Cylindrical valve mechanism for regulated rifle?

[NCmountainShooter]

To preface, I'm trying to think of different ways to feed an axial air system with in-line bore diameter porting. It would be a regulated system to remove the need for varying dwell to pressure amounts.

That being said, has anyone ever used a rotating cylinder to open and close the valve instead of the more typical axially oriented poppet? Picture a solid vertical cylinder with a hole through it horizontally and put that up against a semicircular concave port. In starting position the hole through the cylinder is orthogonal to the port and rotated 90 degrees it is in line with the port. The cylinder could be powered by a hammer strike 90 degrees to the cylindrical surface, likely hitting a flat protrusion at the bottom near the edge of the cylinder. If a spring gives a counter force, the cylinder would rotate a certain amount then rotate back shut. Timing the dwell would depend on how fast the cylinder spins open and shut. Another mechanism for powering the cylinder would preload a certain amount of rotational tension on a trigger mechanism such that the release of the catch would let the cylinder spin 180 degrees open and shut to block the hole again. This could be externally controlled if the spring tension were connected to a dial. This would require rotational springs rather than the more typical length oriented springs.

My main mental conundrum would be how to seal  between the cylinder and the port. An o-ring or possibly tight fit plastic rim could possibly work. It would just need to be able to withstand the friction from the spinning cylinder.

If this is completely non-feasible, please pardon my mechanical daydreaming.

Chris

[rsterne]

I find written descriptions of such mechanisms almost impossible to understand.... A diagram, showing the parts in various stages of firing, would allow my brain to wrap around it.... at least I think it would....

Bob

[Motorhead]

In such Rotary or Spool type Valves, FRICTION between the drum/spool and body is super critical effecting the rotational or sliding speed it can and will move with any know & fixed amount of spring effort exerted. 
Making it able to seal means a tight tolerance between parts ... which equals DRAG being created by VERY CLOSE fitted parts has this fit changing with temperature as well.

Have worked extensively with rotary drum and flat gillitine type valves in small 2 stroke race engines, there tricky buisness when asked to move at very high speed .. yet alone stop and start obtaining a very high surface speed to open/ close the intake aperture quickly then abruptly stop.

Honestly DON'T see it practical for an air gun valve ... not at all !! 

[NCmountainShooter]

Thanks Motorhead! I didn't even know the name for the type of valve. I thought that might be tricky. Unless someone else pipes up with suggestions, I'll file this one in the no-go folder.

[lloyd-ss]

Chris,
The method you describe can be made to work at low pressures, but at 2000+ psi, quite doubtful.  Anything that will seal and hold 2000 psi will experience a cheese grater affect as it is rotated across the port under pressure.  There might be some ultra precision ceramic materials with zero clearances that would work, but I have not seen them.

But, I do have a little shut-off valve that fits on top of a paintball bottle that opens and closes with a 90 degree twist, similar to a ball valve.  It seals with an o-ring that is on the out-put side of the valve so that it isn't forced into the moving part of the valve as the stem is rotated.  The actual flow passage is only about .050", and that helps it to work properly.

There are other methods of sealing a "valve" in a PCP, though.
Lloyd

[NCmountainShooter]

What are the other valve types that would work in line with the bore?

I'm trying to eliminate any obstruction to flow, like the stem from a poppet. What about something as simple as a ball valve? Use a hollow cylindrical hammer, through which the air would pass, to impact a ball or some other obstructing device that is only being pressed forward by a spring. The hammer would need to have a stop to keep it form following the ball and obstructing flow. It would still need to be a regulated system, but I don't see that as a problem with today's technology.

[Bill G]

Balanced chamber quick exhaust valve that uses a spring to upest the ballance.  pressur released fom backside of piston allows piston to move rearward thus removing poppet from flow path.  this allows contained pressure to evacuate bore obstruction violently.  work s like a dump valve and will require a shut off from reservoir during the cycle. 

[lloyd-ss]

[rsterne]

Too small for my old eyes.... *sigh*....

Bob

[lloyd-ss]

Sorry Bob, found out I  couldn't read it either, LOL.
Here is a "viewing friendly" version.  Annular face seal. Even though it isn't a straight in-line flow-through design, it dumps radially 360 degrees right into the barrel.
Lloyd-ss
 

[rsterne]

Got it!.... 150 psi air moves the tubular shuttle open or closed (so must be timed for required dwell).... Amount of flow can be controlled by the position of the maroon inner plunger relative to the throat.... right down to virtually nothing.... Would work great, once tuned, for a regulated gun, would need some kind of timing adjustment for non-regulated....

Like the Condor, the loading port would have to be to the left of the valve, in line with the barrel.... and like the Condor, it will have a lot of volume downstream of the valve seat.... Better, more unrestricted flow (after all, the valve can be made larger than boresize with no penalty).... but a slight pressure drop depending on the relationship between the reservoir and the downstream volume....

This has made me wonder.... What, other than higher opening force (which the balanced design eliminates).... is the downside of running larger than boresize valving and porting in a conventional PCP?....

Bob

[NCmountainShooter]

Got it!.... 150 psi air moves the tubular shuttle open or closed (so must be timed for required dwell).... Amount of flow can be controlled by the position of the maroon inner plunger relative to the throat.... right down to virtually nothing.... Would work great, once tuned, for a regulated gun, would need some kind of timing adjustment for non-regulated....

