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PostPosted: Fri Jan 08, 2016 10:36 pm 
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You can probably use two 2240 springs, one shortened, running on the same guide.... If you close the ends they won't wind into each other....

Bob

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PostPosted: Sat Jan 09, 2016 1:58 pm 
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Spent a little time flushing out my quick sketch (posted on GTA)...thinking to slab side the striker (two sides), the larger diameter portion of the guide rod and the follower (three sides) to allow air movement. Bushing at rear will adjust via pin spanner, guide rod via hex grub screw. Likely use 3/8-24 and 1/4-28 for threads, maybe inset some nylon beads in threads to provide adjustment stability.

Likely still some fine tuning, but should be close...

Image

Another for the project list, thanks Bob. 8)

Al


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PostPosted: Sat Jan 09, 2016 4:16 pm 
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Looks great, Al.... look forward to seeing the results....

Bob

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Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
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PostPosted: Sun Jan 10, 2016 7:51 pm 
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I installed an SSG in my Grouse Gun today.... 2260 PCP Carbine with a 14" barrel and a stock Disco valve and hammer spring.... I used a 2200 spring with 0.90" of preload, which puts it very close to coil bind when cocked....

Previously I got 16 shots with a 2% ES, and 20 shots within 4%, averaging 20 FPE (705 fps with JSB 18.1 gr. heavies), with an efficiency of 1.15 FPE/CI

Now I get 20 shots with a 2% ES and 24 shots with 4%, averaging 21 FPE (722 fps), with an efficiency of 1.50 FPE/CI, an improvement of 30%....

It doesn't seem to matter if the PCP is regulated or not, the SSG can provide big gains in efficiency....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Jan 10, 2016 9:39 pm 
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Great results Bob, for reference how long is your hammer bolt and hex nut used in the SSG for the grouse gun that yielded these results? Looks like I need to order a few 2200 springs from Eric...

Thanks

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PostPosted: Sun Jan 10, 2016 10:00 pm 
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The 7/32" guide is about 2.5" long, and the drilled hex bolt to adjust the gap is about 5/8" (plus the head).... Uncocked it only projects less than 1" behind the back of the tube, cocked about 1-5/8"....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Jan 10, 2016 10:54 pm 
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Thanks Bob, just to clarify is the hex bolt still 3/8?

I see you've switched from 3/16 to7/32 for the hammer bolt.

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PostPosted: Mon Jan 11, 2016 12:26 am 
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Yes, still 3/8".... I use 3/16" or 7/32", whatever is the largest size that slides easily through the hammer spring....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Wed Jan 13, 2016 2:49 am 
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Following up a bit more on my 'adventure' with making an SSG work in my Crosman carbine, I finally remembered where I'd recorded the measured volume of the HiPAC + single extension - it was 35cc, measured with water without the Lane regulator inserted. (In case it seems relevant, I reduced the plenum volume - the entire CO2 bulb emulating portion of the HiPAC - to just 8cc volume using CF tubing.) So subtracting about 2cc (probably bigger than that, closer to 4cc I'd guess, but what the heck I'll be 'charitable' for the purposes of these numbers) for the regulator I get 33cc. Running my shot strings and power levels through Lloyd Sikes' calculator - http://www.calc.sikes.us/1/index.php - I finally get to see how my various springs and best adjustments for each have worked out in terms of efficiency.

Firstly my pre-SSG setup, which used a 40mm long spring 8mm diameter with wire 1mm thick, something I picked up from a gun shop which was about halfway between the Powermax spring (too hard with its 1.2mm thick wire, was bending my cocking knob and bolt gradually after a few thousand shots) and the stock Crosman hammer spring. This gave me 42 shots before regulator setpoint was reached and velocity dropped off more than 1.5%. Sikes' calculator gives me a figure of 1.65FPE/CI. Which is good, I think. This spring sat on the RVA, with a gap of about 10mm between the end of the spring and the end of the hole in the hammer, so a lot of 'negative preload' I suppose. Being a fairly strong spring, and now thinking about it in SSG terms, my guess is that the high efficiency evident was resulting from the hammer (at the time lightened to 48grams) bouncing back from the valve stem and striking the spring with insufficient force to result in a rebound and significant secondary impact on the valve stem. A simpler SSG? Cocking force with this spring isn't difficult for me but might bother some shooters. Certainly nowhere nearly so difficult as using a full-length Powermax spring, for anyone familiar with those!

