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

[rsterne]

For sure, if I was selling them, I would NOT want a design that could pinch you.... Murphy's Law will get you every time.... "If it CAN happen, it WILL happen"....

Bob

[zaphod621]

EDIT: I also have Crosman 2240 and just have to drill the end cap, If someone want I can post the pictures and specs.

Yes post what you have come up with for the 2240. Thanks.

[Tomg]

"TomG, the very first SSG made is on my .30 cal Grizzly, which has an 80 gr. hammer with nearly a 1" stroke, and the SSG guide assembly that comes to a crashing halt weighs nearly 20 grams (20% of the total 100 gr. weight).... The gun is extremely accurate, and doesn't throw "fliers", nor do I notice any disturbance of the gun when fired.... The gun only weighs a bit over 7 lbs. all up...."

Bob, I am not arguing your findings, or anyone else's.
However the fact is that the spring stop happens right before the valve is hit. So what it is hitting is of concern in my book.
It might be that on that particular gun the hit is so consistent and the propagation so predictable that it does not affect the accuracy.  As you well know, harmonics are always present, but if the harmonics act the same way every time, the accuracy stays the same.

[Gerard]

... and in most conventional PCP airguns the valve is hit by the relatively massively heavy striker/hammer BEFORE the pellet starts to move down the barrel. I doubt there is more than a 0.001 second difference between the 'impact' of the SSG'd spring stop and the valve being hit SO much harder by the hammer. Both are, in most PCPs, inline with the bore, zero geometrical offset with the bore meaning zero tangential momentum imparted to the barrel, which means the gun is just being encouraged to react in the same direction the pellet is travelling anyway. I'm no physicist, but in what I've seen with the SSG installation in my 2240 carbine, the pellet moving relatively slowly down the 18" barrel compared to the kinds of power most guys are talking about in this thread, there has been no change in the tiny groups I get with the gun. No POI shift either, comparing to before the SSG's installation. Of course it'd take someone with the right kind of sensor array to measure differences in behaviour... perhaps a laser pointed at a mirror mounted to the side of the muzzle, the reflected beam hitting a graph on a wall across a workshop and tests done before and after SSG installation to determine amplitude and orientation of any detectable changes in bright red dot motion. I'm not going to bother setting that up as I don't see any accuracy changes in my situation so there's no point. Don't notice any difference in the firing behaviour of with my 2260 either, but it's not scoped yet so can't attest to accuracy changes.

[Motorhead]

Happy to read we're all acting civil here as we debate the PRO / CONS of each design shared 

Obviously I'm one of the few here that competitively shoot where BOTH accuracy & efficiency are required.
Certainly the VERY LOW mass configuration I came up with ( Hammer / Stop rod Etc ... ) was purpose built to aid Tune / design attributes already in place. .... So said design for others may be entirely wrong & I get that.
So really no argument of whats best really exists here 

Now ...
Back to talking about other variations, indeed see the version that has the STOP GUIDE as a "cartridge" being a free floating devise independent of hammer while also free of rear cap to likely be the best of all compromises in designs shared to date.

So question after a few statements becomes this  
We understand we're throwing the hammer at poppet stem independent of hammer spring energy 
We understand doing so that hammer bounce between poppet and end of stop rod kills hammer bounce 
We understand as hammer is cocked and held, cant and alignment issues need to be addressed to keep it all bind free 
And ... with a stem of stop rod out the back fingers or hand injury is a possibility 

** Question becomes one of secondary vibrations independent of the hammer moving from being at rest ( Cocked then released ) striking poppet ( Acceleration ) then the sudden (Deceleration) of hammer as it strikes poppet.  This is a two way bump that is 100% physics only mitigated with lower weight / mass.

So if we look JUST AT THE SSG DEVISE ( Hammer spring, Stop rod, Collars & nuts etc ... )
What is the influence it contributes to the shot cycle

I see a spring that stays with hammer have coils oscillating wildly just as the shots happening !
I see a floated SSG device independent of hammer and rear cap to be a SECOND loose part very similar to hammer rattling between poppet and SSG rod & SSG rod also rattles loosely between hammer and rear cap.
I see the original design as presented having ONLY the bare hammer as the loose part, having all the SSG components under tension and not contributing to vibrations AFTER the shot cycle has been initiated.
* Or at least view it as the lessor contributor of vibrations created upsetting accuracy.

