Understanding the Formula for Half End-to-End Run Label in Fittings

[xscad-083]

Hello, I'm trying to understand the failsafe value in this revit OOTB family called cross - plain - pvc-c. The formula goes like this "if(Half End to End Run < Centre to End Branch Label * cos(Min Angle 34) + Socket Outside Radius * sin(Min Angle 34), Centre to End Branch Label * cos(Min Angle 34) + Socket Outside Radius * sin(Min Angle 34), Half End to End Run)".

Here, the if condition is validating that if the value is smaller compared to that condition, it'll do so and so. But why is that used as a failsafe? Centre to End branch Label * Cos (min angle 34) = 35.6 gives the correct horizontal distance but the "socket outside radius * sin (Min angle 34)" = 5.5, does not give the vertical distance properly...it should be 21mm as shown in the pic. The correct formula would be - Centre to End Branch Label * sin(Min Angle 34). Correct if I'm wrong. Thank you.

I'll attach the family just in case.

[iainsavage]

I think what it is doing is preventing a situation where if the branches are angled the intersection between the branch and the main could be further away from the centre than the connection on the main, so it increases the length of the main body so that the junction point always meets the main body.

Without formula:

With formula

[xscad-083]

Yes, You're right. I know what the formula does but I don't understand why it is using this part in the formula "socket outside radius * sin (Min angle 34)". This is supposed to calculate the vertical distance of the branch from the centre like this formula "Centre to End branch Label * Cos (min angle 34)" which calculates the horizontal distance of the branch from the centre of the fitting, that's all. I think its just a buffer value, no significant meaning behind it so I'll be ignoring it unless someone figures it out.

[iainsavage · Accepted solution]

My understanding is that the basic formula works out the distance from centre to the virtual intersection with the end of the branch centreline ("A" below), but you then need to add the OD and thickness of material (adjusted by angle) ("B" below) to get the actual distance to the extreme of the intersection.

[xscad-083]

Maybe that is it. How does the formula calculate that value though? Can't seem to imagine the triangle...I'll look into this tomorrow.

I figured it out. It is making the same angle wrt the reference forming a right angle triangle.