Next up is the very longest shot string I was able to achieve with an SSG. This spring was much longer, again 8mm OD and about 70mm with various preloads tested settling on about 1/3 total length preload. Sikes' calculator gives me an efficiency of 1.51FPE/CI for this 40 shot string, with velocity reduced about 2% from the above 42 shot string. Gap adjustments between 1mm and 5mm from the hammer made little difference, with spring preload and total throw being more significant in tuning this setup.

Then I lightened the hammer to 42grams, and tested a number of spring combinations, mixing and matching until arriving at my original velocity but reducing shot count to 35. Bit of a mixed bag of springs stacked up for that, but it more or less worked. Efficiency with this setup tweaked as best I could was 1.37FPE/CI.

Then I took the thing apart and cleaned everything, inspecting to make sure the regulator wasn't malfunctioning nor anything else going sideways to skew the figures. Nope, the guts looked fine. But I decided to bump up the regulator setpoint slightly from 800psi to 850psi (55bar to 59bar), in case such a low regulator setpoint such as no one else in the community testing the SSG has reported using might be harming my efficiency. Of course many are not using regulators, but still they're shooting down to higher finishing pressures than these. The small change should be enough to notice differences in SSG tuning I reasoned.

I also set about learning to 'make' springs, or more correctly to re-make them. Having a couple of hundred assorted springs, mostly useless for this, I found some much larger OD springs with 1mm wire and dragged them through a washer held in a vise to mostly straighten the wire. Then I wound these onto a steel rod held at both ends in my little lathe (turning the 4-jaw chuck manually while holding the other end of the wire with Vise-Grips) and voilà, 8mm OD springs:

Image

After a bit of practice I managed a few with really even coils. The last, best spring I made, 40mm long, added to a 23mm long 1.2mm wire commercial spring and pre-compressed to about 50mm and a 2mm gap resulted in a 6% higher velocity 30 shot string, with an efficiency of 1.36FPE/CI. Tests with all 'home made' springs of several lengths were giving slightly erratic velocities, all much lower than wanted. A bit too weak it seems.

So that was another failure and I've decided to leave it alone for now as my pre-made and home-made spring options are about used up. Got some 1mm x 8mm springs coming from a factory so I'll try various lengths in single pieces (no more stacking springs!) and see if I can't find better results. But considering that none of the dozens (I've only mentioned the highlights here) of variations I've tested has come close to the 1.65FPE/CI figure with a too-short 1mm wire spring it seems likely that was the best setup I'm going to get to match the various other modifications I've made.

My rookie guess as to the significance of this apparently standalone failure of the SSG to work an efficiency miracle is that I'd already managed that by other means, and any step away from that setup can only harm the tune. Reminds me a bit of art college back about 35 years ago. A couple of our instructors told horror stories of artists who failed to stop when the piece was done, went on to completely ruin what had, briefly, been magnificent work by trying too hard, not putting down the darn paint brush. This isn't quite in that league, but there's a similarity. Fortunately I can easily make another RVA and re-install the known-good spring in the meantime, then go back to experimenting with the new springs arrive.


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PostPosted: Wed Jan 13, 2016 1:19 pm 
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I wasn't able to get one to work in my Hatsan .25 cal AT-44 Long to my satisfaction either.... The gun was shooting 72 FPE with 36 gr. Daystates and would blast Kings at 1070 fps..... There are severe limitations to the length of installed spring in the Hatsan because of the 2" long plastic rear block that holds the trigger.... there is no room for a spring in that space, only a guide.... a spring would hit the trigger assembly.... I was able to get a 20% increase in efficiency with the SSG when the gun was tuned to about 55 FPE (compared to the best previous 55 FPE tune).... but that was all the power I could get and still have any gap in the SSG.... ie trying for more power produced dismal efficiency.... This is more a limitation of available room in the gun than a failure of the SSG, however....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Jan 14, 2016 3:30 am 
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I picked up a much-customized but crazily hot-shooting 14" barrelled .22" 2260 last summer. A back burner project for when I get bored. Today I got bored, so tried an SSG in this one. Got wildly diverse velocities with relatively small adjustments, all the way from the low 400's with 0.030" wire to the high 770's using a mix of harder springs, all with 14.39gr JSB's, using a gap usually around 0.05" or less. Backing off the preload a bit from there I found a sweet spot around 750fps (18fpe) which was sounding very crisp indeed, with a substantial drop on loudness for just a ~30fps drop in velocity. Unfortunately this was at about 1,000psi. At 1,100psi this setup gave 480fps and very quiet, at 1,200psi the pellets barely fell out the muzzle somewhere below 200fps... at 900psi the same settings gave 795fps and loud, bordering on a dump, though actually touching the SSG to the hammer at this point to try an actual dump shot gave a jump to 896fps and extremely loud. So not much range here.

