GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: sb327 on August 29, 2022, 11:22:26 AM
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Got enough done with this one to post a picture. I scaled my pilot valve up and changed the location of the small pilot poppet to be inline with the main poppet.
I’m firing it right now with a solenoid. It’s one of the smaller pancake styles that you can easily get for paintball guns. I’m hitting it with 30volts and it is able to open at 4500psi.
Just getting to start testing. It’s a 30 caliber (.308) 16 twist barrel. I’m using some 88grain .312 bullets I cast and sized to .309.
Dave
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Following! Any pics or drawings of the pilot valve other than your other posts?
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I’ll post some of the internal stuff in a bit.
Here is a video testing the action (free to recoil). This was at 4500 psi and 1024fps. Pulse to the solenoid was 2.9ms.
https://youtu.be/71_ULehKbP0
Dave
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Took me longer than intended for the internal diagram.
When the pilot poppet is opened, the main poppet comes open, the small probe on the pilot stops the incoming air into the pilot chamber, effectively holding the main poppet open. When the pilot poppet returns to its seat, the chamber is allowed to fill and main poppet closes.
I am using a solenoid but a conventional hammer can be used as well due to the probe being able to slide within the main poppet, allowing for dwell adjustment with a hammer strike. With the solenoid I use arduino to control the dwell.
Dave
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Thanks for posting, Dave! Lots going on here for sure. Another question, why is there a vent on the poppet to atmosphere? Is there not enough venting around the poppet stem hole to achieve it fast enough?
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The hole for the poppet stem is a close sliding fit to maintain poppet alignment.
So, yes, it needs a larger escape path.
It’s not drawn but I actually divert that puff of air away from the shooter.
Dave
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David, very cool action build! Boy, that has a lot of power! Hope to see a video when you are finished!
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Thanks for the explanation, Dave! IIRC you mentioned in another thread that your piloted valve was the easiest to open yet? Excellent work.
I received my 1.25" slab of 6061 yesterday. I'm hoping to start on a receiver for a build. Working on finishing my BT65 side cocking lever right now. It's a pain trying to machine parts on a mill when you've removed the dial indicators on the X,Y axis. I thought I had it figured out, but it's still a pain trying to learn g-code. (Side note, Y axis isn't functioning properly, so I switched Y and Z stepper motor leads to help confuse things even more.) ;D :o Needless to say it is making my head hurt. ;D
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I’ll definitely get a video at some point.
I hope the design lends itself to multi calibers, up to 30. The throat is .312” and if you notice in the drawing, I can limit the main poppet lift by screwing the rear section in/out. Since any dwell is created at the pilot poppet, there is no need to open main poppet any further than what allows full bore flow.
Dave
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Thanks for the explanation, Dave! IIRC you mentioned in another thread that your piloted valve was the easiest to open yet? Excellent work.
I received my 1.25" slab of 6061 yesterday. I'm hoping to start on a receiver for a build. Working on finishing my BT65 side cocking lever right now. It's a pain trying to machine parts on a mill when you've removed the dial indicators on the X,Y axis. I thought I had it figured out, but it's still a pain trying to learn g-code. (Side note, Y axis isn't functioning properly, so I switched Y and Z stepper motor leads to help confuse things even more.) ;D :o Needless to say it is making my head hurt. ;D
Since the pilot poppet is only 1/8”, it takes very little force to control the much larger poppet.
Have you started a thread on your receiver build?
Dave
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No, I haven't started it yet. I want to finish making my BT65 a side lever cocking action. I need to get a little experience trying to run the mill and lathe. I haven't used them much in the last 5 years. Completely forgot everything (not much really) I had learned about fusion360, when I made the supports for the barrel and cylinder to hold the scope rail and mount the trigger assembly to. :(
Right now, I'm playing with the mill trying to figure a way to move the required distance without setting up dial indicators on magnetic bases. The mill was a manual 9X42 Enco in the middle of a CNC conversion when I bought it 7-8 years ago. The dials on the axis are no longer on the mill. Right now, I'm using Ubuntu, and line inputting g-code 1 command at a time. :o I feel like Scotty trying to run the Starship Enterprise with a steam engine. Using g-code is faster than fiddling with setting up dial indicators though. ;D I need to figure out how to turn the spindle on/off from the keypad instead of having to go to the VFD. I'll probably research that tonight.
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I’ve seen people use the cheaper digital calipers as a poor boy digital readout. That might be an option in your case. That would drive me nuts not being able to machine manually. The only time I mess with cnc (usually) is when I make a bullet mold on the lathe.
