I need to build a frame that can support at least two heavy bags (punching bags). The bags will way from 100-150 pounds apiece. Due to space restrictions I am building this frame outdoors and it will span my drive way.
My plan is to purchase 3 4x4 treated lumber posts. One will be 16' wide and be the horizontal span. The two vertical posts will be 10'?.
Will 4x4 treated lumber be structurally sound or should I use 6x6? The bags will sway and vibrations from the impact of punches and kicks will transfer through out the structure. Is there a forumla builders use to determine load bearing qualities for my type of situation.
For Fastening I was going to bury 2 feet of the posts in cement. For fastening the posts I was thinking of using metal brace connectors with screws (what size?). Should I use another fastening method (bolts)? Should I use some form of cross bracing?