So while I can of course fiddle with other springs on hand, and the batch being shipped to me sometime of course, I think what I've found is the setpoint for my Lane regulator. None of the half-dozen spring sets I tried delivered anything close to a practical string for more than 5 shots, the ES just getting too large. 70bar for 18fpe and probably quite a few shots down from 1,800psi should make it a fun little backpack carbine, with a 2.5x 20mm scout scope mounted low and total weight of 4.5lbs. So even if a guy like me can't make an SSG work as intended, it has its uses. Certainly much better than a mere RVA for deleting bounce, and more controllable besides with two adjustments available instead of one.


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PostPosted: Thu Jan 14, 2016 2:50 pm 
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Ack. I jumped to conclusions. A bit more fiddling around this morning using the same rather firm spring set (three springs about 1" long each, ranging from 0.9mm but harder than it looks, then 1.0mm, and 1.2mm wire) I finally bumbled across a rather decent string. 21 shots averaging 748fps with 14.39gr for 17.88fpe, shooting from 1,500psi down to 600psi. Plugged the 2260's numbers into Sikes' calculator factoring in the gauge plug loss of volume, the Disco valve's further-forward front seal, and the long filtered fill plug up front, leaving a volume of just under 4 cubic inches or 65cc. Gave a figure of 1.53FPE/CI, which ain't bad. Unfortunately still more than 4% ES:
730 726 741 736 742 750 733 743 749 759 753 757 746 759 766 760 762 755 754 745 737

But hey, I'm not complaining! I finally got an SSG to work for me, which says both that I'm prone to sloppy work and jumping to conclusions in my eagerness to try these sorts of things, and that I might just be able to salvage a better shot count and efficiency from my 2240 with more pellets run through the Chrony and more springs and settings tried. In my previous best setup with the 2260 last June I'd managed 20 shots averaging 16.1fpe, Sikes' calc giving an efficiency of 1.32FPE/CI, which wasn't too bad. The ES was similar with just RVA tweaking to settle on about a 4.5% spread. Maybe I won't bother putting in a regulator after all! We'll see how it settles in after some hundreds of shots, the springs and SSG rod/guide no doubt smoothing out just a little more and dropping the ES.

Edit: Forgot to mention that I also added an O-ring and a delrin spacer behind the valve to help limit hammer travel. Hammer can compress the O-ring slightly, for a maximum valve stem travel of 3mm from closed. This helped a bit right away before building the SSG but didn't eliminate the second strike and burp. As it was, 8mm of stem had been left exposed, though the hammer pin slot only allowed about 5mm of actual poppet travel.


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PostPosted: Thu Jan 14, 2016 8:38 pm 
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Here are all the major variations of the SSG that have been invented so far.... They all share two common traits.... there is preload in the spring, but the spring does not push on the hammer at rest when uncocked.... These two features combine to prevent hammer bounce.... The concept first discussed was to use a Gas Ram to achieve this, but unavailablitly of a suitable unit caused me to simulate the way it worked by using a spring on a guide with a stop to create the preload and a gap to the hammer.... Here are the various configurations suggested to date, some tried and some not.... All these drawings share the same features and were drawn to the same scale, although they may have changed slightly by the time they got uploaded....

1. They have the preloaded spring 10 units long. Spring and guide is shown in black.
2. They have a hammer stroke of 7 units, with enough room for that to occur everywhere.
3. They have an adjuster (shown in red) for the gap between the hammer guide and hammer, which also changes the distance the spring compresses when cocked.
4. The green feature is the end cap, all end caps and gap adjusters are drawn the same size.
5. The hammer is shown in purple, and is longer for the ones that require a deep hole in it.
6. If a sliding collar is required on the guide, it is shown in blue.

Image

Gas Ram suggested by stalwart

Image

SSG suggested by rsterne

Image

Above suggested by Gippeto.

Image

Above suggested by I_like_Irons

Image

Above suggested by rsterne

Image

Above suggested by rsterne

It is not the intention here to show every possible variation of materials or construction, but only the major differences in operating methods.... In my original design, the spring is captive in the rear gap adjusting nut, is accelerated by the spring and comes to a halt just before the hammer hits the valve, wasting the energy used to accelerate it.... After my original design, which several people have tried, two variations were proposed in which the guide was fixed at one end.... In Gippeto's version, it was fixed at the back, adjustably, into the gap adjuster in the end cap.... The guide does not move, the spring does its work pushing against a sliding collar which then pushes on the hammer.... The collar stops just before the hammer hits the valve.... No energy is used in accelerating he guide, only the small collar.... but the weight of the guide does not assist the hammer strike.... In a version proposed by I_like_Irons, the guide is fixed in the hammer and travels with it, but maintains preload adjustability where it threads into the hammer.... It also uses a sliding collar on the guide, but at the back, pushing on the gap adjusting nut.... The weight of the guide takes energy to accelerate, but that energy becomes part of the hammer strike....

