Since the load is still the highest near the end of the pump stroke.... the important calculation should still be the same.... The MA will be the distance the lever moves, divided by the distance the piston moves.... for each degree of rotation of the pump lever in question.... What happens in between (due to the arrangement of the levers) doesn't matter.... it is the results that count....The important thing to take from the above post, IMO, is that the pressure in the pump is NOT the same as the pressure in the valve until the very end of the stroke (at which point the MA approaches infinity).... When the pump arm still has 10 deg. or so to go (where it requires maximum force), the pressure on the piston may only be 1/3 of the ultimate pressure reached.... That was something I missed in previous articles from years past when calculating the force required on the pump arm.... Bob
Don't forget, you can't include the valve volume unless the check valve is open, which when you have the valve near 2000 psi only occurs at the very end of the pump stroke.... Up until then, you are just working on compressing the 1 atmosphere (~15 psi) of air entering the pump into the remaining stroke.... If you have a 7.5" stroke, and have 1/4" of that left to go, then you would be at about (7.5 / 0.25) x 15 = 450 psi.... With a 1.375" bore pump, that is 668 lbs. of load on the piston.... Still a far cry from the 2968 lbf. at 2000 psi when the check valve opens.... The check valve doesn't open until the pressure in the pump exceeds that in the valve....Bob
That is a whole lot of maths. Bob, do you enjoy math puzzles?I appreciate you guys doing all this heavy thinking though I have been pondering the use of an external pump linkage, which would eliminate the need for fancy pump arms and slotted tubes. Thus (in my mind) possibly more than doubling the pump stroke in the same given tube. Truth be told, I have not done any math on the pressures and forces and pump handle lengths etc... I do believe it should be easier to adjust the linkages, by use of Heim joints. The way I picture it though, it would be ugly and heavy. There would need to be a boss that fits the end of the tube, and one on the end of the piston rod. Use 2 pump levers, 2 tie rods, 180* opposed to each other. Instead of pushing the piston and galling the top inside of the pump tube, you'll be pulling a heavy rod supported by a bushing inside the boss on the tube. Now I'm not sure what the theory is... Because traditionally you would be pushing one lever against the receiver ( or wherever it is you hold your gun in your good arm), generating let's say 50lbs maximum force. Now split that in half... I guess the mechanical force would remain the same.... But you won't be bending your tube as the force will be a straight line, not deflected by the wall of the tube. I didn't come up with this idea on my own, I saw a pistol with the basic idea using one lever. Sorry Duane for hijacking your thread. Just been thinking a lot about pumpers. Lol
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