BATTERY OPERATED HIGH VOLTAGE SOURCE

[Paul Burridge]

That'll contain the shards (maybe).
You'r unlikely to keep it under enough tension to keep the tension
below the very low fracture threshold of PVC.
PVC really, really sucks for some things.
HDPE is nice, as it's stable, and does not fracture into shards
like PVC.

Are you a DIY spudgun enthusiast/builder, Ian?
You appear to speak from some unfortunate personal experience. ;-)

 

[Ian Stirling]

Are you a DIY spudgun enthusiast/builder, Ian?
You appear to speak from some unfortunate personal experience. ;-)

Nope, though I have interest in somewhat analogous fields (my long-term
garage project is to build a 4 stage orbital capable rocket, with
orbiting webcam, which involves most of the same problems in much
worse ways).

I have had experience of PVC pipe exploding when used for compressed gas.
Especially when contaminated a bit.
If you look at all the relevant graphs for PVC pipe, and work out the
allowed pressure for gas, it's often in single digits.

And PVC shatters into little shards when it goes, rather than some
other polymers which have much safer failure methods. (HDPE tends to
"shred")

I've never built anything that uses propane to make an explosion.
I hope in the not too distant future to try a LOX/propane rocket engine,
which I again hope will not explode.

 

[Keith R. Williams]

Where are you?
Vermont.

I believe that in most of the states, it is covered by firearms legislation.

Nope. None of that nonsense (firearm legislation) here.

 

[Fred Bloggs]

Nope. None of that nonsense (firearm legislation) here.

Did I read that right? Was that PoCrap, Howard Dean, governor for five
terms there?

 

[Keith R. Williams]

Did I read that right? Was that PoCrap, Howard Dean, governor for five
terms there?

Yup, believe it or not, Schreachin' Howie has a 100% NRA rating. ...not
that he had much choice as a state-wide office-holder.

Though recently he did say that those in large cities should be second-
class citizens when it came to the Second Ammendment.

 

[budgie]

No they don't, unless dramatically overheated.

Errr.... you've obviously led a fairly sheltered life.

Back when I was a teenager, I used to grab my sister's hairspray and a lighter
and go wage flame-warfare on assorted pestiferous insects/spiders. Not too long
after that, there was a case reported in the press of a kid killed doing the
same when the can exploded. While we were all rather incredulous at the chances
of this, we later saw a controlled test in which a significant number of aerosol
cans did explode rather dramatically while being used as flame-throwers.

Since then, CFC propellants have been replaced in most part by hydrocarbon
products - I can't see that reducing the explosion risk.

But hey - if you're happy doing this, why should I care?

 

[Keith R. Williams]

Errr.... you've obviously led a fairly sheltered life.

Back when I was a teenager, I used to grab my sister's hairspray and a lighter
and go wage flame-warfare on assorted pestiferous insects/spiders. Not too long
after that, there was a case reported in the press of a kid killed doing the
same when the can exploded. While we were all rather incredulous at the chances
of this, we later saw a controlled test in which a significant number of aerosol
cans did explode rather dramatically while being used as flame-throwers.

Oh, my! I fear you've misunderstood me, incorrectly! ;-) Cheap
hair spray certainly does make a good flame-thrower (always has,
along with spray-paint). However, hair spray is also good at
killing wasps, hornets, and other critters, sans pyrotechnics or
poisons.

The crap glues their wings together like, well, your sister's
hair. Though your sister might have used the spray-glue to
attract the opposite sex, the bugs attract nothing but the Earth.
It's even safe around kids!

Since then, CFC propellants have been replaced in most part by hydrocarbon
products - I can't see that reducing the explosion risk.

Until the can is breached, where is the risk? ...and that's a
tad harder than lighting a match.

But hey - if you're happy doing this, why should I care?

Lofting potatoes? (and pumpkins/watermelonss make great targets)
What's the harm? In a pinch, you can even "borrow" your sister's
hair spray! ;-)

 

[Paul Burridge]

Nope, though I have interest in somewhat analogous fields (my long-term
garage project is to build a 4 stage orbital capable rocket, with
orbiting webcam, which involves most of the same problems in much
worse ways).

I have had experience of PVC pipe exploding when used for compressed gas.
Especially when contaminated a bit.
If you look at all the relevant graphs for PVC pipe, and work out the
allowed pressure for gas, it's often in single digits.

