In theory, any non-flammable gas can be used as a propellant for the Green Dragon including air, carbon dioxide, nitrogen, argon, helium, etc. The two most practical choices are compressed air and carbon dioxide. In the first part of this article, we will look at compressed air as a propellant gas source.
The simplest way to provide compressed air is to use compressed air cylinders. They are available from a commercial gas dealer by paying a one time deposit and then a fee to have the cylinder recharged or exchanged with a full cylinder. They come in a variety of sizes and pressure ratings and depending on the intended use of the air, the cylinders will have different types of fittings. The three main types are industrial air, medical grade air, and high pressure medical grade air. The latter is found on the SCBA cylinders used by fire departments.
Another possibility is to use SCUBA cylinders. They can be rented for under $10 at a dive shop and cost about $5 to have recharged. However, most shops will only rent and fill cylinders for carded divers. Also, unless you live near an ocean, the nearest dive shop may be hundreds of miles away.
For all types of compressed air cylinders, you need a regulator to reduce the cylinder pressure before connecting to the Green Dragon. The regulator must have the correct fitting and be rated for the cylinder pressure.
In order to compare various compressed air cylinders, you need to know the capacity which is measured in cubic feet. If you let all of the compressed air in the cylinder expand into a big balloon until it was at atmospheric pressure, the volume of the balloon measured in cubic feet would be the capacity of the cylinder. For example, a typical SCUBA cylinder holds 80 cubic feet. With the Green Dragon regulator set to 90psi, you will get about 40 shot per cubic foot of air, so you could expect about 3200 shots out of a SCUBA tank.
The advantages of compressed air cylinders are that they pack a lot of energy into a small space, are relatively inexpensive to get filled, and can be mounted in any orientation on a vehicle. The disadvantage is that there are a number of fitting types that each require a different regulator. Also, if you purchase a cylinder instead of renting, then you will need to have the cylinder inspected regularly by an approved facility.
Another option for compressed air is to use an onboard air compressor system. This consists of a compressor and a low pressure storage tank. The compressor runs intermittently to maintain the tank pressure between a lower and upper limit, typically 120-135psi. At the maximum range and maximum firing rate of the Green Dragon, the system needs to be able to deliver 1.6 cubic feet per minute. For a 12VDC powered system, that will take about 20A to run. This is not a problem for a pickup truck, but is a problem for most ATV’s and UTV’s.
The advantages of a compressor system are that you never run out of air as long as you have power and it can be connected directly to the Green Dragon without the need for an additional regulator. The disadvantages are that it is bulky and takes a lot of power. However, if your vehicle already has a system installed, this may be the better way to go.
In the second part of this article, we will look at carbon dioxide as a propellant gas source.
The simplest way to provide compressed air is to use compressed air cylinders. They are available from a commercial gas dealer by paying a one time deposit and then a fee to have the cylinder recharged or exchanged with a full cylinder. They come in a variety of sizes and pressure ratings and depending on the intended use of the air, the cylinders will have different types of fittings. The three main types are industrial air, medical grade air, and high pressure medical grade air. The latter is found on the SCBA cylinders used by fire departments.
Another possibility is to use SCUBA cylinders. They can be rented for under $10 at a dive shop and cost about $5 to have recharged. However, most shops will only rent and fill cylinders for carded divers. Also, unless you live near an ocean, the nearest dive shop may be hundreds of miles away.
For all types of compressed air cylinders, you need a regulator to reduce the cylinder pressure before connecting to the Green Dragon. The regulator must have the correct fitting and be rated for the cylinder pressure.
In order to compare various compressed air cylinders, you need to know the capacity which is measured in cubic feet. If you let all of the compressed air in the cylinder expand into a big balloon until it was at atmospheric pressure, the volume of the balloon measured in cubic feet would be the capacity of the cylinder. For example, a typical SCUBA cylinder holds 80 cubic feet. With the Green Dragon regulator set to 90psi, you will get about 40 shot per cubic foot of air, so you could expect about 3200 shots out of a SCUBA tank.
The advantages of compressed air cylinders are that they pack a lot of energy into a small space, are relatively inexpensive to get filled, and can be mounted in any orientation on a vehicle. The disadvantage is that there are a number of fitting types that each require a different regulator. Also, if you purchase a cylinder instead of renting, then you will need to have the cylinder inspected regularly by an approved facility.
Another option for compressed air is to use an onboard air compressor system. This consists of a compressor and a low pressure storage tank. The compressor runs intermittently to maintain the tank pressure between a lower and upper limit, typically 120-135psi. At the maximum range and maximum firing rate of the Green Dragon, the system needs to be able to deliver 1.6 cubic feet per minute. For a 12VDC powered system, that will take about 20A to run. This is not a problem for a pickup truck, but is a problem for most ATV’s and UTV’s.
The advantages of a compressor system are that you never run out of air as long as you have power and it can be connected directly to the Green Dragon without the need for an additional regulator. The disadvantages are that it is bulky and takes a lot of power. However, if your vehicle already has a system installed, this may be the better way to go.
In the second part of this article, we will look at carbon dioxide as a propellant gas source.
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