USA manufactured PCP Regulator ( testing and discussion ) * RESULTS POSTED

[MultimediaMan]

No, they do not come with a spacer, most people make theirs from 3/4" O.D. x 0.049"-0.065" Wall Thickness Aluminium Tubing. The OD of the tubing will need to be turned/sanded down to a loose slip fit to the I.D. of the air tube. IMHO, it is better to have a "Diablo" style spacer instead of a tube"Ring" spacer (The Diablo style wastes less volume), but they are much more involved to machine, and generally not worth the effort on a 3/4" I.D. Tube unless you are needing a lot of muzzle energy per shot.

It is generally accepted that 1CC of Plenum volume is required for every 10Ft-Lbs 1 Ft-Lbs of muzzle energy desired.

Technically, the most accurate way to measure the true plenum volume is to measure the volume of the valve body with the valve and valve spring installed and the gauge block with the manometer installed using a liquid such as distilled water or low viscosity silicone oil (5 weight Radio Controlled Car Silicone Shock oil is another good one) using a fine scale graduated cylinder filled to a specific volume of liquid, and dispensing it into the part being being measured until all air is displaced and the meniscus is flush with the top of the part, then note how much oil was used out of the graduated cylinder. (Taking me waaaay back to my Two and Four Stroke engine tuning days...)

Some helpful notations: For 3/4"/0.750" I.D. Air Tubes...

Using 0.049" Thickness tubing will result in 1CC of volume per ~0.183" (4.65mm) of tube length.

Using 0.058" Thickness tubing will result in 1CC of volume per ~0.193" (4.90mm) of tube length.

Using 0.065" Thickness tubing will result in 1CC of volume per ~0.202" (5.13mm) of tube length.

As far as drilling the Breather hole for the Regulator, once you have established the plenum volume and made the plenum spacer, you can Try-fit  everything into the Air Tube, then use a wooden dowel to find the end of the regulator in the air and add the distance from the end of the regulator to the middle of the two Air Tube O-Ring grooves on the Regulator. You may want to favor the air reservoir side a little  in case you want to increase the plenum volume a bit in the future without purchasing a new Air Tube.

For de-burring a steel Air Tube, I prefer to use a BRM Fine-Grit Flex Hone. (Another nod to my engine building days...). If you can find them, inside de-burring bits are also available, but pricey and very fragile in the sizes we are apt to use. I use them in Aluminium though. 

Best,

Matt

[rsterne]

It is generally accepted that 1CC of Plenum volume is required for every 10Ft-Lbs of muzzle energy desired.

I would appreciate your source for that information.... I recommend 1 cc per FPE, and even that will cause about a 100 psi drop in pressure during the shot.... At 1 cc per FPE, and assuming 100 bar (1450 psi) and an efficiency of 1 FPE/CI, the pressure will drop according to the following, using an example of 30 FPE and a 30 cc plenum:

30 FPE will use 30 CI of air at 1 bar.... At 100 bar pressure, that is 0.3 CI of air, which is 4.92 cc (call it 5).... You are starting with 30 cc at 100 bar and using ~5 cc of that so the remaining 25 cc expands to fill the 30 cc space, dropping the pressure from 100 bar to ( 100 x 25 / 30 ) = 83 bar.... The average pressure during the shot is 91.5 bar (1327 psi).... Therefore the gun shoots as if it was running 1327 psi instead of 1450.... For it to have a higher pressure would require the regulator to top up the pressure during the 1-2 milliseconds that the valve is open.... If you install a pressure gauge between the regulator and the valve, you can SEE the pressure drop if the plenum volume is small, and it can take up to a full second to recover completely to the setpoint.... The smaller the plenum, the greater the pressure drop.... You have to compensate for that by running a higher setpoint, or you will have less power than the gun had at the same pressure in unregulated form....

If you carry this to the extreme, like your 1cc per 10 FPE suggestion, for the example of a 30 FPE gun, you only have 3 cc of 100 bar air on deck in the plenum.... If you used all of this air, and expanded it completely to 1 bar, you would have 300 cc of air to work with, which is only 18.3 CI.... To get 30 FPE would require an efficiency of ( 30 / 18.3 ) = 1.64 FPE/CI and I have never seen a regulated gun deliver 30 FPE at that kind of efficiency.... 3 cc of air at 100 bar is about what some pumpers run, and they don't produce 30 FPE....

