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August 2, 2016

PropCad 2015 and MOI units

Notice for PropCad 2015 users - MOI units:

PropCad includes calculations of the propeller's moment of inertia for use in shafting and vibration calculations.


The 2D drawing has a known issue with the units display for Added wetted MOI (SG=1). The issue involves the displayed value on the 2D drawing title block. This value was always reported in kg-m2, but labeled with kg-mm2 when the PropLengthUnits = mm.

The value for Added wetted MOI (SG=1) must be corrected from kg-m2 to kg-mm2 by multiplying the calculated value by 10^6 (or 1000000).


This issue applies to:

 • PropCad 2015.1 to PropCad 2015.4
 • Projects with Prop Length Units = Millimeters (mm)
    Note: Projects in other length units will not be affected


An example of this error is shown below. This project is from PropCad 2015.4 with Prop length units = MM.



This issue has been corrected in PropCad 2016.1 and newer.

 For PropCad 2015 users, this issue has a work-around:


Work-around 1) Change Prop Length Units from Millimeters to Meters.
This will change the corresponding inertial units label on the drawing to kg-m2, which matches the report values for inertial properties.


Work-around 2) Manually correct 2D drawing within PropCad
You can manually correct this value in the drawing using the following procedure:
     Step 1) Open the 2D Title Block options (See Figure 1).

                An example of the un-modified values are shown below:


     Step 2) 
Uncheck the option for the Added wetted MOI (SG=1) from the list, and click “Add” to insert an empty row.
                Now, populate this row with the correct info for the drawing.
                First, calculate the proper MOI value by multiplying the existing MOI value by 10^6 (or 1000000).
                Enter this value into the center cell. Use the correct label of Kg-mm2.

     Step 2) Regenerate the drawing to see the newly added parameter.




2DTitleBlock.png 2DTitleBlock.png
2DTitleBlock2.png 2DTitleBlock2.png
2DDrawing.png 2DDrawing.png

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Article details

Article ID: 93
Category: PropCad
Date added: 2016-08-02 17:30:58
Views: 1281
Rating (Votes): Article rated 3.2/5.0 (29)

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