2016 goals ( efficiency )

[rsterne]

I like the way you presented that data, it's too bad you didn't complete the string with the dual wire spring down to the same end point as you did with the 6# SSG setup.... It would be interesting to see the 10# SSG setup plotted on the same graph as well.... I think the thing you will learn the most by doing that is what to use for your setpoint with the existing porting to achieve your goal of 25 FPE with the 14.3 gr. pellets, which is ~890 fps.... The 6# SSG setup is too far below that velocity, although you may be able to get there with more preload on the spring.... The 10# SSG setup may well be too much, you might need something in between to hit the sweet spot.... It takes some experimenting to find the best combination (of spring and preload) for an SSG, just like you probably didn't figure out your dual wire spring on the first attempt....

Tuning for the "knee" of the curve at 890 fps when regulated means you want to find the pressure / preload combination that puts you fairly close to the top of the curve when unregulated.... If you are on the downslope of the unregulated curve at any given pressure, then at that pressure you will be on the plateau if you regulate to that pressure.... meaning you will have to reduce the hammer strike to get to the knee.... On the other hand, if you on the upslope of the unregulated curve, and select that pressure, you will be on the downslope if you regulate there, causing a rise in velocity once you go off regulator.... This of course only applies if you have a very large plenum.... If the plenum is small, you will have to increase your setpoint to get back to where you were unregulated, to compensate for the pressure drop on firing....

Based on the data you have so far, my guess is that you want to regulate at about 1400 psi.... If you plot enough velocity curves, using the pressure on the horizontal axis like you did, you will get something like this (although this was plotted vs. shot number)....



Notice how you could place a straight edge across the curves from upper left to lower right, tangent to them?.... That line represents the maximum velocity compared to the  pressure.... Here is another representation of that (look at the upper graph)....



You will note that the knee of each curve moves to lower velocity as you reduce the pressure, and you can again place a straight edge from upper right to lower left, across those knees.... What you want to find for your gun, is where does that straight line cross 890 fps, which is your target velocity (in the graph above, the 2200 psi curve comes the closest).... That will tell you the pressure you need.... Since you will probably be using a plenum of about 1/2 cc per FPE (ie 12-13 cc plenum in your case), you will have to increase the setpoint about 10% to get the 25 FPE you want and be on the knee of the curve....

HTHs....

Bob

[shorty]

 

[shorty]

plenum in the valve calculates out just of 25cc being .5" inch diameter and 1" inch long. With the regulator I should be sitting at just over 30cc.

Seriously, thanks for taking the time to run some of the numbers. For me it takes a lot of time and effort. What you do to verify the work makes it better. 

[rsterne]

A plenum 0.5" diam. x 1.0" long is only 0.196 CI = 3.2 cc, which IMO is way too small.... That sounds like just the valve volume?.... If so, I would add almost 1" of length of full ID tube to that for your plenum.... An MRod tube has an internal area of 0.88 sq.in, so one inch of length is 14cc.... If you use a piece of tubing for a spacer to hold the regulator, you have to subtract the wall thickness of the spacer.... If your spacer is only 7/8" ID, that is only 10 cc.... Don't use too thin a wall for the spacer, or this can happen....



I assume you are removing the gauge block, as that restricts the flow into the valve, and just takes up space in the plenum?....

Bob

[shorty]

Whoops, way wrong math there on the plenum.

I used diameter instead of radius. The regulator is one of those huma regs with gauge port built in so that it can breathe through the existing gauge port.

[rsterne]

If that is the case, you may not have much of a choice on increasing the plenum beyond what is built into the regulator.... If you slide it forward with a spacer, the rear O-ring cannot seal to the tube between the gauge hole and the valve.... Scott (Motorhead) may know what the plenum volume is....

Bob

[shorty]

Yeah... Regulator came in.

It took some time getting the old gauge port out but all appears to be fine now. Huma reg with gauge port has been installed and set at 1500 psi. Charged the gun to 2000 psi and took 10 shots at 853 fps.

