DESIGN AND DEVELOPMENT; BEARING SELECTION AND DESIGN Essay Example

Bearing Selection and Design

Bearing Selection and Design

Considering the loading from the gear;

Taking moment about bearing A, then the reactions at the bearing supports will be obtained as follows.

Vertical loading

Giving = 2.33KN

And summing vertical forces, then —-2.33+7=0

Giving = 4.66KN

In the Horizontal direction each bearing offers an equal amount of reaction giving an aggregate of 3KN

Thus = 1.5KN and =1.5KN

Combined reactions at bearings;

= 2.7736KNA =

= 4.90213KNB=

Equivalent radial loads are obtained as follows;

Where; W= basic dynamic equivalent radial loads

X= radial load factor and is equal to 1

Y= axial load factor and is equal to 0 since there is no thrust loading

V= rotational factor which is equal to 1 as the inner race is rotating

= constant axial load

= constant radial load

Equivalent radial load at bearing B= KN

If the expected life for 90% of the bearing is 1500 hours and taking a load factor as 1 at steady state condition,

N is obtained from the equation

Where V=

33m/s =

=

N=1273revs

= 114.5767

Basic dynamic load rating, C,=

Where; k=3 for roller bearings

C=4.90213 114.5767^1/31= 23.8095KN

From SKF tables we select the bearing code 6210

2. If bearing no. 61810 is selected, the value of Basic dynamic load rating ,C, from the tables is 6.76KN

L=³

L=³

L=2.6223 and this is life at 90% reliability

life at 99% reliability will be obtained as follows;

Considering life adjustment factors for operating condition and material as 0.9 and 0.85 respectively and their product equal to

b are constants whose value is 1.17

=0.1026

=0.10262.6223

=0.26905

0.26905601273

=3.5223 hours

ii. Expected life in km

Speed= 120km/h

Life= 120km/h3.5223

=422.68km

3. Life of bearing B= life of bearing A= 114.5767

C=

C=

C= 13.47KN

From SKF table the bearing selected is with the code 61910

4. It’s an overestimate, the reason being that the bearing selection and force application is considered at 99% reliability