Govt. Exams
Entrance Exams
Center distance = m(N₁ + N₂)/2 = 2(60 + N₂)/2 = 90. Therefore, 60 + N₂ = 90, so N₂ = 30 teeth.
Screw efficiency = (Load × pitch)/(2π × effort × radius). It represents the ratio of useful work output to the energy input, typically ranging from 25-90%.
Bearing bore surfaces typically require Ra 0.4 - 0.8 µm for proper fit and performance. Higher roughness can affect bearing life and accuracy.
J = π/32 × (D⁴ - d⁴) = π/32 × (50⁴ - 30⁴) = π/32 × (6,250,000 - 810,000) ≈ 257,484 mm⁴
L10 life is the bearing life at which 90% of an identical group of bearings will complete without spalling, or conversely, 10% will have failed.
The stress concentration factor accounts for stress amplification due to geometric features like fillets, holes, and shoulders that create local stress rises.
Power = (T1 - T2) × π × D × N / 60,000 = (1200 - 400) × π × 0.2 × 600 / 60,000 ≈ 5.03 kW
The pitch angle (also called helix angle) is the angle made by the thread with the axis of the screw, calculated as tan(α) = pitch/(π × d).
While all factors affect coupling design, the material of the shaft itself is not a direct selection criterion. Torque, speed, and misalignment are primary factors.
Shear stress = Load/(Weld size × Length × 0.707) = 50,000/(6 × 100 × 0.707) ≈ 41.67 MPa. The factor 0.707 accounts for the throat area of the weld.
