GGDT Design Library

HVPL-01

Plasticex009 from the Spudtech Forums was kind enough to offer up HVPL-01 (doesn't that roll across the tongue with ease?) for our reading pleasure and information. He has his own webpage dedicated to this gun so if you want more details, feel free to follow that link.

On the other hand, if you just want a quick description, HVPL-01 is a barrel sealing piston valve gun designed to shoot small projectiles very fast using slightly higher pressure air than is normally found in hobbyist pneumatic cannons (the solenoid valve you see in the pic acts as the pilot vent; not as the primary valve). As such, it should be an interesting beast to study. Higher pressures. High Mach numbers. Combining those two should really excercise GGDT's algorithms.

Plasticex009 sent the GGDT data file linked below this paragraph. I've gone in and used the Cv calculator to tweak the valve flow coefficient, but otherwise I am totally taking his word for any data found in the model.

pvpl-01.gdt

With all that said, here's the two data sets compare...

Pressure Measured
fps (avg) 		GGDT
fps 		Deviation
95 psi 856 932 8.9%
100 psi 891 947 6.3%
120 psi 987 1001 1.4%
125 psi 1063 1013 4.7%
130 psi 1080 1024 5.2%

As you can see, agreement is good. Not spectacular, but good. What I do find interesting is it's performance on the ends of the pressure spectrum. At lower pressures GGDT overestimates gun performance while underestimating performance at the higher pressures. This is exactly opposite of the trend shown by the data from my "Shorty" gun. And to be perfectly honest? I have no theories to explain the situation or improve the model. If you have any, I'm all ears.

And for those who want to see it, here's the raw shot data

Pressure Measured fps
95 psi 856
100 psi 891
120 psi 924, 1049
125 psi 1054, 1071
130 psi 1001, 1115, 1085, 1097, 1118, 1065

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