Here are various (hopefully) interesting articles relating to riding, produced by individual PAM club members and other sources as specified.

The Art and Science of Counter Steering. Read
What speed is a safe speed? Read
A TURN FOR THE WORST  Read

The Art and Science of Counter Steering, by Steve Schlemmer

Introduction
Balancing and steering a motorcycle is an intuitive art learnt by trial and error and performed subconsciously. Fortunately for most riders, it is mastered on bicycles at low speed when we're young enough to bounce when we fall off. Look how difficult it is for those who learn later in life.

Motorcycle ROADCRAFT and the system of motorcycle control encourage us to be in the best position and, after achieving the right speed in the right gear, to negotiate each hazard. This requires steering. But how do we actually steer our machines?

There are many misconceptions on this subject and many unscientific explanations. However, there is some straight-forward, underlying physics which can help to explain what's going on when we turn. I'll leave out a number of related details about motorcycle geometry, tyre behaviour and so on. I hope in being selective for this short article I won't myself be accused of being unscientific. You can study this subject in more depth in books and, with care, on the internet.

Basics
First of all we need to remind ourselves of some basics from school and take on a few things we may have missed or failed to understand at the time. Stick with me for a bit - it's worth it.
Inertia is the inherent property of a body to remain stationary or moving at a steady speed in a straight line unless acted on by a force. To turn a body like a motorcycle requires a force to act on it. Unless we are hit by a truck we need to generate this force ourselves. This turning force has to come from the front wheel – see fig 1.

It's convenient to consider all the mass of something like a motorcycle and rider as being concentrated in one point called the Centre of Gravity (CofG). If we relax and keep our arms flexible, the bike and our body can act like two interlinked masses each with its own CofG and we can move the bike relative to ourselves – see fig 2.

To keep a stationary bike upright requires the vertical force of gravity through the CofG to pass through the ground inside the area formed by the wheels and the stand, or by the wheels and our feet on the ground. If a motorcycle in a turn is acted on by one vertical force of gravity and a second horizontal force due to cornering, those two forces have an equivalent single force acting down through the CofG at an angle to the vertical across the bike. To keep a moving bike upright requires this equivalent force down through the CofG to pass through the line between the wheels – see fig 3. To do this, the bike must lean into the curve. If it leans too far, say because one or both tyres slide outwards, the bike will fall into the turn - a low side. If it doesn't lean enough, say because the wheels were sliding and suddenly grip then it will fall away from the turn - a high side.
Finally, before we move on, we need to know about gyroscopic precession. We don't need to understand it, just know about it, and we can experience it by holding a bicycle wheel by its axle. Do try this at home. Take the wheel out of the forks and hold the wheel by the axle with the axle horizontal left to right. Spin it up against the ground like a front wheel going forwards and then roll the top of the wheel to the right about its fore and aft horizontal axis - the wheel will steer to the right. This movement is called yaw – see fig 4, and the size of the force, precession, is dependent on the rate at which you roll the spinning wheel. If you do this sitting in a revolving chair, the wheel will turn you and the chair about the chair's vertical axis. Now spin up the wheel again, but this time steer (yaw) the front of the wheel to the left about its vertical axis. The wheel will now roll to the right. Do try this, it's quite extraordinary if you're not familiar with it.

Now, after these basics we can look at four ways that we steer our bikes.

Four ways to steer
1. Low speed, geometric steering. At low speeds, when manoeuvring, and when we can use the inertia of our body to keep the bike upright, we can steer like a car. Turn the bars to the right and the bike turns to the right. All bike front wheels touch the ground behind where a line through the steering head touches the ground - this is called trail. We can help balance the bike by moving the bars to keep the CofG over the line between the back wheel and the steering head. With the CofG falling to the right, moving the bars to the right moves this line back under the CofG. This is how trials riders stay up without putting their feet down - similarly cycle track sprinters doing a track stand. They both also stand up to maximise the effect of their inertia and of moving their CofG - not recommended in ROADCRAFT

2. Roll gyroscopic steering. This makes a small contribution to steering. If we roll the bike into a lean to the right by pushing it down away from our bodies, gyroscopic precession will tend to steer (yaw) the front wheel to the right, thus turning the bike. This is how a bike will continue on its way without a rider and how we ride 'no hands'. As the bike starts to fall to the right, the front wheel steers to the right and keeps the bike up. It's only a small effect and can't initiate quick or tight turns.

3. Yaw gyroscopic steering. This is the first component of counter steering. When we want to turn our bike to the right we can turn the bars to the left – or push right to go right - and the front wheel will roll to the right and take the bike into a lean to the right. This effect is available at quite low speed if we move the bars quickly enough.

4. Higher speed geometric steering. This is the second component of counter steering. Remember that a bike is stable when running straight and needs a force to turn it. Once the turn has been initiated and a turning force has been generated the bike turns while this force is present. It's too late to lean after the turn starts; the turn and the lean have to be initiated together. We do this by turning the bike out from under us so that, after the turn has been initiated, the bike wheels follow a curve of larger radius outside that followed by the bike's CofG – see fig 5. This requires us to turn the bars left initially to go right – or again to push on the right bar to go right. You see this graphically when watching racing motorcyclists through a chicane where the flip-flop from left to right to left sees the wheels move dramatically across from side to side under the bike while the CofG follows a more gentle, middle line.

Observation and Practice
If you've stuck with me and followed this, watch out for how you use these four ways to steer when riding. When it's safe to do so, try to experience each separate component in isolation. Now, how can you improve the precision of your positioning by improving your bike control? The more we understand our riding art the more we can master the skills we need to ride safely.

