Posted on 03/29/2006 8:15:25 PM PST by JmyBryan
insufficient information.
your friend did not include such things as:
1. source of oxidizer (air or bottled oxygen?)
2. volume of combustion chamber
3. type of ignition
4. mass of projectile
your friend should first look into burn optimization - basic chemistry: at the pressure and starting temperature, what mix of propane and oxygen produces the fastest and most thorough burn? How much radiant heat is produced? What are the chemical products - are they simpler molecules or more complex molecules (simpler molecules -> more propulsive gasses)? what is the pressure-energy falloff gradiant (for "interior ballistics")?
once he has those data, he can design his combustion chamber and feed valves and barrel length accordingly. a ball valve and a combustion chamber is a bad idea. pin-valves are a much better idea.
oh, wait... this is a purely PNEUMATIC projector? you shoulda sed that... when ya sed "propane tank" I got all excited.
I don't have much to do with airguns. sorry.
um...
He will probably want an expansion chamber.
The propane tank's integral necking will not allow enough gas through to max his range. also, when bled directly from a tank, air cools and frequently condenses, which really messes up performance. An expansion chamber allows the operator to bleed in a controlled dose up to a metered pressure and allow it to stabilize, and also allows for a hogging huge release-valve.
concept layout:
tank...>expansion chamber...>ballvalve...>golfball in breach...>barrel...>muzzle
Kids, don't try this at home...
I bow in deference to you on this matter. I am more of an aeroplane and rocket guy. If he had been asking what to use for launching a golf ball...
I am still playing with idea of converting an old RC glider (1m span) into a boost glider. I have deduced that I will need to strengthen the wing spar.
The usual calculation method would calculate the range from a dragless object, then again from alternatives with various objects with different surface features.
Empiracism, the touchstone of theory.
"The usual calculation method would calculate the range from a dragless object, then again from alternatives with various objects with different surface features.
Empiracism, the touchstone of theory."
The range is dependent on the angle of elevation whereas the maximum height seemed like a cleaner measure to me.. I'm not in the air cannon field and didn't know how such things are stated. Obviously for a frictionless object on flat land with no temperature or pressure gradients, one can go back and forth between maximum range and height since max range will always be at 45 degrees..
What I was saying I could not calculate were the effects of rifling and dimpling.
Oh, and rifling is rather effective on round balls fired from old flintlocks. Rifling was so used for a long time before conical bullets became common.
"Oh, and rifling is rather effective on round balls fired from old flintlocks. Rifling was so used for a long time before conical bullets became common."
It does work but it doesnt work as well. Historically, this fact led to the devolpment of non-spherical bullets.
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