Can pellets be too heavy for a springer?

[HectorMedina]

In a word: Oscillation. Seems like we want to minimize that as much as possible.
Yeah?

Yeah!

Problem with a short answer like "oscillations" is that oscillations are present in many devices and they do not break things. It is the peculiar slenderness ratio of the airgun mainspring that creates oscillations that go from one sense to the opposite. And that gets exaggerated with heavy pellets.

But in a nutshell, you are right, reducing the bucking, bouncing and the buzz (the "sproing" and the twang) in an airgun IS desireable. That is why experienced shooters and gunsmiths will always tell you to LISTEN to your airgun.

Thanks!






Héctor

[HectorMedina]

Hector-are heavy pellets less far down the barrel than light pellets when the piston slams down- 9.6/1000 sec in one of those papers?If they are them the "back pressure" would be higher-which would help slam the piston back up
Thanks
Charlie

That is my understanding, Charlie.

And it all starts from a slower cycle that ends in a lower MV.

Most models yield a result that pellets require pretty much the same energy to get engraved, upset, and started in their trip, but IMHE, heavy pellets are slower FROM THE START, and therefore, they are closer to the breech when the pressure starts building to the point where piston bounce back can occur.

Thanks for your insights!




Hector

[Buldawg76]

Thanks, Mike! Just a note, I PREFERRED Ducatis, that was 44 years ago, good memories, but long gone and no interest in getting them back.

Great data and I am very glad that you humoured me, thanks again!

Yes, you are absolutely right, the main difference is in the length; and length brings mass/weight and the chance for a longitudinal wave to settle itself into the operation cycle. Without the length (to diameter), there is no way a spring can experience bounce back.

You are also right that the AVERAGE stress in an engine valve spring is higher than in an airgun spring, BUT, all the stresses in the valve springs go in the same direction, whereas in the airgun spring the stresses even change signs and, for sections of the spring (the beginning and the end), the stresses go from a positive value to the same value but in the opposite direction.
You are probably aware that the overall stress is the mean (average) stress, plus the stress excursion. It is these extreme stress excursions that increase the overall stress in an airgun mainspring to levels that engine valve springs will never experience.

What you refer as the loose guide case is only a matter of degree. Even the tightest guides cannot completely eliminate the longitudinal waves that can settle into long (and unguided for half of their lengths) airgun mainsprings. Here we come to an interesting opportunity: To my knowledge, no one has come up with an outside guide that comes from the piston and extends backwards. If someone was to make an "outside" guide that was sort of a huge top-hat, and that would come back from the piston and engage up to the half of the spring that is unsupported by the inside (rear) guide, we MIGHT have found something that is not only interesting, but useful. The rear guide would provide friction and dampening to the rear section of the spring from the inside, but the forward guide would provide support and friction to the spring from the outside.

What I personally find interesting about Beehive springs is not their external geometry, but their (purported?) egg-shaped sectioned wire. The three dimensional analysis of the dynamic spring stresses gets really complicated, but an egg-shaped section clearly minimizes the stresses on the ID of the spring, while maximizing the resistance on the OD of the spring. Can you tell me if what I understand from them is real? (that the section of the wire they use is eggshaped?)

Square sectioned wire has been tried and it has its own problems, the only way I can see of using advantageously square sectioned wire would be to use a three layered steel ribbon to make those springs and that is going to be hard to test or even try.

Few people realize that airguns have more in common with internal combustion engines than with firearms. So this thread has been a lesson to all (me included).

THANKS!

Hector
Once a biker always a biker even if you don't ride anymore.

Agreed that due to the huge difference in lengths of spring between air guns and engines the stresses are far different and an engines spring likely will never see the bounce back that air gun spring experience except during valve float as mentioned before since when a valve floats the spring has lost all control over the valve and is behaving exactly like one in an air gun that has just been fired and is why they either break or the valve hits the piston if its is what's known as an interference engine ( there is not enough clearance for the valve to be fully open with the piston at top dead center ) hence the valve and piston collide with each other.

