I'm not sure what possessed me to build this. But I needed a place to install a "tire swing". There wasn't enough clearance where the rest of the swings are installed on the side of their play house, so I chose these 2 trees spaced exactly 16 feet apart.

The problem is the trees are probably 70 feet in height, so when it gets windy, they do move around. For this reason, I couldn't just bolt the beam directly to the trees. I had to do it in a way where the trees could still move without ripping out the bolts or the beam and cause the whole thing to crash to the ground.

I suspect the 3x2"x6"x16' beam weighs over 100lbs, which made it hard to hold in place as I was working alone. So I rigged up a pulley system to get it into place about 10 feet up the tree. I built a metal "box" on each end to support the beam. The beam sits in this box, it isn't bolted, screwed, or nailed. This way it can float as the trees move in the wind. I added a thick metal triangle beneath each end for added support. For safety, just to prevent the beam from crashing down, I also installed a loop of cable on each end. The cables are not under tension to ensure they don't cut into the trees over time.

Anything that can support my weight will be just fine with the kids... :)