Looks like they (smartly) filed the patent just before discussing it publicly at Shot Show 2014.
Quote from: mikeyb on January 31, 2021, 06:42:12 AMLooks like they (smartly) filed the patent just before discussing it publicly at Shot Show 2014.Mike, thanks for digging that up! Thankfully the ideas I have in mind don’t infringe on their patents.Motörhead or anyone who wishes to chime in. What do you think is the probability of a manufacturer licensing a technology that is springer specific? I ask because I noticed that many high volume companies have moved their spring designs to gas-rams, yet despite their superior” characteristics many (not all) of these guns shoot like &^^&. I think my question boils down to if its worthwhile creating springer improvements for the mass market? I’m working on the provisional patent, but without giving too much away the idea I have is a feature that is not passive to the user like vibration reduction. Instead, it adds a level of customization that is equivalent to what you can do with some PCPs, without making mechanical changes to the gun.Are springers a dead technology vs. gas-ram and PCP in the eyes of the Gamo/Umarex/Crosmans of the world? -Marty
Watch carefully around the 1:00 minute mark.Nitro Piston 2 (NP2) tech with the piston head and piston body decoupled by a polymer bushing. In my simulations of normal springers I frequently see piston bounce and rebound which (theoretically) wastes significant energy and causes more severe secondary recoil events. I can't simulate this flexible bushing, but if it works like I think it does it's a GREAT IDEA!When the piston comes to a stop the first time on the high pressure pocket of air, the bushing gets compressed, expands radially and GRABS the compression chamber walls effectively acting like a momentary friction brake. This stops the piston from bouncing. No bounce means a lower second recoil event which is better for scope life AND accuracy since the pellet is still in the barrel for another ~2 milliseconds when the harsher bounce event would normally occur. No bounce also means longer duration higher pressure air to push the pellet and no hard piston slam on the empty* barrel after a piston returns from the bounce. *The pellet has usually exited the muzzle when the piston returns "home" after a bounce. At least it does in my simulations.
Quote from: mikeyb on January 31, 2021, 06:23:13 AMWatch carefully around the 1:00 minute mark.Nitro Piston 2 (NP2) tech with the piston head and piston body decoupled by a polymer bushing. In my simulations of normal springers I frequently see piston bounce and rebound which (theoretically) wastes significant energy and causes more severe secondary recoil events. I can't simulate this flexible bushing, but if it works like I think it does it's a GREAT IDEA!When the piston comes to a stop the first time on the high pressure pocket of air, the bushing gets compressed, expands radially and GRABS the compression chamber walls effectively acting like a momentary friction brake. This stops the piston from bouncing. No bounce means a lower second recoil event which is better for scope life AND accuracy since the pellet is still in the barrel for another ~2 milliseconds when the harsher bounce event would normally occur. No bounce also means longer duration higher pressure air to push the pellet and no hard piston slam on the empty* barrel after a piston returns from the bounce. *The pellet has usually exited the muzzle when the piston returns "home" after a bounce. At least it does in my simulations.Agree, it’s a very simple yet practical idea. I would add that the plasticity and gripping characteristics of the bushing would be very important. If the bushing starts compressing too easily just from the initial forward surge it would rob the gun of power before it slams the end of the chamber. On the opposite end the bushing needs to maintain its friction coefficient for the life of the gun, so I’m wondering how long it’s anti-bounce properties last given that it is subject to constant frictions on the recoil stroke. Probably wears out quickly...-Marty
A 95A durometer polyurethane bushing would be my guess. PUR is tough and I would expect it to work as designed at least as long as the synthetic piston seal and air/gas/coil spring. All of these are (or should be) user replaceable were-out items like brake pads & rotors on your car. Something like a minimum 5000 shots or 5 year "drive train warranty"?If my sim is accurate, the initial piston acceleration is on the order of 20 g's. Sounds high, but it really isn't. The "deceleration" sims out at least 20x that. Around 400 g's (or more) is a significant difference so I'm pretty confident the Crosman engineers chose the bushing durometer such that it squishes (that's a technical term ) very little on launch and squishes more than enough on impact to brake any rebound motion.
