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

[Matt15]

That was very helpful, Bob!! I am very excited to try this in my .25 pumper. 

EDIT: Mine will be hidden in the stock since my stock attaches directly to the main tube.

[rsterne]

I'm thinking this might make a BIG difference to the number of shots for the Millennium Pumper.... *grin*....

Bob

[Matt15]

I'm thinking this might make a BIG difference to the number of shots for the Millennium Pumper.... *grin*....

Bob

I bet it would!! Bob, your are a genius!!!

[Motorhead]

  because the large amount of preload prevents the hammer, when it is thrown back by the valve on closing, from storing energy in the hammer spring which is then returned, causing air-wasting hammer bounce....

Am waiting for another to ALSO try using a bumper to further mitigate bounce during the hammers return again wanting to bounce off end of stop rod.

Such as was done here ....



Guess if the basic rod with a gap STOPS BOUNCE DEAD there is zero need ... it is IMO of interest in the finer details if such a buffer in the system helps at all

[rsterne]

Agreed, should be simple to test with and without your O-ring buffer to determine if there is any difference.... I would suspect that at some values of preload (minimal) there could be a difference, while if the preload is higher there might not be.... ie it could affect the threshold where hammer bounce is completely eliminated.... Just a WAG at this point....

Bob

[K.O.]

...................... You can further extend that reasoning to what is happening with the efficiency of the two systems when on the "knee" of the veloicyt vs. preload curve.... With a conventional setup, there is a slope to the efficiency, increasing as you decrease preload.... while with the SSG, it is pretty much either "efficient" (with a gap), or "inefficient" (without one)....
..................................
Bob


the thing that is boggling is that it is such a simple concept; how is it they did not see it before you did? Not that expensive to implement in most of the pcp Platforms I would guess...

[Rivers3Plinker]

"the thing that is boggling is that it is such a simple concept; how is it they did not see it before you did? Not that expensive to implement in most of the pcp Platforms I would guess."

Might be patented by another manufacturer. Might be other issues like reliability or some other liability issue too but I was thinking the same thing. The immense improvements would seem to be hard to overlook by engineering.

[K.O.]

  because the large amount of preload prevents the hammer, when it is thrown back by the valve on closing, from storing energy in the hammer spring which is then returned, causing air-wasting hammer bounce....

Am waiting for another to ALSO try using a bumper to further mitigate bounce during the hammers return again wanting to bounce off end of stop rod.

Such as was done here ....



Guess if the basic rod with a gap STOPS BOUNCE DEAD there is zero need ... it is IMO of interest in the finer details if such a buffer in the system helps at all

I like anything that might dampen vibration in the shot cycle; matters more with an un-regged 50 fpe .25 heavy hammer Mrod than with a regged 14-18-20 fpe .177 light hammer Mrod... I would think?

[Motorhead]

"the thing that is boggling is that it is such a simple concept; how is it they did not see it before you did? Not that expensive to implement in most of the pcp Platforms I would guess."

Might be patented by another manufacturer. Might be other issues like reliability or some other liability issue too but I was thinking the same thing. The immense improvements would seem to be hard to overlook by engineering.

Do know that most OEM rifle stocks tend to go along Monte Carlo grip design having ones thumb around wrist of stock.  Such protrusion as a cocking indicator or stop rod clearly for most ... IN THE WAY !
Once you get some drop in stocks grip area more inherent to target stocks / thumb hole styles do you get clearance.

Also one must be aware ... GET A FINGER / DIGIT in the gap of stop rod to rear cap your going to get a NASTY finger wound !
* Ask me how I know ... ALREADY DONE IT & have nice blood blister on left corner of right thumb !!  OUCH
So for liability of such, unless said SSG is fully covered or enclosed you gotta pay attention !

As too being missed in the design of manufacturers, The STOP ROD as an assembly is subjected to a pretty substantial shock upon every cycle.  We at this point have no data on longevity or fatigue of parts.

As with much that gets designed, once engineers design it the Marketing and Lawyers get final word on what it becomes in the end.   The 2 paragraphs above may Ying/Yang why we don't see such a devise being used on production air guns.

Just a WAG ... Lol
Scott

[Rivers3Plinker]

I can imagine an alternative to the spring loaded rod arrangement would be an electric solenoid using a rechargeable battery pack. Bury solenoid in the back of the tube, put the battery pack in the stock and recharge it via standard micro USB port. What a rogue idea eh?

[Tomg]

If the engineering teams would have "considered" this option or known about the obvious upsides of the SSG, they would have incorporated it. My guess is that the solution is so deceptively simple that it has simply not been tried or developed.
The fact is, from an engineering standpoint, burying such a device in the rear of a pressure tube to make for a clean package (without anythin sticking out, is super simple.
The shock to the system is more than reasonable in over the counter airguns 10-30fpe, only when you go hogcrazy and want 90-160fpe do you get into territory where you need a looooot of air.

