Outline Hydrodynamic/Journal/Sleeve Bearings Rolling-Element Bearings

typesselection of roller bearings

Bearingsall bearings are of course only

necessary evils, contributing nothing to the product or function of the machine; and any virtues they can have are only of a negative order. Their merits consist in absorbing as little power as possible, wearing out as slowly as possible, occupying as little space as possible, and costing as little as possible (Michell, 1929)

Comparing Rolling to Journal Rolling Bearing are better because:

low starting and good operating friction radial and thrust loads no self-excited instabilities less space axially can seal lubricant in bearing

Journal Bearings are better because: fatigue failure not a problem less space radially less noise more tolerant to misalignment less expensive, except for oiling system less operating friction

dee

p g

roo

ve b

all

full

jour

nal

pg. 654 in Norton

                                                                                   

Reprinted From: "Design Data" Teague & Dunn, Machine Elements See http://www.engineersedge.com/bearing_application.htm

Rolling Element Bearings

Ball Bearings

good for smaller sizes, lighter loads

Roller Bearings good for larger sizes, heavier loads handle shock and impact loading well

Plain

Tapered

Spherical

Rolling Element ComparisonsFigure 10-21, Pg. 658 in Norton

Rolling Element Analysis Load Rating

Calculate P lookup C, C0 in tablecalculate for a specific number of cycles

Rating Life, L10

life at which 10% of bearings have failed in millions of revolutions or in hours

Equivalent load for combined conditionsneeded when axial and thrust loads are present

Variable loading

Bearing Selection, P 10-26,27 Get tangential load on Gear 2 from equal &

opposite torques Get radial loads using radial load factor Get bearing reactions in x-dir from gear loads

in x-z plane only Get bearing reactions in y-dir from gear loads

in y-z plane only Get total vector load at each bearing (sqrt of

sum of squares) Calculate needed minimum C, use Fig 10-23