Page 1 of 1

Automatic valve for nerf rifle

Posted: Wed Jul 08, 2009 5:43 am
by inonickname
Well I've been thinking of tackling the nerf scene.. But not with some dodgy nerf vulcan or something..

I've been tossing up over a few different options, such as a 600 psi repeater, a semi automatic and full automatic. The semi and repeater are fairly conventional designs, but I was thinking about this one:

The operating pressure will be 120 psi, and up to 300.

The function is simple. Air enters from the right hand side, forcing the piston open and filling the chamber. When the chamber is full the pressure balance will take effect and the spring forces the piston back, closing the fill valve and firing the gun. Then the cycle repeats.

I think I might have left a vital part out, but you guys should get the idea.

The travel of the piston will also chamber a nerf dart and close the bolt.

I probably left out the crucial part that makes the fill side have a high acting force until the chamber pressure equalizes, then it becomes equal and the spring opens the valve.

Any thoughts, comments, queries?

Posted: Wed Jul 08, 2009 12:21 pm
by mega_swordman
My concern here is the spring closing the chamber. It seems as though you are assuming the spring will remain open when there is no pressure acting against it but it will close when there is a full chamber of pressure. Could you clarify this for me?

Posted: Wed Jul 08, 2009 12:44 pm
by Hubb
mega: It is a type of spool valve / toolie valve combo. The air enters through the right hand side. This forces the piston to force open (towards the barrel). When the pressures equalize, the spring pushes the piston back into place.

Now, for some questions: What kind of loading system do you have in mind for it? What about firing the valve? It looks like all you did was make a separate chamber that auto-fills and I would assume the firing valve will be in front of this?

Posted: Wed Jul 08, 2009 2:36 pm
by cannon monkey
i like only thing i see wrong with it is the spring and pressures dont work together and dont close and dont fire then it full of air no way to degas it

Posted: Wed Jul 08, 2009 2:44 pm
by psycix
And what will prevent this from going pfffffffffffffffffffffft?

Posted: Wed Oct 07, 2009 2:27 pm
by jhalek90
just so you know.... a nerf dart on a small cannon, will not survive any more than 40-60 psi.

My small gun will shoot homemade darts, fast enough to tare the foam to bits in mid flight... and only the tip goes to the target.... stock nerf darts are even weaker and just shred to bits at 45psi.
so 120-300 is WAY over kill.

You can make a nerf gun KILL in a nerf war with just a blowgun, and a chamber/barrel