New Parts for my 2260 & 2560 HPAs

[rsterne]

I'm in the process of tweaking my 2560 HPA.... nothing major, just seeing if I can get a squeek more power (like 46 FPE isn't enough!), and more shots by changing to an 18 CI tank instead of the 13 CI, still regulated to 1600 psi.... The smaller tank is moving over to my 2260 HPA which is getting a reversed tank block like the .25 cal has now.... I'm hoping that the much larger plenum (the entire 2260 tube) will give me the same power (36 FPE for the .22 cal) on 1600 psi as I was getting on 1800 with the small volume between the regulator and valve it has now.... Here are the new parts I've made....



I made an extended valve front end to move the O-rings in front of the roll-stamp on the 2260 tube.... It has a lot larger bore, and is 9/32" at the spring seat instead of the stock 1/4".... The valve spring has been enlarged at one end to 9/32 to increase the flow as well.... The rear half of the Disco valve is bored out to 5/8" ID (from 1/2") to unshroud the poppet.... The flow into the valve is so much larger than out, basically the valve volume is the whole 2260 tube, from a pressure drop point of view.... I thinned out the stem of the valve poppet from 0.157" to 0.109", shortened it 0.100" for increased hammer travel, drilled the throat of the valve to 1/4", milled the exhaust port to 3/16" on a 20* angle, and rounded the corners for better flow....

The hammer has been modified by grinding a flat on the bottom to allow for the extra travel without hitting the sear.... and the cocking slot in the tube lengthened 0.100" as well.... I made a spring guide from steel which sits in the hammer and adds 11 gr. to the weight, the total is now 68 gr. instead of the stock 60 gr.... The spring guide runs in the preload adjustment screw, and provides a cocking indicator as well.... Thanks to Ribbonstone for that idea....



The tank block is the reversed style I came up with a while back, and mounts to the threaded front of the 2260 tube using a drilled out CO2 nut riding on a hollow bolt.... The aluminum bushing carries an O-ring to provide a seal past the threaded area where the tube is full thickness.... O-rings (not shown) between the parts seal everything up.... The lower part of the tank block carries a standard regulator with the bottom of the tank back towards the trigger, and right up against the bottom of the 2260 tube.... The tank acts as the forestock.... In the bottom of the block is a 3-groove Picatinny rail for a bi-pod, sling-swivel, flashlight, or laser.... On top of the tank block is mounted the barrel band.... The vertical air passage is sealed on the bottom by a 10-32 low-profile SHCS carrying an O-ring.... If desired, I can drill and tap a 1/8" NPT hole on the side of the block for a gauge to show the pressure in the plenum....

This valve is also a prototype for a .25 cal pumper I plan to build in the near future.... The port areas exceed 3/16" diameter at all points.... and is the largest I have gone starting with a Disco valve.... It can be fitted with a gauge by leaving a thicker wall in the appropriate location.... and of course a pumper version will need a check valve in the front.... The pumper version will have a volume of about 5 cc....

Bob

[sholo]

... I'm hoping that the much larger plenum (the entire 2260 tube) will give me the same power (36 FPE for the .22 cal) on 1600 psi as I was getting on 1800 with the small volume between the regulator and valve it has now....

Bob

As usual Bob - awesome work!

I would think 36 FPE (2260) is easily attainable with a 13 ci bottle, considering how much you have opened up the air flow passages. On my 2260 (which I used your build as a guide) I'm getting 32 FPE from 16 gr Polymags (heaviest pellet I have...for now) and that is with the stock TP sleeve drilled out to only 5/32" - not even close to how good your valve will flow...

Todd

[Gippeto]

(damn i-phone!)

Todd

Many would agree! LMAO Go Droid and don't look back. ;)


Bob,

Nice work on the parts, looking forward to your build up. .25 pumper sounds interesting as well. :)

Was wondering about a couple things as I've a need to do a couple similar machining bits....

The weaver rail...did you make a form cutter for doing that or doing it in multiple setups? I'm giving serious thought to making the form cutter.

The 1/2-14 NPS...any tips?

Thanks,

Al

[poil27]

played with both i phone and android , android is way bether

[rsterne]

My 2260 is currently using the 18 CI tank at 1800 psi but only about 10cc volume between the regulator and valve.... That really hurts the AVERAGE pressure during the shot.... It has seen over 50 FPE, and currently detuned to 36 FPE (18.1 gr. JSBs at 950)....



