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Shaft Design Screen
The shaft design sketch varies depending on the arrangement selected and design temperature.
The one shown here is for an overhung fan with an inlet box.
Note that although overhung shafts are shown with a reduced diameter at the drive end this is purely as a reminder that this option is available to solve difficult bearing design problems. Normally you would make the bearings the same size for ease of manufacture and replacement of spare parts.
Centrix calculates shaft stress, critical speed, bearing minimum load and bearing life as well as checking the limiting speed for grease lubrication as stored in the database.
It is sometimes necessary for the user to manually change the shaft diameter and hit the 'CALC' button to ensure a satisfactory design. Warnings are shown red and will require some action by the user.
The normal procedure for Centrix in designing the shaft is to start with a shaft diameter similar to the motor shaft and to set the pedestal length to suit the arrangement and motor length. The bearings are positioned on the pedestal and the shaft critical speed calculated. If the critical speed is too low Centrix will increase the shaft diameter to the next standard size and reposition the bearings and check the critical speed again. It will repeat this process until a satisfactory critical speed is found. Centrix then calculates the shaft stress and bearing life and highlight any problem areas.
The user can often manually change the design to eliminate the warnings by trying one or more of the following solutions:
Note that it is sometimes not possible to design a shaft using the bearings provided in the database. In this case you must either manually design the drive arrangement using a cartridge arrangement or oil lubricated bearings or select another fan with a lower rpm.
Bearing Seals can be selected by clicking the BRG SEALS button
An axial distance for the casing seal can be entered by clicking the CASE SEAL button.
For details on the bearing loads and shaft design click the DETAILS button
To change the drive loads and pulley or coupling mass click the DRIVE LOADS button
To see the inlet assembly sketch click the INLET ASSEMBLY button
To view the shaft detail drawing click the SHAFT & HUB DRG button
Click 'NEXT' to proceed