Change Size of Lines?

HI there, first time poster here. I was wondering if there was a way to change the size of all simply drawn lines within a drawing. For example, i have drawn a large truss structure, and each member is 8mm in diameter. I know i could create a simple circle rotate it to the correct position and highlight 1 line and press follow me. However as there are at least 50 different members i would like to try and do it in a quicker way. For the drawing itself, i do not care so much about the connections as it is simply for demonstration purposes (University project). Hopefully the image gives some idea to what i am asking.

Thank you in advance for any advice/help

The main purpose of edges (lines) in SketchUp is to define the edges of faces. The only control for edge thickness is profile edges. To get all of the edges to be profile edges, though, you would need to group each triangle separately. That would also be a lot of work.

There are some extensions that could create the 3D trusswork such as TIG’s Extrusion Tools from Sketchucation. Also conside leveraging symmetry in the model. If there is a line of symmetry, you really only need to model one one side of it. You can copy that and flip it to make the other side.

From the way you’ve triangulated the model, it’s not clear there is a line of symmetry but maybe you just need to change the triangulation. You should also make sure you’ve corrected the face orientation.

There is a line of symmetry going through the center, but this would take almost the same amount of time to do. For the group edges, do i need to have a surface, or could i just have the triangles like a wire frame.

What do you mean?

You could make a group from a set of two or three edges. You don’t need to have a face. But going through your model and selecting edges to make groups will take time, too.

Is it an open truss? If not, what are the faces and how connected to the edges in reality?

If it is just an open tubular structure with a tube along each line, you could just select all faces and delete them. All lines would (I think) become profile edges, and you could set them to be thicker.

Not at my computer, so can’t check. But maybe Profile edges apply only when there are faces?

No, you’ll see profiles for edges that bound only one face in view. If it visibly splits two faces you’ll see a thin edge.
So a wire frame shows only profiles, if enabled.