How is a MacPherson strut mounted?
Discussion
Usually with a spherical joint at the top and bottom.
At the top, the joint is usually direct into the body of the car for a monocoque, but it could also be into the chassis for a car with a separate chassis.
At the bottom the joint is into a wishbone which then connects on into the body of the car at two positions fore and aft. Importantly the strut makes the variable length edge of a triangular base pyramid. The base of the pyramid is actually on the side of the car, vertical pointing upwards.
The wishbone, as a single component, makes the other two edges which are rigid to each other, but mobile relative to the base triangle.
The wishbone allows the strut to change length, and the spherical joints allow the strut to rotate on it's axis whilst it is changing length.
The hub, wheel bearings and stub axle are an integral part of the strut. The lower part of the strut will rotate with the steering.
In practice the top joint is usually a cylindrical bearing shaft captive in a pliant rubber mounting. It mainly sees rotating motion in a vertical axis with just a little twist.
The lower mounting, into the wishbone, sees considerable range of motion in two different axes. Usually it's a proper spherical metal ball in a hard plastic bush.
At the top, the joint is usually direct into the body of the car for a monocoque, but it could also be into the chassis for a car with a separate chassis.
At the bottom the joint is into a wishbone which then connects on into the body of the car at two positions fore and aft. Importantly the strut makes the variable length edge of a triangular base pyramid. The base of the pyramid is actually on the side of the car, vertical pointing upwards.
The wishbone, as a single component, makes the other two edges which are rigid to each other, but mobile relative to the base triangle.
The wishbone allows the strut to change length, and the spherical joints allow the strut to rotate on it's axis whilst it is changing length.
The hub, wheel bearings and stub axle are an integral part of the strut. The lower part of the strut will rotate with the steering.
In practice the top joint is usually a cylindrical bearing shaft captive in a pliant rubber mounting. It mainly sees rotating motion in a vertical axis with just a little twist.
The lower mounting, into the wishbone, sees considerable range of motion in two different axes. Usually it's a proper spherical metal ball in a hard plastic bush.
Edited by dilbert on Saturday 30th July 10:21
dilbert said:
The hub, wheel bearings and stub axle are an integral part of the strut. The lower part of the strut will rotate with the steering.
These days the strut is usually not an integral part of the upright and can be replaced separately. In this case there is no ball joint on the bottom of the strut, either there is a mounting bracket or some kind of collar depending on how it attaches to the upright.Gassing Station | Suspension, Brakes & Tyres | Top of Page | What's New | My Stuff