Your idea of a piston mounted outer spring guide is indeed intriguing and would likely subdue much if not all of the springs erratic behaviors in the gun when fired, but is the Vortek outer guides that are part of the rear inner guides basically doing the same thing just from the other end of the spring or would a dual outer guide system be even better such as the rear outer Vortek guide as well as an internal piston guide that precisely fits over the outer rear guide so that the spring is contained fully thru its entire firing cycle. That should all but eliminate any bounce back or collision of coils when fired since the spring would unable to move in any direction but longitudinal along the actions tube and guides axis.

The beehive springs that Harley uses are still round wire coils with just a decreasing diameter at one end. Not sure if when you refer to egg shaped wire you mean the actual wire profile as being egg shaped versus round wire like air gun spring are now or just referring to the decreasing diameter of the coils. But if referring to actual egg shaped wire I have never seen such a spring or if I have did not notice the wires profile close enough, but I am certain that Harley beehive springs are a round wire of decreasing diameter.

I know that older GM performance engines such as vette motors and Z28s, GTOs etc used a flat ribbon style inner coil spring that was placed inside the outer round wire coiled valve springs as well as being counter wound to the outer spring to help dampen oscillations at higher rpm as well as control valve float in them so those are not without merit either. Metallurgy has grown by leaps and bounds since then so valve spring breakage in engines has also been significantly reduced since the 60s and 70s.

Yes there are far more similarities between the two style springs than most realize and is why I brought it up as well there are difference also. If we are learning as I know I am then we are making progress even if it only baby steps.

Mike







Héctor
[/quote]

[phoebeisis]

Hector-
thanks for your quick answer-so heavier  pellets cause more bounce back than lighter pellets-because the pressure in the barrel is higher when the piston slams down- because the barrel volume under the pellets is less with the heavier pellet- so more pressure means more bounce back-
 causing  more "weird" backward compressions-and this breaks springs probably for the same reason valve float broke springs in the "old days" hence the pretty complicated but pretty cool Ducati solution-
heah-why couldn't air guns "catch" the piston(in a way like ducati) and PREVENT it from bouncing-control its motion-lock it forward?


No wonder one of those papers suggests  spring guides to prolong spring life  (guessing those guides scrape off-friction-some of the "bad rebound" energy-or at least keep is linear-not much wobble up and down)

A question
1)-does my RWS 460 have a guide??($360 new)-looking at diagram seems to show an inner guide-and hard to tell but maybe the piston is hollow-and acts as an outer guide??

Mike-I still find it hard to believe that 5000 cycle life-when motor valve springs get 1 BILLION- couldn't be "price" solved-
your 40 year old Kawasaki-10,000 RPM- maybe 80 per second(guessing those aren't the OEM springs-or tops-)-
But hector assures us air gun springs are equal in quality to pricy car springs-
and that makes sense since even pricy car springs-pricy brands and fast cars-are CHEAP
5000 cycles vs 1 BILLION- a violent 1 BILLION cycles-all because of a little bounce/float

Hey you guys  much have watched that history channel Tacoma Narrows bridge failure-I don't know how much resonance you can get in 20/1000 second-all those back and forth compressions-(but less and less not like Tacoma bridge?)
but 5000 cycles-YIKES!
Never would have guessed 5000 cycles!

[Buldawg76]

Charles
Your RWS 460 does have an inner guide of sorts that is likely a fairly loose fit inside the rear of the spring and you are correct in that the piston is hollow where the spring seats at the front of the piston so it acts as a very loose guide as well does the receiver's tube also but the problem is none of those part are a tight enough tolerance to truly control the spring movement to just a longitudinal direction and is why you likely hear some spring twang or buzz when fired.

The reason of why not is money and labor to hand fit every spring and guides to precise fits so that each gun would be blueprinted so to speak. It can be done but then that 360 buck gun would be 8 to 900 bucks not that those are much if any better. I had a friend who bought a FWB sporter new for 900 bucks and when he got it the barrel was bent so bad you could not see the muzzle end when looking thru the breech with the gun cocked. he did not want to send it back so a picnic bench seat 2x4s with the barrel stuck between them and some leverage and it was straight as could be .

