| Pages:
1
2
3
4 |
Twospoons
International Hazard
Posts: 1326
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline
Mood: A trace of hope...
|
|
I have done this with a plastic shopping bag. Electrolyser made using stainless plates - four cell, driven at 20A, NaOH electrolyte. Took about 5
minutes to fill the bag. I'd estimate around 2 to 3 litres of gas. Goes with one hell of a bang. Ear protection is essential. Video on Youtube -
posted by 'Grogyan'.
My electrolyser could sustain a hydrogen flame on the end of a 1" pipe (just). So a decent flow is possible if you have enough juju.
Helicopter: "helico" -> spiral, "pter" -> with wings
|
|
|
grndpndr
National Hazard
Posts: 508
Registered: 9-7-2006
Member Is Offline
Mood: No Mood
|
|
Sure,SS kitchen flatware.
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
This is demonstrated in GCSE (16 y/o) level chemistry in the UK using a Hofmann Voltameter <----- This is August Wilhelm von Hofmann from the 19th Century, not Albert (the LSD guy) from the 20th.
The apparatus is simply two burettes standing upside down. There is a tiny platinum electrode in what would normally be the tops of the burettes, but
that are now the bottoms (other electrodes can be used, and you can also buy short lengths of platinum wire or mesh cheaper than you'd think; it only
has to be a tiny piece, not a $3k engagement ring).
It's filled with distilled water, which won't conduct on it's own. A tiny amount of acid is added to make it conduct. The water splits and you get
hydrogen in one burette and oxygen in the other.
The demonstration uses the Hofmann apparatus, with the two marked burettes, so the teacher can show very graphically, and with measurements from the
burettes, that there is twice as much gas in one than in the other, as evidence that one is filling with hydrogen and the other with oxygen as a
result of the H2O splitting.
Samples of the gases will then be taken by sticking a test tube over the top, opening the tap to collect some, and trying to ignite the result in the
test tubes.
One will do nothing, but will reignite a blown out splint. The other will produce the infamous 'squeaky pop', but not relight the blown out splint.
This is an excellent method of demonstrating it because it shows the results in different formats. Some people learn by tactile, visual results, yet
are poor at the theory, others are incapable of visualising something but are much stronger with numbers. Combining the two universally gives better
results. Having an engineer who can both use SolidWorks models, but appreciates the finer details of how something is going to behave in the complex
world of reality. Those perfect combinations don't exist, so engineering teams are used instead, and meeting rooms full of biscuits, tea and
whiteboards; and the project leader can then include the word 'synergy' in their reports.  The same is true of pretty much all science projects; e.g. google data mining / this forum.
The electrolysis method is scaled up in Brown's gas (oxyhydrogen) generators.
These are more commonly used by jewellers, who want a very clean flame and to be able to simply fill the thing with water and switch it on and off to
get the gas on demand. Rather than having big, dangerous, expensive cylinders hanging around their workshop. Jewellers tend to use very small torches,
because the rings and necklaces are so tiny. Some of the torches actually use syringe blades as the nozzles, to get a tiny, tiny, invisible flame. The
generators for those aren't much bigger than a lunch box and can go on the desk.
They come on a number of sizes and numerous different models. RioGrande is a very famous, and huge, supplier of the jewellery industry.
They have some of the generators in their catalogue, along with a billion other things related to making shiny, expensive stuff.
People who work with materials that need to be extremely pure like hydrogen fuelled flames, as there is no carbon involved, which will embrittle some
metals, make jewellery look messy and weaken some glass work.
QuickFit produce some of the best lab glass available. I have spoken with them a few times and have a hand written note from them beside me now, along
with a free wash bottle and some details of how they produce the glass. They use natural gas and oxygen torches, and natural gas annealing ovens.
