You are asked to design a plain surface journal bearing to carry a steady radial load of 5.75 kN while the shaft rotates at 950 rpm. The shaft stress analysis determines that an acceptable nominal diameter of the journal is 62.5-mm and an l/d ratio is 1. The shaft is part of a machine requiring good precision. So a minimum radial clearance cmin = 0.040 mm seems appropriate. We shall use SAE 30 oil as a lubricant, at an inlet temperature of 45 oC. Analyze the hypothetical bearing, a) Determine the operating temperature Tave, and operating viscosity μave. b) Determine the minimum film thickness, ho, temperature rise of the lubricant, ΔTC, the total oil flow, Q, and side flow Qs in [mm3 /s], the maximum film pressure Pmax developed in [MPa]. c) Determine the power loss, Hloss in [W], friction torque, Tf in [N-m] d) For minimum radial clearances, perform a design assessment using Trumpler’s criteria.
You are asked to design a plain surface journal bearing to carry a steady radial
load of 5.75 kN while the shaft rotates at 950 rpm. The shaft stress analysis determines
that an acceptable nominal diameter of the journal is 62.5-mm and an l/d ratio is 1. The
shaft is part of a machine requiring good precision. So a minimum radial clearance cmin
= 0.040 mm seems appropriate. We shall use SAE 30 oil as a lubricant, at an inlet
temperature of 45 oC. Analyze the hypothetical bearing,
a) Determine the operating temperature Tave, and operating viscosity μave.
b) Determine the minimum film thickness, ho, temperature rise of the lubricant, ΔTC,
the total oil flow, Q, and side flow Qs in [mm3
/s], the maximum film pressure Pmax
developed in [MPa].
c) Determine the power loss, Hloss in [W], friction torque, Tf in [N-m]
d) For minimum radial clearances, perform a design assessment using Trumpler’s
criteria.
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