2016 goals ( efficiency )

[shorty]

Last year it was power and this year it appears to be efficiency. With that being said I am going to try and go overboard. Now I am sure my thoughts and theories will be wrong (and some may agree) but, that's not going to stop me from figuring it out and sharing with GTA.

My hope is to work it out with the best of the best to get shot strings and power to the highest levels we never thought could be possible for the every day Joe. There's alot of excitement over the SSG which is going to change (if not already) our shot count for 2016 (I am still with the short stiff spring but Ill get over that during this exercise)

 I have always wanted to regulate my marauder and I have always wanted to use the entire pressure range of the gun to get the most shots from a charge. Unfortunately we have had discussions that said regulation uses more air than self regulating ( I don't think so - at this point ) along with many other variables.

So,
I almost have an engineering plan and a budget to buy a regulator. I have started a spreadsheet to help along the way. Now please don't beat me up too bad on the spreadsheet as it is work in progress with assumptions (and I do not have a degree in fluid dynamic or physics).

The engineering plan is to try and:
Step 1: get the wife to allow me to buy a regulator.
Step 2: Perform a factorial DOE on TP size, lift and spring force (SSG or short stiff spring) at the lowest pressure possible for 25 fpe (14.3 grain) (.22 cal) "goal is at or over 1.8 efficiency".
Step 3: Make a zillion assumptions
Step 4:install regulator (at assumed pressure) and appropriate plenum size.
Lastly, hope everything works out like it did in theory and run a string that no one has ever seen before ( hopefully not be embarrassed).

Well,
That's the plan and this is the start of the challenge. I would ( and I am sure ) the rest that follow and or contribute to this post want the same thing as me. A whole lot of shots with just one charge.

We need this for 2016. We need this for GTA. There's nothing better than knowing GTA is the airgun forum of the world and this is the place to be for cutting new airgun technology and we are part of it. This is the site to go to. We are the best.

What you thought last year was good for shot count is going to be blown away this year.

Tim

[rsterne]

You have chosen a great power level and caliber for this experiment.... It's not too much or too little, the velocity range (just under 900 fps) is practical and tend to be accurate, and 14.3 gr. pellets in .22 cal are plentiful and cheap (and that will be a consideration, because you will go through a LOT of them).... My only suggestion is don't focus on too low a pressure, because although it increases the volume ahead of the regulator, the lower pressure is less efficient in driving the pellet.... The higher the pressure, the shorter the dwell can be, while the lower the pressure the more dwell you need to reach your FPE.... and shorter dwell means more efficiency.... It will be a balancing act, like anything else.... Good Luck !!!

Bob

[shorty]

Thanks Bob. I can sure use some help on this one from you  .


My hopes are to understand the dwell at lower pressures. Most of us tune at 2000 psi and greater. I for one never tried tuning at 1300 psi and lower.  Alot of spring changes for hammer and valve along with hammer weight/throat/poppet/TP will be interesting. I hope it doesn't have to go that far.

In the spreadsheet,
The predicted FPE is an assumption (along with other things). At this time I can not figure out the pressure difference across an orifice (TP).

[rsterne]

Well if you figure out the DeltaP, let us know.... Lloyd, Bill, Scott and I haven't been able to do it.... http://www.gatewaytoairguns.org/GTA/index.php?topic=102604.0

Bob

[Bill G]

Don't get too wrapped around the axle with the spreadsheet.  It has taken me several years to get where I am with mine as it has Lloyd and we aren't done.  It is a good tool but it is time consuming and will detract from your collection of hard data.  The reality is that Lloyd has the most accurate version IMO and Bob has mastered it's use.  The data that you publish here will be run through these calculators just too help refine the calculator.  The exchange of information through this forum can result in great advancements in understanding internal ballistics of the PCP in various configurations.  What we need is hard, real world data. 

Bill G 

[shorty]

Ofcourse I am sick this weekend and pretty much lazy. The regulator should be on order soon, I have a working SSG equipped with a 6lb spring,  I skipped all the boring engineering plan and ran some strings to see what pressure regulator range I will be needing.

Yes I am impressed with absolutely ZERO burping or hammer bounce even down to 800 psi. My short stiff spring can not do that. Thank you Bob.

I am looking at this regulator:
http://www.huma-air.com/Benjamin-Marauder-pressure-regulator-with-pressure-gauge-connection

Current valve,TP, and barrel porting.
Hogged out valve at .5"
Dual dimension poppet spring (>15lbs per inch) - .048 wire
Exit TP .2"
TP .168"
Barrel .168"
Stock 6 lb spring on SSG

Charge gun to 1500 and ended just below 1000 I would say it was 950 to be sure.
Shot/FPS  / Psi /   Efficiency
1   777   1500   
2   789      
3   799      
4   800      
5   807      
6   804      
7   809      
8   811      
9   823      
10   834   1400   2.28
11   828      
12   842      
13   840      
14   843      
15   838      
16   840      
17   842      
18   842      
19   844      
20   849   1250   1.65
21   841      
22   864      
23   847      
24   845      
25   845      
26   863      
27   850      
28   832      
29   852      
30   841   1100   1.68
31   839      
32   831      
33   829      
34   824      
35   819      
36   820      
37   809      
38   812      
39   807      
40   801   950   1.57



Looking at the string it appears that between 1200psi and 1250 is the highest power with an efficiency of around 1.66.