There are generators big enough to run a big welding torch. However, I have not once seen a gas welder actually using one (who wasn't trying to sell
it). There is a video knocking around of a guy demonstrating larger scale brazing with one, but he makes a somewhat odd claim about the flame
"adjusting it's own temperature" depending on what it's hitting, to the extent that he implies (if I remember correctly) that it wouldn't burn your
skin if pointed directly at it (which he doesn't do). What he may be seeing is that the generator can't produce enough of the gas to heat large work
pieces, so they are cooler than the flame temperature alone. This is a common mistake in electronics soldering as well, that you should use a low
wattage iron for sensitive work. In reality, that means it takes longer to heat the part to the soldering temperature and the components end up
roasting hot as you wait; and the heat conducts from the lead to the insides.
Gas welding and cutting is rarely used now when it's not heating something BIG. For example, gas cutting torches can cut metal over a foot thick.
There are no plasma cutters or lasers available that can compete with that. Thermal (oxygen) lances can cut metal feet thick, and can also do cement
based materials and clays.
Gas torches are still common around heavy industry, like shipbuilding. As they require no electricity or special optics, they are also used for rescue
work and in remote locations where a plug socket isn't available. Thermal lances are used for heavy demolition and are sometimes used to open the
plugs in iron foundries. They burn colder than acetylene, and don't produce a true flame, but don't rely on fuel evaporating or boiling out of
cylinders, so they can have huge BTU ratings.
A side effect of cutting things that thick with gas is that the torches rip through cylinders. It is easier, and cheaper, to buy the cylinders rather
than start generating the Brown's gas on demand.
As an example of the difference in power between electric (plasma / arc) and gas methods, ESAB will sell you a gas torch that can output around 80 to
90kW of heat, with a normal mains ring managing around 2 to 3kW before you run it into the Brown's gas generator and subsequently suffer losses. 80 to
90kW is three times what the grid fuse on my house can manage, ignoring all the internal wiring and breakers.
Acetylene torches burn at 3300C, 700C hotter than hydrogen torches. This means the work piece heats up a lot quicker.
There are only two higher temperature fuels known. Cyanogen at 4525C and Dicyanoacetylene 4990C. They produce such hot flames due to the massive
amount of energy stored in the Carbon to Nitrogen triple bonds.
Both of them are highly toxic, entirely ruling them out in any realistic production environment.
Other gases used include MAPP and Propylene. Both burn colder than acetylene, but have some advantages in terms of handling and cost.
Plumbers use MAPP quite often, as it is burns hotter (warming the copper to it's soldering point quicker) than propane but can be bottled in little
disposable cylinders. Acetylene can not. MAPP is also more expensive than propane, meaning you need to be used to working quickly and cleanly not to
end up wasting money using it in the first place; e.g. not leaving the torch light whilst you do something else. MAPP smells like acetylene, but not
quite as nice. 
For disposable cylinders, as you'd get from Bernzomatic, oxygen comes in reds, propane in blues, MAPP in yellows. The gas is universally more
expensive, quite a lot more, than it is to buy in refillable cylinders.
A number of people have built their own Brown's gas generators. You can find them by googling things like "DIY Brown's gas".
Reacting aluminium kitchen foil with concentrated NaOH or KOH will produce very large volumes of hydrogen very quickly.
I can envisage people trying to fill solid walled objects with acetylene over 15psi, and having it go off in their face. Oxygen enriched atmospheres
will allow things to combust at massively reduced spark energies. Oil can combust INSIDE regulators and hoses when high pressure oxygen is added.
Welders have even caught fire dusting their greasy overalls off with the oxygen from their torch. In the same way, pressurising a mixture of fuel gas
and oxygen, by blowing it into none elastic container, is a bad, bad, bad idea. As another for instance, if you fill it cold, and then set it outside
and get ready to do something, the heat from the sun hitting it could be enough raise the pressure and set it off.
The simplest method to get the largest bang realistically possible from a gas mixture is acetylene mixed with
oxygen, into a balloon.
