## Ball Bearing

Consider a ball bearing is selected for a unique assembly. If the design requires a radial load of 0.7 N and a design life of 6, what is the minimum basic load rating?

##
__
__**Hint**

**Hint**

The minimum required basic load rating (the load in which 90% of bearings from a given lot will survive 1 million revolutions) is:

$$$C=PL^{1/a}$$$

where
$$C$$
is the minimum required basic load rating,
$$P$$
is the design radial load,
$$L$$
is the design life (in millions of revolutions), and
$$a$$
is the bearing coefficient.

##
__
__**Hint 2**

**Hint 2**

For ball bearings:
$$a=3$$

For roller bearings:
$$a=\frac{10}{3}$$

The minimum required basic load rating (the load in which 90% of bearings from a given lot will survive 1 million revolutions) is:

$$$C=PL^{1/a}$$$

where
$$C$$
is the minimum required basic load rating,
$$P$$
is the design radial load,
$$L$$
is the design life (in millions of revolutions), and
$$a$$
is the bearing coefficient. For roller bearings,
$$a=10/3$$
. However, the problem statement is asking for a ball bearing, so
$$a=3$$
. Thus,

$$$C=(0.7N)(6\cdot 10^6)^{1/3}=(0.7N)(181.71)=127.2\:N$$$

127.2 N