I am thinking of building one of these to trim some trees. What size chain do you think I should use?
You are
WHAT Rather than using the 44 / 55 gallon drum, it may be a suggestion to make a solid platform to attach to the chain. In certain circumstances, those drums tend to collapse in on themselves, and the chains and the drum could crush the person in the drum.
I would make the suggestion that you build for yourself a proper platform. You should be able to build one from timber and some right angle steel. By doing that, you will have room to move and the platform is less likely to be moving around while you are trying to work! If it is set up properly, you will also have room to store your tools while you are working.
If you think about it carefully, you should be able to set it up so that it is forklift and crane friendly.
As for the chain... if it was me, I would be looking to go 1/2" and use D shackles for joiners. When people are in a bucket, you need to be positive with your locking devices. Grab hooks and claws do not do that for me... I would also be looking to use 12' legs on the chain, so that the chain is not angling in where I am trying to work.
Have fun while you are doing your work, but please remember that we want you back here...
in one piece!!!
Ding.