Technical

TECHNICAL FEATURES ARCHIVE

The most recent technical features are listed below, or for a full list of the rest, click on TECHNICAL FEATURES ARCHIVE

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...

Sticking with aluminium

CCM's 450 Adventure frame is the first to be held together by glue

Compared to engines, suspension, brake systems and electronics, a bike frame seems relatively simple. It must be rigid enough to hold a swingarm and forks in place, resist the efforts of a rider, an engine, the ground and physics to twist, bend or deflect it, and be durable for the lifetime of the bike. Ideally it's also light, easy to process in production, cosmetically pleasing and cheap.

But as long as the first two requirements are met, different bikes have different priorities and thus there is no single perfect frame design, which is why we get anything from round, oval, square or rectangular tubes, pressed sections, extrusions, cast or forged sections, usually in combination and made from steel or aluminium alloy (although titanium, magnesium, carbon fibre and even fresh air have been used – the German Windhoff in 1927, 1976 Quantal Cosworth Norton and 1992 Britten V1000 were frameless, with the engine connecting headstock and swingarm. And, arguably, Ducati's Panigale, BMW's flat twins and hub-centre bikes like Bimota's Tesi and Yamaha GTS1000 are frameless). With hundreds of frame permutations over the years, it's rare to hear of a new one.

But a Lancashire's CCM is doing something different: the new GP450 Adventure, MCN's group test winner, has a frame held together by glue (although they prefer 'adhesive', and call the process Bond-lite).

Gluing metal-on-metal isn't new. The idea came from...

Forcing the issue

So we've got all the power we can use. What do we do now?

With traction-controlled streetbikes making more power than a ten-year old World Superbike, and with pressure to reduce emissions and fuel consumption, where do engines go from here?

One answer is more torque. For a given size of engine it could be just as powerful as a bigger engine but at lower rpm, thus cleaner and more efficient – more time to fill the cylinders, longer burn, better scavenging, lower mechanical losses. Be nice to use, too.

But since modern bike engine architecture was established in the mid-80s, the peak torque from a given capacity has remained static. A 1992 Suzuki GSX-R1100 N made...

Holding back the gears

The relationship between gear ratios, torque, thrust and 'retuning' is never an easy one

Honda's new CTX1300 is, at first glance, technically unremarkable. It is, essentially, a stripped-down, half-faired Pan European with sharper steering, a wider rear tyre, a stereo and, somehow, more weight. It has the same 1261cc transverse 90° V4, 'retuned' for more midrange.

But the spec shows this is more, or less, than a retune: a stock Pan makes 125bhp at 8000rpm and 92 lb.ft at 6000rpm. Honda say the CTX makes 83bhp at 6000rpm and 78 lb.ft at 4500rpm. That's a massive 40% less peak power and 16% less peak torque!

Doubtless the curves are reshaped, but it's still a big deficit. Why Honda has done this will be revealed...

Clearance approved

Why it’s important to have room at the top, especially if you’re a valve

MCN reader Ron Smithson emailed with two questions: “Re: Honda’s CB500 range having a 600-mile valve clearance check; imagine the furore if a new Honda Civic (30,000 miles) was the same? Why’s a bike engine different?”

The second question has a straightforward answer...

Going off at a tangent

Why steering geometry is never a straight ahead subject

Indian’s new Classic, Vintage and Chieftain share engines and frames, differing only in trim and styling. Yet while the Classic and Vintage have identical chassis spec, the Chieftain has different numbers: 61mm less wheelbase, 4° steeper rake angle and 5mm less trail. If you were to judge which Indian was sportiest on spec, you’d say the Chieftain. Which is odd, because...

No more crank calls please

Do Yamaha’s new MT-09 and MT-07 really use R1-style crossplane technology?

Lots of people get cross when Yamaha claim their new MT-09’s 850cc inline triple and MT-07’s 689cc parallel twin are crossplane engines. How can they be? They don’t have enough pistons.

The crossplane idea works like this: in a conventional inline four the pistons move in pairs, two up, two down. When the middle pair are at top dead centre, the piston either side is at bottom dead centre. They fire evenly, every 180°, 1-2-4-3. This layout has perfect primary balance because piston pairs move in opposition, but....

Seat of the pants stuff

The science of sitting comfortably is harder than it looks

For a manufacturer, technical challenges aren't all cutting-edge electronics and active suspension. And it's easy to dismiss cruisers like Triumph's new Thunderbird Commander and Horizon LT as low-tech and simple to design. But they have their own challenges like, for example, making a comfy seat. It sounds easy: make it comfy. But there's more to it than that....

In the overlap of the gods

Making one engine fit many roles is all about getting the timing right...