Gonna have to wait till tomorrow to run some strings. 

Don't even feel like going to work tomorrow so I can play 

[shorty]

Ran the very first string with the regulator installed today. Not too bad for the very first time but here it is.

3000psi to 1500psi all shots on regulation
Average 864 fps with 14.3
Min 850fps Max 878
93 shots
3.19%ES
Efficiency 1.84

ES is terrible but I have a feeling my HS adjuster is wiggling around and moving ever so slightly. Iam going to have to tighten it up somehow or lock it down.

A couple interesting things though.

1) I tried maxing out the power with the regulator installed with 21.14 grain pellets. I only could hit 832 fps. That stinks.
2) I measured the plenum from the regulator at around .447" ID and .787" deep along with the valve around 1" deep and .5" ID for a combined plenum of 5.24cc's. Unless there is alot of room between the valve and regulator " I don't think there is" that stinks too.
3) The efficiency of 1.84 at 24 fpe is exactly the same as the table I generated last year for 24 fpe tune using the Dual Wire Spring Pretty cool.
4) I ran out of pellets already.... That stinks.
5) I hope everything settles down and ES gets below 2%.

Not too bad for the first time regulator tune. I find the plenum sizing the most interesting though. 5.24 cc plenum at 24 fpe is less the 1/4 cc per fpe and still a 1.84 efficiency. I don't know what you call it but refill of the plenum between shots was unnoticeable. Shot to shot was less than 5 seconds, just normal chrony shoot testing.

I need to do some more shooting and tuning for now to really try and tune it in. I am going to try and make a new HS adjuster with some kind of indicator on it to show power levels. I love how all you have to do is turn a 1/2 turn down and get 20 fpe and the turn 3/4 turn the other way for 30 fpe. Easiest power adjuster I ever dealt with while keeping the ES stable.

Accuracy ? Only at 10 yards today but 1 holes with those wallyworld chp's

[rsterne]

The plenum indeed sounds too small for the power level you desire.... I would suggest you plot a curve of the velocity vs. the preload to find out what the velocity is on the plateau (ie the maximum), and where the knee is and the beginning of the downslope.... That is the only way to really understand what your gun is capable of, and where to tune it....

Bob

[shorty]

Plenum does sound too small to me as well but the goal was for 25 fpe and as many shots possible at an efficiency of 1.8 or greater. Looking at the chart using the dual wire spring from 1500psi down to 1110 indicates an additional 31 shots with the original 215cc tank.

Just a guess, it looks like there may be an additional 20 or more shots off regulation indicating the gun is tuned right at the top or just behind the knee. I have to get more pellets to prove it though.

That would put the 22 marauder with stock air tube at around 113 shots from a full charge at 24 to 25 fpe. Haven't seen that before or atleast I have not found a post similar to that yet.

You definitely got me thinking about plenum size and efficiency now. Being at 1/4cc per FPE also sounds interesting too since we had a discussion of 1cc vs 1/2cc a while back.

 I got that estimated 1/4 cc plenum from calculating 1500 psi at 24fpe using the volume of the valve,ports, and barrel length plus the volume of air used per shot from the original shot string "off"regulation. I was figuring that I might be able to calculate an optimal plenum size while predicting the shot count at a given power level.

Interesting enough though, the predicted fpe (your guys "delta p") always seemed to max out to 27 or 28 fpe. I thought it was just a bogus calculation but it's kind of holding true with my max power levels.

[rsterne]

It only takes 1 or 2 shots at each preload setting to determine the plateau, knee, and downslope.... You can determine the entire curve on much less than one fill....

Bob

[shorty]

The knee,
1/4 turn HS adjustments using 14.3 grain chp's. I know you write about tuning to the knee. Sometimes it's hard for me to grasp things so what does it mean besides max power at 28fpe using 14.3's and a little over 30 fpe with 21.14's?