Guides are indeed good but no pricey air rifles have guides of the proper diameters to do the correct job required as it is just not cost effective in today market place and I would say Daina ,FWB, HW, and other very high end spring gun makers are pretty much the same in quality of the guides and spring they use as its all about profits and sales.

IMO nothing today is made with the same pride or quality as it was 30 or 40 years ago when we actually cared about what we made and sold and not how much money or profit we could make.

Mike

[phoebeisis]

Mike- thanks for your answer
so my 460 has guides-but they are too crude/loose to be extremely effective
 and Hand fitting-no way
What do German workers make
$40 plus maybe another $20 in benefits- figure another $60-$100 per rifle? for perhaps double the life of a $20 part-that will last years for most folks(hector is right-most air rifles-just sit
You are  right -far less hand fitting type care-
not on a mass produced rifle from Germany that delivered cost me just $360-
RWS probably sold it for just $250-or less-
can't do hand fitting on a mass produced product
Having to compete with the "good enough" very cheap labor  barely adequate QC guns produced in China
means there aren't many-any-hand fitted firearms

China-and the cheap stuff syndrome-oh well-
but china is riding for a fall-adulterating baby milk-selling FAKE anticoagulants-BIG manufacturers doing this- and their HUGE masses of people being urinated on by their elites-
manufacturing will come home-USA wages are down-and china products are rising in price as their wages rise(to prevent another civil war)-and their managed economy-filled with fake numbers-
Glad I don't live in china-
old chinese curse  "may you live in interesting times" 
safe bet they are riding for a fall-not unlike Japan in the 1980's

[Buldawg76]

Charles
With you 100% and only hope we can hold on till they fall as we are also in that never ending spiral like you see at the malls where you put a coin in the top of a funnel and watch it slowly spiral down into the abyss never to be seen again.
Its a &^^& shoot now just to see who falls first.

Mike

[Back_Roads]

 Ok after reading all of this , I miss my slinky , muscle cars and widow makers , but will accept the shortened spring life to get the down range energy and accuracy in wind and range using heavier pellets.
 I do watch how heavy of pellet I use , one can hear it in the spring when it is pushing its limit.
 On an interesting note , I was breaking in a new .177 springer , had about 10 CP 10.5 through it, with fairly little dieseling, grabbed a stray 8 gr polymag, shot it and had a 5 yard vapor trail and sonic/explosive crack. Seems the heavier pellets were reducing the initial amount of break in dieseling. I did try other lighter pellets and had similar results.

[Buldawg76]

Sounds more like a sonic crack from the pellet breaking the sound barrier to me. I only shoot JSB 10.34s in all my 177s including my 2 FWB 300s that shoot them at 575 fps but are deadly accurate out to 55 yards also with them.

Mike

[DOKF]

Designs using gas rams were an effort to improve on the coil springs.

I personally prefer the gas rams, but may be in the minority.


.

Kim;

Gas Struts/Springs (non adjustable) and Gas Rams (adjustable) have been, up to now, a technology in progress. From the air filled Menaldi in Argentina, then the Theoben that copied the principle, then the Nitro Pistons and Vortek units, they have been inefficient (you need to use 45# of cocking force to get 18 ft-lbs back at the muzzle), unreliable (I once went to a Match with a gas strutted rifle, placed at the top of the pack the first day only to discover that the strut had leaked overnight and that I had no operable gun for the second day of the Match), impossible to repair (once a strut leaks, you have to throw it away, and if it is a ram, the process of setting up the fill pressure is so complicated that you need to do it standing next to a Chrono).

I have faith in the technology for the future and I am in fact awaiting a set of N-Tec piston and trigger units to test on a Diana 54, we'll see when the technology really matures and starts offering what simple steel coil springs offer.

 

Will keep you all posted.

Hector

Unfortunate that the technology didn't work for you.  It works well, and reliably for me, but not that I am a target match shooter.

I find the NP pistons easier to cock in my magnum rifles compared to my similarly rated conventional springs guns.  Plus, the pressurized gas is not prone to the same harmonics as mechanical springs, not to mention the twisting and flexing inherent in the coil design.

And the cartridge design makes replacement so much easier for gas rams as compared to coil springs.  No need for spring guides or damping tar.

