I KNEW this would make my head hurt!
We just added a plenum to my daystate wolverine 303 bottle gun. It is roughly a 100 fpe gun.Stock the gun shot 50 grain jsb at 930 fps. After the plenum of 100 cc and reg set to 2600 my gun shot 50 grain at 900 fps. I was hoping for no loss of fps.I only on my phone next few days so I not going to compute all this but if this formula works I will definitely make it into a spreadsheet when I get home.
I see Matt gave me credit for some numbers he used, but they are actually the maximum FPE obtainable per 100 psi drop in a plenum, per cc of HPA, assuming 100% pure Adiabatic expansion of the gas in that plenum.... I have no idea where Matt got the rest of his formula, or the basis behind it.... When I present something like a "Recommended Plenum Calculation", I would try and explain how I developed it... ie I try and "show my work" like my math teachers always insisted.... Since that hasn't been done here, I have no way of knowing the basis for Matt's formula, the limitations of it, nor it's reliability.... I'm not saying it works or it doesn't.... but please don't assume that because I gave him some numbers (for what he keeps telling me is a totally unrelated subject, yet he uses them).... that I endorse this method or not.... He has covered any potential arguments by stating that his "fudge factor" may have to be altered.... His method may be right or may be wrong.... I don't know how he developed it, so I am not qualified to comment on it.... However, please don't credit me.... or blame me.... for the results you get by using it.... I have nothing to do with it....Bob
Quote from: rsterne on June 21, 2017, 11:41:18 PMI see Matt gave me credit for some numbers he used, but they are actually the maximum FPE obtainable per 100 psi drop in a plenum, per cc of HPA, assuming 100% pure Adiabatic expansion of the gas in that plenum.... I have no idea where Matt got the rest of his formula, or the basis behind it.... When I present something like a "Recommended Plenum Calculation", I would try and explain how I developed it... ie I try and "show my work" like my math teachers always insisted.... Since that hasn't been done here, I have no way of knowing the basis for Matt's formula, the limitations of it, nor it's reliability.... I'm not saying it works or it doesn't.... but please don't assume that because I gave him some numbers (for what he keeps telling me is a totally unrelated subject, yet he uses them).... that I endorse this method or not.... He has covered any potential arguments by stating that his "fudge factor" may have to be altered.... His method may be right or may be wrong.... I don't know how he developed it, so I am not qualified to comment on it.... However, please don't credit me.... or blame me.... for the results you get by using it.... I have nothing to do with it....BobNot sure why you have it out for me and I was tempted to make it clear that you don't endorse the idea or subscribe to the beliefs that I do in terms of the numbers provided, but I was certain you would. I am not assuming Adiabatic expansion is all that occurs in an Air Rifle by using these numbers, I cannot stress that enough... Fudge factors are needed in our theories of pcp's Bob as you are very familiar with them if I understand correctly, even Lloyd's internal ballistic spreadsheet uses a fudge factor? I am not trying to avoid argument's, but the reality is there is no need to argue, I am always open for intelligent discussion and I am just publishing a method that worked for me, and I made that VERY clear. I also look forward to hearing people post their results (ie plenum + power level + caliber) so I can fine tune my formula as again I was very clear that I do not have the arsenal of air rifles to do so myself...I made my self very clear and concise because I knew someone like yourself would look for ANY possible way to disagree or argue my current findings which are simply a work in progress...-Matt
I am looking for any advice on opening up the transfer port on the Wolverine if anyone knows how. Barrel no problem, I am wondering about the block.Here is what my gun looks like with a plenum addedhttps://www.gatewaytoairguns.org/GTA/index.php?topic=128202.0
With the proliferation of regulators that vent through the gauge hole, the plenum for the most part is a "fixed" variable. With the older ones, drilling the vent hole in the correct location, made plenum calculation much more important. The psi setting is the main variable for most users today. Is your formula based on the results that you had with your 25 cal? How is the porting tied to the formula? ie my 25 cal Mrod would not achieve your power levels at your psi setting, even if the plenum was the same size.
Quote from: ackuric on June 22, 2017, 03:29:51 PMQuote from: rsterne on June 21, 2017, 11:41:18 PMI see Matt gave me credit for some numbers he used, but they are actually the maximum FPE obtainable per 100 psi drop in a plenum, per cc of HPA, assuming 100% pure Adiabatic expansion of the gas in that plenum.... I have no idea where Matt got the rest of his formula, or the basis behind it.... When I present something like a "Recommended Plenum Calculation", I would try and explain how I developed it... ie I try and "show my work" like my math teachers always insisted.... Since that hasn't been done here, I have no way of knowing the basis for Matt's formula, the limitations of it, nor it's reliability.... I'm not saying it works or it doesn't.... but please don't assume that because I gave him some numbers (for what he keeps telling me is a totally unrelated subject, yet he uses them).... that I endorse this method or not.... He has covered any potential arguments by stating that his "fudge factor" may have to be altered.... His method may be right or may be wrong.... I don't know how he developed it, so I am not qualified to comment on it.... However, please don't credit me.... or blame me.... for the results you get by using it.... I have nothing to do with it....BobNot sure why you have it out for me and I was tempted to make it clear that you don't endorse the idea or subscribe to the beliefs that I do in terms of the numbers provided, but I was certain you would. I am not assuming Adiabatic expansion is all that occurs in an Air Rifle by using these numbers, I cannot stress that enough... Fudge factors are needed in our theories of pcp's Bob as you are very familiar with them if I understand correctly, even Lloyd's internal ballistic spreadsheet uses a fudge factor? I am not trying to avoid argument's, but the reality is there is no need to argue, I am always open for intelligent discussion and I am just publishing a method that worked for me, and I made that VERY clear. I also look forward to hearing people post their results (ie plenum + power level + caliber) so I can fine tune my formula as again I was very clear that I do not have the arsenal of air rifles to do so myself...I made my self very clear and concise because I knew someone like yourself would look for ANY possible way to disagree or argue my current findings which are simply a work in progress...-MattDont bother with that Matt.. If the work in progress would be vetted and confirm, he would be the first one to say he has CONTRIBUTED to your work... LOL
I think me brains just SQRT'd out me ears !!! Cheers,Smoketown
FWIW: your RPV denominator appears to be missing a set of parrens. and don't understand how the units FPE, psi, convert to a volume. For S&G, I calculated 60FPE @ 1000psi = 98cc