Design of journal bearings

all types of journal bearing. Made easy for the students. Easy language to grasp more about.

1. DESIGN OF JOURNAL BEARINGS BY : ALTAMASH ALI

2. CONTENTS Introduction Types Of Journal Bearings Material Used For Journal Bearings Terms Used In Hydrodynamic Journal Bearings Bearing Characteristic Number And Bearing Modulus Design Procedure For Journal Bearings

3. INTRODUCTION In journal bearing sliding action is along the circumference of circle or an arc of circle and carrying radial loads. [1]

4. TYPES OF JOURNAL BEARINGS According to angle of contact of journal bearings [2]

5. CONTINUE ….. According to thickness of lubricating layer [3]

6. HYDRODYNAMIC AND HYDRO STATIC BEARINGS

7. MATERIAL USED FOR JOURNAL BEARINGS 1.Babbit metal Tin base (Tin 90 %, copper 4.5 %, lead 0.5 % ) and L ead base (Lead 84 % Tin 6 %,Antimony 9.5 %copper 0.5) 2. Bronze 3. Cast iron 4. Silver 5. Non metallic bearings

8. TERMS USED IN HYDRODYNAMIC JOURNAL BEARINGS Diametral clearance (c) = D – d Radial clearance (c 1 ) = R – r = (D – d)/2 Diametral clearance ratio = c/d = (D - d)/d Eccentricity is the radial distance between centre of bearing and displaced centre.

9. CONTINUE 5 . Minimum oil film thickness ( ho ) assume ho = c/4 6 . Eccentricity ratio (Ɛ ) = e/c 1 = (c 1 – ho )/ c 1 7 . Short bearing (l/d ˂1) and long bearing (l/d ˃1)

10. BEARING CHARACTERISTIC NUMBER AND BEARING MODULUS Coefficient of friction ( f ) = φ (ZN/p, d/c , l/d ) [1] ZN/p is bearing characteristic number

11. DESIGN PROCEDURE FOR JOURNAL BEARINGS There are two methods for journal bearing design. [4] M . D. Hersey and A . A. Raimondi and J. Boyd

12. M. D. HERSEY METHOD Based on dimensional analysis, applied to an infinitely long bearing. For given Bearing load (W) ,Journal diameter (d) ,Journal speed (N) Find length by choosing l/d ratio from Table 1. Check bearing pressure p = W/ ld Assume lubricant from Table 2 and check operating temperature (to)

13. Table 1 [5]

14. Table 2. Absolute viscosity of commonly used lubricating oil

15. CONTINUE Determine ZN/p and check from Table 1. Assume clearance ratio c/d from Table 1 Determine k is equal to 0.002 for l/d ratio of .75 to 2.8 Determine heat generated Qg = fWV watts Determine heat dissipated Qd = CA( T b – Ta)  

16. A. A. RAIMONDI AND J. BOYD This method is based on hydrodynamic theory used a parameter Sommerfeld number Raimondi and Boyd based on an iterative technique. For L/d ratios of 1, 1:2 and 1:4 and for bearing angles of 360 to 60 extensive design data are available.  

17. Charts have been prepared by Raimondi and Boyd for various design parameters, in dimensionless form, are plotted with respect to Sommerfeld number . [6]

18. CONTINUE These design parameters are given by Raimondi and Boyd Minimum film thickness ( ho /c) Friction coefficient f Flow ratio Qs/Q Maximum film pressure ratio p/ p max Minimum film thickness position θ o

19. REFRENCES [1]. A text book of machine design by R.S . Khurmi and J.S. Gupta reprint in 2011 [2]. http:// www.mdpi.com/2075-4442/3/3/569/htm (accessed on 08/1/017) [3]. http :// www.bearingsensor.com/sleeve%20bearing%20lubrication.html [4]. http :// nptel.ac.in/courses/112102015/30 [5] http :// nptel.ac.in/courses/112102015/20 [6].http :// www.substech.com/dokuwiki/doku.php?id=hydrodynamic_journal_bearing

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