Chapter 14 Bearings. /www2.chicago-rawhide.com. www.traxxas.com. www.continentalconveyor.com. Bearings. Function: Carry load in one or several directions while allowing frictionless motion in other directions Fatigue = F(Pressure, Velocity) 3 main types of Bearings
Fatigue = F(Pressure, Velocity)
I. Ball Bearings
II. Roller Bearings
How to Assemble
-Inner race press fit onto shaft shoulder (FN1, FN2)
-Assembly slides into housing (RC2) between outer race and housing
Precision machine elements such as transmissions, reducers, right angle drives usually incorporate un-mounted bearings
See heim overview powerpoint
Hub Spring Set
P1 = load 1, L1 = life at load 1,
k = 3.00 for ball bearings
k = 3.333 for roller bearings
Example: A ball bearing lasts 3,000 hours at 500 lb, how long will it last at 1,000 lbs? SIMPLE!
Most manufacturers specify basic dynamic load rating, C, which is the load that results in 106 cycles. So, this equation can be rewritten as:
= Design Life for your specific application for a design load of Pd
= Required dynamic load rating for a design life = Ld
Note, these are all L10 lives!!! Which is the life for 90% reliability
Example: A horizontal washing machine rotates at 1,100 rpm. Spec out bearings on ends if the dynamic radial load is 400 lb and static load is 75 lb. Want machine to last 20 years @ 3 loads per day, 30 minute cycle time/load.
Can use charts shown in 14-12 to get C. Or equation presented earlier.
Inner race rotates, then Pd = P = V*R where V = 1.0 if inner race rotates and V = 1.2 if outer race rotates.
Lar = CR * L10
Washing machine example, what if want 99% reliability??
3. What if thrust load is present??? - iteration
P = Load
V = Rotation Factor (1.0 – Inner Race, 1.2 – Outer Race)
X = Radial Factor (.56 if Y>0)
R = Applied Radial Load
Y = Thrust Factor
T = Applied Thrust Load
*Thrust Load Present – Deep Groove Ball Bearing
Usually get for shaft analysis
~1.5 *Must initially guess
Table 14-5 Iterate within reason