SpudFiles

So...I figured it out!

Today I've lathed a perfect Snapvalve from aluminium rod.
The piston is made out of Nylon rod.
It's a beauty, but since i can't take it apart ( might tear O ring) , a photo of the outside is useless.
It's more or less a deliberately misbuilt safety pop-off.

By itself, it is hard to get it to cycle, just like before, but the opening is explosive.When the required presure is reached, it escapes, only to hit a larger surface, giving it much more force to snap open.

I Figured out the next step and I believe I have cracked it:

Full auto, all factors can be adjusted ( volume, cycle rate, activating pressure), no loss of pilot volume pressure, fast opening, fully cut off airflow while opened, thus fully resetting before next cycle.Pressure even assists the main piston spring, and when the snapvalve goes off, that extra opposing force DROPS! Jippy! Even more violent opening!!

You can tell I'm excited...but I'm convinced this ends the search for pressure activated full-auto.
Case Closed

let me know what you think, and questions are welcome!

If it works the way I think it does, then it looks great, should work a treat.

WoW I actually got that good work have a cookie 8)

The right part of it already works, I've got it sitting on my desk.


All I need to make is the T and the blocking rod with the two O-rings on it to block the incoming gasflow.

I'm convinced the pressure actually works for me in this design, rather than against me like in my earlier attempts.Notice the snapvalve piston and the blocker rod are not one piece.This allows for a certain degree of misalignment, wich would otherwise have caused jams.

I hope this get's copied a lot, so it can develop further.
It's no more complicated than a hybrid, so a lot of you guys should be able to pull this off.

@ sticky: Glad you get it, means I 've explained it well, so a lot of people can benefit from it.I just couldn't keep this to myself, fork the competition!

That is amazing! I never would have thought of 2 connections to the chamber. May I ask if/how the ROF adjustment is inside the valve? Additionally, how is open pressure adjusted? Do you have to swap out the spring? Great work

i think i get it (this is the valve on your BBMG right?)... and it looks very good... i may have to try one at some point

About controling all factors:

changing out spring ( or add washers) will up the opening pressure.

Bigger chamber means lower rate of fire, but more boom for your buck

ROF can further be controlled by adjusting the inlet. ( fill chamber slower or faster)

Or you can combine. Stiffer spring, smaller chamber and high flow,

means high pressure shots , low volume shots at relatively high ROF

Stiff spring ( love high press.) Large chamber, low flow, means very low ROF , but a lot of power. etc etc etc.

Notice the area behind the piston is not exposed to pressure. possibly a slot can be made to use a spring on the outside of the valve, so it can be adjusted at all times.

An valve can be added to finetune flow at any given time.
The valve itself does not control all factors but it allows for all of this.

Changing the surface areas on the piston ,Snapvalve inlet hole, and stop-rod will also effect the opening pressure.

thanks for the clarification, pretty much what I assumed but I just wanted to be sure.

Seems this idea is not too complicated.Everybody gets it first time!

Another idea just popped into my mind.
If you take a three way to bypass the block rod, the valve pops once, and then softly hisses untill you release the trigger.
So...in effect, you can switch from full auto to semi!!

Or even freakier:

use the outcoming bust to power a Vortec style BBMG, and you get
brrrrp----brrrrp-----brrrpp
Some sort of weird full auto repeating high energy devastating burst cycling effect.
then bypass and you get single bursts.

mmm..that could be usefull

Nice!
Though I think that that diagram would look better in paint.
Burst firing BBMG's would be a great idea.

BWT, thats probably the most awesome poll I've ever seen.Dont know which one to choose

Only problem for larger calibers is the ridiculous amount of air it eats. Could you put it in such a way that it closes before dumping out all air? The HEAR valve from clide's GB semi had some system that held some pressure in and it certainly made it require less air per shot.
I think that with the right tweaks, you could make the valve close just when the projectile leaves the barrel, so it doesnt waste power, but conserves air.
When the chamber doesnt dump all air, it requires less pressure to rebuild and certainly increases the ROF.

So to clarify (I am having a little trouble), the difference between this and JSR's blowback design is the fact that the airflow is cut off for a split second? I always assumed that the spring by itself would reset the process in the blowback design due to the drop in pressure.

psycix wrote:Could you put it in such a way that it closes before dumping out all air? The HEAR valve from clide's GB semi had some system that held some pressure in and it certainly made it require less air per shot.
I think that with the right tweaks, you could make the valve close just when the projectile leaves the barrel, so it doesnt waste power, but conserves air.
When the chamber doesnt dump all air, it requires less pressure to rebuild and certainly increases the ROF.

Yep, I was actually considering a similar system as an alternative to accomplish something like the HEAR valve, except I probably would have used an air spring and a setup similar to a standard piston valve as seen in the picture below. I believe this basic setup was brought up in discussions of hybrid valves on Spudtech.

The point at which the valve begins to close (it would start close at a certain % of the opening pressure) could be controlled by the sizing of your exhaust port relative to your piston diameter.

Ultimately I decided to go the HEAR route instead because you don't have to set a certain opening pressure which means I can fire off a tank that is dropping in pressure and not have to adjust the valve as the pressure falls or settle for lower pressure shots when the chamber pressure is high. You could probably work around that with some design changes though. It was also easier to attach a sear to the HEAR valve design.

This design certainly does have some nice features.

Excellent work! Take a bow.

It doesn´t allow the chamber to completely empty, although the drop is quite considerable.


If you want it to be more airefficient you could go with a longer barrel so you can downsize the chamber a bit.

But I mean....compare it to the piston and pop/off alternative...
That is wasting air like crazy.

anyway,it is bound to be a gasconsumer due to the high pressure I´m gonna run it at.

At very high pressure, I doubt you would need a very big chamber anyway, so filling would only take a split second.