And PVC shatters into little shards when it goes, rather than some
other polymers which have much safer failure methods. (HDPE tends to
"shred")

I've never built anything that uses propane to make an explosion.
I hope in the not too distant future to try a LOX/propane rocket engine,
which I again hope will not explode.

Sounds a bit ambitious. Do you have any experience in amateur
rocketry?

 

[Paul Burridge]

Nope. None of that nonsense (firearm legislation) here.

Surely there must be *some* restrictions!

 

[Frithiof Andreas Jensen]

Im trying to generate a spark at least as big/powerful as a piezo starter,
like those found in ovens, water heaters etc...

So, you go to one of those "white goods spare parts stores" where in all
likelyhood there will be an abundance of replacement gas igniters of all
kinds - as long as you can figure out which part number it is. They are
cheap.

What's wrong with piezo B.T.W?: It's for a potato gun rite - and you need
trigger to pull anyway.

 

[budgie]

Oh, my! I fear you've misunderstood me, incorrectly! ;-)

Possibly. I certainly read from your post that the hs-can was the fuel source
AND that its discharge was ignited in real time.

Cheap
hair spray certainly does make a good flame-thrower (always has,
along with spray-paint). However, hair spray is also good at
killing wasps, hornets, and other critters, sans pyrotechnics or
poisons.

The crap glues their wings together like, well, your sister's
hair. Though your sister might have used the spray-glue to
attract the opposite sex, the bugs attract nothing but the Earth.
It's even safe around kids!

Ah, but the flame adds that extra dimension - and ironically is probably more
humane.

 

[Ian Stirling]

Errr.... you've obviously led a fairly sheltered life.

Back when I was a teenager, I used to grab my sister's hairspray and a lighter
and go wage flame-warfare on assorted pestiferous insects/spiders. Not too long

Nope.
The can cannot explode unless overheated.
There is no oxygen in there to react with the contents.

 

[Ian Stirling]

Yup, believe it or not, Schreachin' Howie has a 100% NRA rating. ...not
that he had much choice as a state-wide office-holder.

Though recently he did say that those in large cities should be second-
class citizens when it came to the Second Ammendment.

Firearms possesion, sure.
Is manufacture the same though.

 

[Ian Stirling]

Sounds a bit ambitious. Do you have any experience in amateur
rocketry?

No.
However, most of it isn't very relevant.

A solid rocket that burns out after 0.5-5 seconds has very little
in common with one that burns for a minute under power with a
regeneratively cooled nozzle, and with guidance.

Plus, it's illegal for me to make solid rockets in the UK, even for
static testing, without a fireworks factory license, which would take at
least several hundred thousand pounds to obtain.

 

[budgie]

Nope.
The can cannot explode unless overheated.
There is no oxygen in there to react with the contents.

That's what we all thought too.

" While we were all rather incredulous at the chances
of this, we later saw a controlled test in which a significant number of aerosol
cans did explode rather dramatically while being used as flame-throwers."

You want to explain it? I can't, but I saw the test film.

 

[Keith R. Williams]

Firearms possesion, sure.
Is manufacture the same though.

No laws there at all! Firearms can be and are made in basement
machine shops. Of course the federallies get paranoid with some
"enhancements", gun manufacture is perfectly legal. The
"enhancements" don't include bore size or hair-spray load, AFAIK.
I do know several people with spud-guns, and they're perfectly
legal.

 

[Paul Hovnanian P.E.]

Sounds like he needs a stun gun schematic
(ducking and running for cover 8*)
Pat

That's right. Then he can find someone with a design that fits his
requirements, stun them, grab the plans and run. ;-)

 

[Ian Stirling]

That's what we all thought too.

" While we were all rather incredulous at the chances
of this, we later saw a controlled test in which a significant number of aerosol
cans did explode rather dramatically while being used as flame-throwers."

You want to explain it? I can't, but I saw the test film.

How tested?
If being held in some sort of fixture, it's quite concievable that the
can could be heated indirectly by the flame to failure.

 

[budgie]

How tested?
If being held in some sort of fixture, it's quite concievable that the
can could be heated indirectly by the flame to failure.

I can tell you that it wasn't held by a volunteer ...

 

[Ian Stirling]

I can tell you that it wasn't held by a volunteer ...

Can you define "explode".
Are we talking about the can ripping open, or the valve/spray assmebly
failing and simply letting it burn more rapidly without the can losing
integrity.