The 2560 is currently using a 13 CI tank at 1600 psi and has the reversed tank block, so has the entire 2260 tube for a plenum.... and has hit 60ish FPE and currently tuned to 46 FPE (25.4 gr. JSBs at 905).... The current valve flows more than I need in .22 cal (it saw 47 FPE @ 1600) so it's moving to the 2260, and the new, bigger valve will be installed in the 2560....



I wanted to update the 2260 to the reversed tank block / larger plenum, and at the same time swap the tanks so that the .25 cal has the larger tank (since it puts out more power).... My goal is 950 fps with the JSBs in both guns at 1600 psi without wasting air.... I'm not concerned about the flow, the valve can easily deliver the power.... I'd like to keep the pressure under 1600 so I can run a 1.8K burst disc, just because (plus it will give more air available for more shots).... I know I can easily get the performance I want by increasing the pressure, but I'm in it for the challenge....

Al, the pumper project is kind of a "what if", and when I proposed it over on the Green Forum, Steve in NC said I couldn't get the efficiency required to reach my goal (1 FPE/CI, based on total swept volume).... so of course now I have to try.... *grin*.... My goal is 30 FPE in (hopefully) 10 pumps with a 392 size pump (~3 CI) in a Disco tube.... Parts are on the way (thanks, Eric).... On the Picatinny rails, I make multiple setups and passes, they are a real PITA to make.... For the "paintball" fitting, I use a 4-jaw to hold the block, bore the recess for the O-ring (to a total depth of 0.70") with an 11/16" mill (it cuts oversize to about 0.696" ID which is perfect).... I then bore the threaded portion to size (0.740" ID x 0.400" deep).... I do a clean-out groove to the thread depth (0.840") with the point of the threading tool at 0.400" in, and then do a single point thread, using a crank handle in the headstock, turning the lathe by hand (no pucker factor involved) stopping at 0.840" diam in the clean-out groove.... and lastly clean up the finish groove one more time.... Then I clean up the thread with a 1/2"-14 NPS tap (I actually have two, one plug, and one I ground down for bottoming).... If I was better at grinding threading tools and internal threading I could probably lose the taps, but I'm not.... The resulting "paintball" adapter is again, a PITA, but works perfectly....

Bob

[Gippeto]

Thanks Bob....about what I'd assumed...both jobs are going to be a PITA. No way to change the 1/2-24NPS job, but am going to have a go at the form tool...if it works it'll sure make cutting weavers an easy project.

Gonna have to make me a crank handle too...a useful accessory.

Best 'o luck with yer pumper cannon too. ;)

Al

[rsterne]

I made an insert rod for the headstock bore that tightens with an angled taper like a bicycle seat / handlebar post.... added a crank about a foot long from square tubing (welded to the insert rod).... and then a 6" long, 3/4" bolt with a piece of 3/4" plastic pipe on it for a handle.... Man, it sure eliminates the pucker factor when internal threading or threading up to a shoulder.... Unplug the lathe, slack off the belts, engage the threading half-nuts, and don't disengage it until you're all done....

Bob

[rsterne]

OK so I finally got some time between Motel guests to get some time in the shop.... I pulled apart my 2560 and installed the new valve and hammer with the original 13 CI tank regulated at 1600 psi.... With the hammer preload at the maximum, the gun shot 911-914 fps with the 25.4 gr. JSB Kings.... This was about 30 fps LESS than it did with the old parts.... WTF ?....

I started swapping parts, and the hammer wasn't the problem.... with the old valve, the velocity peaked at the same value as before.... I put on my 18CI tank which was regulated at 1900 psi, and gained about 45 fps, shooting 990 fps at maximum hammer strike, still with the old valve.... I tried the new valve, and lost nearly 100 fps, now it was down to 895ish.... So what happened with the new "super" valve with the big ports?.... I was pretty disappointed as I couldn't believe that just the larger ports lost so much performance.... The only other possibility was that I shortened the valve stem an extra 0.020" compared to the previous valve, but I allowed for that in the length of the cocking slot etc.... I was perplexed, and decided to sleep on it....

