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Automotive Mechanics

From transcript: 20ME731 Automotive Mechanics (A)

Cheat sheet

Printable study sheet: formulas → definitions → topic notes → traps.

Formulas

Ackermann: cot δo − cot δi = track / wheelbase
Weight transfer braking: ΔW = (h/L) m a ; roll couple from lateral a
Power P = T ω ; wheel force F = T_wheel / R
Gradeability related to TTE vs m g sinθ + resistances
Brake torque ≈ 2 μ F_clamp R_eff (floating caliper idealization)
Ride: undamped ω = √(k/m) ; damping ratio ζ = c/(2√km)
Understeer gradient ideas: tire cornering stiffness front vs rear
Tractive force ≈ τ_wheel / r ; P = F v
Gear ratio overall = product of stage ratios
Braking: μ N + weight transfer; stopping ≈ v²/(2a)
Ackermann (ideal): cot δo − cot δi = w/l

Definitions

Unsprung mass
Wheel+hub+part of arm — hurts ride/grip if large
Camber / caster / toe / KPI
Alignment angles — contact patch & self-center
SLA / double wishbone
Independent suspension with camber control
Open vs LSD differential
Torque split behavior in slip
Engine braking
Throttle closed drag through driveline
ABS / EBD
Anti-lock / electronic brake distribution
NVH
Noise vibration harshness targets
CG height
Drives pitch/roll transfer — packaging critical
Powertrain
Engine → clutch → gearbox → diff → wheels
Understeer / oversteer
Front vs rear slip angle behavior

Topic-wise short notes

Study these first — one block per syllabus topic. Then read the deep notes below.

Chassis & suspension

  • Ladder/space frame/monocoque trade stiffness, mass, crash, cost.
  • Roll center & instant centers from suspension geometry.
  • Springs/dampers motion ratio from installation leverage.
  • Anti-roll bars tune lateral load transfer distribution.

Driveline & brakes

  • Clutch, gearbox ratios, final drive — tractive effort curve vs road load.
  • CV joints / prop shaft angles — vibration if wrong.
  • Disc vs drum; dual-circuit hydraulics mandatory thinking.
  • Thermal fade: energy → heat in rotors — venting/material.

Tire & vehicle dynamics short

  • Friction ellipse: combined Fx,Fy limited by μ Fz.
  • Load sensitivity: μ effective drops as Fz rises.
  • Understeer if front slip angles grow faster — safe road bias.

Exam traps & quick notes

Comprehensive notes

Chassis & suspension

Ladder/spaceframe; spring-damper; camber/toe/caster effects.

External: SAE student design resources ↗ Milliken Race Car Vehicle Dynamics (ref) ↗

Driveline & brakes

Clutch torque capacity, diff types, hydraulic brake circuits, ABS concept.

External: HowStuffWorks powertrain ↗

Chassis, suspension, tires

Load paths; unsprung mass; camber/toe/caster effects; understeer/oversteer intuition.

External: NPTEL ↗ Engineering Toolbox ↗

Powertrain & brakes

Gear ratios; clutch capacity; differential; hydraulic brakes and bias; Ackermann. BAJA: structure+steering+brakes+integration → 1st place.

External: NPTEL ↗ Engineering Toolbox ↗

Interview Q&A for this subject

Q: What is understeer?
A: Front slip angles grow such that vehicle turns less than commanded — typically safer baseline for street cars.

External: ASQ / quality ↗ MIT OCW ↗