A perfect example of this is a QB79 compared to a QB78.... If you run them at the same regulated pressure, the '78, with a plenum of about 55 cc, delivers a LOT more power and efficiency than the '79 which only has about 5 cc.... Yes, the '79 still shoots, but compared to what the exact same setup does with a larger plenum, it's pretty anemic.... To get it to shoot like the '78 you have to run a higher setpoint, and the more FPE the gun is tuned for, the greater the difference between the two guns....

Bob

[MultimediaMan]

You're right, Bob...I had my units wrong... 1 FPE/1CC... you are my source, in fact. But at least I did the measurements right
 
Edited my post to correct the error...

If you install a pressure gauge between the regulator and the valve, you can SEE the pressure drop if the plenum volume is small, and it can take up to a full second to recover completely to the setpoint....

Oddly enough...




I could look at that little needle all day while velocity testing...

[Pellgunfun]

Boy,

You guys are starting to scare the heck out of me now.  I had no idea I was gonna have to do all that math, and testing and measuring.  Right now I'm getting about 900 fps with a 14.35 gr .22 cal pellet.  Based on Chairgun that comes to 25.80 ft lbs of energy.  I think the total  CC for the BAM B50 is 196cc in the reservoir.  So are you saying to maintain that I'll need about 25.8 cc of air space between the back of the regulator, and the valve?

The inside diameter of the tube is 26.50 mm / 1.0430 inches.

Also "Using 0.049" Thickness tubing will result in 1CC of volume per ~0.183" (4.65mm) of tube length." as a guide.  To get 25.8 cc I would need a spacer 4.72 inches in length.  That can't be right... can it?  That would eat up a lot of my space and greatly reduce my 196cc fill capacity wouldn't it.  Maybe this isn't such a good idea after all.

[MultimediaMan]

It's not as bad as you might think... Those measurements in the post above are for an Air Tube of 0.750" I.D.

Your Tube is 26.5mm I.D.... your spacer would have to be about 24.5mm I.D. or thereabouts. In this case, the I.D. is large enough to where the Diablo-style spacer would waste a little less internal volume.

The internal volume of a 24.5mm I.D. spacer is about 11.98CCs per inch, so for 25.8 Ft-lbs, you're talking about a spacer about 54.7mm/2.153" long plus the volume of the Regulator...

The bonus is a consistent shot string, the downside is slightly fewer shots.

[Pellgunfun]

I'm not exactly sure what you mean by a "diablo style" spacer.  Is there a link to an example?

So I could cut the spacer at 2.1 inches and go with that?

[rsterne]

Yes, you have the right idea.... To maintain your FPE at the same pressure you need to aim for about 1 cc between the regulator and the valve SEAT for each FPE.... Note that the volume inside the valve (and inside a firing pot) count, PROVIDING that you can get more flow into the valve (and firing pot) than out of it.... A firing pot, like they use in a 12 FPE Air Arms, complicates things because it has a tiny air inlet.... so adding a large plenum in front of it does little to nothing, you may as well just stick the regulator right against it.... Those guns are tuned for low power, so they don't need a lot of air....

Note, you can get away with about 1/2 cc per FPE if you increase the setpoint of the regulator a bit, maybe 100-200 psi.... That extra 10 bar or so makes up for the lack of volume, and is the reason in tube regulators work so well in low-medium powered PCPs without requiring a large plenum.... Set the gun up for 12 FPE, use a 6 cc plenum (heck the valve is already 2-3 cc) and increase the setpoint 10 bar and you're golden.... Even at 25 FPE with a 12.5 cc plenum my QB79 Ninja works on only 1200 psi.... However, try and build a gun like my 2560, which shoots 52 FPE on 1900 psi, and you won't do it without a huge plenum.... I use the entire 2260 tube, which is 65 cc....



Bob

[milo74]

Added another reg for marauder rifle ,with 15cc plenum built-in without drilling a breath hole,to install just need to pull the air gauge and block out.the reg is adjustable from 1000psi to 2200 psi.

[Motorhead]

Well played !!

Such FINE regulators your making for us !!