Really don't know ... but is a subject worthy of further discussion IMO.

 

[oldpro]

 I personally didnt see any changes with POI with original version or My version. I would suggest if that your having issues you need more preload on spring and a closer rod clearance, I run mine at around  20 thou with a 12lb spring under tension.

[Tomg]

Gerard, the hit of the SSG and a hammer hitting the valve stem are two very different hits. One is hitting the rear-cap/tube with an absolute stop, no give. The hammer hit the valve stem which gives and moves fwd a little bit, then goes back. I have not measured how fast the hammer moves fwd, but I am willing to bet it is by a huge factor slower than the pellet is leaving the barrel. Whereas harmonics move through metal much faster than both pellet or hammer.

Let's compare apples to apples.

I am sure as more data is coming in, we'll get a result pool that will help build some empirical data.

[Bullfrog]

I'm didn't find any accuracy issues using an SSG on my .25 Mrod (before the gun died), on my brother's gun, or on my .177 Mrod. My design is the basic design except I use one nylon lock nut to set my gap distance.

[quickster47]

First to say, thanks to rsterne for what he shared such a simple and great invention

EDIT: I also have Crosman 2240 and just have to drill the end cap, If someone want I can post the pictures and specs.

I am a 2240 kind of guy since selling my Marauders so I'm very much interested in your pictures.

Carl

[rsterne]

TomG.... are you using an O-ring to stop the rear nut?.... Perhaps just that slight cushion is the difference.... In terms of the timing, that is all easily calculated, and of course depends on the gap between the hammer and valve stem at the point the guide stops.... However, since the total time the valve is open (round trip) on a typical PCP is only about 1 mSec (0.001 sec.) and the total time the pellet is in the barrel is about 2 mSec.... and the time the hammer takes to cross the gap only a very small fraction of a millisecond.... there is no question that with the speed of sound in steel a disturbance to the gun from the guide collision COULD move the gun while the pellet is in the barrel.... Whether or not that is measurable, when you compare the mass and velocity of the guide to the mass of the gun, is another matter.... My gut feel is that just the introduction of that O-ring to (drastically) reduce the deceleration rate of the guide may be enough to eliminate any disturbing effect by it.... but these are the things that will show up, and be conquered, in time....

Bob

[Tomg]

I have not used a o ring. And you might be right Bob, the margins are so small in terms of timing, that that cushion is the difference thats needed.

[Motorhead]

I have not used a o ring. And you might be right Bob, the margins are so small in terms of timing, that that cushion is the difference thats needed.

No O-ring having stop rod smack rear cap crisply ... You INDEED create a shock vibration / motion to the shot cycle !!

[BigTinBoat]

The original version works AWESOME and costs only $10 to build at most! It will greatly improve your gun for the least mount of money BUT As a retailer I cannot put a product into the market place that can potentially hurt someone thats what took me down the road I went down and why my SSG isnt $30. Your not just getting a spring and a guide your getting all the parts pictured above machined and pre set up for and easy drop in. For the do it yourselfers The original design is simple works well and you can easily remove plus its dirt cheap. I think that sums it up for me.

Does that other "$30" device have a possibility of pinching? or hurting in some other different way?

[rsterne]

I don't think we should be dragging this thread off track debating Commercial over DIY versions.... Let's stay with what works, doesn't work, and why.... and let the marketplace decide if there is, or isn't, a market for the SSG commercially.... Some guys can roll their own, some can't and want to purchase, it's as simple as that.... Maybe someday a manufacturer will start installing them OEM.... and then we can comment on how well they work (or don't).... and then start modding them.... *LOL*....

Bob

[oldpro]

 Im with you 100% Bob plus its just plain frustrating trying to explain something new to most people who never seen touched or tested one. Lots of ways to do it and im sure there will be more to come.