Head to head comparison; I'll choose my Benjamin NP XL over my Hat Pat any day, and even my NP2 over the 350 purely for the ease of shooting cycle.  Similar powers, but the rams are lighter, better balanced, and easier to shoot.

My 460 may still be my most accurate shooter out to 30 m, but this probably more due to its general workmanship than its spring.  I would love to see a 460 equipped with a gas ram instead of the spring; I can't help but think it would be an even better shooter for reduced twang and noise, and with a smoother shot cycle.

JMHO  Your results may vary.


.

[phoebeisis]

DOKF/Kim
.
Your icon-WORLDS CUTEST PUPPY!
Bullawg  Death Motorcycle club-in BLACK- not remotely cute
BackRoads has a suitable for Faluga sniper looking rifle-
Hector is shooting-veiled warning maybe
Versus World's Cutest Puppy
How could anyone get snarky and disagree with you-NOT FAIR

But I have to agree on the 460-got mine 4 weeks ago-ran one dry swab down the barrel-
and it was more accurate than I can shoot-right out of the box
A question-I ONLY shoot in my hallway- 10 meters if I stand in the front room
It doesn't seem noisy-and I'm old-and sensitive to noise.
Are these air rifles  seemingly LOUDER outside??

[Buldawg76]

DOKF/Kim
.
Your icon-WORLDS CUTEST PUPPY!
Bullawg  Death Motorcycle club-in BLACK- not remotely cute
BackRoads has a suitable for Faluga sniper looking rifle-
Hector is shooting-veiled warning maybe
Versus World's Cutest Puppy
How could anyone get snarky and disagree with you-NOT FAIR

But I have to agree on the 460-got mine 4 weeks ago-ran one dry swab down the barrel-
and it was more accurate than I can shoot-right out of the box
A question-I ONLY shoot in my hallway- 10 meters if I stand in the front room
It doesn't seem noisy-and I'm old-and sensitive to noise.
Are these air rifles  seemingly LOUDER outside??

Charles
You ever see the movie Harley- Davidson and the Marlboro Man with Don Johnson and Mickey Rourke, well the bike that Don Johnson rode was made by the now defunct bike builders with that logo and it was a 1994 Harley FXR with that exact logo painted on a raw steel tank. the FXR was the best handling bike Harley ever made not that they made any good handling bikes.

It has to do with my other motto of never ride faster than your angels can fly since I have had many incidents on dirt and street bikes that if my angels were not with me I would not still be here so it has significance to me.

Mike

[Buldawg76]

Designs using gas rams were an effort to improve on the coil springs.

I personally prefer the gas rams, but may be in the minority.


.

Kim;

Gas Struts/Springs (non adjustable) and Gas Rams (adjustable) have been, up to now, a technology in progress. From the air filled Menaldi in Argentina, then the Theoben that copied the principle, then the Nitro Pistons and Vortek units, they have been inefficient (you need to use 45# of cocking force to get 18 ft-lbs back at the muzzle), unreliable (I once went to a Match with a gas strutted rifle, placed at the top of the pack the first day only to discover that the strut had leaked overnight and that I had no operable gun for the second day of the Match), impossible to repair (once a strut leaks, you have to throw it away, and if it is a ram, the process of setting up the fill pressure is so complicated that you need to do it standing next to a Chrono).

I have faith in the technology for the future and I am in fact awaiting a set of N-Tec piston and trigger units to test on a Diana 54, we'll see when the technology really matures and starts offering what simple steel coil springs offer.

 

Will keep you all posted.

Hector

Unfortunate that the technology didn't work for you.  It works well, and reliably for me, but not that I am a target match shooter.

I find the NP pistons easier to cock in my magnum rifles compared to my similarly rated conventional springs guns.  Plus, the pressurized gas is not prone to the same harmonics as mechanical springs, not to mention the twisting and flexing inherent in the coil design.

And the cartridge design makes replacement so much easier for gas rams as compared to coil springs.  No need for spring guides or damping tar.

Head to head comparison; I'll choose my Benjamin NP XL over my Hat Pat any day, and even my NP2 over the 350 purely for the ease of shooting cycle.  Similar powers, but the rams are lighter, better balanced, and easier to shoot.

