Solidworks Modeling Help: Geodesic Dome Pentagons, Hexagons, Struts

[Byron C]

I am new to modeling and am trying to draw a geodesic dome consiting of pentagons with 30degree stuts at each point forming a hexagon. The final strut joining the 2 pentagons is not lining up and is too short. Everything is equal and symetrical. What is going on? Should they line up?

 

[minger]

I'm not 100% familiar with solidworks, but are you actually placing the struts, etc? My attempt would be to create the "rings" separately. Then (in Unigraphics) I would bring them in each as a different components in am assembly. From there rather than specifying a position/angle, you can simply give the edges and points constraints. So, rather than edge 10 being connected to point 56 at a 15.223634532°, its just connected to these points. It should force the angles and everything by itself if you constrain it properly.

at least that's what I would try to do.

 

[TVP45]

Moderators,

Am I permitted to refer the OP to another forum? I'm not in any way promoting the site I would refer him to, but this is close to a world class problem due to a bug/quirk/interesting feature in SolidWorks which causes loss of mates in problems like this.

I know how to do this using the "use a larger hammer" method, but I think the OP really wants a more elegant solution than that. Some of the User Group gurus have dealt with this and should be able to help him.

 

[Topher925]

You're going to have to be more descriptive as to how you are doing this? Are you importing coordinates, working off a 3D sketch, sketch/extruding as you go? Place some measurement constraints on the drawing to see if the numbers at least match up.

 

[Byron C]

I am drawing the pentagon (Yellow) on the front plane with sketched lines, the sketch is symmetrical about the Y axis and the top point of the pentagon is at the origin. I then draw a circle on the right plane at the top point of the pentagon (at the origin) and extrude the circle on a sweep to form the round bar pentagon. I then create a 30 degree plane from the top plane through the origin on the top corner point of the sketched pentagon and draw circle on that plane and extrude it to form the short strut(Blue) at 30 degrees. I then mirror the short struts to the other corners of the pentagon. In a new part I then create my long strut(Pink) with a circle and extrude it. I then create an assembly with the pentagon and insert the long strut mating it coincident and concentric to the short strut. I then insert a duplicate of the pentagon and mate it the same way to the other end of the long strut. Then repeat the insert long struts and pentagons and mating process. The final strut that joins the 2 inserted pentagons is not lining up and too short as seen in the pic.