Gearbox stress in Monaco

Monaco challenges

The Monaco Grand Prix is not only one of the hardest stress tests in the Formula 1 calendar for the drivers: the race on the streets of the Principality on the Cote d'Azur also places huge demands on the machinery, and especially the gearbox. Going through roughly 3,600 gearshifts, the gearbox has to give its all on the city track with its many corners. That's extremely hard work – equivalent to one change every second.

However, the fact that in Monaco the drivers have to change gear roughly 20 per cent more often than on tracks such as Monza is not the only problem. "Because of the many undulations and bumps on the city track, the wheels lose ground contact for a fraction of a second every so often," explains Gordon Day from the WilliamsF1 Team. "That makes shifting gear really difficult, even if the gearbox is set up perfectly."

Gearbox design

The days of manual gearshifts in Formula 1 are long past. That makes the work easier for the drivers, who can engage a new gear with a rocker switch on the steering wheel, but not for the gearbox. A gearshift lasts roughly 25 to 30 milliseconds, and a lot of things happen in that short time that have to be coordinated perfectly. For instance, if the driver shifts gear at precisely the moment when the engine speed is increasing quickly because he has just driven over a manhole cover, the whole gearshift can often get out of rhythm. The teams closely monitor how well the gearbox copes with the stress: it is completely dismantled after every race and checked for cracks.

When performing at the limit, the gearbox is subjected to extreme loads. And for his own safety, the driver needs to be able to rely on the fact that all the parts will cope with these strains. No wonder the very best is only just good enough for a Formula 1 gearbox. For instance, the gearbox housing, which has to be as rigid as possible because the entire rear axle is attached to it, is generally made of titanium and carbon fibre. The ball bearings are ceramic and the gear wheels are made of high strength steel. Due to their low weight, aluminium and various plastics are used as additional materials.

A gearbox is a carefully cultured, high-tech product, and its 400 individual parts are all specially produced – right down to the bearings and seals. Naturally, that all has its price: a Formula 1 gearbox, according to expert estimates, costs about 125,000 euros. The reliability of the individual parts varies: while the gear wheels are replaced after every race, the gearbox housing normally lasts for the whole season. The gearbox is fastened on the rear of the engine and connected directly to the carbon-fibre clutch, which costs about 10,000 €, weighs less than 1.5kg and has to withstand temperatures up to 500°C.

In passenger cars, the strains on the gearbox and clutch are much less extreme, but even so the gearbox technology in particular has developed dynamically in recent years. "The trend towards more gears and automatic transmissions is allowing us to develop efficient engine management with speeds that cause lower fuel consumption," says Dr. Christoph Lauterwasser from the Allianz Centre for Technology. "Thanks to modern control technology, the transmission and engine management and the brake and stabilisation systems can be networked together. That means greater driving comfort and the possibility of adapting individually to the specific driving conditions. For instance, the shifting points can be varied from sporty to economical or you can engage or disengage the clutch electronically, depending on the driving situation."

In Formula 1, every team builds its own gearbox. The regulations stipulate a minimum of four and maximum of seven forward gears and one reverse gear. The design of the gearbox is closely linked to the aerodynamics of the car. In 2005, the gearboxes had to become smaller because there was less space available due to the new aerodynamics regulations. This year, the change from V10 to V8 engines has allowed the teams to continue on this reduction diet. However, the actual advantage of the new gearboxes is not their smaller size, but their lower weight. After all, every kilogram saved can be used somewhere else in the car to aid its balance.

The designers guard the facts about the size of the weight advantage like a state secret. They do not even disclose the precise weight of the gearbox, which is between 25 and 35kg. The experts only let one small fact slip: nowadays, the gearboxes in Formula 1 are not only about 20 per cent lighter than five years ago, but also much more robust – which makes them safer.

Allianz Safety Check: Monaco Circuit

"On this narrow city track, which naturally doesn't have the same high safety standards as other grand prix tracks, you can't afford even the smallest mistake. There aren't any real run-off zones, just walls and crash barriers. The eight second drive through the harbour tunnel is particularly critical: the only real full-throttle section in the whole maze of corners. The changes in the light are extreme. At least now they have installed reflectors that guide natural daylight into the tunnel to improve the vision. One small step towards greater safety."