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wich is the safest? PLZ ANSWER

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wich is safest?

pneumatic
3
43%
combustion
4
57%
 
Total votes : 7
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wich is the safest? PLZ ANSWER

Unread postAuthor: Demon » Sat Aug 16, 2008 11:58 am

Hello guys,

i just want to know wich of the 2 spudguns type ( combustion and pneumatic) is the safest?

who had the most chance of blowing up?

im 13, had 5 pneumatics( yes i am a maniac) and i want to try combustion but my father dont want.

maybe if you, experts of spudguns, says then combustion is safest as pneumatic, will convince him. but dont lie.

and yes my english sucks.
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Unread postAuthor: SpudFarm » Sat Aug 16, 2008 12:03 pm

first off your english does suck but that is not a problem aslong as we understand you, and i does.

the safest type of guns is combustions no doubt. tell you father that they make absolute max 100psi and your pneumatic uses that, but has to hold it for a long time..

if you say that you will be allowed
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Unread postAuthor: Demon » Sat Aug 16, 2008 12:11 pm

i know but what he is "scared" of is then so old gaz stucked somewhere will sudendly blow or any sort of accident that happen when you play with explosives,

does that happen?
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Unread postAuthor: Ragnarok » Sat Aug 16, 2008 12:41 pm

Assuming all else is equal, the combustion is likely safer, although you will also struggle to get as much power from it.

Combustions only generate peak pressures of the order of 60-80 psi when they're being fired, unlike a pneumatic which is constantly under pressure, often 100 psi or more.
Drop a cannon that's under pressure, and the results could be nasty.

Combustions do generate shock pressure and heat which does affect the safe pressures, but in a well made cannon made from pressure rated components, that is of little concern.

While I'm here, I'll make the point that combustions do not work on "explosions", although a lot of people seem to labour under the misconception that they do.
They work on rapid burning (deflagration, not detonation) of whatever fuel you have, which heats the gases in the chamber to produce a pressure.

If your father is so worried about such "explosions", suggest he gets rid of his car - it's engine works on exactly the same principles, so if he's that worried about such things, obviously it'll have to go. :roll:
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Unread postAuthor: Demon » Sat Aug 16, 2008 12:48 pm

thanks guys but my father does not want, i dont know why, thanks for had tryed. :cry:
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Unread postAuthor: Ragnarok » Sat Aug 16, 2008 12:55 pm

Demon wrote:thanks guys but my father does not want, i dont know why, thanks for had tryed. :cry:

There's no real reason to fret about it.

My parents don't really want me playing with propane, which is part of the reason I don't really do combustions, so to keep them moderately happy, I do pneumatics instead.

Problem for them is, that they don't realise the pneumatics I build have the power of a combustion a good 4 or 5 times their size. :D
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Unread postAuthor: trollhameran » Sat Aug 16, 2008 1:15 pm

My mum isnt that keen on either, but she'd rather i make pneumatic, probably because I burnt my eyelashes off once. But my dad isnt really bothered as long as I only take his scrap plumbing parts.
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Unread postAuthor: Ragnarok » Sat Aug 16, 2008 1:31 pm

trollhameran wrote:probably because I burnt my eyelashes off once.

Only once? Man, that must be boring - I've done it at least 4 times. :D:P;)
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Unread postAuthor: trollhameran » Sat Aug 16, 2008 1:40 pm

I make up for it with non spudding related incidents though :D
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Unread postAuthor: SpudFarm » Sat Aug 16, 2008 2:20 pm

just tell him it is a pneumatic that runs on pressurized propane :D
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Unread postAuthor: Ragnarok » Sat Aug 16, 2008 3:15 pm

SpudFarm wrote:just tell him it is a pneumatic that runs on pressurized propane :D

As amusing as that idea might be, lying to your parents is not usually a good idea, especially when they're very likely to find out the truth.
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Unread postAuthor: DYI » Sat Aug 16, 2008 3:39 pm

Well, for one, there are no explosive alkanes, they're all quite stable.

Secondly, the obvious "lack of constant pressure" thing, and of course the fact that in a normal combustion spudgun, the pressure is almost always lower than in a pneumatic.

If you build two with the same materials, and use the pneumatic at full compressor pressures of at least 120 psi, it should usually fail first. A catastrophic failure is bad for either one, but that's the nature of these things.

In pneumatic vs. combustion, combustion should always win in the end, simply because you don't need to precharge to the full firing pressure and temperature. You cut gas consumption by a factor of at least 6, and a lot more in a well built hybrid.

So, combustions are relatively safer than pneumatics (due to the decreased pressure duration) at the same pressure, and have much lower gas consumption for better performance, once again at the same pressure. There are no explosives involved, as the mixture only becomes flammable when its two components (oxygen and propane in this case) are mixed in very precise proportions (propane has a flammability range of less than 10% in air). Unless you only want low-powered launchers for entertainment, the choice is pretty clear.
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Unread postAuthor: Hotwired » Sat Aug 16, 2008 4:13 pm

Ehhh I wouldn't put forward a "which would catastrophically fail first under normal use" comparison.

Built properly the answer is irrelevant because they won't.


A combustion of the same size as a pneumatic has less power and in that respect it is safer.
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Unread postAuthor: psycix » Sat Aug 16, 2008 4:20 pm

Many parents get frightened when they hear the words "fuel" and "combustion". They imminently seem to think OMG explosion!
Point out to them that it is a deflagration and not a detonation, easier said:it burns, it does not explode.
Since it just burns, there are no dangerous "rip stuff to pieces" shockwaves.
Furthermore, the pressure is limited and lasts for a short time.

Pneumatics though, are usually more reliable and do not involve high temperatures.

Any well-built spudgun is NOT dangerous. The person using it can be.
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Unread postAuthor: DYI » Sat Aug 16, 2008 4:51 pm

Ehhh I wouldn't put forward a "which would catastrophically fail first under normal use" comparison.


Uh... Why not? They'll all fail eventually under continuous use, whether it takes one shot or 400 years.

It's a given that anything which is properly built will not fail in its operational lifetime, so why include that fact?
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