A New Method for Increasing the Efficiency of a PCP - the SSG

[Motorhead]

Bob and others,

After reading this entire thread a couple of times I would like it if you could explain to me, and perhaps others, how you are calculating the efficiency and what exactly better efficiency means.

Be gentle with me as I am somewhat of a 'newbie' on some of this stuff.

Thanks much,

Carl

http://calc.sikes.us/1/

More air ya save ... move shots per fill or on a Co2 cart 

[Gerard]

Yeah, plugging your gun's numbers into the Sikes calculator - cylinder volume, start and finish pressures, pellet weight, velocity as measured with a chrony then calculated to get an average - will give you efficiency numbers. Basically the PCP equivalent of gas mileage with a vehicle. The higher the number, the further you're going on a tank, or in this case the more shots you're getting per fill.

[rockmike]

Bob and others,

After reading this entire thread a couple of times I would like it if you could explain to me, and perhaps others, how you are calculating the efficiency and what exactly better efficiency means.

Be gentle with me as I am somewhat of a 'newbie' on some of this stuff.

Thanks much,


Carl

http://calc.sikes.us/1/

More air ya save ... move shots per fill or on a Co2 cart 

thanks for that link!

[Rallyshark]

The question I have is on the preload with SSG mod.  If I set the preload very high (but still OK to cock) to begin with and then adjust the gap for desired fps, will I still have a declining string like with traditional tuning or is this a mute point with SSG?  I ask this because I want to switch between heavy and light pellets occasionally and keep preload set for heavies tuned to max FPS.

That is a good question.  I would think you could do that, but I don't know that you'll have the range of adjustment as you would changing the pre-load of the spring.  I'm not sure about that though.  Maybe rsterne or motorhead will answer this one.

[Motorhead]

The question I have is on the preload with SSG mod.  If I set the preload very high (but still OK to cock) to begin with and then adjust the gap for desired fps, will I still have a declining string like with traditional tuning or is this a mute point with SSG?  I ask this because I want to switch between heavy and light pellets occasionally and keep preload set for heavies tuned to max FPS.

That is a good question.  I would think you could do that, but I don't know that you'll have the range of adjustment as you would changing the pre-load of the spring.  I'm not sure about that though.  Maybe rsterne or motorhead will answer this one.

Descending velocity ... pure & simply your over driving the hammer with too much spring energy.

[Rallyshark]

I think it should work OK.... don't see any reason why not....

Bob

Now I just need to source a 5-6 inch socket cap head screw in the 10-24,10-32 range.  I know I can order some, but that doesn't give me instant gratification   I'll see if I can find some locally, like Fastenal or somewhere like that.  I was thinking of securing the section of 4mm allen key to the screw by drilling holes in the head and using a couple of small grub screws.  If you guys have a better idea on accomplishing that, or accomplishing what I'm trying to do as shown in my diagram, I'm all ears.  Suggestions from smarter people than I are always appreciated!

[triggertreat]

The question I have is on the preload with SSG mod.  If I set the preload very high (but still OK to cock) to begin with and then adjust the gap for desired fps, will I still have a declining string like with traditional tuning or is this a mute point with SSG?  I ask this because I want to switch between heavy and light pellets occasionally and keep preload set for heavies tuned to max FPS.

That is a good question.  I would think you could do that, but I don't know that you'll have the range of adjustment as you would changing the pre-load of the spring.  I'm not sure about that though.  Maybe rsterne or motorhead will answer this one.

Descending velocity ... pure & simply your over driving the hammer with too much spring energy.

So it's the same as traditional tuning because of the declining pressure behind the poppet as you shoot I take it.  I think I get it now.  Thanks!

[I_like_Irons]

I think it should work OK.... don't see any reason why not....

Bob

Now I just need to source a 5-6 inch socket cap head screw in the 10-24,10-32 range.  I know I can order some, but that doesn't give me instant gratification   I'll see if I can find some locally, like Fastenal or somewhere like that.  I was thinking of securing the section of 4mm allen key to the screw by drilling holes in the head and using a couple of small grub screws.  If you guys have a better idea on accomplishing that, or accomplishing what I'm trying to do as shown in my diagram, I'm all ears.  Suggestions from smarter people than I are always appreciated!

If an M5 cap screw will fit (its a bit larger than a #10) it already has a 4mm socket.  What I'd do is just glue the thing in place with either a good epoxy like J B Weld, or even Loctite retaining compound. 