Quote from: mikeyb on January 31, 2021, 10:20:11 AMA 95A durometer polyurethane bushing would be my guess. PUR is tough and I would expect it to work as designed at least as long as the synthetic piston seal and air/gas/coil spring. All of these are (or should be) user replaceable were-out items like brake pads & rotors on your car. Something like a minimum 5000 shots or 5 year "drive train warranty"?If my sim is accurate, the initial piston acceleration is on the order of 20 g's. Sounds high, but it really isn't. The "deceleration" sims out at least 20x that. Around 400 g's (or more) is a significant difference so I'm pretty confident the Crosman engineers chose the bushing durometer such that it squishes (that's a technical term ) very little on launch and squishes more than enough on impact to brake any rebound motion.Mike, can the simulation software that you are using calculate the difference in acceleration characteristics between a spring and gas-ram, or springs made of different materials? I've always postulated that gas-rams have better acceleration than a solid spring, but I have not been able to prove it. Thanks.-Marty
Mike, I am so glad I asked you! I was not expecting the acceleration dynamics to be so different, but I guess that’s what I get for thinking in linear terms.Do you think that the gas-ram stroke dynamics might result in more of the compressed air being converted into plasma at the end of the stroke vs a springer?-Marty
Hmm...that's a pretty simple idea. Kind of makes me think of the dead blow hammers, except this one is elastic. As I started watching the video, I thought, "oh, the ram is backwards. What's special about that?" Then I saw what happened at the end of the cycle and it made sense. Unlike the vibration isolation problem for scopes (in another thread recently), this one is a tuning problem: get that spring rate correct and the rest of the mass can deliver the follow up without the typical shock of the cycle and probably a little more dwell, though possibly at a slightly lower peak pressure. In simulation, I too have seen about 20 g's as the sear releases and the huge spike on the bounce. It will be interesting to add this to my model. Michael, will you be able to add this feature to your model? (Do you have discussion of your model somewhere on the GTA? I'd like to read up on it.)
Quote from: MartyMcFly on January 31, 2021, 01:30:34 PMMike, I am so glad I asked you! I was not expecting the acceleration dynamics to be so different, but I guess that’s what I get for thinking in linear terms.Do you think that the gas-ram stroke dynamics might result in more of the compressed air being converted into plasma at the end of the stroke vs a springer?-MartyThere is no way that the compressed air in any spring piston air rifle is even close to a true plasma. Estimates of over 1000 degrees and 2000 psi are probably pretty close to reality, but that's still at least one or more orders of magnitude under what would be needed to create a true plasma state. Hot and luminescent yes, plasma no.Even though the spring force profiles are different, the overall piston travel times are pretty close. A couple hundred microseconds over about 10 milliseconds in my sim. Peak pressures can simulate higher for the air/gas spring action because of the different force profile, but this doesn't significantly change the pellet fpe at the muzzle. The end result is we have two slightly different ways to do the same work with no clear winner or loser. I'm starting to believe some of the high pressure numbers I've seen in my simulation. I've recovered shot pellets from a 200 bar PCP with crisp rifling marks and almost no skirt deformation (ballooning). Other pellets from the same tin shot from an air spring powered magnum break barrel (slightly LESS fpe than the PCP) had significant skirt ballooning and much deeper skirt rifling imprints. That makes me think some of the 4000+ psi peak sim values I dismissed may not be simulation errors.I had experienced tuning coil spring rifles to shoot almost (~98%) as smoothly as equivalent power air/gas spring rifles well before trying the computer simulation. The simulation was an attempt to understand the underlying physics differences between coil and gas springs in the hope I could identify and take advantage of one or more unique characteristics to make a significant tuning improvement. So far the sim has helped me understand why my actual hands-on-tuning and shooting differences between the two springs is nowhere near as large as advertised.
... I believe that we might be attributing too much importance to vibration reduction as the major characteristic that gives PCPs better accuracy and too little to altered pellet ballistics from malformed pellet skirts.I have not run a controlled experiment but I have some rifles that shoot hard alloy pellets more accurately than they shoot soft pellets. Initially I had thought that the alloy pellets had better tolerances and fewer deformations, but after close inspection I am starting to believe that it’s the skirt deformation that is contributing significantly to subpar accuracy in springers relative to PCPs. I would wager a guess that in a well tuned springer the vibrations are reduced enough and the time in barrel is so short that skirt deformation becomes the predominant driver of accuracy (keeping all else equal)....-Marty
Here's a interesting article by Hector.https://www.ctcustomairguns.com/hectors-airgun-blog/category/tests
By the time the piston reaches the end of the compression stroke, the pressure inside the compression chamber can be as high as 3,000 PSI’s and the TEMPERATURE can reach up to 2-3,000 F. Ideally, this set of conditions turn the air into a plasma and this plasma has very little internal friction (viscosity), so that it can flow through the transfer port and into the chamber.
Advertise Here
Share This!