[Edited on 4-2-2011 by peach]
|
|
|
gnitseretni
Hazard to Others
Posts: 282
Registered: 5-1-2007
Location: Colombia
Member Is Offline
Mood: No Mood
|
|
I remember when researching HHO cells that you could get a flame using hydrogen that was hotter than an acetylene/oxygen flame. I forgot the name. I
don't mean hydrogen/oxygen. They passed the hydrogen through an arc, which would rip apart the molecule or something, and on the other side of the arc
it would recombine and it is this recombining of the molecules that generates tons of heat.
EDIT: it's called "Atomic hydrogen welding" 
[Edited on 4-2-2011 by gnitseretni]
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
Atomic hydrogen welding
That's not combustion welding, it's more akin to an arc method.
For instance, some welders will use MAG welding, metal active gas, wherein some of the gas mix is oxygen or CO2, which will react in the arc to
increase the heat, but also lower the purity of the work.
It is going to be impossible for someone who is still working on basic electrolysis to deal with atomic hydrogen, let alone bottle it. Since atomic
hydrogen tends to recombine to H2 rather quickly. This is also similar to free radical experiments, wherein the radicals will recombine so rapidly the
containers will pop as the radicals react.
We were shown a demonstration of this in A-Level organics. The teacher placed a transparent film canister on the desk and proceeded to run a free
radical polymerisation by illuminating the canister with a bright lamp. The top of the canister quickly went airborne.
There are also plasma welders, which are a blend between a plasma cutter and a TIG set. Thermal Arc sell them.
Plasma cutters work around 20 to 30 thousand C. But, in terms of hot stuff, the JET experiment here in the UK has repeatedly produced stable plasmas
well over 100 million degrees Celsius which will, of coarse, melt EVERYTHING on the periodic table; with the core of the sun being a mere 15 million.
CERN's Large Hadron Collider has managed beam lines with proton energies that correspond to a temperature of about 40,000 trillion Kelvin. They
actually have two, and point them end to end into each other, for double the effect on collision and have gone up to 6 milllion, trillion kelvin for a
lead nucleus.
The LHC is the highest energy particle accelerator on earth.
[Edited on 4-2-2011 by peach]
|
|
|
The WiZard is In
International Hazard
Posts: 1617
Registered: 3-4-2010
Member Is Offline
Mood: No Mood
|
|
Actually. For a lot less money I have found that by sucking
cement dust through the plastic hose on my shop vac I can
generate voltages high enough to create the elusive Higg's Boson.
I am storing them as generated in a Bose-Einstein Condensate in the
back of my freezer. Couple of dozen more and a Nobel Prize
is mine for the asking.
djh
----
Do you believe that the sciences would ever had
arisen and became great if there had not beforehand
been magicians, alchemists, astrologers and WiZards,
who thirsted and hungered after abscondite and
forbidden powers?
Friedrich Nietzsche
Die fröhliche Wissenschaft, IV, 1886
|
|
|
crazedguy
Hazard to Others
Posts: 143
Registered: 12-11-2010
Member Is Offline
Mood: You can't fix stupid
|
|
Quote: Originally posted by peach  |
There are also plasma welders, which are a blend between a plasma cutter and a TIG set. Thermal Arc sell them.
[Edited on 4-2-2011 by peach] |
I'm guessing your just talking about the sets that combine both into the case, and just use some of the same innards like the transformer and such?
| Quote: Originally posted by The WiZard is In |
Actually. For a lot less money I have found that by sucking
cement dust through the plastic hose on my shop vac I can
generate voltages high enough to create the elusive Higg's Boson.
I am storing them as generated in a Bose-Einstein Condensate in the
back of my freezer. Couple of dozen more and a Nobel Prize
is mine for the asking.
|
Hahahaha are you going to be the first nobel prize winner from this site?
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
| Quote: | | I'm guessing your just talking about the sets that combine both into the case, and just use some of the same innards like the transformer and such?
|
Nope, they're designed to weld using a plasma jet, as opposed to cut or use an arc directly (as GTAW / TIG does).
Here's a description of the process
Last time I checked, Thermal Arc were the only big name company making plasma welders. I have owned a high end TIG set from both Thermal Arc and ESAB,
and used other well known brands, and Thermal Arc is in the same band of quality; the TA one was a 400 amp DC set (I think that's been discontinued),
and the ESAB was the newer CaddyTig 2200i TA34 AC/DC.
