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McGill CF-2-SB Инструкция онлайн [5/132] 828615

Engineering

GENERAL ENGINEERING SECTION

FACTORS INFLUENCING ROLLER BEARING SELECTION

Example 1:

To find the theoretical L

life of an MR-16 bearing operat-

ing at a speed of 500 RPM and under a load of 1000

pounds:

Basic Dynamic Rating of MR-16 = 8000 pounds.

Use formula:

16,666 BDR

10/3

16,666 8000

10/3

500 1000

= 34,132 hours.

Example 2:

Find the Basic Dynamic Rating required for a CAGEROL

bearing operating at 1000 RPM, with a load of 700 pounds.

The required L

Life will be 20,000 hours.

Use the Formula:

BDR = .054 x P x (L

x N)

BDR = .054 x 700 x (20,000 x 1000)

BDR = .054 x 700 x 155

BDR = 5859 Pounds

Shaft hardness and surface finishes

Where bearing inner races are omitted, the mounting

shaft becomes an integral member of the bearing as-

sembly from a fatigue life standpoint. In order to main-

tain catalog ratings, it is necessary to both harden and

finish shafts properly to attain these ratings. Cleanliness

of the steel shaft material is also important.

For such applications, a shaft surface hardness of

HRC 58 minimum is recommended for both through-

hardening and case hardening materials, and in the case

of carburizing grade materials, case depths should be

sufficient to adequately support the load and contact

stresses. For proper bearing operation, a ground shaft

surface finish of 12 microinches AA should not be ex-

ceeded.

Static load rating

The "static load rating" for roller bearings is that uniformly

distributed static radial bearing load which produces a

maximum contact stress of 580,000 PSI acting at the

center of contact of the most heavily loaded rolling ele-

ment. At this stress level, plastic deformation begins to be

significant. Experience has shown that the plastic defor-

mation at this stress level can be tolerated in most bearing

applications without impairment of subsequent bearing

operation. In certain applications where subsequent rota-

tion of the bearing is slow and where smoothness and

friction requirements are not too exacting, a higher static

load limit can be tolerated. Where extreme smoothness is

required or friction requirements are critical, a lower static

load limit may be necessary.

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McGill CF-2-SB Инструкция онлайн [5/132] 828615

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