So,
Looks like with the correct plenum and a regulator set at 1200 to 1250 psi should yield 108 shots at 23-24 FPE using 14.3 grain with a full charge of 3000psi.

What has got me confused is trying to figure out the estimated shot count. If I use the 1.66 efficiency number and run it from 3000 psi to 1200 psi the potential is 108 shots.
But,
If I work off of volume at 1200 psi, it's approximately 13cuin/fpe at around 16.5psi. If the volume of air can be compressed in half at the same pressure, then shot count should exceed 108 if being charged at 3000psi.
If this is correct the shot count would be at or extremely close to 150 shots. And if you then punch those numbers into an efficiency it would come out to around 2.3 to 2.4.

I can use some help in understanding the predicted shot count based on the theories above. My numbers do not make sense because I have never seen anything like it to compare to. I must be missing something.

[rsterne]

You are using the air at 1200 psi to produce the power you need.... It does not matter what the pressure is in the reservoir.... The amount of air available in the tank is the pressure drop times the volume of the reservoir.... You start at 215 cc (13 CI).... then subtract the volume of the regulator and plenum.... If the regulator is 1.5" long, that is 21.7 cc, and if you use a plenum that is 1/2 cc per FPE, that's another 12 cc, so you will lose about 35 cc, so down to 180 cc (11 CI).... The pressure drop is (3000-1200) = 1800 psi / 14.5 = 124 bar.... so the total amount of air you have available is (11 x 124) = 1364 CI.... If your efficiency is 1.66 FPE/CI, that should produce (1364 x 1.66) = 2264 FPE.... At 23 FPE per shot, that works out to (2264/23) = 98 shots....

HTHs....

Bob

[shorty]

Regulator has been ordered.....

Took a while but it sure did help. Just confuses me going back and forth from atmosphere pressure.

It's nice having a spreadsheet and doing the math upfront. It sure does take the guess work out of tuning.

With that being said, I ran some numbers with the reg set at 1400 psi.That should get me a 2.24 efficiency at 20 fpe and 136 shots on regulation. That's alot of shots if it holds true

Now I can't make my mind up to reg pressure setting. The whole madness is starting all over again.

[rsterne]

If you choose 1400 psi, when you go off reg. (ie below the setpoint), the velocity will increase.... If you are OK with that, you can get higher efficiency by using higher pressures.... You of course loose "headroom" as now you only have 1600 psi of air to play with instead of 1800.... If all you want is super efficiency, and don't care about shot count, set the reg. to 2000 psi....

Bob

[Rdsail]

The best efficiency I have been able to get at 31fpe (jsb 18.1s) is 1.542 efficiency. This is a straight up tune on a disco with a regulator set at 1600. The efficiency was better at 1600 than at 1400 psi. That is a 140 shots string with a 22ci bottle.

the person I built the gun for not too long ago ran a string at 27 fpe and got 180 shots that pushed up the efficiency to 1.688.  I wonder if we lowered the power to 24 if I will reach the 1.8 efficiency.

Then the last thing, would a SSG increase that efficiency by a lot. I wish I still had that gun on hand.

[shorty]

Well,
Maybe I should have followed the plan set out in post 1. It's starting to look like there is NOT plenty of options here using a regulator and being super efficient with a heck load of shots on a full charge with a .22 platform.

The regulator is forcing me into a "fixed" decision of fps,power, and shot count over a fill charge. I am typically used to a HS change from 25 fpe to 50 fpe for backyard plinking to a hog killer.

It is what it is I guess. I am going to have to understand that my longest shot I am going to take is gonna be a max of 50 yards and there's no hogs in the backyard.

Here's why I say what Iam saying:

Current valve,TP, and barrel porting.
Hogged out valve at .5"
Dual dimension poppet spring (>15lbs per inch) - .048 wire
Exit TP .2"
TP .168"
Barrel .168"
10 lb spring on SSG

Charge gun to 1750 and ended just 1050psi.
Shot/FPS  / Psi /   Efficiency
1   926   1750   
2   936      
3   935      
4   939      
5   936      
6   937      
7   938      
8   940      
9   940      
10   933   1600   2.05
11   934      
12   909      
13   929      
14   927      
15   918      
16   924      
17   910      
18   906      
19   899      
20   898   1425   1.68
21   896      
22   891      
23   887      
24   885      
25   883      
26   878      
27   868      
28   865      
29   860      
30   857   1050   0.72

Theoretically
If I where to set the reg at 1600 and shoot from 3000psi to 1600psi I would get 93 shots on regulation for a max of 27fpe using 14.3's and possibly 30fpe with 18.13's.

