Paper packet with a string/wire attached to a parachute to rip it open in flight?

Yeah, they do not like to start loaded, I have not tried it personally but I'd suspect a hard start kit would allow them to start loaded. It's a start capacitor and potential relay to take it out of the circuit after starting.

I actaully use the even larger compressor from a central air unit for filling one of my cannons. It will produce 300 psi out put with 90 si in and stay under its current rating. The larger compressors will provide higher flow rates, not necessarily higher pressure. They will produce much higher pres...

well, initially I was thinking on using shock absorbers. But then I had seen elsewhere(I can't recall right now), that they would not have enough restriction on the return stroke and would move forward just as fast as they retract. Although Since you have had success with them I'm inclined to go tha...

Just a note, the demensions you have indicate sch 80 pipe, you could get such pipe already threaded from most any commercial plumbing supplier or online from places like McMaster. For a cap I believe class 2000 would match the maximum rating of threaded sch 80 pipe

I would verify but the rule of thumb I always hear is 50% reduction from the working pressure of the same pipe unthreaded. here is a table with thread pressure ratings, not sure of its accuracy though. http://www.phoenixforge.com/PTR/Pressure-Temp%20Ratings%20A106%20Grade%20B%20Seamless%20Pipe%20Fin...

I had initially considered gas struts, however from what I could find it would seem they are ill suited as there is not enough restriction on the return so they move back into position too quickly. As for the specifics of the launcher the current estimated weight is 600lbs with a velocity of 1060 fp...

Hey, so I'm planning to do more work on my large hybrid cannon in the fall and my current idea in a line of ever revolving plans is to fit it with a hydraulic recoil system. I have two questions related to this. The first being in general about the recoil forces, with my 4" bore and 1200 psi pressur...

I believe a general rule of thumb is 50% reduction in working pressure for a threaded joint compared to the plain pipe.
And I don't believe sch 10 is even available threaded or used with threaded connections. It is too thin to maintain any levels of pressure capabilities when threaded.

A couple thoughts, I had attempted to use a voltage multiplier circuit for my hybrid and was not sucesfull although for your much smaller one may work entirely fine, something to consider. As for a Hogh voltage feedthrough people have used automotive sparkplugs and various epoxied arrangements. For ...

Yes, you can use threaded metal pipe, there are a number of other joining methods for metal piping not involving welding as well although likely out of your price range. As another note, it might be beneficial to make the effort and find a welder. I've built a large cannon out of sch 80 pvc and anot...

For lower pressures standard soft plumbing solder would be fine especially for smaller sizes. Brazing would definitely be best for pressures near the max rating for the pipe.

I was actaully contemplating the piston air flow issue with cannons, I was thinking that instead of drilling the piston for airflow make it entirely tight like you have and just plumb a small check valve externally from the rear of the piston housing to the chamber. I was thinking purposely picking ...

I would be vary apprehensive of using a tank like this at any pressure anywhere near a person while pressurized. Flat ends are generally a no go, each time it is pressurized the metal flexes which fatigues the weld, so after numerous fillings it may let go with no warning at all, even at 100psi ther...

I actually have used a 240v compressor from a central air unit for filling my large cannon. With 120 psi going in it will put out 300psi at a pretty high flow and be under the current rating. Im sure you could produce higher pressures especially for short periods. Mine has no seperate start cap, it ...