That turned out to be a good decision, at least I think so, I haven't finished the experimenting yet.... I spent the day cutting and trimming the lawn while my ShoeBox was topping off my SCUBA tank and then it hit me.... What if the bigger valve throat was preventing the valve from opening fully?.... Well, not the throat, per se, but the fact that it is bigger means that the area the air pressure is pushing on is larger, so maybe the valve was not opening as much with the same hammer strike.... After dinner I installed the new valve, put a Disco fill fitting directly on the front of the 2260 tube, filled it to 2100 psi and fired a shot across the Chrony.... BINGO!, less than 800 fps.... and each shot I fired the velocity increased until I hit 1600 psi, where it peaked at 914 fps.... I kept shooting until the velocity dropped to 750 fps because I wanted to know how much air this new valve would flow at lower pressures, as I intend to use a similar one in my Disco pumper project.... Well, it turns out it only needs 850 psi to shoot 750 fps.... I refilled the gun and shot a string from 2000 psi down to 1200 with the following results (bear in mind this is only a 67cc tube = 4.1 CI)....

855
875
896
904
904
899
879
854

Average = 883 (44 FPE).... Total FPE = 352.... Air used = 800/14.5 = 55 bar.... CI used = 55 x 4.1 = 226 CI.... Efficiency = 1.56 FPE/CI.... WOW!!!.... That's the highest efficiency I've ever seen in a .25 cal PCP....

Now I have to make a hammer setup that will allow me to use more than 1600 psi, or to at least allow more air to pass through the valve at 1600 psi.... That will be the next project....

Bob

[rsterne]

I built a longer RVA (power adjuster) today so that I can use the hammer spring from a QB 78/9.... I added a spring guide to a hammer I had used in the gun previously which I had threaded to accept it.... The total weight of hammer and guide is 73 gr.... This arrangement has the ability to be adjusted for a much heavier hammer strike than the previous arrangement, in fact to duplicate yesterdays results I had to back it off about 8 turns (1/2") from coil bind.... Using 2000 psi, the velocity was 990 fps from maximum preload all the way to 5 turns out.... At 6 turns out, it was only down 7 fps.... At 1800 psi I could use 7 turns out, and at 1600 psi 8 turns out before the velocity started to drop.... This means I no longer have to worry about getting enough hammer energy.... That is the good news....

The bad new is that even with the new valve with the significantly larger ports, I'm still stalled out at 990 fps with the JSB Kings (55 FPE).... While that's not too shabby for a 22XX based gun, it's the same as I got yesterday with the old valve and a weaker hammer strike.... It's possible that the rest of the porting in the gun (transfer and barrel ports) which were already at 3/16" are the limiting factors.... however, my Hayabusa uses a 3/16" barrel port and I've hit 1060 fps with JSB Kings at 2000 psi with that rifle....

When I set the gun up for the same velocities I shot in yesterday's string (8 shots starting at 2000 psi, peaking at 905) I got a virtually identical string.... However, the gun used more air to do it, and on the last shot or two, you could hear some hammer bounce.... It used 1000 psi instead of 800 to produce the same results.... so the hammer bounce is costing me about 20% on efficiency, and I'm pretty certain that is only in the last half of the string, when the pressure is under 1600 psi.... I have seen hammer bounce before (rarely) and it seems worse when there is more preload on the valve and a lower spring rate than when the hammer spring is stiffer with less preload....

Anyway, I have learned something about valve throat size.... As you go larger, it requires more hammer energy to open the valve at the same pressure.... Without that, the peak of the velocity curve will move to a lower pressure.... This makes perfect sense, it's just the first time I've seen it first hand.... It also explains why my Hayabusa required a stronger hammer strike at 2000 psi than anything I had tried previously.... it had a 1/4" throat just like this valve.... The next test will be to put back in the old valve (with a 0.234" throat) and test it with the new hammer with guide and QB spring....

Bob

[rsterne]

Tried some heavier pellets today with the hammer spring preload 3 turns out (more doesn't help).... These were shot at 2000 psi....

25.3 gr. JSB Kings - 990 fps = 55 FPE
30.9 gr. H&N Baracudas - 940 fps = 60.6 FPE
35.3 gr. EunJin Domes - 900 fps = 63.5 FPE
41.7 gr. EunJin Points - 855 fps = 67.7 FPE

I guess I can't complain too much, this is 10% more than I've ever had before with a 22XX based PCP.... and within 10% of my Hayabusa....

Bob