I used a weird different method. I hate fishing in the same pond as everyone else.

[rsterne]

Other than the slight "notch" in the curve at 1.5 turns HS setting, which makes it a bit hard to decipher, the "plateau" is evident at 1.75 turns and above, at ~935 fps.... no amount of added preload will produce a significant increase in velocity, but it will burn up air in a hurry.... Once below 1 turn, (below 880 fps) you are on the "downslope" of the curve, and the efficiency will increase dramatically the lower you go in velocity.... In between (at 1.25-1.5 turns) is the "knee" of the curve, where the velocity starts to decrease, and simultaneously the efficiency increases.... Somewhere on that part of the curve will be your best balance between power and efficiency.... If you compare 1.25 turns with, say 2.5 turns, you will notice only a 3% percent difference in velocity (912 vs 939), but it could easily use twice the air per shot at 2.5 turns....

If you tune on the downslope, in a regulated PCP, when the tank pressure drops below the setpoint, the velocity will initially INCREASE.... and the further you are down that slope, the more noticeable that will be.... However, your efficiency will be great, because you are using tiny sips of air at a pressure higher than you need to get that velocity with that gun.... It's like shooting an unregulated PCP tuned to peak at 2000 psi at 2500 psi.... quiet and efficient.... If you tune on the plateau, you are wasting air, pure and simple.... the gun will be loud, and you need to reduce the preload.... and when you drop below the setpoint the velocity tanks immediately....

On the knee of the curve, where the velocity just starts to drop below the plateau velocity, it's like shooting an unregulated PCP very close to the peak of the velocity curve.... If you use the lower part of the knee (at 1.25 turns on your graph), it is like shooting an unregulated PCP that peaks at 1300 psi at just over that, say 1400.... Since you are on the high pressure side of the peak velocity, the gun will be quite efficient.... When the tank pressure drops below the setpoint of the regulator, the velocity will increase slightly (just as it would in an unregulated PCP) as the velocity peaks and then start to slowly decline.... This can extend the shot string at least 10% below the setpoint before you notice any real drop in velocity.... This adds quite a few shots to the usable string.... THAT is where I like to tune my regulated PCPs, and where you will find good tuners like Motorhead want to operate as well.... You also tend to get the lowest ES, because you are operating at, and just either side of, the peak velocity.... ie right in the "sweet spot" for a PCP.... Using this tune, and a 1400 psi setpoint, you should be able to shoot down to 1200 psi before refilling and not even notice the velocity change....

Now that you have determined this curve, you can use it to decide if you need to change the setpoint.... If you want a velocity around 880-910 fps, leave it alone.... If you want more power, you need to raise the setpoint.... If, on the other hand, you want to tune for, say, 800 fps, you can reduce the setpoint.... Any time you change the setpoint.... or even make a large change in pellet weight (eg. 14-21 gr.), you need to determine the position of the new "knee", because it will change.... Higher pressures (or heavier pellets) will move the knee to greater hammer spring preloads.... and vice versa....

HTHs....

Bob

[shorty]

So in a nut shell,
Predictions I made using my spread sheet was very similar to looking at the knee and the way you tune a regulated gun. Except that, when setting up a regulated "in tube regulator" your not getting what you get "it is what it is". Your actually predicting what you should get if you choose to regulate and you have the capabilities to achieve a goal or desired effect.

Big difference in my eyes for any tuner. Which I am not and never will be because I am difficult.

Well atleast the way I see it. I am so darn happy things worked out.

So did I do good or what on the very first time doing a regulated conversion? Your opinion really does mean something to me.

Thanks Bob.

So I did a good job for the first time out or what? Give me a pat would ya.

[rsterne]

So if I understand things correctly, with the 14.3 gr. at 1 turn out, you got that string in post # 27, as 860ish fps?..... That then corresponds to just at the start of the downslope on the above chart?.... If so, then that is just about where you want to be.... great job !!!

