Piston Valves Explained Visually
Posted: Mon May 14, 2007 11:21 pm
I had this posted on Spudtech, but I am reposting it here to hopefully help some people out and allow for discussions/updates.
Well I made this flash animation in hopes to explain piston valves for the most part. Let me know if this helps anyone figure them out. Those who already know, please point out if you spot something wrong.
You may need to watch it several times because there are many things going on at once. Stepping through the frames one by one on Phase 3 would probably help too. Try to figure out what things are changing while firing and why they are changing.
This assumes you know the relationship between pressure, surface area, and force (pressure * surface area = force)
Phase Explanations
Applies to all Models
Phase 0: Basically just the gun in its pre-use state. No pressure in the gun.
Phase 1: An air source is connected behind the piston. Air enters the pilot chamber and the pressure pushes the piston against the rear of the barrel or chamber port.
Phase 2: Air continues to flow through the input and leaks around the outside of the piston or through an equalization hole into the main chamber. Once desired pressure is reached, the input flow is cut off and the gun is ready to fire.
Phase 3: The exhaust valve is opened and the pressure begins to fall in the pilot chamber. The exhaust must exhaust faster than the equalization hole can leak air back into the pilot. Once the force pressing on the back of the piston falls below the force acting on the front of the piston, it begins to slide back. Suddenly there is more surface area exposed on the front of the piston, and the jump in force slams the piston back leaving an opening for air to flow into the barrel to accelerate the projectile.
The exhaust valve is closed and a new projectile loaded. The gun is then back to it's original condition, ready for the cycle to repeat.
The main thing to notice between the different types are the forces caused by pressure. Of course forces can be changed by changing the piston/sealing port diameter, but in the general scenario like the one shown, with a constant barrel diameter between all types and a tee slightly larger than the port, the barrel sealing valve will have the same forces as coaxial in the closed position. Barrel sealing will have the highest opening force, coaxial will be in the middle, and chamber sealing will have both a low closing force and a low opening force.
Well I made this flash animation in hopes to explain piston valves for the most part. Let me know if this helps anyone figure them out. Those who already know, please point out if you spot something wrong.
You may need to watch it several times because there are many things going on at once. Stepping through the frames one by one on Phase 3 would probably help too. Try to figure out what things are changing while firing and why they are changing.
This assumes you know the relationship between pressure, surface area, and force (pressure * surface area = force)
Phase Explanations
Applies to all Models
Phase 0: Basically just the gun in its pre-use state. No pressure in the gun.
Phase 1: An air source is connected behind the piston. Air enters the pilot chamber and the pressure pushes the piston against the rear of the barrel or chamber port.
Phase 2: Air continues to flow through the input and leaks around the outside of the piston or through an equalization hole into the main chamber. Once desired pressure is reached, the input flow is cut off and the gun is ready to fire.
Phase 3: The exhaust valve is opened and the pressure begins to fall in the pilot chamber. The exhaust must exhaust faster than the equalization hole can leak air back into the pilot. Once the force pressing on the back of the piston falls below the force acting on the front of the piston, it begins to slide back. Suddenly there is more surface area exposed on the front of the piston, and the jump in force slams the piston back leaving an opening for air to flow into the barrel to accelerate the projectile.
The exhaust valve is closed and a new projectile loaded. The gun is then back to it's original condition, ready for the cycle to repeat.
The main thing to notice between the different types are the forces caused by pressure. Of course forces can be changed by changing the piston/sealing port diameter, but in the general scenario like the one shown, with a constant barrel diameter between all types and a tee slightly larger than the port, the barrel sealing valve will have the same forces as coaxial in the closed position. Barrel sealing will have the highest opening force, coaxial will be in the middle, and chamber sealing will have both a low closing force and a low opening force.