Theory of Machines (Mech)

Mechanisms:

• Link, kinematic pair, kinematic chain, mechanism, machine.
• Slider-crank: converts rotary to reciprocating (IC engines).
• Four-bar linkage: basic of all mechanisms.

Gears:

• Spur gears: parallel shafts.
• Helical: smoother, higher loads.
• Bevel: intersecting shafts.
• Worm gear: large reduction.

Gear ratio: N1/N2 = T2/T1 (rpm inversely related to teeth count).

Belt drives:

• Open belt (same direction), crossed (opposite).
• Velocity ratio: N1/N2 = D2/D1.
• Slip: 1-2%.
• Length of belt: L = (D1+D2)/2 × π + 2C + (D1-D2)²/(4C).

Cams:

• Convert rotary to reciprocating with custom motion.
• Types: knife-edge, roller, flat-faced follower.
• Cam profiles: SHM, parabolic, cycloidal.

Governors:

• Maintain engine speed despite load changes.
• Types: Watt, Porter, Proell, Hartnell.
• Sensitivity, isochronism concepts.

Balancing:

• Static + dynamic balancing of rotating masses.
• Balancing in single + multiple planes.

Flywheel: stores rotational KE; smoothens power fluctuations.

RRB JE focus: gear ratio calculations, belt drive problems, simple cam profiles.