GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Engineering- Research & Development => Topic started by: CableStop on August 15, 2021, 05:37:27 PM
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I designed this regulator to allow for external adjustment while under pressure and easy disassembly. The yellow plug on the left end of the diagram is the adjustment screw which also holds the internals of the regulator in place, unscrewing it lets you remove everything for maintenance. It works similarly to a normal regulator except for the spool is inverted and fixed to the housing.
I actually came up with this concept for an unrelated project but a I modified it a little to make it better for airgun use. I'm not sure of any applications for it but I figured I'd put it out there in case anyone wants to mess with it themselves.
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Does the red piece seal against the light green piece to stop the flow?
Dave
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What is the pink made of? It looks like it presses up against the red. Looks like pink needs a spring guide?
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The green T shaped piece is the sealing surface, made out of something like Delrin, the red slides back and forth and seals against it. The pink is basically just a washer for the spring to seat against, ideally the spring is fitted tightly enough inside the red tube that it doesn't need an inner spring guide, but I don't know for sure that it won't bind up.
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Ok, so it appears me, that adjusting it, as designed, only increases preload on the spring but does not change how far the spring gets compressed AT CLOSING.
Therefore, it wouldn’t adjust the pressure. You need to be able to adjust the ‘seat’ or the spring. But not both.
Hope that made sense.
Dave
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Ok, so it appears me, that adjusting it, as designed, only increases preload on the spring but does not change how far the spring gets compressed AT CLOSING.
Therefore, it wouldn’t adjust the pressure. You need to be able to adjust the ‘seat’ or the spring. But not both.
Hope that made sense.
Dave
Yes that made perfect sense and I think you may be right, I will need to rethink that portion.
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Spring pushes the reg and you put pressure in to that the red part will be pushed to the back wall and stays there, or I'm missing something here?
Marko
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I have looked at this drawing several times, and I can't see how it would be adjustable.... My confusion was not helped by the colour of the "light green T-shaped piece" sitting against the yellow adjuster, as I am a bit colour blind, and they look nearly identical to me....
Since the reg. is closed (no flow) when the red piece seals against that piece, and at that point the spring has some given load, all that happens when you adjust the position of the yellow piece is that the whole assembly (light green plus red) moves inside the blue housing.... The load on the spring does not change, so neither does the setpoint pressure....
I get that the purple washer is just a seat for the spring, so it can be considered to be part of the red piece, and moves with it.... There appears to be a tiny vent (on the bottom) for the space between the green stem and the red shuttle, to keep that area at atmospheric pressure.... All the other internal spaces will be at the setpoint pressure.... There is a net closing force caused by the output pressure acting on the difference in area between the right end of the red shuttle, minus the area of the green stems (left minus right).... So, yes I think the regulator would have a setpoint dictated by when the force (to the left) on the red shuttle (piston) equals the spring force (to the right).... When the setpoint pressure is reached, the red shuttle hits the "light green" seat, and flow stops.... However, I don't think adjusting the position of the yellow piece changes the force on the spring, only the position of the assembly....
Bob
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Yeah you guys are correct about the lack of adjustability as designed. I have a modified design that should fix the adjustability issue but I don't know if it will react quickly enough to effectively regulate pressure. Delrin has to compress and decompress far less than an o-ring in order to seal and the longer travel may be an issue.
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Like that if you feed pressure in from the top hole nothing will happen, the red part just stays where it is now.
Try to understand surface area vs pressure difference is what drives the regulator. Now you have two equal forces working away from each other on the two O rings.
Marko
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Not only that, but you are still simultaneously adjusting the position of the seat AND the preload on the return spring.... They MUST be independant of each other to adjust the regulator output pressure....
Marko is correct that regulator would not allow any air inside because the inlet port is between 2 O-rings.... In addition, your design has so many O-rings there are just that many more failure points....
Bob
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Marko,
As far as I can tell the spring should open the valve and the gas pressure on the other side should shut it. The dark green T is fixed to the blue housing so it doesn't move and seals one side of the red piece from the pressure to create an imbalance. When pressure drops on the side of the lower hole the spring can push the red piece out of the o-ring and allow gas to flow.
Bob,
Yeah it has too many o-rings at this point to be practical. Making the vent work made it a lot more complicated, the original design allowed for a much simpler vent system without all the layers that need to nest together. I do think the adjustment should work in the updated design however, since the seal stays in a fixed position the red piece will have to compress the spring further to seal.
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Are you saying that the seal is created by the red shuttle sliding through the O-ring to the left of the HPA inlet?.... I suppose that might work, but I can't imagine it would have a narrow pressure range, as you would desire.... I think the setpoint would be unstable.... However, since the seal is fixed, and you are varying the spring preload, it should indeed be adjustable....
You would have to build it to see how stable it is in operation.... The two O-rings on either side of the HPA inlet have higher pressure between them than the pressure outboard of them.... They would therefore be subject to "stiction", the left hand one on closing, and the right hand one on opening.... The same goes for the two sealing the green piece, but in the opposite direction.... This may or may not cause a pressure difference after sitting for a while....
Bob
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You need to have and awfully stong spring to overcome the force of the two O-rings at reservoir pressure to open the reg once the low side drops.
To be honest looking at the design it probably bottom out if it opens and the end surface area is reduced to the o-ring size on the green pin and i wont close again.
Too many if's and whats, but Go for it if it feels like it should work.
Marko
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Quickly sketched over. This would keep seat and spring adjustment independent of one another.
Dave
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I like the concept of adjusting the spring preload, instead of the seat position.... The Ninja adjustable (developed by Travis, with some input from me) uses ball bearings moving in from the sides to increase the tension on Bellevilles, instead of moving the seat, as per most regulators.... Adjusting the seat by turning it is not desirable, because it tends to mark up the seat material when under pressure....
If it is your intention to install this regulator inside a tube, where it would be fed from the left end, then your adjustment is no longer external, of course.... This is how 90% of adjustable regulators are adjusted, they must be removed to change the seat position....
Bob