Never Mind the Bullocks, Here's the Science (3 page)

If she had hit the brakes hard, she might have avoided the crash.

But her driving skills had become rusty over the years, and she had never done an Advanced Driving Course. For some unknown reason, she believed that if she planted her foot as hard as she could on the brake pedal, the car would skid out of control.

And so, with the car in front rapidly looming larger in her
windscreen, she pressed carefully on the brake pedal and, in perfect control, smashed into the car in front. The damage to both cars cost many thousands of dollars to repair and probably wouldn’t have happened if she had hit the brake pedal hard enough.

But she isn’t alone in thinking this way.

History of Cars and Brakes

In 1885, Gottlieb Daimler built a petrol Internal Combustion Engine motorbike (just a wooden pushbike with a motor), and Carl Benz built a petrol Internal Combustion Engine three-wheeler car (which had a top speed of about 13 kph). The next year, Daimler fitted his engine to a horse carriage, thus creating the world’s first four-wheeled car.

The first car brakes were modified bicycle brakes, activated by steel wires. In 1902, Louis Renault invented the drum brake. In a drum brake, a brake shoe covered with friction material pushes against the inside of a drum, fixed to the road wheel. The friction material, being inside the sealed drum, is not in the moving air. This means that the friction material cannot readily get rid of any heat that it may generate. Indeed, after repeated braking—e.g. coming down a steep hill with a big load—the friction material can get very hot and lose its friction. This loss of ability to slow down is called ‘brake fade’.

In 1908, Henry Ford began large-scale mass production of the car. The price plummeted, making cars more affordable. The first all-steel body was built in 1914.

At the time, car brakes were activated by steel wires which needed very careful adjustment to make them pull equally on each wheel. In 1921, hydraulic brakes were invented. They automatically applied equal pressure to each wheel brake. By the late 1920s, brakes on all four wheels were becoming popular.

In the 1960s, disc brakes—with their greater resistance to brake fade—became more common in motor vehicles. In disc brakes, friction material is squeezed against a rotating disc, fixed to the road wheel. Because both the friction material and the disc are in the moving air, they can more readily get rid of their heat. Nevertheless, after very severe repeated braking, even disc brakes can fade.

Friction Ain’t Friction

It turns out that when a car brakes hard, there are two types of friction involved—‘Static’ and ‘Dynamic’. And Static Friction is not as great as Dynamic Friction.

Imagine this scenario: you brake as hard as you can, planting your foot on the brake pedal with all your force. All the brakes work well, grabbing the road wheels so firmly that they come to a complete halt. This is called ‘locking the brakes’ or ‘locking the tyres’. Your car slides down the road, slowing fairly rapidly, with a small patch of rubber on each wheel being your only contact with the road. These four patches of rubber get very hot, and rubber smoke gusts into the air as strips of rubber leave the tyres and melt into the road. This is accompanied by a loud screeching noise.

It’s all very satisfying, but there are two problems with this scenario.

First, while each patch of rubber was getting very hot as the stationary tyre skidded down the road, you lost all steering ability. You could turn the steering wheel either way, but it would make no difference to where the car went. Therefore, if your car was aimed slightly off the road when you locked the brakes, you would veer off the road in that direction—for as long as your brakes were locked. Of course, you could take your foot off the brakes and regain steering control—but you would no longer be slowing down.

Second, you were not stopping as quickly as you possibly could. The Static Friction (when your tyre is static, and no longer rotating) is not as great as Dynamic Friction (where the tyre is not locked, but still grabbing the road).

What to do?

Anti-Lock Braking System (ABS)

Well, if you were a professional racing or rally driver, you’d know what to do. You would apply the maximum amount of pressure on the brake pedal that would almost (but not quite) lock the brakes. And if you felt the brakes lock, you would back off the pressure, and then re-apply it. But the vast majority of drivers are not skilled enough to do this.

Back in 1929, French aircraft and automobile enthusiast Gabriel Voison invented an Anti-lock Braking System (ABS) for aircraft. It first appeared in cars in the 1966 Jensen Interceptor FF. And Mercedes-Benz introduced the first fully electronic four-wheel ABS system in 1987. Today, practically all new cars have ABS—and if a car you’d like to buy doesn’t have ABS, don’t buy it!

ABS relies on your hitting the brakes as hard as you can. Then it monitors each of the four wheels. The moment that one wheel begins to rotate a lot slower than the other wheels (and is about to lock up), the ABS drops the hydraulic pressure to just that wheel. It then re-applies the pressure. Modern ABS can do this 20 times per second. What you, the driver, feels is the brake pedal ‘pulsating’ or vibrating under your foot. This is a little disconcerting at first but is entirely normal.

With ABS, not only can you stop in the minimum distance, but you can also steer the car in any direction you aim it. I love ABS.

I Can’t Stop this Feeling

When there is a sudden lifting of the foot off the accelerator pedal, AND a sudden shift of the foot from the accelerator to the brake pedal, BUT the driver has not applied vigorous pressure, THEN the Brake Assist system takes over and applies full braking power. It somehow ‘recognises’ that a panic stop is needed, and takes control.

During emergency braking, the Anti-lock Braking System (quite different from Brake Assist, but you have to have it for Brake Assist to work) prevents any risk of wheel locking and thus helps you better control any loss of grip (i.e. you can both steer and brake at the same time).

In Australia, in 2003, the Monash University Accident Research Centre discovered that ABS reduced the number of multiple-vehicle crashes by 18%, and the number of crashes where the car ran off the road by 35%.

But drivers still have to know how to use their brakes properly.

