Hi all.
Is anyone here familiar with PCP air rifles? Especially the more powerful ones (such as the Career Dragon or Sam Yang rifles).
I'm designing my own one, but since I haven't had a chance to disassemble a PCP rifle, I have no general idea about the dimensions of the valve or the transfer port, nor the weight of the hammer, so that the air flow would be optimal. I guess the physics behind this is not very simple, requiring knowledge of fluid dynamics, but for me the most important thing is that it would work - preferably so that it'd be useful for shooting
Let's consider the following setup: A regulated reservoir of 800 PSI, a simple poppet valve, a hammer plus a spring, and .45 caliber barrel of 28 inches length.
Now, the transfer port should be as short and as large a diameter as possible. In my design the diameter of the port is 4 inches - this shouldn't be a problem.
However, I can't decide what diameter the valve stem head should be so that it would pop open upon impact of the hammer AND allow adequate amount of air to escape through the transfer port to proper the bullet to around 700-800 fps. This of course depends on the weight of the hammer and the spring strength. However, there must be some kind of recommendations?
Also, since there is no downstream pressure at all, the venturi effect comes into play at the point where the air escapes through the valve, being the narrowest part of the air passage. How narrow should the passage be at minimum?
If anyone here has done this kind of stuff and explain how you've done it in your project, or disassembled a big bore PCP rifle, I'd most appreciate for info. Of course I could go do all this through pure experimentation (which is what I'm eventually going to do), but I'd like my design to make even somewhat sense before I start machining the parts
The attachment shows the very basic principle of the valve design
Is anyone here familiar with PCP air rifles? Especially the more powerful ones (such as the Career Dragon or Sam Yang rifles).
I'm designing my own one, but since I haven't had a chance to disassemble a PCP rifle, I have no general idea about the dimensions of the valve or the transfer port, nor the weight of the hammer, so that the air flow would be optimal. I guess the physics behind this is not very simple, requiring knowledge of fluid dynamics, but for me the most important thing is that it would work - preferably so that it'd be useful for shooting
Let's consider the following setup: A regulated reservoir of 800 PSI, a simple poppet valve, a hammer plus a spring, and .45 caliber barrel of 28 inches length.
Now, the transfer port should be as short and as large a diameter as possible. In my design the diameter of the port is 4 inches - this shouldn't be a problem.
However, I can't decide what diameter the valve stem head should be so that it would pop open upon impact of the hammer AND allow adequate amount of air to escape through the transfer port to proper the bullet to around 700-800 fps. This of course depends on the weight of the hammer and the spring strength. However, there must be some kind of recommendations?
Also, since there is no downstream pressure at all, the venturi effect comes into play at the point where the air escapes through the valve, being the narrowest part of the air passage. How narrow should the passage be at minimum?
If anyone here has done this kind of stuff and explain how you've done it in your project, or disassembled a big bore PCP rifle, I'd most appreciate for info. Of course I could go do all this through pure experimentation (which is what I'm eventually going to do), but I'd like my design to make even somewhat sense before I start machining the parts
The attachment shows the very basic principle of the valve design