101 Ways Not to Build a Chicken Tractor ...

Well, the predator issue came to a head. We can't be certain which dog actually broke into the tractor, but we're guessing it was Jomo since he's been the one most curious about the gals.
Sunday morning I went out to check on something, and to my surprise saw some of the chickens very much enjoying their free-ranging in our yard, between an apple tree and the lilac bush. I hollered for Justin, and he, Shannon, and I began trying to catch the girls.
Apparently the brilliant idea I had of using a rubbermaid tote for a nest box was flawed. It had a latch-able lid, and we cut the bottom out, with the bottom facing into the tractor. This allowed us to latch and un-latch the top to check for eggs. We attached it to the frame with screws. The corner of the lid was gnawed on and then unlatched. Birds got out. We found one of our Buff Orpingtons dead within. One of our Dark Brahmas, also inside the tractor, who I thought was just terribly shaken up, apparently was very injured and Justin had to put her down. Apparently the dogs figured out the chickens aren't toys, since the only ones wounded or killed were in the tractor, the ones in the yard were allowed to hang out.
We ran out to Lowe's and picked up some lumbar. Justin built a nice wooden nest box, similar to the one on the coop. We put a nice lock on it so that no curious little pups, racoons, or even biddies can open it to see what is on the other side. They're safe now and back to laying eggs, though we still need to redo the sides to further Jomo-proof the tractor.
To say Sunday was disappointing would be an understatement. We lost two layers, we couldn't even eat the meat. We had to spend money and an afternoon trying to hastily fix the problem. It was disappointing, but all I could think about was a quote from 'National Treasure'. Nicholas Cage says how Edison failed 101 ways before making a working lightbulb. When asked about his invention he said he found 101 ways NOT to make a lightbulb.
This is what true learning is. Learning from your mistakes, learning from your failures. Not letting them get you down too much, to the point where you don't try again, and try something new.