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2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 1 of 15 Suspension Systems - 1 Topics covered in this presentation: Basic Suspension.

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Presentation on theme: "2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 1 of 15 Suspension Systems - 1 Topics covered in this presentation: Basic Suspension."— Presentation transcript:

1 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 1 of 15 Suspension Systems - 1 Topics covered in this presentation: Basic Suspension System Spring Types Suspension System Construction

2 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 2 of 15 Basic Suspension System allow rapid cornering without body roll when the car leans to one side. keep tires in firm contact with the road at all times and conditions. prevent body squat (tilting down at rear) when accelerating. prevent body dive (tilting down at front) when braking. allow front wheels to turn for steering. keep the wheels vertical and in correct alignment at all times. The primary purpose of a suspension system is to support the weight of the vehicle and give a smooth ride. It is desirable that it should also:

3 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 3 of 15 Elementary Suspension System The steering knuckle is ball-jointed to the control arm to allow for vertical and horizontal movements. A control arm that pivots on the vehicle frame. This simple example has a coil spring and built-in shock absorber. In a modern car, the typical suspension components are: All of the components are attached to the frame. Coil spring Shock absorber Steering knuckle Frame Control arm

4 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 4 of 15 A solid axle tilts with road bumps. Independent Suspension This is the preferred system for most modern cars. This causes both wheels to be tilted. Independent suspension allows one wheel to move up or down without appreciably affecting the other. The design of the control arm keeps the wheel upright. Solid axle Independent Suspension

5 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 5 of 15 Coil Spring There are four main types of springs in common use: This consists of a spring-steel rod wound into a coil. It is ideally suited to independent suspension. This is the most common type of spring used by modern vehicles. Coil spring Coil Spring Leaf Spring Torsion Bar Air Spring

6 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 6 of 15 Leaf Spring Flat plates of spring steel are bolted together. This type used to be common but is now only used on a few rear suspension systems. The front end of the spring is bolted directly to the frame. A swinging shackle at the rear permits the length of the spring to change when it is flexed. U-bolts and plates clamp spring to axle housing. Swinging shackle

7 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 7 of 15 Torsion Bar A strut bar prevents front or rear movements of the control arm. When the control arm is moved by the suspension, the twisting motion of the torsion bar resists the movement. Torsion bar Strut bar Control arm The other end of the torsion bar is attached to the control arm so that it twists as the control arm moves up or down. One end of the torsion bar is fixed to the vehicle frame. Vehicle frame Steering knuckle connects onto control arm

8 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 8 of 15 Air Spring This is normally a two-ply rubber cylinder filled with compressed air. It has similar rebound reaction to a coil spring. Rebound (expansion) allows the control arm to move down when there are hollows in the road surface. This is especially adaptable to automatic leveling systems. The air spring is much lighter in weight, compared with its steel sprung equivalent, resulting in increased economy and an adjustable controllable ride.

9 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 9 of 15 Control Arm A control arm holds the steering knuckle, bearing support or axle housing. The control arm is connected to the steering knuckle by a ball joint. Control arm bushings act as bearings. The control arm is free to move up and down with the suspension. Rear suspension control arms may have bushings at both ends. Control arm Steering knuckle Ball joint Bushings

10 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 10 of 15 Control Arm and Strut Rod The control arm is attached to a frame or cradle. Rubber bushes on both the control arm and the strut rod soften the action and absorb shocks. The picture below shows a typical independent suspension front wheel unit. The other end of the control arm is attached to the steering knuckle. A strut rod prevents forward or backward movement of the control arm. Steering knuckle Control arm Strut rod Frame

11 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 11 of 15 Ball Joints Ball joints allow limited movement in all directions. The drive axle must allow universal movement. Ball joint is short for ball-and- socket joint. Two pivots, one above and one below, keep the wheel vertical. A front wheel system is shown, including a steering knuckle. Drive axle Hub Steering knuckle Lower pivot ball joint Upper pivot ball joint

12 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 12 of 15 Shock Absorber The function of a shock absorber is to reduce spring oscillations (up and down movements) following a road shock. The upper end (top mount) is attached to the frame and the lower end (bottom mount) to the suspension unit. A pressurized gas chamber is sometimes added to prevent air bubbles in the oil causing foaming. A piston and valve assembly moves in an oil-filled cylinder. Movement is controlled by the valve, rate-of-flow, restriction. The cylinder is enclosed in a dust cover. Piston and valve assembly Oil cylinder Pressurized gas chamber Top mount Bottom mount Dust cover

13 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 13 of 15 MacPherson Strut Shock Absorber This is a combined coil spring and shock absorber assembly. The upper pivot is the strut mounting to the frame. Bump stops or rebound bumpers prevent metal-to-metal contact. The lower spring seat is part of the shock absorber body. A ball bearing mounting at the top allows steering movements. The shock absorber is inside the strut. Metal strut tube houses shock absorber reservoir, valve, pressure tube etc.

14 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 14 of 15 Stabilizer (Sway) Bar The purpose of the stabilizer bar is to prevent excessive body leaning when turning. Links both the lower control arms together. When one end of the bar is deflected in either direction (up or down), the bar tries to pull the other side in the same direction, this has the effect of stabilizing and controlling the suspension. When cornering, the outside of the body tends to drop, which twists the bar and limits the amount of the sway. Stabilizer bar

15 2. Suspension Systems - 1 Theory Support Automotive – Steering & Suspension 15 of 15 Track (Lateral Control) Bar A track bar prevents side-to- side rear axle movement when cornering. One end of the track bar is fastened to the axle, the other end to the frame on the opposite side of car. Support bracket Diagonal brace Rear (solid) axle Track bar


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