Question

A journal bearing has a shaft diameter of 78.00 mm with a unilateral tolerance of -0.02 mm. The bushing bore has a diameter of 78.10 mm with a unilateral tolerance of 0.06 mm. The bushing is 36 mm long and supports a load of 2 kN. The journal speed is 720 rev/min. For the minimum clearance assembly find the minimum film thickness, the heat loss rate, and the maximum lubricant pressure for SAE 10 and SAE 30 lubricants operating at an average film temperature of 60 C.

Answer 1

Solution Tadial clearence. Caleulate minimum the Can We bmin= The brushing bore diameter Here CMin 2. max The sha tt diameer. 16.10-18 bmi 18.10 mm Cmin dz 16 Mm 0.05 mm Cwin diameter atio leng th Calculate to the We Can Here: L 36 mm 36 o.y62 18 Mm O S o.y62 shaft Yadius of the Caleulate Lhe We Can Y 78 39 mm Load due Caleulate pre csure We Can Here w= 2kN or) 2xlo3N L 36 mm 2 103 0.1122 MPa uuu 8L P 3618) SAE 20 att 60c dynamic Viscocity for obtain the Wle Can Units temperabure in chart 12-13 Viscocity SI from the number using Caleulate Can the Somerfiel We belo eion NN p

min -3 ie.5 mp.s x/o*Pa x 120 mPa 39 .05 o.122 MPa x Jo6 fa MPa 0.1897 Variable and film for thickness chart 12-16 From fiyure minimum film thickness at Yatio ecentricity obtain the and o.S - ho C 0.29 - = *4 0.05 Co.29) minimum .oI4 mm film The thickness = 0.014mm friction Vniable Coeffi cient of Froin figure 2-18 chart for Ceefficient fnictitn variable S= O.1897 and o.S obtain the 39 f-S. .oS 0.00654 - 39 torque Teguired Totate shaft he te Calelte the T- T o.0665y x2x 16 x 39x4p to the Tate of ocake which is equal heat cdulte the the fm Work on Hoss 2TNT 120 Tev xmin min |.m) 2 TT 38.5 u 38-5 W

From ijure 12-21 Chart for maximum film the ressure mazimum the film Pressare ratio t and L0,5 P Pmax 0.3 Pi - Pig 6.7122 Pmax Pmax= 2 .26 MPa 2.2GIMa is maximum lubnicant pressure for (AE 26 dynamic viscocity 12-12 Viscocity temperture obtain G fam figare the for SAE in SI Units Chart M31 mPa.S S= AN Yev 120 min min X MPa 34 S = 6.DS 6.7122 MPa x /b6P^ MPA 0,374 thickneis Yariable film chart for Minimum fare 12-16 From Ailm thickneis minimum obtain the ccentvicity ratio and S = 0.374 and Variable at bo 0.41 O.y2 (0.0s) minimum ln thickness The D.021 mn Df friction Vaniabk Fgure effi cient l2- chatfor From Vaniable aE s= 0. 314 obtan the friction Coetticient of and

8.5 f= d.o 109 torque shaft Yotate Tsired tthe CaJulate T (fxN)Y х 39 mmXt kN mm O. 8S NM. Т- the work on which rate heat loss Calculate the the film 21TNT Hloss (12a vey]win win — 6ч п X в4 и maximum film the chart for determining maxtmum fimpresgure 12-21 From Yntid at sz0.314 obtain press are" the 0.38 Pmax oTI22 o.38 Pmax 1. 8142 MPa Pinax 20 iS Pressure for SAE Lubricant maximum the Therefore Mра .