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#1
Old 01-21-2009, 05:54 PM
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Roller bearing VS tapered bearing.

Under the same loads, made of equal material, same operating environment as to contamination and quality of seals, etc., Which is the better load carrier and and has better life expectancy?

If the tapered use grease and the roller use an oil bath, how does that change the outcome?

Straight non turning spinning weight and turning spinning weight ( auto front steering wheel?
#2
Old 01-21-2009, 06:53 PM
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Not an expert, but tapered roller bearings are normally used for axial loads rather than straight radial loads. An automobile front wheel would seem to have both kinds of loads. all the ones I ever repacked have been tapered roller bearings. And that was on rear wheel drive cars, but I don't think it would make any difference.
#3
Old 01-21-2009, 07:10 PM
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Most FWD cars use non-serviceable double-row ball bearings on the front (a page in TechOne mentions this). Newer 4WD trucks and SUVs have unit bearings on the front axle, but I'm not sure whether these are also ball bearings.
#4
Old 01-21-2009, 07:27 PM
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Depends on HOW they're loaded - radially, axially, some combination, steady or varying, what loads ...

A tapered roller bearing can take thrust (axial) loads, albeit in only one direction so they're generally installed in opposing pairs, as on a car axle. A radial load with no axial component will induce a thrust load, as the cone tries to squeeze out one way. Also, a tapered bearing will have fewer rolling elements, and that generally means lesser radial capacity.

There are people who devote their careers to bearing applications. There are too many considerations to give you the blanket answer you want.
#5
Old 01-22-2009, 06:19 AM
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Divergent, possibly erroneous nitpick- the bearings under discussion never have "seals" (elastomeric ) but rather, "shields", and then rarely, IME.
#6
Old 01-22-2009, 10:35 AM
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Quote:
Originally Posted by Carson O'Genic View Post
Divergent, possibly erroneous nitpick- the bearings under discussion never have "seals" (elastomeric ) but rather, "shields", and then rarely, IME.
True.... And you're right, 'nitpick'

New condition.
Everything zactly the same except... Just a spinning weight powered by whatever, what lasts the longest, taper pair in a reasonable amount of grease or equal rollers, same surface area as the tapers, not ball, bearing surfaces in a reasonable amount of oil? Assume slow enough rotatopm that heat build up is not an issue.

Maybe a general, grease or oil bath = best for slow rotation speeds, less than 100 RPMs? 500 RPMs, 1000 RPMs and weight increases? Where would the break even point be?

Don't rail cars use oil? (heavy but some need for taper bearings due to side loads?

Any bearing geeks out there?
#7
Old 01-22-2009, 10:51 AM
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This is from Shigley's Mechanical Engineering Design:
Quote:
Use Grease When:
The temperature is not over 200F
The speed is low
Unusual protection is required from the entrance of foreign matter
Simple bearing enclosures are desired
Operation for long periods without attention is desired.

Use Oil When:
Speeds are high
Temperatures are high.
Oiltight seals are readily employed
Bearing type is not suitable for grease lubrication.
The bearing is lubricated from a central supply which is also used for other machine parts.
As others have said, there's no one answer to your question. If there's no axial load, cylindrical roller bearings. It starts to get complicated after that, though. Shigley devotes an entire chapter to bearings. It's quite complex, yet easy to grasp. There's no easy way to sum it up, but, in general, the bearing manufacturer gives specifics based on some standard they use to test the bearings, and the life drops quickly as more load is applied. There are tables and tables of data, and one would need all variables to make an intelligent decision.

ETA: Also, what do you mean by "equal"? Equal price? Equal shaft size? Equal roller size? Equal load capacity rating?

Last edited by Santo Rugger; 01-22-2009 at 10:52 AM.
#8
Old 01-22-2009, 02:33 PM
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I guess that is as good an answer as there is, no point in beating this horse anymore. Thanks people, all were helpful answers...

Last edited by GusNSpot; 01-22-2009 at 02:33 PM. Reason: typo
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