Steve Schlemmer

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What speed is a safe speed? By Steve Schlemmer

On 10 September, PAM members listened to a lively presentation on a deadly subject. Mr Roger Jewell, on behalf of Devon Drivers’ Centre, gave short excerpts from their Speed Awareness Course. This course is offered as an alternative to penalty points for riders and for drivers convicted of speeding offences.

There is currently significant concern about the level of deaths and serious injuries to motorcyclists. Motorcyclists make up only 2% of road traffic but suffer a quarter of all fatal accidents. The number of fatalities is rising against an overall reducing trend for all vehicles.

Speeding, as in breaking the posted speed limit, is not a common cause of accidents. However, excessive speed for the conditions definitely is. Collisions occur only between moving vehicles or between moving vehicles and stationary objects. You could argue, therefore, that if the moving vehicles involved had been travelling more slowly then they could have stopped in time to avoid collision.

The largest single reason for collisions is loss of control leading to leaving the road. The next biggest one which the rider is responsible for is a head on collision when cutting a corner. We can all see that these can be associated with exceeding the safe speed for the conditions.

Judging the appropriate speed depends on the speed awareness of the driver or rider – this was the main thrust of Roger’s presentation. With chilling photographs and thought provoking video clips Roger demonstrated that even a small increase of speed above that at which you could stop on your own side of the road in the distance you could see to be clear would result in a significant impact.

The physics and maths involved are complex but here’s a simplified view that we can use ourselves to demonstrate the point.

The chart below plots speed in mph on the vertical axis, against distance in metres on the horizontal axis.

At each 10 mph interval there is a horizontal line showing the speed constant during the thinking or reacting time - a constant period of 0.7 seconds at any speed. There is then a falling curved line taking the speed down to zero over the braking distance. This assumes a constant braking force and a constant deceleration. The braking part of the stopping distance increases with the square of the speed.

The rising curved line shows the total stopping distance against speed. These numbers are based on the Highway Code distances for good conditions in a straight line. They need to be increased significantly for poor conditions. Let’s use the chart to create some example situations.

Stopping distances chart Copyright © 2007 Steve Schlemmer Plymouth Advanced Motorcyclists.

Example one - You are riding in a 30 limit where, at 30mph you would be able to stop safely in 23 metres. But you are actually riding at 40 mph when a truck suddenly pulls out from a blind exit 23 metres ahead. You travel half that distance at 40mph while you react and you hit the truck still doing 30mph. Even at 35 mph you’d hit the truck doing over 20mph.

Example two - You are riding in a busy crowded High Street where a safe speed is 20 mph and you would be able to stop in 12 metres. But you are actually riding at the speed limit of 30mph when a child runs out from behind a car 12 metres in front. You will travel 9 of those 12 metres, horrified, while you react and you hit the child still doing over 25mph.

Example three - You are riding at 60mph on a single carriageway subject to the national speed limit. Approaching a left hand bend, the vanishing point, beyond which you cannot see the road ahead, is 45 metres away. The maximum speed at which you could stop safely on your own side of the road in the distance you can see to be clear is about 45mph. But you continue towards the bend at 60mph to find that the dead ground hides a broken-down car on your side of the road. Even if you could stop in the bend in the same distance as you could in a straight line, you hit the car, or worse a truck coming the other way, at over 40mph.

Incidentally, it seems that as well as being poor at judging speed, we are generally not good at judging distances either. Next time you set off for a ride look down the road and point out an object 72 metres away – the stopping distance for 60mph. Now before you ride away, walk 90 paces down the road. That’s really 72 metres.

Overall, the Devon Drivers’ Centre presentation was a real opportunity for reflection, a timely reminder of the risks we take when riding and how we need to take responsibility for managing them. Many thanks to the Centre and Roger for supporting us in our intentions. All who attended would recommend the course should it ever be possible, for whatever reason, for you to attend.

Steve Schlemmer

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A TURN FOR THE WORST (Driving tip from the IAM)

Have you ever found yourself braking in a bend simply because it was sharper than you originally thought?

If you have, then have a think about how you actually go about assessing the severity of bends. If you get it wrong, the consequences are potentially very serious, particularly on rural roads, which still dominate crash statistics.

And it is not just young, inexperienced drivers who get "caught out" by bends. It is here that, in the jargon, most "single vehicle accidents" take place.

There are a number of clues we can take from the environment to help us. The most obvious are the road signs and markings. There are other less obvious ones: the line of the trees, hedges, buildings, street lights or telegraph poles (although remember that sometimes telegraph poles run through fields, so don’t follow them!).

The actual width of the road can be a factor: the narrower it is, the less space you have to manoeuvre. Skid marks on the road are an indication of past mistakes. The position and speed of other traffic can also provide you with valuable information. Another particularly useful way of assessing a bend is to use the “limit point analysis”. The limit point is the furthest point which you can see, i.e. where the left and right hand sides of the road meet. To use this technique first make sure that you can stop before you get to it, then simply ask yourself: is it getting further away? If it is and you can see further ahead, then your speed should be fine. On the other hand if it is getting closer, then you could continue to reduce speed until the limit point begins to move with you and your view opens up again.

This technique takes a bit of practice but it will help you to link your speed with your range of vision and allow you to stop in the distance seen to be clear. And in roads where you can’t see through the bends it gives you a reliable and practical solution to a difficult judgment problem.

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