Brake Assist

Even back in the 1990s, a few car manufacturers were well aware of this gap in the education of many drivers. In 1992, Mercedes-Benz tested drivers in a simulated emergency braking situation. The results proved to be very interesting.

The act of braking has two parts—first, shifting your foot onto the brake pedal and, second, applying pressure. In the Mercedes-Benz study there was no real problem with the first part. In an emergency situation, about three-quarters of drivers tested would shift their right foot very quickly from the accelerator to the brake pedal. The problem occurred with the second part. Over 90% of drivers simply would not press the brake pedal hard enough to achieve maximum braking.

It seemed that, deep down, many drivers believed the myth that heavy braking makes you lose control of your car.

For this reason, Mercedes-Benz (and others) began to develop a system that they called ‘Brake Assist’. Mercedes-Benz introduced it in 1996 and, to their credit, made it standard on all of their cars by 1998. BMW and Volvo followed soon after. There are moves in Europe to make Brake Assist compulsory on all new cars sold in the European Union.

So how does Brake Assist work?

When there is a sudden lifting of the foot off the accelerator pedal, followed by a sudden shift of the foot from the accelerator to the brake pedal, and the driver has not applied vigorous
pressure, then the Brake Assist system takes over and applies full braking power. It somehow ‘recognises’ that a panic stop is needed and takes over.

Of course, the system takes into account your road speed, as well as other conditions. It is clever enough not to activate when the driver is an enthusiast or racing driver doing heavy braking as they enter a tight corner at high speed. So enthusiasts would still have fine control of their braking.

However, the average driver is not so skilful. Typically, the average person can get a car to come to a complete stop from 100 kph in about 73 m—but Brake Assist can reduce this to about 40 m. Today, many manufacturers (including Toyota, Nissan, Ford and Audi) have begun to introduce this kind of technology into their vehicles and one day soon it may be standard on all cars, worldwide.

Practise Panic Stops

Ever since I got my licence, I have been a car enthusiast (as opposed to somebody who just uses a car to get from A to B). About once a year, I will drive to a deserted road and practise doing a panic stop, so that the muscles of my right leg don’t lose the muscle memory of what an emergency stop feels like, and (just as importantly) so that my brain knows how the car will behave (e.g. pull to the left or the right). I practise a few such stops, starting at low speeds and gradually working my way up to around the speed limit. I also taught this skill to my kids when they were learning to drive.

Most drivers will never experience a panic stop in their entire driving career—unless the Brake Assist system turns it on for them. You need to practise braking hard while you’re still alive, to avoid bringing your driving career to a dead stop…

Safety and Cost

There are two different philosophies regarding safety features in cars.

One philosophy is that you get the extra safety features only if you pay extra. This is what happened to me when I changed over from a large seven-seat car to a smaller five-seat car. In a collision, having extra mass helps you survive. In the smaller car, we no longer had the extra mass. The ‘equaliser’, in this case, was the safety feature of lots of airbags. Unfortunately, the only way we could get lots of airbags was to get the luxury model with dead cow and dead tree (which we didn’t particularly want), reversing camera (handy, but we could live without it), Satellite Navigation (handy, but not a necessity) and the additional airbags (essential).

The other philosophy is to maximise safety. In other words, all new cars (even the cheapest) should be equipped with all the latest safety features.

I think the latter should be the
only
option.

Absinthe’s Murky Past

I remember the incident with brilliant clarity—or at least I think I remember it, bearing in mind the fallibility of memory. I was a first-year university student studying physics and hanging out in Wollongong’s only coffee bar (at that time). The subject of absinthe, the dazzling green alcoholic drink with the very murky past, came up in conversation. I declared that it was the ‘wormwood oil’ in absinthe that drove its adherents mad.

How easy it is to be both confident and wrong. It seems that the wormwood oil was innocent. The culprit was the very high level of alcohol that was needed to keep the wormwood oil dissolved and the emerald-green liquid crystal clear.

Absinthe History

Absinthe was often called the ‘Green Fairy’, because of its colour. It was very popular with Parisian artists, poets and intellectuals of the late 19th and early 20th century. Absinthe was thought to stimulate the creative juices in a special way that alcohol did not. However, it exacted a hefty price—a disease associated with absinthe, called ‘absinthism’, which involved terrifying hallucinations, enfeeblement, epileptic attacks and insanity. The attacks of ‘absinthism’ seemed to be very different from the ones associated with alcohol, and were blamed on wormwood oil.

Wormwood is a small shrub belonging to the daisy family. Its essential oil has been used medicinally for thousands of years—against intestinal worms, for labour pains, and for liver and gallbladder complaints. In medieval times, wormwood oil was used in alcoholic drinks in the Val-de-Travers region of western Switzerland.

In 1797, a Major Dubied and his son-in-law, Henry-Louis Pernod, opened the first absinthe distillery in the Val-de-Travers region. Absinthe’s popularity spread quickly, and in 1805 Pernod opened another factory over the border in Pontarlier, France.

Absinthe was widely used by French troops in the Algerian conflicts of the 1830s and 1840s, because of its effectiveness as a tonic and an antimalarial medication. It was also thought ‘that it is an agreeable bitter, that it gives an appetite, and that it gives tone to weak digestions’. The troops brought their love of absinthe back home to France with them.

In France, by the 1870s, 5 pm was
l’heure verte
(the ‘green hour’) when people gathered in bars to drink absinthe. Various rituals and ceremonies became associated with the preparation of the absinthe. Spoons were made with special slots to allow the absinthe to drain through a sugar cube sitting in the spoon. (The sugar counteracted the bitter taste of the absinthe.) Occasionally the absinthe-soaked sugar cube was ignited, with much ceremony. And adding water to the absinthe could lead to a magical clouding of the previously clear drink.