Page 83 - The Tribology Handbook

A13 Oscillatory journal bearings

RO LLI N G B EAR1 NGS
Rolling bearings (Le. ball, roller and needle bearing) may also be used for oscillatory motion, but preferably where the
load is unidirectional, or at least varies with moderate gradient.
~ ~~~ ~ ~~
Static (or near static) loading Dynamic loading
Bearings are selected on the basis of their load-carrying capacity. Bearings are selected on the basis of their required
life before failure.
Examples :
Examples :
CONTROL ROD *' small-end bearings in engines and compressors
plunger-pin bearings in crank-operated presses
connecting rods in textile machinery
connecting rods in wood reciprocating saws

aa f
MOVING PARTS 10 0.53
20 0.65
30 0.72
/ j \, 45 0.81
0.89
60
; I \ 75 0.95
90
1.0
La-J-aA SKF
Rule : Rule:
Use manufacturers figures for the static load coefficient C, multiplied by (1) If a > 90°, each oscillation is considered as a
a factorfsuch that: complete revolution, and the bearing life is
f = 0.5 for sensitive equipment (weights, recorders, etc.) determined as if the bearing was rotating.
f = 1.0 for crane arms, etc. (2) If a < 90°, the equivalent load on the bearing
f = 5.0 for emergency cases on control rods (e.g. for aircraft controls). is reduced by a factorf, taken from the table
above. The calculations are then carried out
as under (1).

ENGINE SMALL-END BEARINGS
I 2-Stroke I
Type of engine ------I 4-Stroke
Large
engines
Type of bearing and NEEDLE BEARINGS: A series of Single central
oil grooving single axial oil PLAIN circumferential oil
grooves
groove. For small
interconnected BEAR'NG bearings, sometimes
by a
rential groove only oil holels)
Type of gudgeon pin Surface finish
f d=B better than
0.05pm CLA
D dw D/3 Material:
L Surface hardened
-_ steel
Bearing material and 21-35 MN/mZ 3000-5000 Phosphor bronze Lead bronze up to Phosphor bronze
allowable pressure* Ibf/in2. The load capacity 2540 MN/mz 25 MN/m2 3500 Ibf/in2 up to
varies, refer to manil- 3500-4300 Ibf/inz 50 MN/m2
facturer's specificatioiis 7100 Ibf/in2
-__I__
Type of f?icticn Rol1ir.g frictioa Mixed to bcjundary Mostly mixed lubrication, but may be fully
friction hydrodynamic under favourable condition
-___ --
== 1 ym/rnm of d I 1-1.5 ym/mm of d * 1 pm/mm of d
Fits. Piri/Pkon 36; Ring1 I
conrod P7
__ - - - - - - - - __ __-- I
-
Remarks This type of bush is Liable to corrosion in plain
suited where ihe loading i often made floating mineral oil. An overlay of
uni-directional iri a fixed steel bush lead-base white metal will
reduce scoring risk
___ - __ - _______- __- --
* Bearing pressure is bascd on projected bearing area, i.e. B x d (ref. sketch above).
AI 3.3