Forward Venting COAX....

jeepkahn · Thu May 07, 2009 5:26 pm

I was studying the pictures of the avalauncher and I think I just figured out how to have the vent at the forward end of the chamber instead of the backend...

The coolest part of this layout would be that you could use the backend as a shoulder stock have the trigger/vent device at the midpoint of the gun, and keep your pilot volume small....

Anybody wanna guess at layout/configuration/design???

Or maybe I should enter it in the contest???

Hmmm...decisions decisions....

Technician1002 · Thu May 07, 2009 5:38 pm

jeepkahn wrote:I was studying the pictures of the avalauncher and I think I just figured out how to have the vent at the forward end of the chamber instead of the backend...

The coolest part of this layout would be that you could use the backend as a shoulder stock have the trigger/vent device at the midpoint of the gun, and keep your pilot volume small....

Anybody wanna guess at layout/configuration/design???

Or maybe I should enter it in the contest???

Hmmm...decisions decisions....

It's been done. Sprinkler valves use it. A pilot valve built into the center of the piston will do it every time. It operates by "Pulling the cork" out of the back of the piston so the vent is open to the chamber through the piston.

jeepkahn · Thu May 07, 2009 5:43 pm

I know it's been done, but I'm not doing it the way you describe....

Look at these pics, also your valve played a part in my soon to be gun...

jeepkahn · Thu May 07, 2009 5:59 pm

Sorry double post, but didn't want images to get twisted upside down...

the red is the cylindrical piston that seals on the inside to the barrel, to the outside to the chamber and to the breech when filled/closed, the blue is the vent which cause the piston to move FORWARD to Dump similar to your dump valve... A true bullpup coax... and the green is the ball stop pin... and the purple is the spring for piston impact absorption...

edit, can someone please resize...

Technician1002 · Thu May 07, 2009 6:00 pm

jeepkahn wrote:I know it's been done, but I'm not doing it the way you describe....

Look at these pics, also your valve played a part in my soon to be gun...

With that hint, a QDV without any vent in the back could simply be knocked back to trigger and returned with a spring or string. A small pilot hole through the piston would keep the "pilot" area at normal pressure. The trapped volume of air in the pilot area would return the piston back to a nearly closed position without a spring.

A trigger assy would simply push the piston back to trigger. The trigger would however be in the air flow path and contribute to turbulence.

edit, can someone please resize...

After you copy/pasted the resize, I deleted my photo.

jeepkahn · Thu May 07, 2009 6:03 pm

and you could actuall increase the rear portion of the chamber for more volume without adding piston size... and this layout will actually help mitigate recoil....

the picture is exageratedly long, but it's the method of firing that I think has potential...

daccel · Mon May 18, 2009 11:35 pm

That's a neat adaptation of coax! It would allow for a bolt action breech at the rear. Mmmm... aesthetics.

*eyes retired bolt action hybrid...*

Technician1002 · Mon May 18, 2009 11:44 pm

daccel wrote:That's a neat adaptation of coax! It would allow for a bolt action breech at the rear. Mmmm... aesthetics.

*eyes retired bolt action hybrid...*

I have considered a breech through the valve bolt, but haven't come up with a super reliable way to prevent the bolt from ejecting into my body parts, so for now, I am still using the screw on pipe cap. Using spuds and other juicy projectiles could cause some problems with the seal and lubrication. I am giving it a lot of thought.

daccel · Tue May 19, 2009 12:31 am

Wouldn't need a perfect seal, just tight enough to minimize blowby but still slide, unless you're an efficiency nazi. Or o-ring it, if you feel the need.

This is how I pictured it working. You could add multiple lugs to the bolt as needed. I guess it all hinges on your barrel strength, though.

Or don't stand behind it when firing

.

Technician1002 · Tue May 19, 2009 2:50 am

daccel wrote:Wouldn't need a perfect seal, just tight enough to minimize blowby but still slide, unless you're an efficiency nazi. Or o-ring it, if you feel the need.

This is how I pictured it working. You could add multiple lugs to the bolt as needed. I guess it all hinges on your barrel strength, though.

Or don't stand behind it when firing .

For a lighter weight part I was thinking in the lines of this in a QDV. I don't like the length of the breech out the back of the chamber in my drawing.

