Sets parameters for calculation of a plain bearing.
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Access: |
Ribbon:
Design tab
Power Transmission panel
Bearing Calculator
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Preview |
Displays the preview dialog box of the plain bearing. |
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Advanced |
Opens a dialog box for inserting the detailed data that controls the calculation process. |
Type of Strength Calculation
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Design of minimum journal diameter |
Designs the minimum journal diameter. |
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Design of bearing clearance |
Designs the bearing clearance. |
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Lubricant selection |
Selects the suitable lubricant. |
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Check Calculation |
Performs the strength check. |
Loads
Loading is entered through Force and Journal Speed.
Dimensions
Enter basic design dimensions for plain bearing mountings.
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Journal Surface Texture |
The value of the relative width, which is a basic datum affecting the bearing calculation, is calculated for a specified journal diameter and bearing width and with respect to the bearing lubrication system design. At lower pressures, long bearings seize up, but short bearings do not. The reason is that the load capacity of relatively long bearings is reduced by the edge overload induced by shaft deflection. The maximum load capacity uses a bearing with a relative width of about 0.4. That is why the value of the relative width in the range from 0.3 to 1 is recommended in bearing design. Lower values are selected for circulation-system lubrication where greater oil flow through the bearing does not matter, and greater values for short-term lubrication where increased splash would mean excessive lubrication losses. The program can calculate radial plain bearings with a relative width in the range of 0.2 to 1.5. |
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The size of the specified surface texture of the bearing journal and bushing, together with the smallest of hard particles in the oil, affects the value for the minimum thickness of hydrodynamically effective lubrication layer and therefore the selection of necessary lubrication also. The surface texture size is entered on the basis of the recommended values for the selected bearing materials. The surface texture of the bearing journal is usually selected in the range of 0.2 to 0.8 microns for normal machining; the bushing surface texture is usually in the range from 0.4 to 1.6 microns. When maximum friction happens (frequent start-up and running-out, great pressure and small speed, swinging movement, insufficient lubrication), it is necessary to choose the smallest surface texture of sliding surfaces. The quality of sliding surfaces can be further improved with bearing running-in. |
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Diametral clearance |
The size of diametral clearance is determined by the selected type of bearing journal mounting in the bushing. Fits H8/f8, H7/f7, H6/d6, H6/e6, H6/f6, and so on, are the most frequently used. From a specified mean value of diametral clearance, the value of relative and hydrodynamically effective diametral clearance is calculated in the dialog box, with respect to the surface texture of sliding faces and reducing the diametral clearance due to bushing pressing-in and the thermal expansion of bearing parts during operation. The relative diametral clearance is another very important design parameter that substantially affects the bearing properties. Its value is mostly in the range of 0.0005 to 0.004. Small values of relative diametral clearance are suitable for bearings with a heavy load, working at a slow sliding speed and vice versa. |
Journal Material
Select the check box to open Material Database and select a material. Edit the properties of the material, if needed.
Bearing lubrication method
If a lubrication system with recirculation is used in the bearing, a portion of oil which has passed through the vacuum lubrication layer returns into the pressure layer and remains in circulation. Due to lubrication cooling, it is sometimes advantageous to use lubrication without circulation where the oil passing through the lubrication layer is wiped off or flushed. See the Wiping of lubricating oil on the first scheme and the Flushing of lubricating oil on the second scheme:
Lubricant inlet through hole/pocket or axial groove
Operating conditions
In the Operating conditions section of the main window, a suitable lubricant is selected, which ensures the hydrodynamic ability of bearing lubrication. The lubricant input temperature, pressure and the ambient temperature of the bearing are entered according to the bearing design type. The expected lubricant mean temperature at the bearing exit is preliminarily user defined. The program then calculates a real temperature at the outlet when the lubricant selection or the main bearing calculation for checking is started. The mesh size for the oil filter specifies the filter permeability and affects the minimum thickness of hydrodynamically effective lubrication layer. The layer should be in the range of 2 to 15 micro.
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Lubricant |
Select the check box to open Material Database and select a material. Edit the properties of the material, if needed. |
Results
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Displays the calculated values. |
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Bearing capacity |
Displays not only data describing bearing loads and capacity, but also the data about the limited operating conditions. |
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Bearing pressure, Max. pressure at lubrication slot |
The value of maximum pressure while running and the weight of specific bearing pressure during the start and run-out are directive data for design of bearing bushing material. Specific bearing pressure in the range of 1 to 5 MPa is considered to be a lower specific bearing pressure. The maximum reaches values of about 30 MPa and 70 MPa for short-time impact loading, but only with the correct selection of journal and bearing material. |
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Sommerfeld number |
The dimensionless Sommerfeld number values and relative journal eccentricity are the main data describing the bearing capacity. The recommended Sommerfeld number value ranges from 1 to 15. Due to small specific pressure during fast sliding speed, there is a danger of irregular bearing function for a Sommerfeld number lower than 1. For values greater than 15, there is a danger of contact between the sliding faces. The recommended value of relative journal eccentricity ranges from 0.7 to 0.96. For lower values an irregular journal function, due to vibration, can happen. When exceeding the upper limit, maximum friction between peaks of surface roughness happens. |
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Bearing thermal balance |
Displays the results of the bearing thermal balance calculation. Use the Calculation Assistant Logs Window to present the records about the calculation progress. It includes recommendations for changing bearing input parameters, if the proposed bearing with the selected lubricant does not satisfy the conditions of hydrodynamic lubrication and they do not suit the specified load. |
Summary of Messages area
Displays the reports about calculations. To open the Summary of Messages area at the bottom of the tab, double-click the double line at the bottom of tabs or click the chevron.