McPherson independent suspension system is one of the most used in the front but can also be mounted on the rear. This system is one of the simplest independent suspension designs and most used in the steering wheels, for its simplicity of manufacture and maintenance, the cost of production and the little space that occupies. Its mechanism forms an articulated triangle formed by the lower arm, frame and spring-damper.
The lower figure shows a detailed model of a McPherson suspension with lower arm and stabilizer bar.
The spindle of the wheel is connected to the hub allowing rotation of the latter by means of a bearing. At the same time the spindle is attached to the frame through two elements characteristic of any suspension McPherson:
The lower arm which is attached to the spindle by an elastic connection (ball joint) and connected to the frame by a bush.
The helicoidal spring-damper assembly. The damper is fixedly anchored to the top of the spindle and the spring is concentric to the damper and is secured by two upper cups and lower. The damper is attached to the frame at its upper part by means of a needle bearing and a fixing plate. In the front wheels, it becomes necessary the existence of this axial bearing since the damper to be fixed to the spindle rotates with it when acting the steering.
The McPherson type suspension forms an articulated triangle-type mechanism formed by the lower arm, the spring-damper assembly and the chassis itself. The side of the triangle that corresponds to the spring-damper is of free compression so it only has a single degree of freedom: the tensile or compression of the elastic elements and damper. When all the stresses on the chassis are transmitted through the spring-damper, a more rigid dimensioning of the body is required in the bearing area of the fixing plate.
The stabilizer bar is attached to the lower arm by a link and to the frame by means of a bushing, and in this case a forward link.
Currently exist many variations as to the replacement of lower seat that can be performed by a lower triangle, double transverse link rod with longitudinal tie, etc. These latter systems have also been called “false” McPherson, but in any case, they all use the damper as a guiding element and maintain the articulated triangle structure.
The classic McPherson suspension has the stabilizer bar as a longitudinal strut, while the so-called “fake” McPherson already absorb the longitudinal stresses with the very arrangement of the element anchor that replaces the lower arm.
The lower figure shows a McPherson schematic where the lower arm has been replaced by a triangle which is attached to the spindle by means of a ball and to the cradle of the motor by means of two bushes. The rest of the components are similar to that of a conventional McPherson.