You could probably use a DC welding set as a power supply for electrolysis, if you've got one handy; as well as other bits of electrochemistry, like
plating.
Thermal Arc's site
[Edited on 5-2-2011 by peach]
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
It's combustion, all right, or at least
chemical recombination with oxygen, which is more-or-less the same thing. The way to think of it is that the arc is a point-of-use atomic hydrogen
generator, through inefficient brute dissociation of H2. So you're actual burning 2 H + O2 rather than H2 + O2. Admittedly it looks like an arc, but
the arc does not directly heat the weldment. The energy from the arc is transferred into the system according to the enthalpy of the reaction 2 H
--> H2, released in the combustion process, leading to the higher flame temperature.
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
As I understand it, oxygen isn't part of the equation. The heat comes from the atomic hydrogen recombining to H2.
|
|
|
crazedguy
Hazard to Others
Posts: 143
Registered: 12-11-2010
Member Is Offline
Mood: You can't fix stupid
|
|
I know quite a bit about welding but have never heard of paw welding actually, I could try using my welder for electrolysis, but its a mig and for
some reason that seems like it would be hard on the machine even though its doing what its suppose to completing a circuit that is.
Two things I will probably try either using a power supply for a computer, or something with propane because I know there is an oxyacetylene set
around house or just put propane in a balloon and fill it up with air.
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
If the welder has a current limit built into it (and it should do, given the likely hood of it happening), it should be able to withstand being
shorted.
MIG welders are constant voltage supplies, whereas TIG are constant current.
The newer generations of computer processors use absolutely staggering amounts of current. It's amazing when you think about it, that they contain
such super precise, microscopic, delicate elements, yet have what is not far off a welder attached to them. They are all powered by
switch mode supplies. Switch modes are incredible compared to linear supplies, in terms of their space, weight and power saving. Linear supplies are
the weapon of choice for extremely precise and quiet output. Walt Jung is famous for designing a linear regulator that produces less noise in it's output than a battery - the so called 'Super Regulator',
favoured by audiophiles, and much discussed at diyAudio.
Switch mode supplies also require someone who has a high level of ability with electronics to design them to take a universal input, to regulate under
all conditions, feature low noise in the output and emit little RF noise. This makes small production runs of them expensive, particularly if the
output doesn't adhere to one of the standards used with semiconductors (for which there are premade controllers and layouts). Since computer PSU's are
churned out by the million and go obsolete quickly, you can find them for next to nothing, or in bins.
The way they are built is far more technically complex than a linear regulator, making it less of a simple task to regulate the output voltage and
current. Whether or not that's an issue in your experiment is another thing. Most bits of chemistry aren't bothered by a bit of electrical noise from
a switch mode supply, and you can dump voltage or limit current using brute force resistance if need be; not particularly pretty or compact, but
effective.
As MIG welders are relatively low voltage devices, it won't take a lot of resistance in their way to reduce the current. But the resistor will get
hot. I have seen people using some very unique methods of controlling when building DIY plasma cutters.
The amount of current flowing will also depend on how much acid you use in the water. You could simply start with pure water, and add acid until
you're happy with the current and rate of evolution.
