Now the real purpose of the post: A fun question. What is The Theoretical Maximum Muzzle Velocity that you can get from a PCP? The answer is all basic physics and you only need 3 equations, all of which have been around for close to 400 years. We will be using Imperial units ( feet, pounds, and slugs) and seconds.
There is nothing wrong if the correct unit is used in calculation but when compared to real world it is good to understand that scale indication is already mass value. Because scale is set, calibrated in another word, to give directly the mass value. It is calibrated using suitable standard mass.By the difference between those two I mean that 1 kg mass is weighting appr. 9.81 -9.82 Newtons and that difference, 19 - 18 grams is about 1.8 % of 1 kg. So if scale reading, which is mass, is converted to mass by gravity, there is an error of about 2%. I agree there are a lot of error possibilities, so why add one to to formula knowing its wrong?If you convert something, you should calculate the weight from scale reading, it is a mass value although the scale is actually measuring force.
The Three Basic Equations –1) F = m x a (Force equals mass times acceleration) Rearrange to get a = F/m2) d = 1/2 a x t2 (distance[barrel length] equals one half of the acceleration, times the seconds spent in the barrel squared) Rearrange to get t = square root of [(2 x d)/a]3) v = a x t ( muzzle velocity equals acceleration times time.)You have to use all 3 equations together to get the velocity so we’ll dive right into it.Using the rearranged versions of equations (1) and (2) to substitute for “a” and “t” in the velocity equation (3), we get v = (F/m) x {sqrt ([2 x d x m]/F)}
wwonka, It's nice when we each take our own crooked paths and end up at the same place. Thanks for going to the trouble of doing that.The powder burner comparison really is a different animal, and quite complicated. Same with springers. For the volume of uncompressed air that a springer uses, they make a LOT more power than a similar volume of un-compressed air (standard cubic inches of air) in a PCP. Thermodynamics and lots of heat. The math for PCPs is complicated enough without adding all that heat, LOL.Lloyd
Here’s an example of working backwards from a theoretical max velocity to what we might actually get from a real PCP..25 cal , 25 gn, 24” barrel , 3000 psi, infinite tank volume, zero dead volume between the valve and pellet. No deductions taken for any losses within the PCP system. Valve is wide open.1) Max Theoretical velocity and FPE, with the valve staying open until the pellet leaves the barrel:2292 fps, 292 FPE (more like a powder burner, LOL)Now let’s start deducting for the losses within the system:2) Reduce the tank volume to 230 ccs.2241 fps, 279 FPE3) Add the mass of the column of air that must be accelerated in the barrel behind the pellet:1562 fps, 136 FPE (major reduction ! )
The value of g gets a bit wonky over oceanic trenches.Lloyd
Douglas, Is the name similarity a coincidence?Lloyd