I suppose you could try hitting it from behind with Guided Missiles as well. I haven't tried this, but (most?) robots will completely ignore Guided Missiles coming at them, so in theory you just have to steer them into its tailpipe.
It'd take a lot of patience, though. You can only guide one missile at a time. I also don't know if even a full load of 40 of these missiles would be enough to destroy the big bot.