Dave
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I’ve seen people use the cheaper digital calipers as a poor boy digital readout. That might be an option in your case. That would drive me nuts not being able to machine manually. The only time I mess with cnc (usually) is when I make a bullet mold on the lathe.
Dave
I was actually thinking of adding a DRO, then the VFD went out, so I replaced it instead. Now that I've started using Ubuntu and LinuxCNC, a DRO would be redundant. I can input a line of Gcode and tell the table or z axis where to go withing .0005", and I don't have to crank the handles. ;D I'm actually starting to enjoy it after a couple of days use. 8) Still trying to figure out what's going on with the Y axis. It only moves if I use a speed of 3"/min or higher. I don't know if the Geckodrive is weak or something else is going on. I need to switch the X/Y axis and see if it's still doing it. That might narrow it down to either the stepper motor or the Geckodrive. If it's still doing it then it would indicate a problem with the breakout board, I think? ??? The Z axis isn't really a good indicator because it's a smaller stepper motor. I noticed the other day that the X stepper motor was quite a bit warmer than the Y stepper motor, so that might indicate a problem with the stepper motor. They have constant voltage going to them either moving them or "braking" them, so they get warm.
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Very cool stuff Dave-excellent! 8)
Jesse
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Playing catchup here. How are you controlling the dwell of the solenoid? found the answer , auduino. very wise,.. one more question , aside from the pressure rebalancing in the chamber, is there a spring returning the larger poppet to home.? what impreses me the most is how you get all thise stuff to seal reliably , no easy feat,, ( i see the spring now its wrapped around the major poppet. brilliant
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Impressive!
One suggestion, instead of a piston port and o-ring around the piston, why not eliminate both and rely on air leaking past a tight-fitting piston to fill the pilot chamber?
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Rob,
I think it does good job at sealing because, while static, both poppets are basically conventional in that they do not have a reduced holding force on them like a bv does.
Jackssmirking,
I run the oring for consistency mainly. Since it is pressured from both sides while static, stiction is not a factor.
Also, if you notice the probe on the pilot poppet, it’s purpose is to essentially block the chamber from being filled during the dwell portion of the cycle. (It also creates a closing force for the pilot)
But you are correct, it would function as you describe.
Dave
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I did get a mold made for this and have shot a few. Don’t have it quite set up for accuracy testing yet, just crony stuff. But hey, they didn’t hit sideways, so that’s good.
It’s 96 grains and I’m pushing it from 980-1000. It drops at .310 then gets sized to .309. The nose (bore rider) drops at .302.
Hope to get some more done before going back to work but have been pretty busy on other ‘have to do’ stuff.
Dave
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96 grain at 1000, 213 fpe beast! :D seems this valve would do well in 9mm also
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Been a while since an update on this one.
It gets attention between other projects. It is my most interesting project for me. I’ve made a few internal valve changes to effect how the main poppet responds to the pilot.
In the process of trying to figure out some things, I’ve added pressure sensors (as I noted in Bob’s thread). With the sensors, I’m able to visualize on the oscilloscope what is going on and when.
I have also recently switched the caliber to 22 instead of 30. That made a significant change in the rise time of pressure at the breech.
I was needing to build a new shooting bench due to the age and deteriorating condition of mine. I decided to get a very tiny building built locally and sold as a deer blind. I want to be able to set up my test equipment and not have to bring it back inside each time. This should accommodate that quite well (plus I can heat and cool it, lol).
Hopefully my data collecting and understanding of what it tells me continues to improve.
Dave
The picture of the little building below is similar to what I’ll be making into my shooting shed.
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that gun is quite an accomplishment. Be nice if you could use the arduino or rasberry Pi to tune it on the fly,, Have you had a chance to compare similarities to the umarex hammer >?
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I’ve not studied the hammer yet.
To be able to tune via arduino, the valve really needs to respond digitally (on or off with little variation). As originally designed, it had (and still somewhat has) a bell curve like a conventional valve. For tuning to pressure, the ideal scenario would be a linear decrease in power on a single setting as tank pressure drops.
I am getting closer to that scenario but it has been challenging, which is fine with me because it’s been quite a joy. More failures than successes, lol.
I’m at work and I don’t have my personal computer but below is a snapshot of the oscilloscope after swapping over to the 22 barrel. I also decreased the main poppet lift to help speed the cycle of the valve.
As you can see, the pressure rise is a lot faster than when it was set up for 30 cal. Remember the throat id is .312”.
Dave