I was wondering if your original design would work for a mid chamber port with the pilot in the rear instead of the front?

jagerbond · Tue May 19, 2009 5:42 am

Here's a sneek peak on something we've been working on... A little bit different than the previous posted drawings but along the same lines. We've off set the barrel/chamber ports to increase efficiency of air flow.

We're putting a new, larger, O-ring on the donut and should be testing by the weekend.

Specs:
5 " diameter chamber x 40"L
2" diameter AL barrel x 72"
3:1 CB ratio

Technician1002 · Tue May 19, 2009 6:19 am

jagerbond wrote:Here's a sneek peak on something we've been working on... A little bit different than the previous posted drawings but along the same lines. We've off set the barrel/chamber ports to increase efficiency of air flow.

We're putting a new, larger, O-ring on the donut and should be testing by the weekend.

Specs:
5 " diameter chamber x 40"L
2" diameter AL barrel x 72"
3:1 CB ratio

Sweet!

I like it. Just a question, to provide less restriction, would fewer ports be advisable. It looks like only 1/2 the circumference is ports. On mine with 3 ports the 2 inch pipe has a circumference of 7 inches. With only 3 bars in the ports 1/2 inch wide, only 1.5 inches of the space is not ports.

That style will need a very aggressive pilot as when the chamber empties, the piston will attempt to move to the low pressure side re closing the ports. It lacks the positive feedback to pop open on it's own when triggered.

USGF · Tue May 19, 2009 6:27 am

Tech, Mike made the slots at an angle from centerline to create a spin. We calculated for slot area much larger than barrel area. He will also incorporate the same style cone we made for Grock's 4" valve. I think there is even rumors of 2 stroke style exhaust ports on the piston to dump the piston quicker and keep it back.

I may be spilling too many beans.....

I may lose my job

BTW, what little function testing I witnessed was very successful!!

Technician1002 · Tue May 19, 2009 6:42 am

USGF wrote:Tech, Mike made the slots at an angle from centerline to create a spin. We calculated for slot area much larger than barrel area. He will also incorporate the same style cone we made for Grock's 4" valve. I think there is even rumors of 2 stroke style exhaust ports on the piston to dump the piston quicker and keep it back.

I may be spilling too many beans..... I may lose my job

BTW, what little function testing I witnessed was very successful!!

The area is not the issue. It is good and engineered for. I'm looking at long skinny ports. Long ports mean a long piston stroke to uncover them. I was thinking of covering more of the circumference in port width so a shorter stroke will open the same area in less time. The less metal the better with just enough for structural integrity.

However when thinking of the O ring on the outside.. Keeping the rings out of the ports becomes a problem as they will want to fall in. It looks like you have thought this out and are one step ahead of me on that one. Lots of rounded ports is best to keep the o rings out of the ports.

Good luck. It looks like a winner. Hope to see a video soon.

As a breech loader, it could even hold a few rounds in the breech to be advanced one at a time with a multi position bolt. Wow. I like it. Keep the breech loading secret. Who knows, it may support semi auto or full auto operation. Supprise me with a video.

I hope you keep your job. It must be a great one.

jagerbond · Tue May 19, 2009 6:45 am

Technician1002 wrote:It looks like only 1/2 the circumference is ports.

They run full circumference and area is 130% barrel area.

Technician1002 wrote:That style will need a very aggressive pilot as when the chamber empties, the piston will attempt to move to the low pressure side re closing the ports. It lacks the positive feedback to pop open on it's own when triggered.

Not sure what you mean, our testing so far the piston slam back and it dumps fast. We are simply pulling the 1/4" quick disconnect off after filling to 125PSI.

Beauty is breach loading. So load projectile and add plunger bolt to seal rear of barrel and fire.

Also, based on this same design it can be converted to a hybrid. With the Hybrid, there is a light spring added behind and to re-seat the piston, gas is injected in to the chamber area then, through the pilot, air is added to desired PSI filling both the pilot area and chamber through one way valve. Upon ignition, the piston starts moving back, compressing the pilot air and also uncovering exhaust ports (as USGF noted) allowing the piston to retract . Of course we will step it up to AL chamber material.

Mike
Sureshot Inc. / http://www.ultimatespudgun.com

Forward Venting COAX....

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