CALM
Revision as of 21:11, 18 December 2005 by 67.180.152.250 (talk)
Compressed Air Launcher Modelling Program
by AKBiocca
The CALM modelling software works by computing the amount of air that passes through the valve every 100 microseconds, subtracting the from the pressure chamber and adding it to the bore. The force on the (tennis ball) Projectile is computed, the net acceleration, velocity, and new position. New pressures are computed for the bore and chamber. This is repeated until the ball leaves the bore. This allows us to see what is happening in some detail.
The CALM program is written in the Python language, and is in source code format, so you can see how it works and even make changes.
CALM Example
Computer Modelled Performance* CSV-19 Compact Sprinkler Valve 19 inch Launcher webpage at: http://www.qsl.net/wb6zqz/csv19/index.html system Cv 5.0 Ballwt 4.0 ounces chp oal chl bbl fps sec xbp xcp ht tofl 30 19 8 14 79 0.020 0.2 20.5 76 4.4 40 19 8 14 105 0.017 1.3 29.7 117 5.4 50 19 8 14 123 0.015 2.5 38.8 146 6.0 60 19 8 14 138 0.014 3.7 48.0 168 6.5 70 19 8 14 151 0.013 4.8 57.1 188 6.9 80 19 8 14 162 0.013 5.9 66.3 205 7.2 Cv = system flow coefficient, gpm per psi chp = chamber pressure in psi oal = overall length inches chl = chamber length bbl = barrel length fps = velocity feet per second sec = barrel time in seconds xbp = exit bore pressure xcp = exit chamber pressure ht = peak trajectory height in feet tofl = time of flight in seconds * note that these performance numbers are uncalibrated and subject to change based on measurements with your own launcher. The Cv value can be adjusted to fit your specific results. They seem to be quite close to the Dacron line measurement, however measurements with new synthetic line were 20% higher. As the line ages the performance at higher heights drops slightly due to increased drag from wear on the line.
