Input detailed data that controls the calculation process.
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Access: |
Ribbon: Design tab  Power Transmission panel Bearing Calculator  and on the Calculation tab, click Advanced. |
Diametral clearance change
The radial clearance is the most important design parameter for radial plain bearings. Just the size of the diametral clearance significantly effects the whole calculation for sliding mounting. It is necessary to include every factor that can cause even the slightest change to the diametral clearance in order that this calculation be precise, as far as possible.
Such factors may be pressing the bushing into the bearing housing or the expansion of bearing parts due to heat build up during operation. Use this section to enter the data necessary for calculating the diametral clearance change caused by one or both the previously mentioned effects. Knowledge of some material properties that are used in the designed bearing is necessary for this calculation. In the following table, the necessary material properties (for example, modulus of elasticity in tension, Poisson's ratio and coefficient of thermal expansion) are presented.
|
Material |
Modulus of elasticity [MPa] |
Poisson's ratio[-] |
Factor of thermal expansion[degrees C-1] |
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Low carbon steels |
210 000 |
0.30 |
11.7 . 10 -6 |
|
Grey cast iron |
110000 |
0.25 |
10.5 . 10 -6 |
|
Aluminum alloys |
70000 |
0.33 |
19 ~ 25 . 10 -6 |
|
Magnesium alloys |
34000 |
0.30 |
25 . 10 -6 |
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Tin bronzes |
105000 |
0.35 |
17.8 ~ 18.4 . 10 -6 |
|
Aluminum bronzes |
110000 |
0.35 |
16.2 ~ 17.0 . 10 -6 |
|
Brasses |
95000 |
0.35 |
18.1 ~ 19.9 . 10 -6 |
Tip: All calculated relations for the calculation of diametral clearance change are presented in the Engineer's Handbook.
Check calculations
Specify whether the checking calculation should be made for maximum and minimum value of the diametral clearance. The calculation of the diametral clearance mean value is enough for bearings carrying a lighter load. Both diametral clearance limit values should be calculated for bearings carrying a heavier load or bearings with higher sliding speeds. Both mean and maximum diametral clearance values are determined by the journal mounting in the bearing bushing. Fits H8/f8, H7/f7, H6/d6, H6/e6, H6/f6, and so on are the most frequently used.
Checking the calculation is done for both diametral clearance limit values in the same procedure and with the same calculation relations as the for the mean value of diametral clearance.
Bearing thermal balance
This dialog box section can affect the calculation of bearing thermal balance. While running, the thermal power originates in the bearing, due to friction losses. This power is in balance with the heat conducted from the bearing. The majority of originated heat is conducted away from the bearing by the lubricant. Cooling of bearings with ambient air is usually important in bearings at the outer side of the machine. For that reason it is desirable to include a portion of friction power transferred into surroundings into the bearing thermal balance.