The two remaining versions I have proposed, to take advantage of the above ideas, but without requiring the guide to be fixed to either part, it remains free-floating, with a gap to the hammer adjustable by the red adjuster.... Both versions require the sliding collar.... In the first version, the guide remains stationary and the collar slides, like in Gippeto's, requiring no energy to accelerate it, but does not contribute any to the hammer strike.... In the second version, the guide travels with the hammer, while the collar stays still, like in I_like_Irons version.... which requires energy to accelerate the guide, but it gives that energy back as part of the hammer strike....

The versions where the guide stays still at the back don't stick out the back of the gun, but require room inside the hammer to accommodate the guide during the cocking stroke, so the hammer has to be deeper than the stroke.... The versions where the guide move with the hammer don't stick out the back as far as my original version, but require that the back end of the guide, including the diameter of the stop nut, be able to clear the inside of the gap adjuster without interference or hanging up.... Each version will have it's own limitations, advantages and disadvantages.... Some will be suitable in some guns and not others, and vice versa....I hope by showing all the versions in one place that might help clarify their similarities and differences....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Jan 14, 2016 9:09 pm 
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Excellent post thanks Bob.

New springs should arrive tomorrow in time for more testing this weekend :)

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PostPosted: Sun Jan 17, 2016 10:42 pm 
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I rebuilt the first gun (2260/Disco) I converted to the SSG today, using the last drawing in the post above.... It uses a much shorter spring guide that moves with the hammer, so the energy is not wasted.... Here are the two types.... I stole the spring from the top one for the new one, on the bottom....

Image

The top one has a long guide that stops when the rear nuts hit the gap adjusting bolt.... The bottom one has a sliding aluminum collar that pushes against the end of the gap adjusting bolt when you cock the gun.... and the stop nut slides back inside the adjusting bolt.... When you fire, the guide accelerates with the hammer, and just before it hits the valve, the stop nut hits the collar and carries the collar with it.... All the moving parts provide their energy to the valve.... The gap adjusting nut must be larger in diameter to allow the stop nut to pass through the center when the gun is cocked.... The collar is centered in the front of the end plug, which keeps everything aligned.... You can see how much shorter the new setup is than the original, and when cocked, the stop nut stays inside the gap adjusting bolt, as in the photo below....

Image

The photo above is with the gun cocked.... Compare that with the photo below of the original SSG setup, also with the gun cocked....

Image

There is no longer a pinch point to worry about, and it looks MUCH nicer and more compact....

How does it work?.... FABULOUS !!!.... When I first assembled it, I used 0.1" less preload than I did in the original version, because I expected a stronger hammer strike and I didn't want to go past where I wanted to end up.... Well, it turned out I should have reduced the preload by 0.2", because I had more velocity than I wanted from the heavier hammer strike.... When I cranked it up (with no gap) it was well over 1000 fps with Kings, and I just happened to have some of the new 34 gr. King Heavies here, so I tried them.... With a minimum gap I was in the mid 800s, which was 55 FPE, compared to the best I could do with the old SSG with the Kings of 50 FPE.... So, I pulled it apart, increased the preload to maximum with the 2200 spring, and was rewarded with even more velocity.... By maxing out the spring to coil bind (preload, no gap), I hit 948 fps (68 FPE), which is harder than this gun has ever shot before.... Once I backed it out to get a tiny gap, it was shooting right at about 900 (62 FPE), but it was using a lot of air, so I backed it out another turn, and settled for a peak velocity of 880 fps with a 5-shot string from 2000 psi down to 1300.... The average was 866 fps (57 FPE), at an efficiency of 1.30 FPE/CI.... which is pretty astounding for a mildly modded Disco with the small tube from a 2260....

I really like this version of the SSG, particularly for guns where you need lots of hammer strike to get the dwell for high power with heavy pellets.... It still has the advantage of eliminating hammer bounce, but it doesn't waste the energy the spring puts into the guide, instead it uses the weight of the guide to increase hammer strike and dwell.... In addition, it is much more compact, and the guide can be hidden inside the adjuster, providing the hammer stroke isn't too long (this gun is 0.65").... All in all, I think it's a significant improvement over the original.... particularly for higher powered PCPs....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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