A couple of days ago I made this attempt at creating a tube wrench for undoing that 41mm nut in the middle of my transmission. I started with a bit of steel tubing that caught my eye in an auto parts store -- it's a coupling for welding exhaust lines together, but after beating rather vigorously on it for twenty minutes or so it became a rough approximation of a 41mm wrench.
At a guess I'd say it rounded over at around 100 foot-pounds of torque.
My friend the 41mm nut didn't even laugh this time. Just a smirk.
I found another exhaust coupler that is exactly the right internal diameter to become a 41mm wrench. Instead of just beating on it, I squeezed it most carefully in a vice to achieve a hexagonal form. I had to tap it into place with a hammer (which seemed a promising thing -- the tighter it fits the better n'est ce pas?)
I think it got up well over 150 foot-pounds before deforming to the point of uselessness.
For some reason a scene from Monty Python's "Holy Grail" keeps running through my head -- "All the other kings said I was daft to build a castle in a swamp, so I built it anyway; just to show 'em! ... "