[K.O.]

I by the way am still lobbying for T.H.O.R. system maybe for the rear cocker (air hogs 90 fpe up)

yep the heavy hammer rear cocker would have a significant pince hazard to it but for high fpe maybe worth it.

[rsterne]

Today I pulled apart my 2560 and fitted the SSG system to that.... Here is a photo of the gun before the SSG was fitted....



It is a twin to the 2260 I did earlier, except uses a 17 CI tank regulated at 1800 psi instead of a 13 CI regulated at 1600.... This allowed it to also get just over 4 magazines per fill (they are 8 shot mags) shooting 25.4 gr JSB Kings at an average of 949 fps with an ES of 9 and an efficiency of 0.96 FPE/CI for 35 shots.... The gun used a QB spring with a small amount of preload, and if turned up to 960 fps had audible hammer bounce and a decrease in shot count....

The SSG is very similar to the one on the 2260, with a 7/32" spring guide, but longer to accommodate the QB spring, so it projects further from the back of the main tube, just like the previous RVA does in the photo above.... This gun, even in the previous version (with the guide acting as a cocking indicator), requires you to lay your thumb along the side of the stock instead of wrapping it over the wrist, where it would be touched by the end of the guide when cocked.... I'm already aware of the ability to get pinched, anyone who has ever used a rear-cocker will have done it more than once, and learned to hold the gun accordingly.... In my new Monocoque PCP, it is buried DEEP inside the main tube, so not an issue.... It took a bit of playing on this gun to find the correct adjustments, but it was worth it.... I was rewarded with 50% more shots at slightly higher velocity.... I can now get 7 magazines (56 shots) averaging 960 fps (52 FPE) with the Kings, ending at 1400 psi with a 2% ES, with the first 52 shots within under a 1% ES (9 fps) ending at 1500 psi, which works out to 1.48 FPE/CI, over a 50% improvement.... I have gone from 4 solid magazine per fill to 6, without having to be at all concerned about the velocity dropping off, even with a 2900 psi fill, which is what I get with my Pony tank in the field.... The gun uses only 28 psi per 52 FPE shot....

Once again, I am astonished at the increase in shot count when operating on the knee of the curve by using the SSG.... As long as it has a gap to the hammer (this gun had 1 turn = 0.042"), the report is much quieter, just a clean SNAP, with no telltale BUURRRPPPP of hammer bounce.... Both of my Varmint rifles now have a 50% higher shot count than last year, 6 magazines instead of 4....

Bob

[Motorhead]

Nice !! .... it does seem the heavy hammer / bounce prone systems are seeing the largest improvement.
Likely as talked about previous, due to closing valve no longer carrying hammer along with it.

Outstanding results indeed !

[PakProtector]

On a Gen1 Marauder, you'll need to rest your thumb on the end of the bolt handle or risk the damage mentioned by Scott.

There is another spring energy sapping effect...you lose some of the spring mass kinetic energy as well. It looks like a 1/4" aluminum rod will do adequately for the spring holder. Thanks to Travis for showing the assembly with a nyloc/pem nut so there need only be one nut getting in on the spring energy division. Will need to counter hold the rod more tightly to set preload though...
cheers,
Douglas

[rsterne]

Douglas, I found that since I am retrofitting, and already know where the knee of the curve is, and therefore what velocity I am tuning for, I turn a shoulder on the back end of the rod (where the adjustment is in my case) and then use a single nut tightened against the shoulder.... I just sneak up on the required preload until I can get slightly more velocity than I want with a tiny gap, turning the shoulder a bit further down the guide at a time.... Most of the time you only need to vary the preload in increments of 0.1" (although the last adjustment sometimes I go half that).... Then all the final tuning is done with the gap adjustment only.... Once I find the tune I want, I cut the threaded end of the guide off flush with the nut, apply a drop of blue Loctite, and tighten the nut against the shoulder.... We'll see if it ever comes loose or sheds the nut over time....

Bob

[oldpro]

 With Bobs permission Ive been given the go ahead to build a run of Sterne SSG for the Mrod. Im working on a commercial Sterne SSG right now and should work out all the bugs and have a protective cap also incorporated so as to protect ones digits.

[cilami]

With Bobs permission Ive been given the go ahead to build a run of Sterne SSG for the Mrod. Im working on a commercial Sterne SSG right now and should work out all the bugs and have a protective cap also incorporated so as to protect ones digits.

What about a Sterne SSG for the Prod?

[PakProtector]

With Bobs permission Ive been given the go ahead to build a run of Sterne SSG for the Mrod. Im working on a commercial Sterne SSG right now and should work out all the bugs and have a protective cap also incorporated so as to protect ones digits.

It looks like for an attempt at maximum output a 3" spring can be used in the Gen1. Can your design accommodate such a thing? This with MSC #: 06812234
cheers,
Douglas

[oldpro]

Next on the list will be the Prod.