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Sensor and sensibility

Our bikes are being micro-managed, literally. Microchips are as much a part of 21st century riding as an engine and wheels.

We're familiar with solid-state electronics in biking. Ignition swapped points for transistors in the 1970s, then went digital in the 1990s. Now, the need for greater power, fuel efficiency and emissions control means modern engines only work with computer-controlled fuelling, ignition, combustion and exhaust. When we open the throttle we pull the strings, but the ECU calls the shots. To do it, the ECU needs an accurate view of the world. And it gets it through its sensors...

Putting gyroscopes under the microscope

A gyroscope is a rigid circular or spherical mass rotating around an axis and for over 100 years motorcycles have come with three of them: a front wheel, a rear wheel and a crank (if you're being pedantic you could include cams, balancer shafts, gearbox, clutch etc).

The classic mechanical model of a gyroscope ranges from the very small – electrons spinning around an atom's nucleus – to the very large – the Earth. They possess a number of interesting properties, but the one that matters to us is called precession. Its effects aren't always intuitive (to say the least) but they can be helpful in steering a bike. So they're worth having and, if you're designing a bike, worth knowing about...

Naturally self-centring

Why balancing a bike feels like the most natural thing in the world...

Most of us have an innate feel for balancing a high centre of gravity on a relatively short wheelbase. Say, like a motorbike. Its centre of gravity is the point at which the sum of the surrounding mass is zero, and is largely determined by the location of the engine, the heaviest part of the package. Usually the CoG is midway between the wheels (half the wheelbase) and 60 to 75cm off the ground; just above the engine, in front of your knees.

Or at least it is until you get on...

Giving me good vibrations

Bikes make lots of vibrations, some good and some bad. Here's why...

Anyone with fingers knows bikes vibrate, sometimes strongly enough to make picking your nose impossible. But how we perceive vibration depends on its type, pattern, frequency and cause.

Bikes are subject to different types of vibration. A bumpy road creates random forced vibration at medium to high frequency (around 5-35 Hz depending on vehicle speed). It's perceived as unpleasant, as is head buffeting caused by wind turbulence. Engineers and aerodynamicists try to minimise these bad vibrations.

But we usually talk about engine vibration. There are many sources...

Pressure is good for character

Just when they develop flat torque curves, we want peaky ones back again

From the launch of Yamaha's new Super Ténéré: "The exhaust pipe connection between the two headers is discontinued to give more character to the engine. The link pipe gives a flat feeling to the curve, so removing it makes the engine a bit more peaky."

This is all about exhaust gas. When a four-stroke is tuned for power it means more revs, and so the cylinders have thousandths of second to fill with fresh mixture, compress it, burn it and pump it out again. To get enough mixture in and out, inlet valves open early and exhaust valves stay open for longer – so both are open at the same time. This is valve overlap...

Sticking the knife in forks

Funny front ends? You must be joking

Twenty one years ago BMW launched the R1100RS with a Telelever front end. It's gone on to be fitted to the most popular bike of the 21st Century, BMW's GS. Yet still – apart from BMW's other forkless system, Duolever – conventional telescopic forks survive on all other bikes, including MotoGP. Why?

Life is one big drag

The high (and low) pressure world of aerodynamics

A road cone is more aerodynamic blunt end forwards (if you fill the hole in first). Same goes for a bullet. And most cars – if you geared them to suit you'd get better fuel economy driving in reverse.

Intuition says, aerodynamically, a sharp, pointy front end is more important than a sharp, pointy back end. For you Ferrari and Lamborghini owners, sadly, this is wrong. A falling raindrop points us, literally, in the right direction: pointy at the back. It's seven times more aerodynamic than a pointy wedge. If you cut the 'nose' off a raindrop, its drag increases by 6%. If you cut its tail off...

Engines are a waste of energy

Given the amount of work petrol does, it's amazing your motor uses so little to go so far so fast

It takes just 100cc of unleaded mixed with 800 litres of air – or two and a bit Tequila shots in four large garden water butts – for your engine to accelerate you from a standing start to 150mph under half of a mile away in around ten seconds. And it's even more impressive when you consider...

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