Was there not an experimental bike frame built that was highly pressurized (nitrogen) to increase its rigidity?
I know they do this with helicopter rotor blades, as a crack-detection method, and the infafous Porsche 917 racer had an aluminum tube space frame that was also pressurized only to detect cracks.
The theory is that under internal pressure any tube frame would be far more rigid than otherwise. Does anyone know what work has been done on this admittedly "odd" notion?