Vehicle Systems, Chassis, Transmission and Brakes
Driveline path
The power flow is clutch or torque converter → gearbox → propeller shaft with universal joints → final drive → differential → half shafts. A single-plate dry clutch with a diaphragm spring is the norm in cars; the release bearing must have specified free play or the clutch slips. Constant-mesh and synchromesh gearboxes are standard because sliding-mesh boxes wear dogs and cannot be shifted quietly.
An open differential delivers equal torque to both wheels but allows different speeds - that is why one wheel on ice spins while the other stays still. Axle types are classified by what the shaft carries: a fully floating axle carries torque only (bearings on the hub take load), semi-floating carries torque plus bending, three-quarter floating carries torque plus part of the bending.
Steering, suspension, brakes
- Ackermann geometry: cot φ − cot θ = b/L, with b the track and L the wheelbase; inner wheel steers more.
- Wheel alignment angles: camber (in/out at top), caster (steering axis tilt), toe-in, kingpin inclination, scrub radius.
- Suspension: leaf springs, coil springs, MacPherson strut, anti-roll bar; the shock absorber damps, it does not carry load.
- Brakes: drum brakes are self-energising but fade when hot; disc brakes cool better and resist fade; ABS modulates pressure to prevent wheel lock.
Worked example
Engine 3000 rpm, gearbox 3:1, final drive 4:1, rolling radius 0.30 m. Wheel speed = 3000 / (3 × 4) = 250 rpm. Distance per revolution = 2π × 0.30 = 1.885 m. Speed = 250 × 1.885 = 471 m/min = 28.3 km/h.
Traps
- Believing the differential sends more torque to the faster wheel; it does not.
- Mixing caster (steering-axis tilt) with camber (wheel-plane tilt).
- Forgetting that drum brakes, not disc brakes, are self-energising.