[SpiralGroove]

Hey Motorhead,

A few Questions:
Does this newer version represent a noticeable improvement vs. the older style or is it just the "bells/whistles" convenience of not having to drill the air tank? 
Practically speaking, do you think being locked into a 15 cc internal plenum is limiting?
Does the seemingly added length reduce overall tank volume vs. previous model or about the same as "old" + plenum?

Thanks again.........Not trying to pick, just understand,
Kirk   

[rsterne]

I assume you don't have to drill because it vents through the gauge hole.... Using the space that the gauge block occupied as the (internal) plenum makes good sense, but the necessity for O-rings may mean that the ID is smaller than a simple tube spacer.... Just a WAG as I've never seen one.... Nicely made though!!!....

Bob

[Motorhead]

Hey Motorhead,

A few Questions:
Does this newer version represent a noticeable improvement vs. the older style or is it just the "bells/whistles" convenience of not having to drill the air tank? 
Practically speaking, do you think being locked into a 15 cc internal plenum is limiting?
Does the seemingly added length reduce overall tank volume vs. previous model or about the same as "old" + plenum?

Thanks again.........Not trying to pick, just understand,
Kirk   

Had inquired to the wall thickness of the plenum if it would hold 1/8-27 threading and a gauge ? .... was told the design shown only has @ .070" wall, so No gauge on this one.

As too the better / worse with a fixed 15cc plenum ?
Keep in mind volume you also have within valves I.D. and threw its cap ... likely total volume enough for tunes up to @ 30 ft lbs covering realistic need of .177 & .22 applications. Venting out the gauge hole allows removal to stock reg-less use if wanted.

That said ... it will NOT replace the typical universal fit type where you have greater freedom of increases or decreases in plenum volume.
Universal types while needing a drilled vent hole are better suited to tuners who understand the manipulation of all the valve dynamics and not needing or wanting simple drop in convenience 

JMO ....
Scott

[rsterne]

I agree, if the plenum is 15cc plus maybe another 3cc for the valve, you will definitely be OK for any .177 project, and .22 cal for the power you would normally go for with a regulator.... Since it's adjustable up to 2200 psi, you can dial the power up, all that will happen is the shot count will drop....

Bob

[SpiralGroove]

Thanks again Motorhead and Bob,

- What is the significance of the gauge discussion (are we referring to the potential of adding an external pressure gauge)?

- Since this version offers adjustable psi up to 2200, how is this different than changing the set-point up to 2000 psi on the "older one".  It is much harder or not possible to adjust the setpoint?

- Since my thinking is purely aimed at the BAM B50, remaining HP volume in front of the regulator is critical for more shots.  Does this regulator's seemingly larger mass reduce this remainder?

Let me know if I'm blowing smoke!

[rgb1]

What are the cross sectional sizes of the piston o-rings for this unit?
1/16......3/32.....2mm ?

[milo74]

What are the cross sectional sizes of the piston o-rings for this unit?
1/16......3/32.....2mm ?

1/16

[milo74]

Just finished this one,should fit disco,prod and 1720.with 9cc built in plenum,adjustable from 1000 to 2000psi without drilling a breathe hole.

[Geoff]

The way I found where to drill the breathe hole was I dropped in my plenum, shoved a dowel rod down until it hit the end of my plenum and marked it.  then laid the rod next to my barrel on the outside using my mark as the end, laid the regulator on the dowel and marked the outside of the tube with a sharpie.

My breathe hole is almost on top of the regulator hole.   I realize it doesn't matter where it is as long as it is between the orings, however it was pretty neat I managed to get it that close.

[strever]

hi Milo
is there a difference between the 1720 & the 1701 ?
i just acquired a 1701 and am interested in a regulator for it
and the Milo regulator in my Mrod is doing great

Just finished this one,should fit disco,prod and 1720.with 9cc built in plenum,adjustable from 1000 to 2000psi without drilling a breathe hole.

[milo74]

hi Milo
is there a difference between the 1720 & the 1701 ?
i just acquired a 1701 and am interested in a regulator for it
and the Milo regulator in my Mrod is doing great

Just finished this one,should fit disco,prod and 1720.with 9cc built in plenum,adjustable from 1000 to 2000psi without drilling a breathe hole.

It fits 7/8 tube with .745 id,1702 and 1701 ,I think share the same tube.