Self Adjusting parameter inside nested family

[tim.perkinsSHINE]

I'm fairly new to Revit families.  I have a Generic Model family that has several parameters that are working fine with the exception of getting the length of a angled brace.  In the shot below, the adjustable parameter that drives the non-working parameter is the "Main Strut Length"  The angled brace must stay 4" max from the center of the cross brace.  When the Main Strut Length is changed, the angled brace must adjust length to meet the right plane minus the setback distance of 1/8".  I have not been able to get the angled brace length to adjust using reference planes, reference lines or by any other means.

Is there anyone that can help my out?  

[Alfredo_Medina]

The unistrut family is a simple extrusion without a length parameter. You need a length parameter in that family. 

Once you have it, that will be your "c" side, or hypotenuse of that triangle. You know "b", and you know "A". Now you need to find "c". 

To make it exactly at the point where you want, so that the bottom of the unistrut has that exact gap of 1/8", probably you need more trigonometry, or probably you can put that gap in the unistrut family.

For more information about trigonometry for Revit, visit this link (credits to Klaus Munkholm and others in Revitforum) : https://www.revitforum.org/node/1126?t=1046&page=22

[tim.perkinsSHINE]

I have set the length parameter in the brace piece and still I cannot get the family to completely work.  All of the horizontal or vertical pieces are working fine, but it's 45° brace and mounting bracket that I can't get to adjust as I change the width and length of the family main struts.

[Alfredo_Medina]

Did you associate the length parameter from the nested brace piece to a parameter in the host? (the hypotenuse of the triangle)

[tim.perkinsSHINE]

I have associated the "N1001C Length" in the strut family to the main family "Brace Length".  I can change the "Brace Length" and the N1001C Length" will update.  What my problem is, is that I can't get the "Brace Length" to automatically update when I adjust the "Main Strut Length".

I have also tried the Trig approach.

I have started over with this brace.  I can constrain the ends of the brace with reference lines and everything is working.  As soon as I place a dimension and add the parameter "Brace length" or the side A / Side B for a trig calculation, and assign the parameter, I get the "Constraints are not satisfied" error message.  If I leave the "Brace Length" dimension without assigning a parameter and adjust the "Main Strut Length", I get the "Constraints are not satisfied" error message.

[Alfredo_Medina]

It's difficult for me to determine the exact reason, but I can think of these possible reasons:

1) You aligned and locked both ends of the nested family of the brace to references in the host. When you want to control a linear element, align and lock only the starting point, then associate its length parameter to a parameter in the host.

2) Or... there are extra angular parameters. Sometimes there is more than one angular parameter controlling a rotation.

3)Or... you have created constraints (align & lock) to faces or edges of existing solids, instead of to reference planes or reference lines.

[ToanDN]

Try the attached family.  It is R2024 so you will need to rebuild it in R2023.

[tim.perkinsSHINE]

ToanDN,

Can you tell me what changes you made?  I don't have 2024, and it will take a while for my IT to install after I submit a request for it.

[ToanDN · Accepted solution]

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@tim.perkinsSHINE wrote:

ToanDN,

Can you tell me what changes you made?  I don't have 2024, and it will take a while for my IT to install after I submit a request for it.

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See GIF.

[tim.perkinsSHINE]

ToanDN,

I just followed you screencast and the family now works.  I'm not sure why, but thank you!

[Alfredo_Medina]

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@tim.perkinsSHINE wrote:

"... I can constrain the ends of the brace with reference lines and everything is working.  As soon as I place a dimension and add the parameter "Brace length" or the side A / Side B for a trig calculation, and assign the parameter, I get the "Constraints are not satisfied" error message..."

That, what you said there: "I can constrain the ends of the brace..." is one of the reasons I mentioned in message # 6 above, that when you control the length of a nested element, you only need to constrain one end and then associate parameters. If you constrain both ends, you get that kind of error. I am glad to see that the issue was solved. However, as per your last message, you still don't know why, which, in my opinion, would be more important than having someone else fix it for you. 

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[tim.perkinsSHINE]

I agree 100% that I should know why. The issue is that I am out of time in my schedule to complete this project. I'm not giving up, but instead have to move on to the next project in my schedule. I will need this family in another project I'm sure, and will come back to this when I run into it again.