, and flexible in its uses.

The bikes you can walk into a store and buy are generally put together to get as close as the price point will allow to what a pro would race on. At the top of the range they ARE what a pro would race on, and as you go down the range the weight goes up and the carbon evaporates, but the general idea remains the same.

My bike is very different. It is long and low, because I have short legs and a long torso. The bottom bracket is lower than normal which makes the bike even lower. The geometry is ‘slack’, that means the head and seat tubes lean back a degree or two more than today’s race inspired bikes. Those two features of the frame’s design mean it is very easy to ride: it goes straight, it corners as if it is on rails, my toes can reach the ground easily from the saddle.

Steel is an amazing material for bike frames. It is strong, light, repairable, and has a natural springy compliance that is unmatched by anything else. Other materials can be stronger, lighter, and more marketable in the 21st Century, but steel is hard to beat for a long term ride.

The frame is designed with plenty of space for big tyres. Race bikes are optimised to fit tyres of around 25mm. The Benson easily fits 32mm bags, and might swallow more if the brakes allowed it. DB tracked down some super light touring tyres that are pricey but beautiful to use, run at about 80psi they smooth out even the worst of New Zealand’s rough chip roads. Big tyres are not the handicap you might think they are: on less than a perfectly smooth surface a flexible tyre with lower pressure actually rolls more easily, but the big payoff is comfort. I can ignore my road bike for weeks, then pull it out and ride 100kms with no discomfort during the ride or afterwards.

The kit and the wheels are as old as the bike, mid-range Campagnolo and Ritchey rims. DB built the wheels, which are still dead straight and round. The Campag gruppo is scarred but still functional, the right shifter was rebuilt after about 12 years (by DB) with new bits inside for fresh shifting. The gear range the bike runs is lower (easier) than usual, an idea that has caught on with mass-produced bikes of late. While they now carry very low gears for getting beginners up long hills, they still have top gears most sport cyclists will never really need, my Benson doesn’t. High gear is 50 X 14.

The bike has been round Taupo in 4.28, and could go faster if it didn't have me on top of it. It has also through Chinese Menu, a Grade 3 singletrack in Whakarewarewa Forest. It has been on a trip through the Forgotten Highway. It has had three paint jobs (it gets a hiding).

If I had to choose one bike to take to a Desert Island I would probably refuse to go, but if it was unavoidable and the island had anything resembling roads I would probably choose the Benson. One thing for sure, I will never sell it.

Ready for anything, second paint job. Ready for anything, second paint job.

The first paint scheme. Fitted with stupid wheels for Taupo one year. They were too light for somebody of my volume, and eventually gave up the ghost during K2. The first paint scheme. Fitted with stupid wheels for Taupo one year. They were too light for somebody of my volume, and eventually gave up the ghost during K2.

Third paint job, fillet brazed beauty, with false lugged seat junction and DB designed seat stays. Fillet brazed beauty, with false lugged seat junction and DB designed seat stays.

Dig that fork crown, and those fillet brazed tube junctions. Hand made in Onehunga. Priceless. Dig that fork crown, and those fillet brazed tube junctions. Hand made in Onehunga. Priceless.

Another view of business end. Note hand made sleeves on head tube, brazed on barrel adjusters, and St Christopher's medal DB procured off a dodgy Italian junk vendor at the Madonna del Ghisallo, the church that celebrates cycling on the course of the Giro di Lombardia. Another view of business end. Note hand made sleeves on head tube, brazed on barrel adjusters, and St Christopher's medal DB procured off a dodgy Italian junk vendor at the Madonna del Ghisallo, the church that celebrates cycling on the course of the Giro di Lombardia.