Journal Bearing

A journal orbit study must be done to optimize the clearance space between the journal and the bearing surface. The study must provide the minimum oil film thickness (MOFT) and the Peak oil film pressure (POFP). Values of these parameters for the optimized clearance are important factors. The MOFT is used in the calculation of the oil flow, temperature rise, and heat balance. According to Conway-Jones and Tarver [1993], about 52% of the heat generated in connecting rod bearings in automobile engines is carried away by the oil flow. Approximately 38% of the remaining heat flows into the adjacent main bearings via the crankshaft. The remaining 10% is lost by convection and radiation. In the case of main bearings, about 95% of the total heat is carried away by the oil flow, which is estimated to be more than five times the flow through the connecting rod bearings, which were fed by a single oil hole drilled in the crank pin. The POFP is the guiding factor in the selection of a bearing life.
[source : Subramanyan, P. K. “Crankshaft Journal Bearings” The Engineering Handbook]

Calculation of Diameter based on static loading on crank shaft due to thrust force by piston.(excel sheet) Bore X stroke | 73 × 79.5 mm | Max Combustion pressure(kPa) (Source: http://www.carfolio.com) | 30 | Force on piston | 12.549795 | | | Thrust on connecting rod | 12.78505755 | Angle (sinϴ=sinØ/(9L/R) (Source: Heywood) | 0.192135793 | Tangential force shaft FT | 9.190442405 | Radial force on shaft FR | 8.887826779 | Reaction on bearing Due to FT | 4.595221203 | Reaction at on bearing due to FR | 4.443913389 | F equ. | 12.78505755 | crank length(mm) http://www.carfolio.com) | 120 | Crank pin length(mm) http://www.carfolio.com) | 40 | Bore diameter(mm) http://www.carfolio.com) | 73 | | | Angle with line of stroke of crank shaft(rad)(Source Heywood) | 0.61 | Limited shear stress(N/mm2 ) (Source Shigley’s ) | 30 | Bending moment due to radial load Mc