# Dealing with local coordinate systems and bearing forces

**URL:** <https://prepomax.discourse.group/t/dealing-with-local-coordinate-systems-and-bearing-forces/2057>\
**Category:** General Questions\
**Created:** [October 9, 2024, 12:00am UTC](https://prepomax.discourse.group/t/dealing-with-local-coordinate-systems-and-bearing-forces/2057 "2024-10-09T00:00:25Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![lucas\_bueno](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/lucas_bueno/32/1168_2.png) [@lucas\_bueno](https://prepomax.discourse.group/u/lucas_bueno)\
**Post date:** [October 9, 2024, 12:00am UTC](https://prepomax.discourse.group/t/dealing-with-local-coordinate-systems-and-bearing-forces/2057/1 "2024-10-09T00:00:25Z")

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Hello everyone, I hope you’re all doing fine!

After some time away from structural analysis, I returned to PrePoMax and gladly found amazing new features in which the local coordinate system shines the most for me. To try this new tool, I decided to create a simple “bolted” joint with some RBEs simulating the connection and tried using a local coordinate system to extract the forces from the middle hole so I could use them for hand calculations such as bearing and tear-out margins of safety.

 ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/c/c21252b8584747ee41b3893219ca6b08e5e867d5.png)  
 ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/e/eed23ab556675b6a5a0dcc7b5c58c585e5285f7e.png)

In this small adventure, I faced the first issue: I could not assign a local CSYS to random nodes that had no loads or BC applied to them. Is there any way to force a \*TRANSFORM card in some random nodes? I did a workaround using a dummy load in the local CSYS for the nodes I wanted to transform.

 ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/e/e784792de6fd142c65b2baa81e98f327bd89c1d9.png)

With the coordinate system working, I expected to read non-zero forces in the local Y direction. Here the next challenge showed up: Since the “totals” command does not work for local CSYS, I had to extract the sum from the history output in Excel:

 ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/8/838346c2107a38ef19442d0528fd7c087205bcfb.png)

This is not so practical for a single hole, and probably it would scale up for very complex joints. Therefore, I would like to ask if there is a better workflow out there for this type of problem!

Best regards,  
Lucas.

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**Author:** ![jbr](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@jbr](https://prepomax.discourse.group/u/jbr)\
**Post date:** [October 9, 2024, 1:17am UTC](https://prepomax.discourse.group/t/dealing-with-local-coordinate-systems-and-bearing-forces/2057/2 "2024-10-09T01:17:34Z")

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> [@lucas\_bueno](#):
>
> Therefore, I would like to ask if there is a better workflow out there for this type of problem!

It would be best to write a python script to do the post-processing for different holes.

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**Author:** ![lucas\_bueno](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/lucas_bueno/32/1168_2.png) [@lucas\_bueno](https://prepomax.discourse.group/u/lucas_bueno)\
**Post date:** [October 9, 2024, 9:06pm UTC](https://prepomax.discourse.group/t/dealing-with-local-coordinate-systems-and-bearing-forces/2057/3 "2024-10-09T21:06:50Z")

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That’s a good idea! I wonder if it would be possible to transform the total forces output by calculix in the PrePoMax post-processing… it would help a lot as well. But for now python and/or Excel work fine.