What’s the similarity between Ducati’s 2009 1198 superbike, the Multistrada, Diavel and new 1200 Monster? Yes, they share versions of the 1198cc Testastretta engine. The versatile V-twin has gone from sportsbike to adventure bike to power cruiser to naked in just five years.

You’d think their disparate riding dynamics couldn’t be achieved with the same engine. So how does the 1198 Testastretta fit such different roles?....

Tough Torque

KTM’s 1290: why they call it PR ‘spin’

KTM test rider and ex-500cc GP racer Jeremy McWilliams says the new 1290 Super Duke is the torquiest bike he’s ridden. KTM claim it makes more at 2000rpm than the 990 Super Duke at peak (70 lb.ft). That’s a lot of big torque talk.

Torque is often wrongly thought of as a measure of engine performance at low rpm. Big V-twins have ‘lots of low-down torque’, and inline four sportsbikes ‘lots of top-end power’, as if the two are discrete and opposite. They are different, but not opposites...

Compounding: The Problem

Ever wondered why your rear tyre wears down in the middle but not at the sides? It’s safer that way...

At first glance there’s nothing in common between touring on a Triumph Tiger 800 XC and a 250bhp MotoGP prototype. But there is.

I recently had a 3000-mile ride on a Tiger. Its Bridgestone Battlewings were 4000 miles-old at the start and, as you’d expect, the rear squared-off as the ride went on. 7000 miles isn’t a bad total, and the bike maintained its steering and stability. But eventually it shimmied a bit over white-lines as it rolled across its squared-off centre. And with plenty of tread left on the edges, it seemed a waste of rubber to chuck it away.

So why don’t manufacturers make rear tyres harder in the middle where they wear the most?...

Fuelling about with maps

Selecting a power mode on your bike? The future’s already been mapped out. Literally.

Fitting a litre sportsbike with a castrating low power engine mode sounds like a bad idea, even if you call it ‘Rain’ mode. And few electronic aids are as contentious because engine modes are, technically, voluntary restrictions. Each is, broadly speaking, an overlay of instructions directing the ECU to manipulate and reduce engine performance.

But what actually happens when you push that button...?

Playing the frame game

Frames have got uglier and cheaper, but they’re straighter than ever. Suspension, on the other hand...

Last week’s Techwatch talked about how current production engines have close tolerances and matched components, and how automated mass-production reduces variability. If a modern engine makes 100bhp today, in 12 months’ time it’s likely the same model will also make 100bhp (although early BMW S1000RRs were an exception – bikes varied by up to 15bhp, and no-one knows why....

Putting up with intolerance

Sometimes the worse something fits, the better it works...

It’s long been a biking myth that in Japanese engine assembly plants, female workers are preferred to males for some jobs on the production line because they have smaller hands and greater dexterity. Having spent time at Suzuki’s vast Takatsuka Engine Plant in Hamamatsu, I can safely put that one to rest; it’s not true. They have plenty of both on the production lines.

But while I was there I saw something else intriguing:...

Swingarms and (bumpy) roundabouts

Ducati’s Panigale 1199 has a single-sided swingarm. The new 899 has a double sided swingarm. Now that’s a good idea...

It’s intuitive to grip a wheel at the end of each axle to give yourself maximum control of stability and alignment (or, if we’re talking about front wheels, steering). It’s certainly easier – it’s more effort to play wheelbarrows if you only using one arm to hold the barrow wheel. But it also looks cool if you wave with your free hand.

And so it is with swingarms:...

Variable Rates Of Interest

Variable valve timing: meet the engine technology that just won’t go away

In the list of pointless engine gimmicks, you’d surely put variable valve timing at number one. Only three production bikes have automatic VVT: Honda’s VFR800 VTEC (crude, two-stage system), Kawasaki’s 1400GTR (more sophisticated but barely noticeable) and, between 1991 and 1998, Suzuki’s Japan-only R-version 250 and 400 Bandits (crude and unnoticeable). And all of them gimmicks.

So what is VVT, and why do we keep hearing about it?...

Fins ain’t what they used to be

Why air-cooled bikes are having a water-cooler moment

In the news of their 2014 Touring range upgrades, Harley-Davidson smuggled a phrase rarely associated with the Milwaukee ironmongers (VRods aside): liquid-cooling. Before purists protest, Harley limit the ‘Twin-Cooled’ engines to four top-end models: the Ultra Limited, Electra Glide, Ultra Classic and Tri Glide trike. Which isn’t even a bike. But then it’s not really liquid-cooling either.

It’s fair to say the 45° V-twin has never enjoyed a reputation for cutting-edge tech; Harley are reputed to employ more designers than engineers.

