It has been well over a year now and i wanted to post an update on the build. I don't have an exact number but i have successfully brewed at least 50 batches now with this setup and thought it appropriate to share the results - and no, it has not burned down yet. i am also providing some new pictures of the final build.
first and foremost, i took the very sound advice that some of you posted and swapped out the chain link fence poles with 1/2" galvanized steel pipes. these things are solid. thanks again for this feedback.
second, i must say i am very pleased that i started this project. it has taken my brewing to another level. going from BIAB on my kitchen stove to this has been great. BIAB has its benefits and is a very legit way to brew, but it also has some pretty big limitations.
Third, I had though that it was possible that i was going to need to add heat shields around the burners and it turns out that it is definitely necessary, at least with the burners i am using. The heat generated laterally from these burners as it spreads out from the bottom of the kettle is way too much for wood to handle. fortunately the heat shields were very simple to make, just cut out some metal flashing and poke a few holes in it for the poles.
I also do not have the pump yet, so for now manually transfer hot water from the hot liquor tank to the mash tun with a pitcher for the sparge. This is really the only laborious step in the process aside from cleaning but the cost for the pump is hard to justify when it is only being used for how water.
Otherwise, the build has remained essentially the same and the concept has been proven. for almost nothing i was able to build a very usable brew tower out of scrap wood in my back yard. Adding the burners, the gas pipe and fittings, paint, and heat shields, wheels, and screws brought it to about $120-140. i picked up two old kegs for $30 each and cleaned and polished them, a cooler from home depot for another $50 or so, and a new wort chiller for $90 bringing the total cost over everything in the pictures to about $350. the chiller was expensive but it makes a huge difference. coupled with the fact that i can use the old chiller now as a pre-chiller in a pot of salty ice water i am getting 10-15 min chill times on 6 gallons of wort, which makes me happy.
looking around at options available on the market i feel this is a considerable cost savings for the equivalent in store bought equipment. It was my hope that this post would encourage some other like minded (lazy and cheap) folks to build their own sculpture as well. you wont be disappointed. thanks for reading, and happy brewing.