I want to create a play structure for a super swing. A super swing is like a tire swing in that it can travel in all directions and spin like crazy. I used to have it on a tree branch but we moved to a house with no suitable limbs.
I was planning on using two 6x6x12 vertical posts set 2 feet deep in concrete with one 6x6x16 cross bar. I was going to use two diaginal pieces in the interior to help with any bowing.
I am mostly worried that the cross bar will break from the forces of the swing. I can set the posts deeper to reduce the forces (or if the depth is insufficient), but I would like to maintain the 10 feet above ground if possible.
Any other advice or suggestions appreciated.
Best Answer
A swing frame must be very rigid or the energy put into the swing gets sapped, causing it to quickly lose momentum. This is why you rarely see swings on posts. I'd stick with a proven design, the A frame. If you really must use vertical posts, go at least 3 feet down. With 10 feet above ground the torque will be quite strong.
Interior diagonal braces effectively reduce your beam span. You could easily cut 3 feet from each side, leaving 10. I'd trust a select 6x6 to span that just fine. The braces must be securely fastened, though. I'd consider mortising them into the beam and posts.