With that being said,
It looks like I have a choice to make. A normal powered .22 backyard plinker at 20fpe with over 140 shots per "full" charge or 27fpe/30fpe on a full charge for 93 shots.

I was hope-ing when I first started this post that I was going to be a little different than typical regulated .22 marauder. Maybe hit some shot counts and power levels that we have not observed yet.

I am not sure if it's looking like what I expected.

[rsterne]

If you tune for the higher FPE, and then reduce your hammer spring preload (or increase the gap on the SSG), you can retune with just that simple adjustment for less FPE and increased shot count.... The only thing you must be aware of, is that when the pressure drops below the regulator setpoint, your velocity will INCREASE.... The reason is that when detuned, and on the regulator, you are shooting on the upslope of the shot string you would have unregulated....

Bob

[shorty]

I ran a close to as possible tune using the dual wire spring (short stiff spring) instead of the SSG. Nothing else changed. I started believing that the SSG was going to limit the full capabilities of tuning at different power levels when using the regulator.

Current valve,TP, and barrel porting.
Hogged out valve at .5"
Dual dimension poppet spring (>15lbs per inch) - .048 wire
Exit TP .2"
TP .168"
Barrel .168"
Dual wire spring (short stiff spring).

Charge gun to 1600 and ended just 1100psi.
Shot/FPS  / Psi /   Efficiency
1   782   1600   
2   797      
3   800      
4   806      
5   816      
6   819      
7   815      
8   815      
9   821      
10   817   1500   2.29
11   832      
12   840      
13   832      
14   841      
15   843      
16   843      
17   856      
18   847      
19   841      
20   847   1400   2.49
21   857      
22   855      
23   866      
24   865      
25   877      
26   871      
27   868      
28   871      
29   881      
30   877   1250   1.75
31   880      
32   874      
33   867      
34   870      
35   872      
36   862      
37   865      
38   860      
39   856      
40   851   1100   1.75


Efficiencies are higher with a higher power. I am going to stick with the dual wire spring. I have a feeling the extra weight of the SSG was adding just an extra small amount of dwell.

[shorty]

A small table for comparison

[rsterne]

Statistics are like a bikini.... what they reveal is enticing, but what they conceal is vital.... I see you comparing three different power levels.... However, if you set your mind to it, you can prove just about anything.... Good luck with your build, I'm sure that if you approach it with an open mind, you will learn a lot....

Bob

[shorty]

I hope I do learn something here. Too me, if the math adds up it should work and I did go into this with an open mind. That's why I gave the SSG an opportunity. I have some humility.

I am also doing the math upfront so that I can understand how many shots I "should achieve" at a given regulator setting. Also, what I should be able to achieve in power and shot counts with just a hammer spring adjustment.

It's not over yet as the regulator is not here. I just hope that this reg set up and homework upfront does just as good as our master regulator tuners are doing if not better.

 

[shorty]

Been thinking about your comments all day and night.

Bob, I am not understanding what your indicating with the numbers. It would appear as if you see something in the data that I am missing. I re-ran the numbers and matched up the 6lb SSG vs dual wire spring to matching pressures in a graph.

The goal of me installing this regulator is to maximize the shot count over a full charge and pushing the efficiency to the max over a capable fpe range of the porting.

If you see something that I am missing, please help and point it out.

If your opinion is that Iam steering the data or fudging something, please point that out too. "I assure I am not".

If there is an error in the data, I would really like to get it squared away before I set the pressure on the regulator and install it. 

My next set of strings I plan on doing will be for FPE range around a specific pressure. I want to know what fpe ranges can be used while being on regulation and then calculate the expected shot count at those given power levels.

The more I look at the last 3 strings the more I am getting excited about installing the regulator. It sure would be great if the data supports the real build. So, if you think I am missing something please point it out.

[BigTinBoat]

Been thinking about your comments all day and night.

Bob, I am not understanding what your indicating with the numbers. It would appear as if you see something in the data that I am missing. I re-ran the numbers and matched up the 6lb SSG vs dual wire spring to matching pressures in a graph.

I could be wrong, but I think he is eluding to the fact that the "reason" the SSP has a higher efficiency (in your chart) than the SSG (with 10lb spring) is due to the FPE being lower with the SSP.

[shorty]

The chart shows the comparison of the 6lb SSG vs dual wire spring NOT the 10lb SSG.

[BigTinBoat]

The chart shows the comparison of the 6lb SSG vs dual wire spring NOT the 10lb SSG.

sorry, didn't mean chart, I meant the table