New Regulated AirForce PCP Concept

[calinb]

Here's my TalonP carbine ("TalonC"):



I can spin my CAD design of the stock to hold a second 13 cu. in. tank containing a regulator and use the original AF tank as a plenum (and repository of additional air to burn after "falling off" the regulator). I could put the second tank directly under the first tank but, ergonomically, it seems to make sense to put it off to the side, like this bungee and zip-tie mockup:


The bottom of the second tank is actually flush with the butt of the stock, though it doesn't appear so in the photo. If I were to position it directly underneath the existing tank, there's less length available for plumbing, though removing the regulator bonnet and replacing it with a much shorter custom machined cap could streamline the assembly in length too. Underneath is more aesthetic. To the side (as shown above) is probably more ergonomic, with plenty of room for the strong hand to access the grip.

With a little duct tape, I can probably even plumb and shoot it before designing and 3D printing the new stock. The braided steel air transfer hose can connect to the 3k output side burst disc NPT port of the regulator, because I don't need 3k protection (the entire system is 3k on both sides of the regulator). Swapping the 5k burst disk and foster fill nipple positions will make things fit best in the side tank orientation. The foster fill fitting can be removed on the original tank to connect the other end of the hose. A 90 degree elbow or two might tidy up the routing of the hose.

This tank's regulator is set to 2400 psi and the twin tank combo should give me about 20 optimum accuracy shots where I'm currently tuned for a 22 cal. barrel.

The gun actually feels pretty good when shouldered bungied-up like that and it's still not too heavy with two small tanks. Sure--using a second tank for just a plenum might seem wasteful of tank volume, but it's such a simple design and the "plenum" provides additional air after falling off the regulator at least.

The way I currently have this gun tuned for heavy 22 cal. pellets, I get about 12 shots between 3000 psi and 2400 psi but the accuracy is unsatisfactory for me after about shot #4 or #5. With the regulator at 2400 psi, I expect to get 12 accurate shots between 3000 and 2400 psi and then, while drawing down both tanks to 2200 psi, I expect to get 8 more accurate shots. So about 20 accurate shots vs. only 5! That seems worth it to me.

Comments and thoughts?

[rsterne]

The braided steel air transfer hose can connect to the 3k output side burst disc NPT port of the regulator

Whoops, the burst disc threads on the regulator are NOT tapered 1/8"-27 NPT.... They are 3/8"-24NF straight threads.... They do not seal on a taper, using Teflon tape.... they require sealing at the bottom, where the soft copper end on the burst disc tightens against the shoulder on the bottom of the hole in the regulator....

Bob

[RichH]

The braided steel air transfer hose can connect to the 3k output side burst disc NPT port of the regulator

Whoops, the burst disc threads on the regulator are NOT tapered 1/8"-27 NPT.... They are 3/4"-24NF straight threads.... They do not seal on a taper, using Teflon tape.... they require sealing at the bottom, where the soft copper end on the burst disc tightens against the shoulder on the bottom of the hole in the regulator....

Bob

No where near that size, I would guess 3/8"-24 most likely

[calinb]

The braided steel air transfer hose can connect to the 3k output side burst disc NPT port of the regulator

Whoops, the burst disc threads on the regulator are NOT tapered 1/8"-27 NPT.... They are 3/4"-24NF straight threads.... They do not seal on a taper, using Teflon tape.... they require sealing at the bottom, where the soft copper end on the burst disc tightens against the shoulder on the bottom of the hole in the regulator....

Bob

No where near that size, I would guess 3/8"-24 most likely

I didn't look close enough at the burst discs (didn't pull them). Yup. You're correct; they are 3/8. Too close to 1/8 NPT to re-tap too, I think.

I'll need to find room at the bonnet (or custom bonnet replacement) to connect the hose, like you did with your inline regulator.

Doing last minute Christmas stuff today. I see Photobucket is cooperating now but I can't study your Condor thread until tonight but, while you're thinking about your plenum in the stock design, keep in mind that I can design and print a stock for you. (Have a look at the photos above for an idea of what I can do.) If you have a 3D CAD program (FreeCAD will work and it's free), you could design it too, but solid modeling CAD has a learning curve to it, if you've never done it. I'm interested in the project. I can see myself buying a Condor.

[quyang]

You're on the right track, although you don't know the real reason for this pattern. Congratulations, this is one of the few explorations I've found on the forums that I agree with.

[calinb]

You're on the right track, although you don't know the real reason for this pattern. Congratulations, this is one of the few explorations I've found on the forums that I agree with.

The pattern is a method to obtain the use of the original tank to provide a more than satisfactory plenum volume, which is important in regulated PCPs. Sure--a 13 ci volume is a bit overkill for a plenum but, when the gun "falls off the regulator", it also provides more shots on the "backside" of the curve than a minimally sized plenum (which provides virtually nothing at all on the backside of the pressure curve).

I've been running this dual 13 ci tank setup with a fixed 2400 psi regulator for about two years now. The second tank did not have to be placed to the side. It's on the centerline of the stock at an angle that fits and complements the underside of the stock.

It works great! I'll have to check my chrony data as I've not looked at it for a while but I'm getting something like 30 good shots at close to 40 ft*lbs with an 18" 22 cal barrel and JSB Heavies. The extra tank adds weight, of course, but ergonomically, there is no downside. The tanks, plumbing and custom 3D printed stock all permit a prefect cheek weld for me and the lowest possible line of sight on an AirForce gun, which still has too high of a scope/line of sight height for my tastes, even so.

I'd take some photos but the gun is torn down. I'm re-plumbing it for an adjustable Ninja regulator and a new tank retention design in the stock.

[jmohme]

Very interesting. I am looking forward to future updates on this.
I have a TalonP also and am quite happy with how it performs after Talon Tunes worked their magic on it, but still, alway looking for ways to improve things.

[calinb]

Here's a shot string with 14.3 gr. boxed Premiere pellets. So about 35 ft-lbs with a regulator shimmed for 2300 psi.

It did better with JSB Heavies and 2400 psi. More energy of course, but also more consistent velocity and not too bad of a reduction in shot count. I can't find the chrony data, ATM.

When I redesign it for my new externally adjustable Ninja reg, I'll be able to experiment much more easily. I need to find some time to CAD up the changes to the stock that I have have planned to implement a better method of air tank retention and then 3D print up a new one.

[quyang]

Hello my friend.

By watching your speed record. Your speed needs to be more stable and closer. Your speed range is as high as 30ft / s, or even higher? This kind of speed cannot achieve good results in long-range precision strike.



Over the past 20 years, I have explored various improvement schemes in detail. Secondary decompression, electronic instrument control pressure, electronic instrument control valve, various complicated sensors and valves. However, the final plan was finalized about 5 years ago. My plan is similar to your structure, but the reasons for using this plan are quite different from your starting point.



I use 8.6g slug 222M/S 。 Each refueling can be photographed more than 30 times. The speed fluctuation range is + - 0.3m/s, and the speed fluctuation of + - 1m / s can be achieved in the worst environment.

[rsterne]

IMO, the first 32 shots, within about 30 fps (2.8%) will be good to about 75 yds.... At 100 yds. you might look to tighten that up a bit, or your vertical dispersion may exceed 1 MOA.... Yes, the best results would be obtained with zero velocity change, but most people (and rifles) cannot shoot good enough to see a change below 2% ES at 100 yards.... JMO....

Bob