Deconstructing Formula 1: Under the skin

As I have said before during this series of articles on deconstructing a Formula 1 car, mechanical packaging is the biggest hurdle to overcome when designing a grand prix car.

In order to improve the airflow movement around the outer surfaces of the car, every aerodynamicist wants the body surfaces of their car more or less shrink-wrapped around its mechanical components. In a theoretical world this would be fine, but controlling the underbody temperature to reduce the risk of a mechanical failure, such as burned wiring or pipework, is no mean feat.

The biggest user of space and the most complicated challenge to overcome in terms of internal space saving is the engine cooling system.

A modern day F1 engine is built to give maximum performance when it is mounted within the chassis. This means minimising the cooling requirements so that as much airflow as possible can be used to produce downforce. To achieve this, the engines are built with internal tolerances that mean they have to be heated up to 80 degrees C before they can even be started, or risk internal damage or possibly even a seizure. Moreover, because of this they have a very narrow circuit-running temperature band; if it slips outside the 75-85 degrees C band, it could be catastrophic.

While the car is on the track, maintaining a water temperature of around 120 degrees C and an oil temperature of around 110 degrees C, at varying speeds on circuits as different as Monza and Monaco - while also coping with differing ambient temperatures from 15 degrees C at Spa, to 35 degrees C in India - is no simple matter.

The basic principle of creating a cooling package is to measure the size of the radiator core against the engine heat rejection figures from the engine suppliers. There are no shortcuts in this area. Many have tried - including myself - and then, after initial circuit testing, been forced to shoehorn in a bigger radiator.

As you will see from the pictures, all teams go for a radiator core around 50mm thick. This is the most efficient, and going any thicker to cut down on the area required is not a compromise.

After you have this core area, the inlet for the duct will need to be placed into a clean, high-pressure airflow that covers about 20 per cent of it. The exit should then be placed in a low-pressure area that covers around 30 per cent of the radiator core area. This sizing and placement will give a reasonable pressure drop across the radiator core, and packaged within a car concept, will be a reasonable place to start aerodynamic testing. However, it's very easy to cheat the science at this point and reduce the cooling to an inadequate specification. It will give better downforce figures, but reality bites back when the car hits the track!

Taking a look at the different ways the teams go about packaging this requirement shows that underbody aerodynamics are as important to a car's performance as its external surfaces.

I remember at Barcelona in 1998 Patrick Head was standing by one of his cars, which was well down the grid, and beside one of my Jordans and saying at the top his voice to Geoff Willis: "Geoff, underbody aerodynamics that's where the problem lies!" As usual, Patrick was right, at that time no one really bothered with body surfaces around the engine - it was just an inefficient open space.

Red Bull

The Red Bull radiator lies at quite an angle. This is not a problem as long as the inlet duct is efficient and there are no airflow separation problems that cause the front face of the radiator core to be exposed to weak areas of airflow.

On the exit side of the radiator, the exhaust primary pipes are close to the back of the radiator and when the car is on the grid this can cause overheating because of the heat radiation with no airflow. But once the car is moving it will have little effect as long as the open volume is still above the 30 per cent mentioned earlier. Any less than that and it will start to cause a blockage.

The engine fairing is there to minimise the volume changes as the airflow goes through the car, and keeping this consistent helps reduce the risk of increased turbulence, which would affect the airflow efficiency.

Renault

The Renault's radiator is actually at more of an angle to the airflow, this is because the team is the only one to have a forward facing exhaust system. The exhaust tailpipe runs underneath the radiator and continues forward to the leading edge of the underfloor, where it turns 90 degrees and faces outwards, exiting it. High energy exhaust flows across the leading edge of the underfloor and the small corner wing that sticks out from the sidepod creates more downforce from these areas.

At the time the team came up with this concept it was very good, but as the season progressed there was no direction for improvement whereas the other teams improved the rearward diffuser blown exhaust exits. The consequence of this is that Renault got left behind. With the exhausts facing forward, it does not have the same amount of blockage behind the radiator, but if this is managed correctly, it is of little consequence.

McLaren

This is actually a picture of the 2011 McLaren at its press reveal last January, and does not have all the ancillary components that complicate the overall package. It does however show in some detail the internal engine airbox snorkel. Not many years ago this component would have been much larger and more of an expanding duct from the inlet to where it joins onto the trumpet tray. The front and rear side profile would also have intersected at the very extremes of the trumpet tray itself.

As developments have moved on it was found that this original type of design did not offer equal trumpet airflow and that in moving the air around the internal volume it was also moving fuel around this area, reducing the potential efficiency of the engine performance. The Japanese engine manufacturers of the mid-1990s would have gone berserk if a chassis designer had proposed an air box snorkel of this design -in their opinion, bigger was better.

Ferrari

This picture of the Ferrari shows the mess of electronic boxes and their associated wiring harnesses that are all required to be packaged somewhere on the car. Each one of these boxes requires some form of cooling and anti-vibration mounting, and that's a major design exercise in itself. Their placement needs to be as far away from any form of heat source as possible.

Also shown here, forward of the top of the radiator, are two of the four side impact tubes that are required to meet the very stringent FIA crash tests. The other two are lower down and probably attached to the floor. When the floor is put in place they will then be fastened to the chassis to distribute the side impact loads. We saw this area of the Sauber being tested to good effect in Monaco by Sergio Perez. Happily he walked away.