Hybrid Piston Valve Design

[frocksie]

I am designing a hybrid piston cannon and I would like to attain 8x mixes.

The design is an improvement of this design. I am wondering what material I should use for the chamber of the cannon.

I either want to use 6061 aluminum or steel. Both have pros and cons.

6061 aluminum will not rust and is lightweight, but it loses strength when welded.

Steel on the other hand is heavy and rusts, but is easy to weld and does not lose significant strength when welded.

Thoughts?

Note: The scale of the drawing is noted in the picture comments

[Moonbogg]

Use aluminum and employ bolted connections. You can build it entirely yourself this way by drilling and tapping holes. I say base the design off of this assembly method. I have learned first hand that welding aluminum is very expensive and a stronger, cheaper and more repeatable design can be achieved with bolted connections. The stress calculations are more straight forward when you don't have to take into account the weld characteristics.

[Technician1002]

If you reverse the locations of the barrel and chamber on the valve, it may produce a more rapid opening when the prssure builds past the balance point. A little larger pilot area is a good idea so the piston can move all the way open without too much sudden rise in pilot pressure from compression.

Disclaimer.. Never built a combustion, or hybrid. I may be wrong on this.

[kenbo0422]

Technician1002: Your observations are for piston pneumatic. In a combustion, the quick high pressure from the burn is what will force the valve open, as opposed to releasing the pressure from the pilot side. The configuration is correct. But, your suggestion to increase the pilot size is also correct. That valve needs to blast wide open.

[frocksie]

Moonbogg, how would I seal the chamber? O-rings? I am not exactly sure if a bolted construction would work for this particular launcher. Would you mind clarifying?

Technician, I think that this configuration is easier to built and should be fine in terms of performance, but I agree that a larger pilot volume is a good idea. Also, would you suggest using a UMHWPE piston on this gun?

[Moonbogg]

I was thinking it would need redesigning. If you want to weld then this looks like a good launcher. I was just thinking of ways to make it cheaper. Make sure they have room to work around all the joints.

[frocksie]

How might you propose to redesign it? I would like to keep the general design, but I am open to some changes.