Chassis design (Mondeo 3)

Servo support: two steering racks with different gears

A - Hydraulic oil circulation, 1 - Energy absorbing element with driver's airbag, 2 — Steering rack with cardanic division,	3 — Lower steering column trim, 4 — Upper trim of the steering gear stand, 5 - Oil cooler.

The chassis is responsible for the good dynamic parameters and ride comfort in the Mondeo. Theoretically, in all conceivable road situations, it should strictly coordinate the position of the wheels on various road surfaces and during any movement.

But that's only in theory - in practice it's nothing more than a compromise that should come as close to the ideal as possible. A Sisyphean task involving industrial-strength computers, state-of-the-art software and - around the globe - countless test runs under various conditions. Because the wheels of your Mondeo not only have to "spin", they also have to - as unnoticeably as possible - make targeted up and down movements and changes in direction while driving: even when braking or accelerating, various forces arise that seriously affect the chassis.



And here teamwork is needed, when all components are strictly coordinated with each other and suit each other. The chassis includes the suspension and shock absorption systems, wheel suspensions of the front and rear axles, the steering mechanism and the wheels themselves with tires. The brake system, which is also an integral component of the chassis, is described in detail in a separate chapter "Brake system".

It's a delicate matter - the balance of the chassis

Even in the age of computerization, well-designed wheel suspensions are a difficult task: the wheels must constantly be at strictly defined angles to the vehicle's axis. As soon as your Mondeo crosses, for example, an uneven surface or negotiates a sharp bend, forces inevitably arise that change the geometry of the wheels. At the same time, the wheels must never lose contact with the road surface, otherwise, due to the action of centrifugal forces, your Mondeo would end up off the road along the shortest path. To prevent this from happening, the wheels cushion the shocks relative to the body: in collaboration with the shock absorbers, the springs "parry" the impacts, they "discharge" the road surface. Shock absorbers should actually be called vibration dampers. Since they do not dampen the shocks themselves, but only weaken the natural vibrations of the springs and tires.

Steering mechanism and driving safety are linked together

Driving dynamics and road safety, among other things, depend on the fact that the wheels turn reliably in the right direction. This pair must do everything sensitively and purposefully. The steering mechanism response is also strictly coordinated with the axles and steering mechanism geometry.




The Mondeo chassis is a good example of how a premium mid-size car – in terms of comfort and driving safety – does not require big compromises. The front wheels of the Mondeo are "disciplined" by MacPherson shock absorbers, the rear wheels work separately – on the rear axle, "baptized" in Ford Jargon Quadralink. The rear axle works with track correction, which makes the Mondeo quite a pleasant car to drive. All components of the rear suspension are supported by a separate auxiliary frame, it is – to reduce noise – screwed to the bottom.

TECHNICAL DICTIONARY

Steering geometry terms Wheel alignment: The front wheels are slightly closer to each other than the rear wheels (rolling on each other). This helps to equalize the friction between the wheel and the road surface, which would "pull" the left wheel automatically to the left, and the right wheel is forced to the right. To maintain the movement of the steering wheel and the forces applied to the steering wheel rim when turning, the inner wheel turns more when turning compared to the outer wheel - positive wheel alignment turns into negative wheel alignment (the wheels in the back are closer to each other than in the front). A typical picture of positive wheel alignment is when the front wheels are closer together at the front than at the rear. Wheel alignment: the tilt of the wheel to an imaginary vertical line passing through the center of the wheel. Reduces the impact of the road surface on the steering mechanism, reduces the forces acting on the wheel when turning, and the friction of the wheels on the surface. The front wheels of the Mondeo have a positive camber - they are located at the top in the wheel well slightly further from each other than at the bottom on the ground. Transverse inclination of kingpin: the tilt of the steering axis relative to the vertical line. If we assume that the line of such an axis is directed to the ground and measure the distance to the center line passing through the wheel (the central point of the contact surface of the tire), we obtain the rolling shoulder. In order to avoid the effect of interfering forces on control, it is necessary that the rolling shoulder be as small as possible. Together with the negative toe-in of the wheels, the transverse tilt of the kingpin causes, among other things, the effect when the car is slightly raised at the front with broken wheels. Negative wheel alignment: the distance (in the direction of travel) between the supposed extended line of the steering axle to the ground and the center point of the tire contact surface. This toe-in allows the wheels to stretch (not shift). Stretched wheels are necessary to align themselves straight and maintain stability in that position. Wheel parameters: A: Negative wheel toe-in, B: Wheel camber, C: Kingpin caster.