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A place to ask general spud cannon related questions.
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Unread postAuthor: BigBang » Tue May 02, 2006 11:57 am

Hello All,

As some of you already know, I have developed a fairly comprehensive and ever expanding suite of calculators for use in the design of combustion spudguns. I built my first hairspray fueled spudgun way back in 1994, but this project began in the summer of 2002 when I learned how to fuel my spudguns with propane. I initially wrote my calculators in Matlab, but have re-written them, so to speak, in Excel so that more people might be able to use them. The ProMeter (i.e., Propane Meter) suite now contains 5 calculators which I'll describe briefly below:

1) ProMeterES: This is the "ESsential" 1X fueling calculator in my estimation. As with all my calculators, fueling can be with either propane or MAPP gas. Some important PVC design data is provided, and several fueling sensitivity charts are provided.

2) ProMeterHX: This calculator is for NX hybrid mixes. I provide single and multiple step fueling solutions, in 0.25X steps, up to 5X mixes. Lean and rich mixtures are examined, and peak pressure estimates are given. Some relevant PVC design data is provided and there are charts for fuel meter pressure, and the pre-ignition combustion chamber pressure.

3) ProMeterOX: This calculator is designed for NX oxygen enriched mixes. I provide single and multiple step solutions, in 0.25X steps, up to 5X mixes. Peak pressure estimates are provided, as is some relevant PCV design data. Also provided are charts for O2 and fuel meter pressures, and the pre-ignition combustion chamber pressure.

4) ProPressure: The ambient atmospheric pressure is a variable in each of the three calculators provided above. If you have access to a barometer calibrated for absolute pressure in your area, use the value it provides. However, if your barometer is calibrated for sea level equivalent pressure (sometimes called "relative" pressure), or if you only have access to barometric pressure readings reported through various newspaper or radio services, this calculator may be of assistance. All reported barometric pressures have been adjusted to standard temperature sea level conditions. The ProPressure calculator reverses this conversion and provides an atmospheric pressure estimate at your local altitude and temperature. For reference, however, this calculator is probably only useful for the most anal retentive spudder, or for those struggling to dial in an optimum hybrid mix. In most cases, assuming an ambient pressure of 14.7 psia or 30 inHg will be sufficient.

5) ProMach: This is a speed of sound and Mach number calculator. Inputs include projectile speed, reported atmospheric pressure, ambient temperature, humidity and local elevation. You will see that temperature is the dominant effect.

I hope you find these calculators of use to you. If you find bugs or have suggestions for improvement I would love to hear from you.

Happy Spudding,

Edit - Fixed some printing problems (5/4/06)
Edit - Added a C:B ratio calculator in ProMeterES (5/17/06)
Edit - Clarified "calibrated" in the ProPressure discussion.
Edit - Fixed copper pipe dimension errors in ProMeterES (6/15/06)
Edit - Updated peak pressure calculations using GasEq (12/4/06)
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Download and un-zip the archive to find the five calculators contained in ProMeterSuite. Enjoy!!!
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