Bob

[Motorhead]

Shorty,
It would be pretty good bet your ES figures being wider than you were hoping is PELLET related.
Crosman pellets vary enough in head & skirt size / weight that even shot in a well tuned know low ES rifle with do the same thing.
At that weight @ ... some JSB RS 13.4 or Exact 15.9's shot with no other changes to rifle would be more telling to ES fluctuation your seeing and not knowing the origins to why.

JMO,
Scott

[shorty]

Thanks Bob. It sure does mean alot.

Scott,
Thanks for the info on the CHP's from wallyworld. They are pretty inconsistent with weight. I have been waiting for you to post and give some insight to my expedition since you are known as one of the best regulator tuners on GTA with the marauder.

I think the biggest problem is with my HS adjuster. It's extremely loose and moves very easily. Gonna try and fix that this weekend with a brass adjuster with gauge marks for power levels.

[Motorhead]

Yup, wiggly parts, dragging springs on guides, hammer & tube drag inconsistencies Show there UGLY head making an otherwise great tune look worse than it actually is.

[lloyd-ss]

Shorty,
A couple of questions if you would be so kind.
Is the side of the Marauder rifle version of the Huma reg tapped for the standard Marauder pressure gage? 
And are you using the pressure gage?
Are you happy with the plenum volume that the reg provides?
Thank you!

Just a side note about adjusting the Huma reg, and you might have already come up with your own solution.  I have found the Huma reg to be very accurate and repeatable when adjusting the pressure up or down.  At first I was taking the reg in and out of the gun to make the adjustments.  Draining all the air is bad enough, but removing the reg is not easy.   I ended up just flattening the end of an aluminum rod to make a super long screw driver to reach down inside the tube and and make the adjustment.  Works like a charm, BUT, make sure you draw two index marks with a Sharpie on the end of the reg so that you can see how much you have turned it by looking down inside with a flash light.  Otherwise you'll loose your adjustment and won't know what you have. Those tiny adjustments won't be noticeable on the Marauder gage. 

Excellent work, BTW!
Lloyd-ss

[shorty]

Sure thing LLoyd,
The regulator is tapped for the standard pressure gauge.
I am using a 4ksi pressure aftermarket pressure gauge (stock one crapped out a long time ago).
Not so happy with the plenum (right now).

I am not too sure of what's going on with the shot to shot consistency.

I think there is something more about the plenum sizing in regards not only to power but more importantly (too me right now) shot to shot consistency.  All the reading I have done on everyone Else's reg set ups are typically always below 3% big plenums. Been thinking a lot about how the regulator works " in my head" and everything in my mind is pointing to inconsistent lift during the droop on the regulator ( I think it's called droop ). Don't think it is a dwell issue at this time due to the efficiency numbers.

I know it's not the engine (spring and hammer) being inconsistent because every time I come off regulation, the consistency comes back. The only thing that makes sense to me is that the inconsistent droop from the regulator caused by the Static COF (or when the pellet starts moving at different rates due to what ever ).

I just don't know what the problem is right now, although Npunk42 is running the same Huma regulator in his 22 and is observing the same inconsistencies. His reg is set at 2000psi, mine at 1500psi. My porting is .168" and his is stock. He is running an SSG and I am running my dual wire spring. Still, with all the difference in the porting, reg setting and power plant only leaves the plenum or just a plain ole crappy reg. I don't think it's the regulator. It better not be for $130 bucks.

The regulator appears to be consistent when firing and looking at the gauge. Hard to tell if it's perfect but appears to drop and go back to it's original position every time.

I do notice a tone change when a high fps or low fps is fired though. More so on the low fps sound. Don't know what it means yet.

I know it may sound stupid to some, but I am going to try a hammer stop again against the valve body to control lift more precision or atleast give more control to it.

Anyway,
Thanks for commenting in the post and I too agree that adjusting the regulator was straight forward and accurate. I have not played with the repeatability yet.