Pneumatic anti-armor gun (mini football launcher)

[paranoiddroid]

A mate of mine is designing a mortar for me at the moment Il post the design here when he's done.

A QEV is probably the easiest means of triggering something like this at consistant pressure and stuff each time. Have you thought about using one of the cheap Chinese QEV that are available they have decent reliability apparently.

An other option is going to a modified sprinkler valve design which would make the trigger easy to do you could use a blow gun type trigger.

Breech loading should be fairly easy to be honest.

Here's one idea http://www.spudfiles.com/pneumatic-cannon-database/topic1401.html basically a waste gate valve

This is essentially the design iv used before on potato cannons.

https://m.youtube.com/watch?v=Pj9HRxT8jtg

[ardrummer292]

The biggest issue I'm having is locating valves with a sufficiently high pressure rating. The Charlie G will be running at 150 psi for some rounds, while the mortar will need valves capable of withstanding 250 psi. Most QEVs and DCVs are only rated to 125 psi.

[paranoiddroid]

The rating on the box isn't accurate generally most QEV's can go much higher.

Why do you need so much pressure iv seen cooaxial guns that use WAY WAY WAY less pressure and still hit 200ft like 60psi getting you there. That sounds like a ludicrous about of power for Nerf footbals

[ardrummer292]

My main performance parameter is muzzle velocity. I've read that the acceptable maximum is either 200, 230, or 250 fps. I'm still trying to figure out which of those numbers is the standard.

Since I'm trying to keep the launcher's overall dimensions fairly close to the real Carl Gustav, secondary chamber volume and barrel length have been limited. This leaves operating pressure as the main performance-altering variable.

When you say most QEVs can function at higher pressures than advertised, is that specifically in reference to diaphragm (not piston) variants? Even if I could run the QEV above specs, I'm not sure that the DCV (with the same max psi rating) could handle it.

In addition, I would ideally like to maintain a minimum 10% factor of safety based off the pressure rating of the lowest rated part. Since the factor of safety rating on these valves is industry proprietary information, I won't know exactly how close I am to causing a potentially dangerous component failure.

[paranoiddroid]

Check spudfiles honestly iv seen pressure tests done on there that do give well more than 10% as a safe pressure.

And my point was that iv seen coaxial pnuematics give 200ft on 60-80psi.

Honestly if i we're you the Muzzle velocity isn't something that id be using as a target.

What sort of numbers are you getting with GGGT if you are using it?. Punch in your air chamber and barrel lengths and have A minimum range target

[ardrummer292]

Here's my specs:

2in Nerf mini Vortex pocket football, 34 g
CO2 at 124 psi
27in barrel
1:1 chamber to barrel volume ratio
10 degree elevation

I'm getting about 200 fps and just shy of 300 feet of range.