Since I was on my way down to recharge my cup of coffee, I thought I'd take a photo of some linear supplies I have. These are rated at 6Vdc and 30amps
each. Something that should be immediately apparent is that they are big compared to a computer PSU (they're about a sack of cement in weight each),
and it's not due to them using older technology, but an inherent side effect of how they regulate the output;
Because the supplies filter mains frequency electricity, they need very large capacitors
SM power supplies use very high frequencies, and the magnetic field from an inductor is proportional to the frequency of the current through it, so
they can use tiny magnetics. These mains frequency ones, however, have to use big lumps of iron in the transformer. The rest of the supply is made up
from pass transistors mounted to heat sinks. The transistors are functioning like variable resistors, and simply dump unwanted voltage across
themselves. This makes them get very hot. Even if you're not bothered about the wasted electricity, you need to be bothered about the heat. Without
the big heat sinks, the transistors would cook themselves almost instantly. Switch mode supplies don't 'dump' unwanted voltage or current, they
generate it on demand. There was a big boom in welding when inverters, which are switch mode, came out, and you could suddenly have really high
current supplies in something you could actually move without a crane. The fancy ones from ESAB, Lincoln, Miller and Thermal Arc with all the digital
controls on the front are a result of someone putting a lot of effort into designing the switch mode supply. It is basically a mini power station,
rebuilding the power and allowing you to shape into different waveforms, currents, voltages, frequencies, pulse widths, durations and all the other
colours of the rainbow - they're high output waveform generations more than power supplies, in my opinion
[Edited on 5-2-2011 by peach]
|
|
|
crazedguy
Hazard to Others
Posts: 143
Registered: 12-11-2010
Member Is Offline
Mood: You can't fix stupid
|
|
Those are pretty cool power supplies, I don't think ill use my welder for a power source its cold out side and the welder is in the garage and don't
want to set it up inside.
Not sure how I will use a computer power supply to make it work with all those leads that come off of a psu but ill figure something out.
Wish I had a tig welder, used to be really good at doing Al when I had welding class, I used to think I wanted to be a welder.
Never could convince my dad to buy a tig to fix the boat.
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
There are endless guides about wiring computer PSU's up to use them as fixed voltage supplies, so I won't explain it here. Google for 'lab (or bench
or DIY) supply computer PSU'. It's as complex as gather the wiring spools together into a group and finding the one the PSU uses as a 'wake up' signal
when the button is pushed on the front.
AC TIG sets certainly are appealing but, having bought one, I discovered the amount of things I wanted to weld that needed the AC simply wasn't enough
to justify the cost of having AC on it. Most people never encounter magnesium in welding, so that leaves aluminium. And quite a lot of things made
from aluminium can be made from steels, just using less of it.
More of the things I'm interested in are stainless, which wants DC. And a DC only set is a lot cheaper.
If you need to fix aluminium, and can't spend out on an AC set, there are hard soldering / brazing kits you can get with special fluxes that will let
you do it with gas torches. Something that doesn't work with normal rods and torches.
Failing that, break out the pop riveter. Riveting is still a good idea on long
welds. The Liberty / Victory ships of WW2 used an entirely welded hull. Which then tore open in the sea. The rivets where put back after enough of
them sank.
[Edited on 6-2-2011 by peach]
|
|
|
grndpndr
National Hazard
Posts: 508
Registered: 9-7-2006
Member Is Offline
Mood: No Mood
|
|
Constance Tipper of Cambridge University proved the fracture problem was caused by cold temp steel embrittlement not the welds themselves.The fix
wasnt to replace welding but reinforcement.A total of some 3-12 liberty ships were lost directly attributable to cracking out of some 2700 liberty
ships built.Not a bad safety record structurally speaking considering
an emergency wartime measure.The ships were intended to have a service life of 5yrs.Most were sold following the war and eventually(commercial
interests) just scrapped due to old age/economic decisions not structural worrys.FWIW
Source; Wikipedia
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
This same riveting analogy occurs in the molecular structure of the metal it's self, via things called Cottrell atmospheres
|
|
|
grndpndr
National Hazard
Posts: 508
Registered: 9-7-2006
Member Is Offline
Mood: No Mood
|
|
Good Stuff, Thanks!
The Titanic disaster may not have been so disaterous(smaller open sea hull failure,longer time afloat) had the steel not suffered the same
embrittlement(poor quality steel/riveted hull).Of course the iceberg had some effect.
[Edited on 6-2-2011 by grndpndr]
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by peach | | As I understand it, oxygen isn't part of the
equation. The heat comes from the atomic hydrogen recombining to H2. |
You are correct. I was mistaken.
|
|
|
peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by grndpndr | Good Stuff, Thanks!
