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Old 07-20-2011, 05:46 PM #22
Pnuemagger
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Yoda,

So having squared off edges on the valve will HELP efficiency?!? The current working model (below) has the valve port milled at a 20* angle from the feedneck hole so there is no hole in the bottom of the body to seal and so the gas is moving forward before it gets to the bolt. Plus, I planned on porting the inside of the spool exhaust to aid flow. See image below of most recent changes.

Your saying that these features could *hurt* efficiency?

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Old 07-20-2011, 05:56 PM #23
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Originally Posted by pbjosh View Post
Also in that vein, the smaller 1mm orings are generally not considered okay for moving components? I think they might be fine, but there is a reason most manufacturers don't use them.
Generally, in all industrial applications, dynamic orings should have the thinnest cross section possible to allow the pressurized fluid to deform & seal the oring while having a sufficiently high width/diameter ratio. As that ratio decreases the probability of spiral failure goes up.

So you don't want big thick orings just because you can fit them (they might not seal low pressures) but you also don't want slender large orings that twist and tear themselves up. It's just one of those design balances that engineers have to figure out for a specific application. About all you can do for overly thin orings is design for minimal squeeze, maybe undersize the oring a bit so it hugs the gland, and lube the **** out of it.

Last edited by Pnuemagger : 07-20-2011 at 06:03 PM.
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Old 07-20-2011, 06:15 PM #24
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Not at all, features like that are advantageous to efficiency. I meant only the leading edge/edges of the transfer ports themselves. Easiest depicted in plan view.

Shown are quarter inch circles, one of which has had the leading edge squared off. The distance between the ports leading edges is identical in each variation.




Here, the ports have advanced 1/8" forward. The squared off leading edge has an appreciably larger area able to flow compared to the round variant (approximately 1/3 better).


I thought you had mentioned doing something like that, but going back I had misread something.
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Old 07-21-2011, 03:33 PM #25
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I was thinking 1mm was not acceptable due to this:

http://www.allorings.com/gland_metric.htm

Though we are not talking about a setup that is running close to 100bar (1400psi?)

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Old 07-21-2011, 06:10 PM #26
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That chart also has no check mark next to dynamic for 1mm cross section o-rings.

I'll be using one dynamically in the next few weeks, I'll let you know how it goes
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Old 07-21-2011, 07:08 PM #27
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Oring choice in my design has no change on machining the body.
Most of the work will be in the body and frame. A new spool and front cap will iterally only take a few hours to make.

I'm going to go ahead and use the 1mm orings and just make a new spool if I have to.
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Old 07-25-2011, 12:29 AM #28
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Not sure what I am missing. Once the air is vented from in front of the valve, what is going to drive it forward?
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Old 07-25-2011, 01:28 AM #29
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Originally Posted by Gryphon43 View Post
Not sure what I am missing. Once the air is vented from in front of the valve, what is going to drive it forward?
It's a unbalanced spool. once the air thats in front of the spool vents, it becomes unbalanced and the air inside the spool pushs on the rear sail and pushs it forward.

I hope that helps clear it up for you
I'm sure y0da can explain it alot better then I can.
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Old 07-26-2011, 12:37 PM #30
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Not sure what I am missing. Once the air is vented from in front of the valve, what is going to drive it forward?
The front diameter of the spool is the complete diameter of the bottom tube... and the very rear diameter of the spool has a smaller diameter (see how the rear fits inside of the cup sealing the back of body). So when air is in front of the spool it has maximum reward force because it's pressure acting on the full diameter of the tube. But because the vented area in front of the spool is greater than the area of the step at the rear of the spool, the spool will move forward when the front air is vented... the rear pressurized area is now bigger than the front pressurized area.

Basically, instead of a tridional bolt sail found on the spool, the entire spool itself is basically the bolt sail. 100% of the dump chamber and airflow happens within the spool.
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Old 07-31-2011, 02:16 AM #31
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Ok, to save alot of long drilling and machining of the front of the body,

-make the front reg a dummy, this will save the long drilling

- move the noid closer to the ram section, right bellow it to save air on transition

-gas through grip frame, make the transfer hole in the front spine, its almost a straight line to the dump chamber fill hole

heck you could probably make a mini relay reg work, and mill the feedtube for either 7/8 collar like the creed and legend, or ego7+ both platforms hold up very well and then you dont have to do do that fine threading.
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Old 08-02-2011, 09:48 AM #32
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Ok, to save alot of long drilling and machining of the front of the body,

-make the front reg a dummy, this will save the long drilling

- move the noid closer to the ram section, right bellow it to save air on transition

-gas through grip frame, make the transfer hole in the front spine, its almost a straight line to the dump chamber fill hole

heck you could probably make a mini relay reg work, and mill the feedtube for either 7/8 collar like the creed and legend, or ego7+ both platforms hold up very well and then you dont have to do do that fine threading.
#1) What front reg? The main reg screws into the vert ASA, there's no long drilling involved. I was going to use a sidewinder or 2 Liter. The front cap of the bottom tube is just hollowed out for more volume... there is no "front reg" or LPR.

#2) The solenoid is already blow the spool ram/sail... it can't get any closer.

#3) Gas through grip frame would make getting air ot the solenoid more troublesome. Plus, I'd be very limited on my choice of ASA Reg & dropforward.

#4) the feedneck is going to be 13/16" press fit.
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Old 08-02-2011, 01:01 PM #33
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1, i meant the vertical reg/hpr, it would save on macining the entire area at the front.

2, my bad on this one as i assumed the sail was the rear one as it looked like the bumper was there.

3, either way you have to drill the transfer holes i guess.

4, ok then.
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Old 08-07-2011, 04:36 PM #34
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Honestly not sure how to do the transfer port taking advantage of that, you would want something that isn't going to be a speedbump for the ball. The port in a PGP is tiny and likely why it isn't an issue. It would probably take some form of manifold on the bottom of the gun to seal it properly afterward, but a slot may be a safer approach than a hole.

Then again, it may move fast enough that it is not a problem. A few other methods that should help between cupping the bolt face to provide a slight lift from the bottom of the bore or a wire running along the bottom of the bore across the hole acting like a wire detent so that it can't fall into the hole at all.
I know magger said it would add complexity but I just wanted to explore the placement of the transfer hole in front : ). What about using the space between the end of the barrel thread and end of the barrel for the transfer hole and make a gap between the barrel and breach about a 16th of an inch for air to enter the breach. Should provide more than enough flow and is less likely to be a speed bump because of the smaller gap. Also would putting the transfer hole in the breach infront of the bolt cause a lot of turbulence?
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Old 08-18-2011, 10:03 PM #35
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How exactly are you going to seal the transfer hole? You have to drill through the bottom if you keep the two tubes together and if you plug the hole with a screw as per usual either it will stick into the tube and not let the spool move, or not stick into the hole and tear orings. OR you could make a custom one that is shaped to the tube and indexed but that is a MAJOR PITA. Unless you put enough angle on it that you can drill it down through the feedneck. (then you'll just need a sine table/4th axis in your machine to drill the hole accurately).
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