My 460 may still be my most accurate shooter out to 30 m, but this probably more due to its general workmanship than its spring.  I would love to see a 460 equipped with a gas ram instead of the spring; I can't help but think it would be an even better shooter for reduced twang and noise, and with a smoother shot cycle.

JMHO  Your results may vary.


.

Kim
Do you know that Hatsan Vortex rams are actually a recreation of the old Theoben ram in that they can be depressurized and are filled with HPA air not nitrogen or other inert gases. You use the same fill fitting probe that you use to fill their PCP guns so they have a release screw and a fill port and the one I have that will eventually find its way into a B-19 clone called a Firepower FP-1 states on the side of it to not exceed 125 BAR pressure, but my point is that the pressure in them can be fine tuned to each person needs and desires.

Mike

[DOKF]

Charles,

My springers (HatPat, 350, 460) are all noticeably loud for my neighbours, thus too loud.  My NPXL, NV, and NP2 rifles are all much quieter, and don't seem to draw attention from the neighbours. 

I am trying hard to avoid the fate of another member who ran afoul of the neighbours ...

I don't think they are any louder outside, but hard for me to compare as it displeases the wife when I shoot indoors.  ;-(

[DOKF]

Mike,

My Hat Pat is a traditional spring, not a ram.  It might be worth a try to put a ram in it; could tame the beast without losing too much useful power.

In the meantime, I just use it out in the country far from prying ears.  Still fun to play with.

.

[HectorMedina]

Hector
Once a biker always a biker even if you don't ride anymore.

Agreed that due to the huge difference in lengths of spring between air guns and engines the stresses are far different and an engines spring likely will never see the bounce back that air gun spring experience except during valve float as mentioned before since when a valve floats the spring has lost all control over the valve and is behaving exactly like one in an air gun that has just been fired and is why they either break or the valve hits the piston if its is what's known as an interference engine ( there is not enough clearance for the valve to be fully open with the piston at top dead center ) hence the valve and piston collide with each other.

Your idea of a piston mounted outer spring guide is indeed intriguing and would likely subdue much if not all of the springs erratic behaviors in the gun when fired, but is the Vortek outer guides that are part of the rear inner guides basically doing the same thing just from the other end of the spring or would a dual outer guide system be even better such as the rear outer Vortek guide as well as an internal piston guide that precisely fits over the outer rear guide so that the spring is contained fully thru its entire firing cycle. That should all but eliminate any bounce back or collision of coils when fired since the spring would unable to move in any direction but longitudinal along the actions tube and guides axis.

The beehive springs that Harley uses are still round wire coils with just a decreasing diameter at one end. Not sure if when you refer to egg shaped wire you mean the actual wire profile as being egg shaped versus round wire like air gun spring are now or just referring to the decreasing diameter of the coils. But if referring to actual egg shaped wire I have never seen such a spring or if I have did not notice the wires profile close enough, but I am certain that Harley beehive springs are a round wire of decreasing diameter.

I know that older GM performance engines such as vette motors and Z28s, GTOs etc used a flat ribbon style inner coil spring that was placed inside the outer round wire coiled valve springs as well as being counter wound to the outer spring to help dampen oscillations at higher rpm as well as control valve float in them so those are not without merit either. Metallurgy has grown by leaps and bounds since then so valve spring breakage in engines has also been significantly reduced since the 60s and 70s.

Yes there are far more similarities between the two style springs than most realize and is why I brought it up as well there are difference also. If we are learning as I know I am then we are making progress even if it only baby steps.

Mike

Thanks, Mike!

The current Vortek PG-2 systems use an inner guide (very normal), and an outer guide (so far, only Vortek uses it). BUT they are both at the rear, as you know.

What I am envisioning is a system that would "encase" the spring. On the inside from the rear, and on the outside from the front. MOST systems nowadays use a TopHat (an inheritance of the die and stamping industry). But if the TopHat was extended backwards to surround the spring, we could have a system that is not piston mounted (you do not really want to alter the weight of the piston), but that works as BOTH the TopHat AND the outside guide.