[PakProtector]

The .22 Marauder I have the SSG in is more accurate than when I started. This one is an 8 gram affair, with a smoooshy o-ring for a bumper between the depth stop and the spring preload nuts. With the preload and spring k I am running it *NEEDS* to be a 90D one, perhaps even a polyurethane one. Fortunately there is an o-ring store down the street from work...

The hammer interface has a rounded end, cut to the old OE spring diameter and the striker set screw flush with the hole in the hammer. Cock binding does not seem to present me any issue.
 The next implementation will be done floating and use smaller OD springs. The endcap is cut out to 9/16-20 threads so I can run the jam nuts through it, and still have enough engagement of the washer/collar. Stick-out should be minimal, and if I make the depth nut long enough nothing will stick out the back past it.

The .224 will get the floating one, maybe with the .42 springs, maybe with .36 OD...probably going to try the .420 so I can get an apples-apples test when running the same pre-load.

If the results are not better, I will put it back to the way it is... High preload is a good thing. With the pellet-shooting .25 I want to do a direct compare to efficiency/shot count v. the Wicked NBH.
cheers,
Douglas

[PakProtector]

Bob, on the last diagram on post 356, one does not need to make a socket for the collar( in the depth nut). Lock up the jam nuts and chuck the screw in a lathe and take a bit off their corners. The nuts will then act as the rear guide. This coupled with a depth adjuster long enough to contain the stroke will render the device 'safe' from thumbs stuck where they might otherwise get into harm's way. For 10-32's this is likely going to be OTO .400-.405 diameter...that will leave me to use a Z drill of .413. and cut the collar at something less than 9/16-20 minor diameter.

Or...if we can be sure the depth nut is well within the end cap, the collar can be cut to its minor/tap drill dia and leave the nuts a bit more clearance in the depth nut. It is certainly useful to run 3" of spring as this app can yield a bit more length for it to hide in, at least with the Gen1 end caps.
cheers,
Douglas

[thelast88]

Yes post what you have come up with for the 2240. Thanks.

I am a 2240 kind of guy since selling my Marauders so I'm very much interested in your pictures.

Carl

First to say, my 2240 have a little shortened hammer spring to get the most usable shot string from a single CO2 cartridge.

Now, here is what you need to make SSG for Crosman 2240. In my local store all the parts from the picture was about $0.25! 
1. One bolt, approximately 2" long, thick exactly enough to go through the OEM spring of 2240,
2. Two nuts that matches the size of the bolt, or one nut with plastic lock (if you want to using only one nut, then you have to made thin slot for screwdriver on the bolt for tuning),
3. Two washers and two o-rings that matches the size of the bolt (not necessarily required).



Then, you have to measure the bolt diameter and find the drill bit that's just a little bit bigger than that. My bolt was 0.189" (4.8mm metric) and I was used 0.2" drill bit to drill the end cap.
You need to drill from the inside because it will be perfectly centered (it is tapered inside, at least in my case). After you have drilled it, you may have to sand the hole.




Also, if the head of the bolt is bigger than a hole in the back of the hammer, you have to process the head until it can freely go in the hammer.

And the last, you need to assemble your SSG device for 2240 but that's easy part.
I don't need to use washers on this, but they would be required if you want to increase power. O rings are used to reduce impact.
Length of the bolt remains the same because you want to have free floated hammer, you just have to put washers inside the end cap and in that way you will get more pretension on the spring, thus more power. 




My string is the same as I tuned it earlier, but with much less noise and without burrrrrrppppp...
AVG speed was something like 375fps with JSB Exact Heavy 18.13gr (5.6-5.7fpe) but I don't really want to measure a whole string. (it's that long)


That's it, enjoy your 2240 with SSG! 

PS: Bigger pictures are in the attachment!

[zaphod621]

Thanks 88, that looks perfect for the Crosman co2 pistols. Don't really need to worry about pinching like you do on the Disco and Gen 1 Mrod. Going to the hardware store today for bolt and nuts.

[quickster47]

thelast88 thanks so much for the great pictures and your insider's information.  Now I'm off to my spares boxes to find the pieces I need to put one of these together.

Carl