Centre of gravity
The centre of gravity is perhaps the single most critical area of any racing car weight consideration. It must be as low as possible to the ground, and this is not only because the weight act through it, but also because all accelerative forces of acceleration, braking and cornering work trough it.
Any force that acts through the CoG has no tendency to make the car rotate.
Center of gravity location can be defined as:
- The balance point of an object
- The point through which a force will cause pure translation
- The point about which gravity moments are balanced
The center of gravity (CoG) is also called center of mass.
The center of gravity location must be referenced to a 3 dimensional coordinate system. CoG location is directly a function of the coordinate system in which it is referenced. It is measured relative to a reference datum using moment balance equations.
If you apply the force in a direction that does not pass through the CoG, it will make the car rotate unless it is balanced by another force.
For a racing car, the CoG is located between the front and rear wheels and as close to the ground as physically possible, and this is not only because the weight act through it, but also because all accelerative forces of acceleration, braking and cornering work trough it.
You know from traveling in a road car that when the driver brakes, the car dives down at the front. Equally, you have experienced rolling in corners, and squat - the car sitting down in acceleration if you put your foot down hard enough. These movements you feel are accelerative forces, and they are acting through the centre of gravity. Much of their control is owed to suspension design, but a high centre of gravity won't help. Lower center of gravity - less rolling, squatting and diving, less weight transfer.
However, it is not only vertical centre of gravity position designers are interested in - it must be on the centerline of the car, and its position between the front and rear wheels will determine how the braking and accelerative forces is spread between front-rear or left-right wheels. It is good to have the static weight distribution tuned in way that the centre of gravity is positioned closer to the rear of the car, as this puts more weight on the rear wheels and provides more traction, but some F1 teams think differently (see Weight Balance).
As well as this, the vehicle should have a low polar moment of inertia. This basically means how easy it is to move car around, and if the designer concentrates the weight close to the centre of gravity, he can achieve this, and obtain a responsive racecar. These criteria are, of course, also dependent on where the wheels are in the first place - and the F1 wheelbases are so long that with a low centre of gravity and such stiff suspension, squat and dive are significantly minimized. Any wheelbase changes are often to change static load distribution and reduce weight transfer rather than improving stability.
There is only few companies in the world manufacturing Centre of the gravity machine. They are a highly sophisticated and expensive piece of equipement.
One of them is Space Electronics, the world's number one manufacturer of aerospace mass properties measurement instruments.