[Rallyshark]

I'm getting close!  I was able to locate some 6" 10-24 cap head screws, and got the section of an allen key fitted and secured.  I also got the pre-load adjustment screw drilled out(thank you cobalt drill bits).  I had to do all this with vice grips, a drill, and a dremel.  I think it should hold up just fine though.  I ground down the allen key's base, and then cut a slot in the head of the screw.  It is secured with a 4-32 set screw which I secured with red locktite, and ground that down flush.  As you can see with the pictures below, it all fits in the set screw perfectly, so that should allow me the movement I need.  Hopefully, the end result will be a full pre-load adjustment, and gap adjustment without taking anything apart.  Now I have to machine the the stock, trigger block holder, and safety for clearance.  By machine, I mean dremel  

[Rallyshark]

Well, for my particular gun, I found most of what Bob said to be completely true.  It works okay in the AT-44, but just not worth it if you want any real power.  The way the gun is made just doesn't allow the SSG to really shine.  Don't get me wrong, I was able to get an efficient tune shooting at 25fpe, and more so at 20fpe.  I think I got 60 shots at 25fpe before coming off the reg with a few more usable ones after it came off the reg.  I didn't finish the 20fpe string, since I was just wasting pellets and will never use the tune.  For a .177 AT-44 you could get a ton of shots I'm sure! 

My issue came when I tried to get it up to the 35fpe range, and then my increases in efficiency were minimal at best.  With the springs I have on hand, there is no way the gun was going to make it up to the 50+fpe range.  Keep in mind, my gun is was already tuned very well in the 30fpe range with an efficiency of 1.37, so in my case, the SSG isn't the best option for where I like my gun shooting.  Like I said earlier, I think it would work very well for a .177.  I could easily see it getting 80+ shots in the 18-20fpe range!  I got to see that the SSG does indeed work, but it was basically a lot of time used for results equal to what I already had.  I did manage to maintain pre-load and gap adjustment without taking the gun apart, but it was much more tedious to do so, and I removed it and put it back to the way it was. 

If I had more springs to play with, and more patience/time, I could probably get it shooting a little better in my gun, but I'm just going to chalk this one up to a learning experience  

[rsterne]

You should try it on a 70+ FPE AT-44 in .25 cal.... pretty much a waste of time, unfortunately.... The SSG just isn't compatible with the Hatsan design at those power levels....

Bob

[Rallyshark]

At least you have lots of parts and tools to play with Bob,lol!  My dog is very happy that I'm done trying to make that work now.  She got severely neglected over the last two days, because I'm the only person she has to hang out with...  At least, I can say I gave it a try.  Now if I had a .177, I'd be all over it then.

[wll2506]

http://calc.sikes.us/1/

Motorhead !

Thank you for the link, great.

wll

[OZ Harry]

With relevance to short springs, lack of pre-load, lightweight hammers, ballistic hammer phase, and repetitive hammer strikes - with and without relevant (air wasting) hammer bounce.
I hope you find this video of interest.
I made it in 2012 to show how a free flight hammer, driven by a  spring tuned without pre-load, can largely defeat repetitive valve opening and hence the air waste from hammer bounce. Frame speed 1000 frames /sec.
The rifle is a standard FX Elite (equivalent single shot FX Royale 500)  .25 tuned to shoot at approx 45 fpe for 90 shots.
Please be patient with the 4 hammer strikes at approx (seconds) 04, 35, 1:02, 1:38
The first strike opens the valve for the shot; the other three "bounces" don't seem to have enough energy to produce further significant valve openings.

http://vidmg.photobucket.com/albums/v392/Kyogle/FXElitehammerstrikesvalvebounceVeryslow.mp4

Approx hammer to valve stem gap.

http://img.photobucket.com/albums/v392/Kyogle/FX%20Elite%20hammer%20not%20touching%20valve%20stem%20free%20flight_zpsbhxlpgq5.jpg

Kind regards, Harry.

[rsterne]

I tried holding my mouse pointer level with the end of the valve stem, and the occlusion of the hole by the hammer appears to pass that point just slightly on the 2nd strike, but not on the subsequent ones.... so I would agree it is not likely wasting much air.... Great video, BTW.... Is the Royale regulated or not.... any idea what the pressure drop was for the 90 shots?....

Bob

[OZ Harry]

The FX Elite is regulated.
I am remiss in not yet finding the shot string so only have the bare summary figures from previous posts.

