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

[rsterne]

Steve, there is some confusion about the "knee" of the curve, which occurs at any constant pressure (eg. a regulated gun), and the "peak" of the curve for an unregulated PCP.... Read these two threads to understand the difference....

Regulated.... http://www.gatewaytoairguns.org/GTA/index.php?topic=74919.

Unregulated.... http://www.gatewaytoairguns.org/GTA/index.php?topic=91915.

When at constant pressure, increasing the hammer spring preload will increase the velocity (the "downslope") only up to a point.... Eventually the valve will be open so long that it is still open when the pellet leaves the muzzle, at which point, no amount of preload can add any velocity.... but it will still add dwell to the valve, wasting air.... That region is the "plateau".... Where the plateau transitions into the downslope, as you reduce hammer spring preload, is what I call the "knee" of the curve.... It is where you tune a regulated PCP (or at any given constant pressure) to have the best balance between power and efficiency....

In an unregulated PCP, as the pressure changes, you have a whole bunch of "knees" one for each pressure.... but if you look at your fill pressure (the highest pressure you use), you will find the same plateau/knee/downslope as with a regulated PCP....That represents the absolute maximum velocity you can get with that PCP with the combination of porting, barrel length, pellet, and pressure you have.... If you tune just below the knee of that curve, as the pressure drops, the velocity will increase, the way it is supposed to in an unregulated PCP.... How far below the knee you go, will determine how much the velocity increases, and so the ES of your string....

HTH's.... Bob

[SynRodSteve]

Thanks for the link to that thread.  Helps a lot!  .  On your internal SSG, it seems that the preload is NOT adjustable once you get the length of the guide tube set?  It seems like you'd want to be able to adjust the preload depending on what you are doing with the gun on a given day.  Am I missing something?  I have a Marauder in 25 and will likely start building one of these soon. 

[rsterne]

Steve, I have enough airguns that I set each one up for a specific job, including a specific pellet at a particular velocity.... so I set the preload to accommodate what I need (ie touching the plateau for that pellet).... Then I use the gap adjuster to fine tune the velocity.... You can back it off a long ways in velocity without much movement, BTW.... it is very sensitive to the amount of gap....

If you wanted to be able to adjust the preload on the internal guide, you would need a locknut arrangement, or something like a NyLoc brake in the stop nut.... with the front of the stop nut counterbored for the guide tube to have end play inside.... It's not as easily adjustable as the original SSG, but a lot cleaner and shorter, and won't pinch your fingers....

Bob

[SynRodSteve]

I should have asked this in my prior post as well.  On the Marauder, you can adjust the striker length to shorten or lengthen the hammer throw.  With the SSG, is the striker just flush with the hammer face? 

[real7]

Anyone that has done Bob's "original" SSG on a Marauder, did you remove the stroke screw in the hammer? If you did, what did you replace it with?

Anyone ?

[Motorhead]

I should have asked this in my prior post as well.  On the Marauder, you can adjust the striker length to shorten or lengthen the hammer throw.  With the SSG, is the striker just flush with the hammer face? 

My SSG devices are being used on pretuned regulated M-rod actions where FULL HAMMER stroke was already in use.  Applying the SSG did not change this.

[rsterne]

I think you will find that most knowledgeable tuners max. out the hammer stroke in the MRod, even replacing the movable striker with a recessed on made from a ground off setscrew or similar to increase the stroke beyond stock....

Bob

[oldpro]

 Im getting tired of agreeing with BOB LOL. But hes correct because the Mrod has a very short hammer stroke and therefore limited hammer energy. The SSG is a great device because you use it at full stroke minus 40 thou. + or - for given speed needed for given fpe requirements.   

[SynRodSteve]

Travis, have you found a good spring, length, preload and gap as a starting point for the Synrod(25)?  950ish fps?

[oldpro]

I have with a WAR valve in place. All the parts are on order for the first production run. I have sent two rifles off to their new homes with SSG in place and the customers have been super happy.

[SynRodSteve]

Ah...but not sharing?     I also have the WAR and NBH in mine.  Looking to make up my own SSG but was hoping to get specs.  I'm leaning toward the more recent version reported that is all internal (floating).  Looking forward to seeing what you've achieved with SSG in the M/Srod.

