Designing the Platform

Next, I needed to design a sturdy platform that would both fit in the allocated space, and be a good sturdy foundation for the rest of the treehouse.

After drawing up the layout of the tree trunks on the computer, it looked like a 8' X 16' platform would fit nicely between the trunks. I originally had thought of using all 5 trunks, and perhaps making a pentagram shaped floor, but the nice square 8' X 16' platform looked larger, and much simpler to make.

The next trick was determining how to attach it to the tree. Since we'd be building in a multi-trunk tree, I had to take into account the independent movement of each trunk. I tried coming up with all kinds of sliding brackets, similar to what other people have done. The result was a lot of complicated brackets that looked expensive to make. Plus, I wasn't really sure they'd work in all possible scenarios.

One of my friends suggested suspending the entire thing via chain. The more I thought about this, the better it sounded. It would definitely solve the trunk movement problem, and I liked the idea of a suspended platform that would perhaps have more movement than a fixed point platform.

I spent a bunch of time at Mcmaster.com reading up on hardware that looked appropriate. I eventually arrived at using a combination of eyebolts, shackles, turnbuckles, and chain. I went with the largest eyebolts I could find (1" in diameter), figuring that they were going to be the weak point of the system. The eyebolts pictured below are rated at 10,000 pounds if pulled along the line of the bolt. Since I'd be pulling on them perpendicular to the bolt, they'd support significantly less weight before failing.



I didn't want to just run the eyebolts through the frame of the treehouse. I was afraid that they'd deform the wood, with all the eventual weight that'd be resting on the frame. Instead, I drew up a bunch of various right angle brackets and plates that would help distribute the load over a larger portion of the beams. After showing the various designs to my dad and other friends, I settled on some simple 1/2" thick right angle pieces, along with some 3/16" plates.





With these decisions in place, I updated the CAD drawing, and ordered a bunch of hardware. I hoped we wouldn't change too many aspects of the design once we started building, mainly because of the investment in the hardware.