In the common systems, the fore section of the spring is completely unsupported, both on the inside and on the outside and, while this will prevent the breakage of the rear section of the spring (most common), it will not prevent all the havoc in the fore section of the spring.

Problem with this development is the wide variability of inside dimensions on OEM pistons. But it is an idea that merits more thought and, perhaps some development.

The other areas that I have already researched into and created solutions are the weight of the piston, securing the spring to the piston, and reducing the piston's tendency to bounce by making the compression chamber walls "grip" the piston.

Last thing that I think is important to say is that the S-N curves of metal fatigue are linear on a logarithmic scale. That means that for every little problem we solve, we can gain one order of magnitude of life cycles. Conversely, every degree of freedom we allow to the spring's "flailing" reduces the life of the spring by an order of magnitude.
A spring that, if it was short, and contained, and had no bounceback, and . . . would last hundreds of millions of cycles, when given all the freedoms that exist in an airgun, reduces its life to mere thousands.

Anyway, thanks again for the discussion!





Hector

[HectorMedina]

Hector-
thanks for your quick answer-so heavier  pellets cause more bounce back than lighter pellets-because the pressure in the barrel is higher when the piston slams down- because the barrel volume under the pellets is less with the heavier pellet- so more pressure means more bounce back-
 causing  more "weird" backward compressions-and this breaks springs probably for the same reason valve float broke springs in the "old days" hence the pretty complicated but pretty cool Ducati solution-
heah-why couldn't air guns "catch" the piston(in a way like ducati) and PREVENT it from bouncing-control its motion-lock it forward?


No wonder one of those papers suggests  spring guides to prolong spring life  (guessing those guides scrape off-friction-some of the "bad rebound" energy-or at least keep is linear-not much wobble up and down)

A question
1)-does my RWS 460 have a guide??($360 new)-looking at diagram seems to show an inner guide-and hard to tell but maybe the piston is hollow-and acts as an outer guide??

Mike-I still find it hard to believe that 5000 cycle life-when motor valve springs get 1 BILLION- couldn't be "price" solved-
your 40 year old Kawasaki-10,000 RPM- maybe 80 per second(guessing those aren't the OEM springs-or tops-)-
But hector assures us air gun springs are equal in quality to pricy car springs-
and that makes sense since even pricy car springs-pricy brands and fast cars-are CHEAP
5000 cycles vs 1 BILLION- a violent 1 BILLION cycles-all because of a little bounce/float

Hey you guys  much have watched that history channel Tacoma Narrows bridge failure-I don't know how much resonance you can get in 20/1000 second-all those back and forth compressions-(but less and less not like Tacoma bridge?)
but 5000 cycles-YIKES!
Never would have guessed 5000 cycles!

Charlie;

You are absolutely right. Someone should do something to "catch the piston", and I have done a few things when someone asks me to create a gun for heavy pellets, specially in the Diana sliding compression chamber full size family (48, 52, 54, 460, 56, & 470):
For one I use a heavier piston. The reason should be clear by now: if the mass of the pellet creates inertia that creates bounceback, an increase in the mass of the piston RESISTS better that bounceback.
Secondly, I use an Integral TopHat in my pistons. This "grips" the spring and makes the spring and the piston one unit.  Again, this adds mass to the piston, but also avoids the condition where a longitudinal wave travelling in the spring can "separate" the spring's face from the piston (the spring bouncing back independent of the piston because the spring is lighter and can move faster).
Thirdly, the architecture of the ORing seal creates an expansion of the ORing if the piston tries to move back with any real speed, therefore "gripping" the walls of the compression chamber. In the mathematical model this would be like increasing the friction of the piston to the compression chamber ONLY at the end of the compression cycle.

With the new ideas that came out of this discussion, I think I will try a sleeve inside the piston to act as an outside guide to the spring. Of course that will limit me to use either Titan or Maccari springs, as a sleeve tight enough to really contain the spring would interfere with PG-2 kits, but both remaining springs are good quality anyway.