But it’s also unfair to say. Designing a Harley engine might not be as challenging as building a 250bhp MotoGP engine that does 26 laps on 21 litres of fuel. But making an air-cooled motor sound and feel true to the Harley archetype yet meet stringent noise and emissions regulations is a challenge nonetheless.

Reading between the centrelines

Why the désaxé layout has become the latest fashion in engine design

Question: what has Yamaha’s new MT-09 inline triple got in common with their 2010 YZF450F motocross single, Honda’s MSX125 monkey bike and CBR250R, Kawasaki’s ZX-10R, Triumph’s Tiger 800, 1200 Explorer and Trophy, the Horex VR6, a 1979 Hesketh V-twin, a 1932 Ford V8 and an eighteenth century steam engine?
Answer: they all use the désaxé principle, in which the vertical centreline of the crankshaft is offset to the centreline of the pistons (désaxé is French for off-centre).
To picture it, imagine a side-on engine cut in half. Draw a line from the centre of the crankshaft up through the cylinders. On most bike engines with the piston at top dead centre, the line intersects the con rod and through the middle of the piston.
In a désaxé engine the crankshaft is set back a few mm (or cylinders forwards) so the line from the crankshaft no longer passes through the centre of the piston but to the rear of it.

Extra sensory perception: how our bikes know more than we do

Modern bikes are smarter than ever. But they can’t see into the future. Yet.
BMW’s HP4 is a clever bike. An array of more than 30 sensors stream info to its ECU, making our five (or six?) human channels of data acquisition seem inadequate. But we don’t have to reign in 190bhp… which is why bikes have brains too.
The BMW, along with Ducati’s Multistrada and Panigale, and Aprilia’s Caponord and RSV4 R APRC, is at the current summit of bike IQ. But most modern bikes have some of the following going on the moment you turn the key:
Electromagnetic pulses count spokes in ABS rings around both wheel hubs, measuring speeds and looking for differences. The ECU uses the info to activate its ABS system, and also feeds the data into a map of engine management, and traction and anti-wheelie control. It also delivers road speed to the clocks.

Yamaha Three-Cylinder Cross-Plane Concept

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Yamaha has intrigued the bike world with the unveiling of a prototype three-cylinder engine at Cologne, sparking some wild speculation by saying it comes with a cross-plane crankshaft.

Ducati Multistrada 2013 Skyhook technical

Ducati_MTStech_02

There are two main technical advances on the 2013 Multistrada. One is a package of upgrades to the engine, but the second is the real headline: Ducati Skyhook Suspension, semi-active electronics have arrived in motorcycles!

BMW K1600GT torque comparison

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Considering BMW`s claim of huge torque figures at low revs for the new K1600GT (full riding review here) and the GTL, which has an identical engine and drive line, it`s something of a surprise to find the bike demands a downshift or two to accelerate sharply when overtaking.

How ABS works

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It`s still commonly thought that ABS works by comparing the speeds of the front and rear wheels, releasing brake pressure if these should differ significantly. This is wrong.

Ducati 1199 Panigale Engine

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Ducati`s 2012 Panigale 1199 is powered by the most radical engine seen in any production motorcycle.

Bosch ABS testing

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The adoption of ABS on bikes is years behind the car world. Across Europe only a third of bikes over 250cc is fitted with it, while one in 33 smaller two wheelers have ABS. Yet almost all new cars have it, so what`s going on?

BMW Semi-Active Suspension DDC

BMW_DDC_02

BMW is the first company to announce semi-active suspension for motorcycles. The new system, called Dynamic Damping Control (DDC) will be appearing on 2012 models as the next logical step forward from the existing ESA II electrically adjustable suspension.

BMW K 1600 TFT display

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Yet another innovation on the BMW K 1600 machines is very obvious from the saddle - the TFT display screen. TFT stands for Thin Film Technology, and while it`s a form of liquid crystal display, it differs in an important aspect.

Désaxé engines

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Kawasaki`s 2011 ZX-10R Ninja is bristling with state-of-the-art and new technology, but like so many ideas, some can trace their roots back a very long way. The Ninja`s engine uses a désaxé layout, which means the centre line of the cylinders is offset, and rather than crossing through the centre line of the crank as on most engines, it passes 2mm in front of it, on the exhaust side.

BMW K 1600 Adaptive Headlight

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How do you get a headlight beam to stay level when a bike is leaning over? That`s what BMW has managed with its latest raft of world-leading technology on the K 1600 series.

Honda Dual Clutch Transmission

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Rather oddly, Honda stresses that the new Dual Clutch Transmission fitted to the VFR1200F is not an automatic transmission, but electronic manual transmission. Yet it patently is automatic!