Like the Condor, the loading port would have to be to the left of the valve, in line with the barrel.... and like the Condor, it will have a lot of volume downstream of the valve seat.... Better, more unrestricted flow (after all, the valve can be made larger than boresize with no penalty).... but a slight pressure drop depending on the relationship between the reservoir and the downstream volume....

This has made me wonder.... What, other than higher opening force (which the balanced design eliminates).... is the downside of running larger than boresize valving and porting in a conventional PCP?....

Bob

The bore or larger sizing eliminated sonic choking does it not?

[NCmountainShooter]

Sorry Bob, found out I  couldn't read it either, LOL.
Here is a "viewing friendly" version.  Annular face seal. Even though it isn't a straight in-line flow-through design, it dumps radially 360 degrees right into the barrel.
Lloyd-ss
 

Neat design! I had something similar that was still axial I'll post later to see what you think. Bob has already seen it but maybe more eyes can see a better solution to the problem.

[lloyd-ss]

...............

Like the Condor, the loading port would have to be to the left of the valve, in line with the barrel.... and like the Condor, it will have a lot of volume downstream of the valve seat.... Better, more unrestricted flow (after all, the valve can be made larger than boresize with no penalty).... but a slight pressure drop depending on the relationship between the reservoir and the downstream volume....

This has made me wonder.... What, other than higher opening force (which the balanced design eliminates).... is the downside of running larger than boresize valving and porting in a conventional PCP?....

Bob

The dead air space between the valve and the bullet can be pretty much eliminated by  a falling block/sliding block arrangement immediately downstream of the valve. The block slides out to the side, the bullet is loaded into the block, and it is then slid back in.  Some tapered surfaces are usually required to seal the HPA.  This is similar in application to I think what is called a tap loader.

re: bore-size valving: in general, I have found that the larger the valve, the more difficult it can be to meter very small amounts of air repeatably.  If the application is not in that range, it ought to work fine. 

Lloyd-ss

[rsterne]

Yes, if the valve is larger than the bore, then sonic choking would occur (in the barrel) only when the airflow reaches Mach 1 at whatever pressure is present at the time.... which means not until the pellet exceeds Mach 1 at the muzzle.... If you don't shoot beyond 950-1000 fps, it would never be an issue.... As examined in the thread on Sonic Choking, it isn't a hard limit anyway, sonic choking causes a reduction in pressure downstream of the choke point, which reduces (but doesn't stop) acceleration after it occurs.... 

I wasn't thinking of using a .50 cal valve in a quarterbore.... but on the other hand if the flow rate is adjustable, it might mean one valve body for any caliber.... A muzzle loader could eliminate the dead air space as well.... *grin*.... or a break-action like a shotgun.... Would have been a good solution for my .410....

Bob

[NCmountainShooter]

My idea was to have a sleeve that move forward to open a space for air flow through, then have a cone shaped plug follow that and close the port. My idea would have been limited by struts going back to the closing mechanism and spring, but that can be done far enough from the port to not limit flow. The other way would be to come from below like in your design. The timing would be adjusted with the distance between the sleeve and the plug and however you slow down the plug. I had thought of using lugs to force it to twist and slow down or make a suction behind the plug as it closes. The suction idea might even allow some self regulation depending on pressure. Pardon the bad drawings. I couldn't get any software to draw it in.

Edit: My idea does have more dead space behind the bullet but maybe you can see a fix for that.
Edit 2: just to be clear, my idea was to have this all screw into a small tank then have that tank filled from a regulated cf tank.

Chris

[lloyd-ss]

Have you looked at the details of the valves in the Airforce bottles?  Similarities and very good performance.

[NCmountainShooter]

Have you looked at the details of the valves in the Airforce bottles?  Similarities and very good performance.

I've never had access to one of those or design details.

[lloyd-ss]

Have you looked at the details of the valves in the Airforce bottles?  Similarities and very good performance.

I've never had access to one of those or design details.

Try here:
http://www.talonairgun.com/forum/

A search will turn up diagrams and photos of the valves.

[Bill G]

Those are nice designs.  Lloyd, where does the switching pulse come from on that patent?  It could be done by solenoid i suppose but the air coming off the reservoir would have to be regulated down to 150 psi.  The design that I've been working on works more like a dump valve.  It is fed from a regulated reservoir and recharges the dump chamber once the firing cycle is complete.  piston movements are very small.  I find that I can use smaller porting since I have no dwell to contend with.  I do have a small amount of dead volume. The dead volume consists of the head thickness of the dump chamber, so it is very small.  The con is, that you have to decide on how large of a dump volume that you want.  Bob referred to 50% of barrel volume in a post some time ago and that works out in the model.  50% happens to be the volume used at the minimal psi to get most power with highest shot count.  There is some change in the model as you go to smaller calibers.  Big bore seems to follow the 50% rule to the tee.  Efficiency looks like it will be improved greatly according to my model.  Lloyd, your balanced valve for your big bore project is what got me on this design. My building issues are the same as Bobs.  The force of the piston moving rearward is big and dangerous.  In fact, I won't even show pics because I feel it would be irresponsible.  It wont take long to have a failure at this point.  Yea, I tried it at only 1500 psi and it is spooky.  Evidence of onset of failure after only 60 cycles.  Learned a bunch though and I'm currently pondering how to overcome this issue.  The new design looks promising but more complicated.  Unfortunately, complicated = time.

Bill