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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