The Titanic disaster may not have been so disaterous(smaller open sea hull failure,longer time afloat) had the steel not suffered the same
embrittlement(poor quality steel/riveted hull).Of course the iceberg had some effect.
[Edited on 6-2-2011 by grndpndr] |
I seem to remember the titanic also had another problem in that the interior walls, that were supposed to seal off the flooded sections, didn't run
continuously up through her.
When one section flooded badly enough, the water would rise up a few decks and spill over into the next section. This was offset by the bilge and
trimming pumps shifting the water, but those pumps aren't designed to prevent gross flooding.
It pains me to say it, but the Titanic was registered to the port of Liverpool and had Liverpool on the hull. That same port is within walking
distance of my house and I routinely drive past the shipyards. One of my friends in school did his apprenticeship at the Cammell Laird yard and I get the gas for science experiments from the suppliers of the local shipyards. A substantial number of the naval vessels
were built at Lairds; aircraft carriers, submarines, destroyers...
I will try to dodge some embarrassment by stating that the Titanic was actually built in Belfast, in Ireland, and set sail from Southampton. The three
chief designers were staff at the Harland and Wolff yard in Belfast - so I'm pointing fingers for the blame at them!
I think there were 16 wall sections in total. Knowing what the ship was designed for, I wouldn't be surprised if at some point in it's design at least
one person had said to the yard, "We can't have those big steel walls on the upper decks, they look terrible!"
Liverpool is the closest dock to Ireland, and I routinely see tanker trucks of Guinness going by. In fact, someone wrote to the local paper
complaining about the noise. The ship's construction was founded in Liverpool, hence it being her port of register.
As with all accidents, one of the positive outcomes is being aware of how significant a previously overlooked problem can be in preventing a
recurrence.
[Edited on 6-2-2011 by peach]
|
|
|
White Yeti
National Hazard
Posts: 816
Registered: 20-7-2011
Location: Asperger's spectrum
Member Is Offline
Mood: delocalized
|
|
I would go with a long fuse. The shock wave from a firecracker will not provide better combustion than a fuse. The best way to ignite this stuff would
probably be to put a spark gap in the centre of the balloon. That will give you the bang you're looking for.
|
|
|
jock88
National Hazard
Posts: 505
Registered: 13-12-2012
Member Is Offline
Mood: No Mood
|
|
I was going to do the following very kewl display. I have not seen a similar idea on youtube or SciMad which I find surprising.
Make soap bubbles (lots of them) using an explosive mixture of Propane/Oxygen and stream them into a flame where they will pop/explode like
firecrackers.
This is simple to do. Take a oxy/propane torch and extinguish a neutralized flame by swirling the cutter in some water. You are then left with
explosive gas which you can use to blow bubbles using the end of a childs bubble blower gun.
The bubbles will be streamed towards a flame.
Has anyone done this?
It will be done in a large open shed.
|
|
|
Ral123
National Hazard
Posts: 735
Registered: 31-12-2011
Member Is Offline
Mood: No Mood
|
|
http://www.youtube.com/watch?v=ypTADUYQ5ZI
hydrogen/oxygen is weak due to it's low density, butane/oxygen is the most powerful, readily made mixture.
|
|
|
jock88
National Hazard
Posts: 505
Registered: 13-12-2012
Member Is Offline
Mood: No Mood
|
|
Thats one big balloon. I will have lots and lots of small bubbles.
|
|
|
Morgan
International Hazard
Posts: 1705
Registered: 28-12-2010
Member Is Offline
Mood: No Mood
|
|
A long tube instead of a balloon.
Google translation
"Long hydrogen + oxygen collected by electrolysis tube by sealing the to fire someone."
爆鳴発火チューブ
https://www.youtube.com/watch?v=bCpjDWsIIvQ
|
|
|
Fenir
Hazard to Self
Posts: 68
Registered: 7-5-2013
Member Is Offline
Mood: No Mood
|
|
I was under the impression that the rivets on the Titanic failed due to high sulphur content.
|
|
|
| Pages:
1
2
3
4 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
