SpudFiles

Hi there,
I thought about a hammer valve that doesnt need extreme hammer force to open and came up with the idea in the first pic. Basically you push the valve part in, whicht should be really easy because theres no force applied to the piston as far as I imagine. With that one could even make a self recocking hammer, nò?

Maybe even like in the second pic, where no hammer at all is needed, but instead a spring pushes the bolt into the chamber part. I would place the trigger in the middle of the endseal, not like in the picture.
Any idea if this would be possible to archieve, especially with higher pressures, could that seal anyhow?

That would certainly work but you have to add a return spring so that the piston at the chamber closes again. What you have drawn is a balanced design, there is the same amount of force on each side of the rod. Once the chamber is open it stays open.

It's the same in your 2nd picture. In order to work, the way you've imagined it, you need to make the right piston bigger than the left.

Thats not how I intend it to work.

I posted the actual idea before.
You push the bolt in, the valve opens and lets air in the virtual second chamber.
When it reaches the second seal (on the right) the air itself pushes it back so there would be no need for a return spring.

No, you don't get it... as soon as the valve opens it becomes unbalanced as just one side of the piston is exposed to pressurised air...

sure, you've added a second seal (on the right) but that just makes everything balanced again (assuming that the surface area of both surfaces is the same)

you still need a spring to close the valve

I'm afraid "some guys here" were right, as long as there is no air pressure in the purple areas, the piston remains balanced and will not move without external influences other than chamber pressure.

hmm sure? why there in the back? I would press there, so no pressure needed?

For better flow and less dead space between the valve and projectile, I opted for a variation. The piston is pulled to the rear and the barrel is attached right to the valve outlet. The piston is lower mass.



Sketchup model of this is here;
http://sketchup.google.com/3dwarehouse/ ... revstart=0

Yep Technician, But any chances that you could make this a semi-auto? cause thats my primary target

I leave an air hose attached and it fires once per pull. A barrel with a feed hopper will take care of reloads. Semi auto is indeed possible. Due to the nature of the valve, it pretty much fully depletes the chamber on each shot due to the high flow of the valve. It does not re-close in the few milliseconds the chamber takes to fully deplete.

It does pack a serious punch when it fires. I've dented a car and a washing machine using just marshmallows for projectiles. I have not yet clocked marshmallows with that launcher.

if you want to build a semiauto you either need:

1. a valve that opens for very fast for a short period of time (hammer valves work like that)

2. or a 3 way valve

There is no other way that I know of

@Guerilla Guy:What exactly do you want to achieve? Do you want to open the valve manually, then it fills the small chamber around the bolt (between the seals), then closes the left seal again and releasing the measured amount of air trough the barrel?

because this is how I understand that:

You push the bolt in, the valve opens and lets air in the virtual second chamber.
When it reaches the second seal (on the right) the air itself pushes it back so there would be no need for a return spring.

That would work as long as the right seal would have larger cross area as the left one, as Poland_Spud already explained.

When the piston slams to the right (with the force = pressure x cross area difference), the left seal could shut off the inlet from the main-chamber, releasing the small amount of air into the barrel.

Notice that all of the described would only work if you got the position of the 2 ports in relation to the position of the seals on the rod right.


(Maybe it would help you to just think in areas, the pressure pushes against, if there is the same area on both sides, there will be also the same forces into both directions, what means the piston/bolt is balanced/not moving)


the only problem would be that if you have a trigger directly attached to the rod, it will slam back at your finger, instantly after being pushed, what makes this specific design a rather bad one IMO.

Ah yes, and perhaps you will have to drill a hole trough the complete bolt (lengthwise), to make sure their wont be air pressurized in the back/left of your piston
(the purple part in Jacks diagram), when you push the bolt in, and act like a air-cushion, that avoids the rod of being moved very far, in any direction ...

EDIT: I typed slowly and I got logged out of spudfiles while submitting the message, so I send it again, now its three post to late or so....