Here is the test stand for testing the rocket. There are five 4,500 psi tanks, three and two connected separately. All tig welded steel tube. Most are aware that an arc scratch makes a high pressure tank worthless. When I called the welding supply they said rental only on a 4,500 tank. I asked if I paid my rent on time every month, would they ever want to see their tank? This led to some laughs, then I found some from a paintball guy to buy. Before you think I am insane for welding on a high pressure cylinder, I'll explain in further pictures. This set up is a test for a carbon fiber tank that is going into a hydroplane. I put a two foot deep heavily re-barred pit for cement. The frame is bolted with fourteen grade eight one inch bolts to fourteen 3" diameter steel bars eighteen inches long with plates welded to the bottoms. There is roughly 14,000 pounds of cement-but-I have now seen 9,500 lbs of thrust so far and if I were to pressurize to the maximum 4,500 psi it would exceed the weight of the cement in pushing thrust. Of course it's not directly lifting so it's not a problem, but I'll never push it that far anyways.
The hole in the cylinder to connect tanks was cut on a cnc mill, the slugs that were removed were EDM'ed to make test bars to be tested on my tensile machine. The test bars were tested as is and after welding to insure strength at the welded joints. The tank is rated for 4,500 lbs, tank test pressure 6,750 psi. Tensile testing showed the burst pressure of the tank was at least 9,000 psi and more likely closer to 10,000 psi. All connecting tubes were 4130 chrome moly steel.
The hole in the cylinder to connect tanks was cut on a cnc mill, the slugs that were removed were EDM'ed to make test bars to be tested on my tensile machine. The test bars were tested as is and after welding to insure strength at the welded joints. The tank is rated for 4,500 lbs, tank test pressure 6,750 psi. Tensile testing showed the burst pressure of the tank was at least 9,000 psi and more likely closer to 10,000 psi. All connecting tubes were 4130 chrome moly steel.