[rsterne]

Steve, I think Travis is selling the SSGs for the MRod.... I can understand him not being specific about parts....

Bob

[I_like_Irons]

Well, my Dacron cable failed.   It suffered from abrasion due to rubbing on the exposed hammer adjustment pin in the Armada.  I need to get more clearance and perhaps a protective sheath on it before continuing with that design. 

I have now made an SSG that follows what I originally designed with a page from rsterne, and it does not protrude past the end cap.  I put in a 1/4--28  bolt with the head cut off and filed flush with the hammer face.  A e-clip groove holds the spring captive well inside the spring guide.  There is now a bit of clearance with the spring compressed. 

First impressions (I've not yet shot any strings), is that the cocking effort is a bit lighter and a whole lot smoother.

Here is a cut-away view of what I built. 

[rsterne]

Looks nice, David.... I'm not surprised the cable failed.... Good Luck with the new one....

Bob

[SynRodSteve]

Bob.....can't blame a guy fer tryin!    Travis makes good stuff...I'm anxious to get a hold of one. 

[oldpro]

Description: .25 marauder stock reworked valve with SSG .187 barrel port
Notes 1: 2800-1800psi
Notes 2:
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 25.40
Temp: N/A °F
BP: N/A inHg
#          FPS  FT-LBS      PF
23    895      45.19    22.73
22    889      44.58    22.58
21    891      44.78    22.63
20    890      44.68    22.61
19    916      47.33    23.27
18    891      44.78    22.63
17    906      46.30    23.01
16    908      46.51    23.06
15    908      46.51    23.06
14    912      46.92    23.16
13    912      46.92    23.16
12    903      46.00    22.94
11    903      46.00    22.94
10    910      46.71    23.11
9    895      45.19    22.73
8    912      46.92    23.16
7    898      45.49    22.81
6    887      44.38    22.53
5    909      46.61    23.09
4    888      44.48    22.56
3    883      43.98    22.43
2    900      45.69    22.86
1    903      46.00    22.94
Average: 900.4 FPS
SD: 9.8 FPS
Min: 883 FPS
Max: 916 FPS
Spread: 33 FPS
Shot/sec: 0.1
True MV: 900 FPS
Group Size (in): 0.00


Sent from my iPhone

[oldpro]

Opened up the stock valve and barrel port then added the SSG, tuned and got around 28 shots but My crono has only 1 working IR light so I got miss reads  I deleated the miss reads and the above string is whats left of string. several first shots miss read so string starts high and looks like it has no curve but it does LOL. SSG are being made now and will be on website shortly, I will also be offering a SSG install and tune all in one for big savings.

[Ribbonstone]

One “nay” for the cheap experimenters who make simple SSG’s.

If the spring can kink up, then it can act as a striker limiter.  Idea here is that the striker is “free flight” at the end of the stroke.   If the spring binds inside the striker, then the adjustment deosn’t let the spring  “fly free” and acts as a terminal stroke adjustment.

(One testis to grab onto the lock nuts of the SSG, pull back, and if it moves the stricker back and cocks the gun, the spring is binding inside the striker.)


Use a guide that is large enough to exclude spring kinking…but no so large that it binds the spring….and you should be good.

[rsterne]

I agree 100%.... I mentioned using as large a guide as possible earlier.... thank you for confirming that....

Bob

[PakProtector]

One “nay” for the cheap experimenters who make simple SSG’s.

If the spring can kink up, then it can act as a striker limiter.  Idea here is that the striker is “free flight” at the end of the stroke.   If the spring binds inside the striker, then the adjustment deosn’t let the spring  “fly free” and acts as a terminal stroke adjustment.

(One testis to grab onto the lock nuts of the SSG, pull back, and if it moves the stricker back and cocks the gun, the spring is binding inside the striker.)


Use a guide that is large enough to exclude spring kinking…but no so large that it binds the spring….and you should be good.

LOL...on the only SSG currently running, you will need bionic fingers to pull the spring guide back by hand. The pellet shooter OTOH, can probably deal with lots less spring. That one is getting a floating SSG so, nevermind...
cheers,
Douglas