Ayrton and the vacuum cleaner

A couple of weeks ago I finally got around to seeing the documentary "Senna" about the life of the late Ayrton Senna. Three things really stood out for me. The first was the tremendous on board footage, something we're used to now but which at the time was only rarely seen. The second was  the fly on the wall coverage of the pre-race drivers meetings which revealed their anxious anticipation of what, certainly to them, was a matter of life or death. The third was that there still didn't seem to be a clear explanation of why Senna's car left the track when it did; though no doubt that he probably would have walked away from the accident if the cockpit had been strong enough to prevent a piece of the front suspension from spearing him through the helmet.

One of the changes that were introduced after his death was the introduction of a much tougher cockpit with raised sides to prevent precisely this type of injury. I can remember being taken to the races and from trackside being able to see not only the driver's head but also his shoulders and arms as they worked at the wheel. Whereas Jackie Stewart would go through a series of bends with just a couple of flicks from one side to another other great drivers, such as the late Jochen Rindt, would look like they were in a permanent battle with the wheel. Nowadays we can get some sense of these different styles from the on board cameras but with nothing like the immediacy of the older more dangerous days.

But even though the sport is much safer the same laws of physics apply. In order to go around bends very quickly you need to apply a tremendous sideways force and the only place this can come from is from friction between the tyres and the road surface and this depends on just three things, the tyres, the track surface and how hard the two are pushed together.

If you look at the Formula 1 cars from the Fangio era you'll see that the cars were streamlined so that they would pass through the air as easily as possible. But, in the 1960s designers began to incorporate wings into their designs. Unlike the wings on an aeroplane these were designed to push the car down rather than lift it up. By doing this the maximum frictional force between the tyres and the track  was increased and they could go round corners much more quickly, albeit at the expense of some speed on the straights.

In the 1970s engineers at Lotus began to treat the entire car as an inverted wing and, in particular, exploited what's known as the ground effect. By getting air to travel smoothly and quickly underneath the car you could lower its pressure. This allowed the higher atmospheric pressure on the upper surfaces to push the car down onto the track. Some teams even experimented with fans, to actively suck air out from under the car, and with skirts along the edges to stop the lowered pressure simply pulling air in from the sides.

Some of these experiments turned out to be dangerous, but danger was then part of the appeal and it tended to take serious accidents before regulations were changed. For example, in the 1993 season Williams, the team that Senna was later to join, exploited advances in computing to run a car with active suspension. What this meant was that a computer controlled the suspension so that the ride height remained constant no matter what the driver was doing. This meant that the airflow under the car was smooth and stable and that they could corner at very high speeds without risk of coming unstuck. Partly because of its expense, which the smaller teams couldn't afford, this system was outlawed just before Senna joined the team and Williams had to retrofit the car with conventional suspension.

In the build up to the fateful Grand Prix Senna was concerned about the unpredictable way in which the car was handling on its conventional springs. And when I say concerned I mean really worried. As it was the worst actually did happen and whether a broken steering column caused the accident or was caused by it has never been fully established. What is known, however, is that rapid changes in the ride height, for example caused by bumps, could dramatically alter the downforce and hence the grip and ability to go round corners.

Meanwhile, in a future world, I've been doing my roughly once weekly vacuuming. Paying a little more attention to this task than is usual I noticed that if I did the job more slowly there was greater resistance to motion. Presumably by sucking air out form under the head of the vacuum cleaner is generating groundforce and pushing the rim that surrounds the head of the cleaner more firmly into the carpet thereby making it harder to move. Pushing the vacuum cleaner faster tends to make it bump over the surface and allows air to leak in at the sides. This reduces the groundforce and makes it easier to push. However, it also means that the cleaner isn't doing the job as well as it might and so I've now quite consciously slowed down so that I can, as it were, feel the suck. In this case slower definitely means better.

So, while I don't know for sure why Senna's crash occurred there may be clues to be found in such a humble act as vacuuming a carpet. If education, and in particular scientific education, is about anything at all its about making connections between what might otherwise seem to be disparate phenomena. 

Note to Mr Gove (current UK minister in charge of education) facts have their place as weapons in an argument not just as things to be regurgitated on request.

+ My perhaps surprising interest in motor racing is partially explained in the Big Prize