As part of my upcoming tree house build, I intend to install a swing-set between two trees. These trees stand apart and are unrelated to the rest of my build. The trees are 12 ft apart. I want to do it right; however, it seems like overkill to use 1 inch lag bolts and heavy duty tree house sliding brackets meant to hold up much larger structures (and which would cost nearly $200). I assume I will use a pressure treated 4x6 as the swing beam, but that is up for discussion. At 12 feet, the swing-set will probably hold three swings. The swing beam will be mounted about 7 feet off the ground. If anyone has any insights or thoughts, my questions are:
What size swing beam should I use?
Can I use 3/4 lags for this part of the project?
Are there any commercial brackets I can use pr re-purpose?
Can I make a bracket by threading the lag bolt through some pipe and then a u-bolt around the pipe and through the swing beam?