FAQ
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Introduction
This page aims to answer some of the common "Which is better?" questions seen on the forums in a simple manner.
Normally, there is no simple resolution to the question, because if there were, you wouldn't need to ask it. For example, if we knew pneumatics were best, then you wouldn't see any combustions.
It's not as simple and clear cut as people asking the question might think. However, this page will hopefully give you the information you need to make the decision for yourself, depending on what is most important to you in your launcher.
Combustion vs. Pneumatic
"Which is better, Combustion or Pneumatic?"
This is probably the most common question that gets asked on the forums, and the big problem with it is that it is unanswerable. Without knowing what a person wants from a spudgun, nobody can put one type ahead of another.
However, most experienced spudgunners will agree on this short list if muzzle velocity or muzzle kinetic energy is the only criteria used for ranking the guns:
Where down is increasing "power" but also increasing difficulty to use, build and cost.
Below are the main advantages and disadvantages in easy lists to help you decide on your own:
Combustion cannons
Advantages:
- Usually cheaper and easier to build.
- Less sensitive to minor leaks (such as around a threaded cleanout plug).
- Usually quicker to refuel and reload.
- More portable. Just needs a can of some flammable vapour.
- Can be made bigger, but still kept practical.
- Easier to later upgrade.
Disadvantages:
- Less power, with a upper limit to what is practically possible (with all safe fuels).
- Less controlled (Maintaining consistency and altering power)
- Often inconsistent and unreliable (Advanced Combustion launchers can overcome this, but often cost more to construct).
- Potentially noisier. This can be remedied to some extent by having a good Chamber to Barrel Ratio.
- Very large chambers are more prone to DDT, although this is only likely to occur in chambers that are very long, on the order of 10m or more, depending on a whole host of other variables. The diameter of a tube is directly related to its DDT runup distance, i.e. the wider the tube, the less likely detonations are
Pneumatic cannons
Advantages:
- Normally more powerful, with less of a "ceiling" to power (The particle speed of the gas does limit power to some extent).
- More controllable and consistent, as power can be varied with pressure.
- Easier to simulate, with reasonable accuracy, in a modeling program such as GGDT.
Disadvantages:
- Takes longer to fill, unless you have a decent compressor or bottled gas (Especially true with large chambers).
- More expensive, particularly if you include the cost of a compressor or regulated CO2.
- Less portable.
- More complicated to construct and much less forgiving of construction problems (such as weak or leaking joints and fittings).
- Leaks are a greater problem since the gun needs to maintain pressure for the entire time between filling and firing. (And, leaking can cause a valve to open prematurely.)
Hybrid Cannons
Advantages:
- Extremely powerful, sometimes capable of thousands of ft·lbs and supersonic velocities.
Disadvantages:
- Must be made of metal to be considered safe.
- Requires the replacement of a burst disk after every shot (with exceptions).
- Requires a source of compressed air (not CO2) as well as compressed gas.
- Fairly expensive to build.
As a final note, a large majority of the launchers that Spudfiles (and other similar spudgun forum) users build are pneumatic cannons, but amongst people who don't take it up as a hobby, combustion cannons are more common.
Working on
To come soon
- Metal vs. Plastic
- Boys vs. Girls (I'm kidding about this one)
