Machinery's Handbook, 31st Edition
Thrust Bearings
2417
14a) Factor X : From Table 5, X = 11.9 approximately 15a) Total flow of lubricant required: . . . Q 30 R # = =
119 107 042gallon per minute
16a) Bearing-capacity number:
. 60 049 083 # . 2
=
=
. 0023
C
n
17a) Flow factor: From Fig. 10, q = 1.48 18a) Actual hydrodynamic flow of lubricant: . . . .
. 294 4800 19 0003 148 23 0317gallon per minute 1 # # # # = =
Q
19a) Pressure flow:
. 68 19 164 10 30 0003 23 1 15 086 0050gallon per minute 2 5 3 2 # # # # # # # = + = ^ h 20a) Actual flow of lubricant: . . . Q 0317 0050 0367gallon per minute new = + = 21a) Actual bearing-temperature rise: . . . . t F 0367 119 106 344 # ° ∆ = = 22a) Comparison of actual and assumed temperature rises: Now Δ t and Δ t a are within 5°F. 23) Minimum film thickness: . . . h 2 0 003 1 0 86 0 00021 inch o = − = ^ h . . . . . . . Q This analysis may now be repeated for other values of c d determined from Fig. 6 and a complete lubrication analysis performed and plotted as shown in Fig. 11. An operating range for c d can then be determined to optimize minimum clearance, friction horsepower loss, lubricant flow, and temperature rise. Thrust Bearings As the name implies, thrust bearings are used either to absorb axial shaft loads or to position shafts axially. Brief descriptions of the normal designs for these bearings follow with approximate design methods for each. The generally accepted load ranges for these types of bearings are given in Table 1 and the schematic configurations are shown in Fig. 1. The parallel or flat plate thrust bearing is probably the most frequently used type. It is the simplest and lowest in cost of those considered; however, it is also the least capable of absorbing load, as can be seen from Table 1. It is most generally used as a positioning device where loads are either light or occasional. The step bearing, like the parallel plate, is also a relatively simple design. This type of bearing will accept the normal range of thrust loads and lends itself to low-cost, high- volume production. However, this type of bearing becomes sensitive to alignment as its size increases. The tapered land thrust bearing, as shown in Table 1, is capable of high load capacity. Where the step bearing is generally used for small sizes, the tapered land type can be used in larger sizes. However, it is more costly to manufacture and does require good alignment as size is increased. The tilting pad or Kingsbury thrust bearing (as it is commonly referred to) is also capable of high thrust capacity. Because of its construction it is more costly, but it has the inherent advantage of being able to absorb significant amounts of misalignment.
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