Cable Analysis on a Traversed Profile : Softree Technical Systems Support

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Cable Analysis on a Traversed Profile

Updated May 19, 2016


This article applies to:
  • Terrain Forestry
  • RoadEng Forestry

The tutorial files referred to in this article can be installed from the Updates section of support.softree.com or from your CD/Flash Drive provided at time of software purchase. See Getting Started for additional information on tutorial files and the location of file install folders.


Cable Logging Example

Any Terrain feature can be used as a ground profile for Cable Analysis, including imported or draped features. In this example a traversed profile (Deflection-Line or D-Line) will be analyzed for acceptable deflection, clearance, load, and tensions.

1. File | Open \Cable\cables.ter. This example utilizes Logging Setups stored in this otherwise empty Terrain file.

2. File | Insert File select SOFTREE-Traverse Document (*.TR1,*.DB1) from File of Types.
Select \ Cable\dline4.tr1. Press Open.

3. Make sure Include Side Shots is disabled. Press OK.

4. File | Retrieve Screen Layout )\training\training cables.ilt. This sets up window positions and a large number of display options suitable for Cable Analysis.

5. Highlight the Profile or Data Window, by selecting either window’s title bar. From the main menu, select Cable AnalysisïAssign Setup to activate the D-Line Assign Setup dialogue box shown in the figure below.

6. Fill in all of the setup Parameters shown below. Select Slackline. Press the Select button to select the corresponding equipment. In this case it is the Thunderbird TY-90. Press OK. The dialogue box should now appear similar to the figure below.

Figure 1: D-Line assign setup dialogue box

Figure 2: dline4.tr1 with cables.ilt applied.

This analysis shows simple percent deflection at thirds. In this analysis the only important result is clearance for a given deflection.

7. Select Cable Analysis | Calculation Parameters to activate the D-Line Calculation Options dialogue box shown below.

Figure 3: D-Line calculation options dialogue box.

Note that Simple third point Deflection is selected and the value of % Deflection (Equivalent mid span) can be modified. The options displayed are contained in the screen layout loaded in step 4.
\training\training cables.ilt
All types of analysis will be examined in the next few steps.

8. Enable the Maximum flying load given clearance option. Note that Clearance is the only parameter that can be changed. Press OK.

Your screen should now appear like the figure below:

Figure 4: Deflection analysis with maximum flying load given clearance option

Notice that the Cable Data Window shows a constant clearance (to top of carriage) above ground of 12.0m, and the load varies at each of the above stations. This analysis shows how much load you can lift at any point (given the desired clearance) and what deflection you would need to achieve this. At every point one of the cables is at its working tension and is therefore limiting any increase of load. See the Creating a Logging Setup section for information on defining and modifying working tensions.

Note: The Maximum flying load given clearance option does not model an actual yarding process as the skyline length would have to be adjusted continuously and it does not make sense to change the load every few meters.

9. Cable Analysis | Calculation Parameters, select the Minimum deflection given load option. Press OK.

The screen should now appear similar to the figure below.

Figure 5: Deflection analysis with minimum deflection given load.

As you increase the load the cable will sag more and more. Deflection has to increase so that the tensions on the cables do not exceed working tension. Unlike the previous example, the Minimum deflection given load option does model a possible yarding process. The solid red line in the Profile Window represents the path the top of the carriage (where the cables join) would traverse if the operator adjusted the skyline dynamically to keep his cables at maximum working tension.

This is not likely to happen for the current Slackline system (with a separate skyline) but may be reasonable for a running skyline logging setup.

10. To investigate Deflection for fixed skyline given load option, open Cable Analysis | Calculation Parameters.

11. Select Deflection for fixed skyline given load. Note load and the %Deflection can be user defined. Press OK to accept changes.

The screen should now appear similar to the figure below.

Figure 6: Deflection analysis with deflection for fixed skyline given load option.

Deflection for fixed skyline given load shows the carriage path for a realistic yarding process for this setup.

12. Select Cable Analysis | Calculation Parameters and change the Load to 25000lb (or 11,000kg if you change the units combo box). Press OK. Note that a red bar appears in the Errors sub-window under the profile. Click on the red bar; an error report will inform you that in this area the skyline has exceeded working tension. Press OK.

13. Go back to Cable Analysis | Calculation Parameters and change % Deflection to 12. Press OK. Note that the error bar has disappeared.

14. File | New. Do not save changes.
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