Yes your 460 has an OEM guide. Inside guide. It is somewhat loose to get the most power out of the platform, but do not worry, if / when your OEM spring breaks, you have several choices: You can use a Vortek made OEM-substituting spring. Those are designed to be a tighter fit to the OEM guides. You can replace the whole assembly with a Vortek K Yield kit, a Maccari ZRT kit, or have  a custom guide made for the Maccari Monolith spring. You can also get a Titan # 14 spring and make a custom guide.
You have choices, from $19 to $200.

What were you saying about "how fa$t you want your bike to go?"

Keep well and thanks!





Héctor

[HectorMedina]

Unfortunate that the technology didn't work for you.  It works well, and reliably for me, but not that I am a target match shooter.

I find the NP pistons easier to cock in my magnum rifles compared to my similarly rated conventional springs guns.  Plus, the pressurized gas is not prone to the same harmonics as mechanical springs, not to mention the twisting and flexing inherent in the coil design.

And the cartridge design makes replacement so much easier for gas rams as compared to coil springs.  No need for spring guides or damping tar.

Head to head comparison; I'll choose my Benjamin NP XL over my Hat Pat any day, and even my NP2 over the 350 purely for the ease of shooting cycle.  Similar powers, but the rams are lighter, better balanced, and easier to shoot.

My 460 may still be my most accurate shooter out to 30 m, but this probably more due to its general workmanship than its spring.  I would love to see a 460 equipped with a gas ram instead of the spring; I can't help but think it would be an even better shooter for reduced twang and noise, and with a smoother shot cycle.

JMHO  Your results may vary.


.

As I said, Kim I still have hope in the technology. In a couple of months or so I should receive the parts from Germany to changeover a 48 to an N-Tec 48, I would love to use the solution in the 54, but to judge differences the 48 seems a better platform; we'll see then how things TRULY compare.

Depending on how that works, changing from a coil spring to an N-Tec powerplant should be a question of a change of piston and trigger, something that should cost around $200 at most. Is this worth it? I don't know, but the great advantage of the Diana line is that most new technologies are completely retro-fittable into older guns.

So, stay tuned!

;-)

Keep well and shoot straight






Hector Medina

[Buldawg76]

Thanks, Mike!

The current Vortek PG-2 systems use an inner guide (very normal), and an outer guide (so far, only Vortek uses it). BUT they are both at the rear, as you know.

What I am envisioning is a system that would "encase" the spring. On the inside from the rear, and on the outside from the front. MOST systems nowadays use a TopHat (an inheritance of the die and stamping industry). But if the TopHat was extended backwards to surround the spring, we could have a system that is not piston mounted (you do not really want to alter the weight of the piston), but that works as BOTH the TopHat AND the outside guide.

In the common systems, the fore section of the spring is completely unsupported, both on the inside and on the outside and, while this will prevent the breakage of the rear section of the spring (most common), it will not prevent all the havoc in the fore section of the spring.

Problem with this development is the wide variability of inside dimensions on OEM pistons. But it is an idea that merits more thought and, perhaps some development.

The other areas that I have already researched into and created solutions are the weight of the piston, securing the spring to the piston, and reducing the piston's tendency to bounce by making the compression chamber walls "grip" the piston.

Last thing that I think is important to say is that the S-N curves of metal fatigue are linear on a logarithmic scale. That means that for every little problem we solve, we can gain one order of magnitude of life cycles. Conversely, every degree of freedom we allow to the spring's "flailing" reduces the life of the spring by an order of magnitude.
A spring that, if it was short, and contained, and had no bounceback, and . . . would last hundreds of millions of cycles, when given all the freedoms that exist in an airgun, reduces its life to mere thousands.

Anyway, thanks again for the discussion!





Hector
[/quote]

Hector
I wonder if a Vortek kit could possibly be modified to use the rear outer spring guide in front around the spring inside the piston as you are suggesting with a top hat made so that it would be a tight enough fit in the forward end of the Vortek guide and spring to do as you have suggested by locking the top hat and guide to the front of the spring. Since the Vortek outer guides fit the spring for the gun they are intended for quite well and are designed to go into the piston when cocked I believe for the most part it would only require some minor machining to the guide to make it fit on the other end of the spring and reside at the front of the spring not the rear and could have the hole for the top hat machined to a snug fit on the top hat so it would all be basically one piece.