There were not many Elites released, less than 40  I read. So there are not many shooters who have actually reported data. Scott DeCapio of Colorado reported this shot string from 3400/240 fill from his FX Elite.
Quote Scott:
 
" I also ran a string over the chrony. 25.4g JSB's from a 3400psi fill:

1-10: 881,886,888,886,886,885,885,880,880,880
11-20: 882,881,881,880,879,881,878,881,878,884
21-30: 884,881,877,876,885,888,887,881,880,883
31-40: 883,881,881,881,880,876,882,885,882,883
41-50: 885,882,882,881,877,879,882,884,881,879
51-60: 880,886,891,885,881,888,882,884,890,889
61-70: 889,891,894,894,890,897,897,897,891,895
71-80: 893,906,898,899,900,897,902,904,899,906
81-90: 898,901,894,899,902,901,902,899,904,901
91-100: 899,897,902,904,903,901,902,904,905,906
101-110:903,903,906,901,897,899,899,899,899,893
111-120:896,894,889,886,886,883,883,880,877,877

That's 120 shots

HIGH: 906 LOW: 876 EXTREME SPREAD: 30fps

Average: ~885fps for about 44.5fpe ... " End quote

Unfortunately he didn't mention end pressure either (which is not uncommon).
But I can't think that it could have been much under say 120 bar 1740 psi  given that his 120th shot's  velocity was 877 fps/ 43.38 fpe.
That would give 1.52 fpe/cuin or  10.8 bar-cc/fpe  at 44.5 fpe av.
Unfortunately Scott's house was washed away in a big flood high up in Colorado and I guess he lost all his fine rifles.

One day I will repeat my data.  It is quite some time since I just ran shot strings (pellet waste at the price here).  So will have to wait 'til I am doing  some target work with that rifle in .25 cal.  Presently it has the .22 ST barrel - I may run a string with it..
As I wrote, I hoped that video may have found some interest; I don't remember others showing anything similar. ... Best regards, Harry.



 

[triggertreat]

I’m sending a special THANK YOU to Bob Sterne for pioneering the DIY SSG.  I also want to thank Travis (OldPro) for his work on this too.

Bob, I don’t know which I’m most impressed with, your pioneering or your comments back on page 32 of this thread where said you wanted to put this idea out to the airgunning community to see how it will be developed over the next couple of years.

This is my idea I came up with.  My version of the DIY SSG allows me to keep the factory look and to adjust the gap and spring tension separately without taking the gun apart in any way.



The results have been positive as you can see my progress here reading from right to left.  The far right spreadsheet (H&N 01) is where I started with a Bstaley O-Ring buffer mod, but wanted to shoot the 21.14gn at 850 fps.  The DIY SSG accomplished this for me as you can see in my latest test (H&N 04).  I'm getting more shots with a higher FPS and still within a 4% ES.



Thanks again!

[Buldawg76]

I’m sending a special THANK YOU to Bob Sterne for pioneering the DIY SSG.  I also want to thank Travis (OldPro) for his work on this too.

Bob, I don’t know which I’m most impressed with, your pioneering or your comments back on page 32 of this thread where said you wanted to put this idea out to the airgunning community to see how it will be developed over the next couple of years.

This is my idea I came up with.  My version of the DIY SSG allows me to keep the factory look and to adjust the gap and spring tension separately without taking the gun apart in any way.



The results have been positive as you can see my progress here reading from right to left.  The far right spreadsheet (H&N 01) is where I started with a Bstaley O-Ring buffer mod, but wanted to shoot the 21.14gn at 850 fps.  The DIY SSG accomplished this for me as you can see in my latest test (H&N 04).  I'm getting more shots with a higher FPS and still within a 4% ES.



Thanks again!

Keith
I like your DIY SSG but the order you have the pieces laid out does not seem to be the way it is assembled if I am understanding the concept of the contained SSG. Also the extra hole you drilled and added a screw in the end cap is that to prevent the adjustment nut from turning inside the end cap to set spring tension.

Could you please line the parts up in the correct order of assy or loosely assemble it so we all can see just how you have it put together in its working condition. Is the 1/4 x 20 SS bolt not supposed to go thru the stroke adjuster hole you drilled out in the hammer with the o ring on it before inserting in the hole in the hammer and then the drilled nut, then plastic washer, spring, steel washer, nylock nut and then that assy inserted into the end cap with extra screw loosely snugged on nylock nut to prevent it from turning when adjusting the spring tension but still allow it to move in or out to set free play for hammer.

If that is not the correct sequence of parts please clarify as to what is or if the way they are laid out in the picture is the correct sequence of assembly.

Thanks Mike   

[triggertreat]

Mike, just pull the bolt and O-ring out of the spring and insert it through the hammer.  The rest of the image is in order.  I was just trying to keep the image within this forum limits and my cameras range.

" extra screw loosely snugged on nylock nut to prevent it from turning when adjusting the spring tension but still allow it to move in or out to set free play for hammer."  Yes that's correct.  It sticks through the inside of the end cap about 1/32" which is enough to do the job without interfering with the movement of the nut.

[Buldawg76]

Keith
Thanks that what I was thinking but just wanted to clarify it since I am going to make a DIY one of my own and like your design a lot.

Mike