Hall Consulting's
Hybrid Gun Design Tool


Load/Mix Calculator

Determining a gun's performance is all well and good, but to make the shot happen in the real world, first you have to properly charge the chamber with fuel and air. This tool aids in accomplishing this task.

Metering Pipe Data -> Diameter
If a fuel metering pipe is to be used, input the diameter of the pipe here. Note that this diameter is saved as part of the gun's configuration.

Metering Pipe Data -> Length
If a fuel metering pipe is to be used, input the length of the pipe here. Note that this diameter is saved as part of the gun's configuration.

Metering Pipe Data -> Volume
The volume of the metering pipe as determined by the diameter and length. This is simulation output displayed for the user's convenience only.

Nominal Mix -> Propellant
The fuel to be used. Options exist for butane, MAPP, and propane. Note that the support for MAPP gas isn't accurate at this time.

Nominal Mix -> Mix
HGDT assumes a stoichiometric mixture of fuel and air. The mix number determines at what pressure this mixture is stored. A value of "1" corresponds to 1 standard atmosphere, a value of "2" corresponds to 2 standard atmospheres, and so on. Note that HGDT does take atmospheric conditions into account (see: configuration). Thus, a user at 5,000 feet altitude will actually have to pressurize his gun a bit to get a 1X fuel load.


Meter Pipe Pressure -> Regulator
Regardless of whether a regulator is used or not, this is the pressure the metering pipe should be filled with fuel.

Gas Volumes (@ ambient) -> Fuel
For those who prefer to measure their fuel/air via positive displacement at ambient pressure (ex: the use of a syringe), here HGDT lists the volume of fuel required for the desired mix. This number has been corrected for local atmospheric conditions (altitude).

Gas Volumes (@ ambient) -> Air
For those who prefer to measure their fuel/air via positive displacement at ambient pressure (ex: the use of a syringe), here HGDT lists the volume of air required for the desired mix. This number has been corrected for local atmospheric conditions (altitude). Note that this is additional air required over and above the air that would normally be in the chamber at the start of a fueling evolution.

Chamber Pressures -> Start
For those who prefer to do their fueling using pressure as their metric of choice, the start pressure is exactly that: The pressure one should see in the chamber at the start of the charging process. Usually this number will be zero, but it could be negative for those operating in the region around 1X. Not that I expect anybody to work with a vacuum pump, but if you see a negative number it's probably a good indication that you'll want to use some of the volume-based fueling methods.

Chamber Pressures -> Post Fuel Inj
The pressure one should see in the chamber after fuel injection. For a 1X mix at sea level this will be 0. For virtually anything else it will be a positive number.

Chamber Pressures -> Post Air Inj
The pressure one should see in the chamber after supplimental air injection. Note that this is not a pressure change, but rather the final pressure in the chamber after fuel and air have been added.

Combustion Pressure -> Max Theory
The maximum theoretical pressure to be seen in the combustion chamber. This value is almost certainly higher than any value that a properly functioning gun will ever experience, but sometimes burst diaphrams don't blow when they're supposed to blow... (Note: As of this writing, the values I'm seeing are a bit lower than most published values. I am investigating this but as yet do not know if the published values simply don't take certain variables into account or if I'm messing something up.)


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