Once assembled onto the front of the spring it would be mostly a single unit of spring, guide and top hat as a locked together unit.

I am also very interested in your experiment with the n-TEC ram in the D48 platform since I have one and with a Vortek kit in it and even though its a soft tune kit it is still a scope breaker and has killed two Hawke varmint scopes to date. The SF adjustments goes out of calibration to the point that at one time it will show the correct yardage for the actual distance shooting and then after that shot it will be blurry and when adjusted will read up to 50 yards different and back and forth from there with every shot. Hawke has been very good about replacing them but I would like to be able to shoot it with out playing musical scopes.

Mike

[HectorMedina]

Hector
I wonder if a Vortek kit could possibly be modified to use the rear outer spring guide in front around the spring inside the piston as you are suggesting with a top hat made so that it would be a tight enough fit in the forward end of the Vortek guide and spring to do as you have suggested by locking the top hat and guide to the front of the spring. Since the Vortek outer guides fit the spring for the gun they are intended for quite well and are designed to go into the piston when cocked I believe for the most part it would only require some minor machining to the guide to make it fit on the other end of the spring and reside at the front of the spring not the rear and could have the hole for the top hat machined to a snug fit on the top hat so it would all be basically one piece.

Once assembled onto the front of the spring it would be mostly a single unit of spring, guide and top hat as a locked together unit.

I am also very interested in your experiment with the n-TEC ram in the D48 platform since I have one and with a Vortek kit in it and even though its a soft tune kit it is still a scope breaker and has killed two Hawke varmint scopes to date. The SF adjustments goes out of calibration to the point that at one time it will show the correct yardage for the actual distance shooting and then after that shot it will be blurry and when adjusted will read up to 50 yards different and back and forth from there with every shot. Hawke has been very good about replacing them but I would like to be able to shoot it with out playing musical scopes.

Mike

Hiya Mike!

Vortek uses a number of washers inside the outside guide (he, that sounded funny!), one of them is steel (to allow the spring to turn), the other is an elastomer. These two washers contribute SIGNIFICANTLY to the smoothness of the Vortek kits.
Getting the spring to "grab" the piston when the rear Vortek guide lip has been machined off may be complicated, but you are right, let me look into it.
IF the piston can be grabbed by the spring (as in my current HMO pistons), then there really is no need for a top hat. The Top Hat's MAIN job is to center the spring on the piston stem and therefore impede the springs from developing a bent.
The OTHER role of the TopHat is to create a vaccuum between spring and piston if the spring wants to bounce back independently of the piston (as I usually do with the Walthers). This, while not "grabbing" the piston as in a mechanical fit, still reduces noticeably the bounceback, and therefore, will prevent breakages.

BTW, Titan (UK) springs are wound in such a way that the OUTSIDE of the spring is a close fit to the inside of the piston. I MAY try the Beehive egg-shaped ends (now that you explained to me what they are) and see if there is any advantage. Since the wire diameter is pretty much what we use here, the inside guides are HUGE, but those are stationary, so they do not contribute to the general entropy/havoc of the system.

I gave up on Hawke scopes a LONG time ago. I have not tested their AG SF models, those should be much better prepared for the 48 than their Varmint line. Perhaps youy should think about upgrading to one of them next time you have a chance  (  http://www.hawkeoptics.com/airmax-30-sf-riflescopes.html )  .

USUALLY. MOST of the time, when a gun kills scopes (D54 excepted), it is the seals the ones you should inspect first. The D48 is a powerhouse, but it should not kill (especially with a soft tune) Air Gun rated scopes. Reason is simple: even with an artillery hold, the weight of the system resisting recoil is the gun+scope+torso+arms and hands, this is a much greater weight than in the 54, where only the action and the scope are resisting the recoil. The proportion is about 10 to 1.
IF the seals are not right or if the timing of the gun is not right, whether gas spring/strut/ram or metal spring will kill the scopes regardless of whether they are airgun rated or not.

JMHE

I'll keep you all informed.

Keep well and shoot straight!





Héctor