Question 1:Which of the bearings given below SHOULD NOT be subjected to a thrust load?
Question 2:Two identical ball bearings Pand Q are operating at loads 30 kN and 45 kN respectively. The ratio of the life of bearing P to the life of bearing Q is
For ball bearing
P.(L)1/3 = C
Given: PP = 30 kN
P2 = 45 kN
Question 3:A lightly loaded full Journal bearing has Journal diameter of 50 mm, bush bore of 50.05 mm and bush length of 20 mm. If rotational speed of Journal is 1200 rpm and average viscosity of liquid lubricant is 0.03 Pa s, the power loss (in W) will be
Given: dj = 50 m m = 0.05 m
dB = 50.05 = 0.05005 m
lB = 20 mm = 0.02 m
N = 1200 rpm
μ = 0.03 Pa– sec
Frictional factor, f = Shear stress x Area
Question 4:A Journal bearing has a shaft diameter of 40 mm and a length of 40 mm. The shaft is rotating at 20 rad/s and the viscosity of the lubricant is 20 mPa.s. The clearance is 0.020 mm. The loss of torque due to the viscosity of the lubricant is approximately
= 400 N/m2.
Force = dA = 400 × 3.14 × .04 × .04
Torque = Force × .02
= .040 N-m
Question 5:A natural feed Journal bearing of diameter 50 mm and length 50 mm operating at 20 revolution/sec. carries a load of 2.0 kN. The lubricant used has a viscosity of 20 mPa.s. The radial clearance is 50 mm. The Sommerfield number for the bearings is
Question 6:A ball bearing operating at a load F has 8000 hours of life. The life of the bearing, in hours, when the load is doubled to 2F is
Question 7:Which one of the following is criterion in the design of hydrodynamic Journal bearings?
Sommerfeld Number, also known as Bearing Characteristic Number,
Question 8:The basic load rating of a ball bearing is
Question 9:The dynamic load capacity of 6306 bearing is 22 kN. The maximum radial load it can sustain to operate at 600 rev/min, for 2000 hours is
Number of revolutions in life = 2000 × 60 × 600
= 72 × 105 revolutions
∴ L = 72
Maximum radial load =
= 5.29 kN
Question 10:To restore stable operating condition in a hydrodynamic Journal bearing, when it encounters higher magnitude of loads
Question 11:In thick film hydrodynamic Journal bearings, the coefficient of friction
Question 12:Spherical roller bearings are normally used
Question 13:Starting friction is low in
It is due to thick fluid friction from the start.
Question 14:If the load on a ball bearing is reduced to half, the life of the ball bearing will
LP3 = C
⇒ L2 = 8L1.
Question 15:The expected life of a ball bearing subjected to a load of 9800 N and working at 1000 rpm is 3000 hours. What is the expected life of the same bearing for a similar load of 4900 N and speed of 2000 rpm?
L (P)3 = constant
t2 = 12000 hours