blown gasoline forge

[junker]

i saw an add for the oxy/gasoline torches the other day and it got me to thinking. can you make a gasoline forge? maybe pressurize an old propane tank with fitting from an air compressor and the just have a pour in tube with a cap so that it can be filled and then closed and pressurized. it seems to me that gas is cheaper than propane (atleast where i live) would this even be possible? would it need smaller nozzles to atomize the fuel properly? would it even get the steel up to proper heat? if anyone has any experience or even some harebrained guesses they'rd be much apreciated.

[Nakedanvil - Grant Sarver]

i saw an add for the oxy/gasoline torches the other day and it got me to thinking. can you make a gasoline forge? maybe pressurize an old propane tank with fitting from an air compressor and the just have a pour in tube with a cap so that it can be filled and then closed and pressurized. it seems to me that gas is cheaper than propane (atleast where i live) would this even be possible? would it need smaller nozzles to atomize the fuel properly? would it even get the steel up to proper heat? if anyone has any experience or even some harebrained guesses they'rd be much apreciated.

I suspect it would wore fine. Gasoline burns very hot a has more BTU per gallon than propane. Some people put a lot of work into oil forges, but often can get the oil cheap or even free. Around here, propane is cheaper than gasoline. How much cheaper is gasoline than propane and how long would it take you to recoup your effort?

[pkrankow]

Gasoline burners crossed my mind too, but I would use a fuel pump, or limit the vessel to a gallon or so for safety reasons. There is a reason the pressurized outboard motor fuel tanks are not used anymore. I have heard many tales from old timers going out fishing and BOOM! hot sunshine on a pressurized 1/4 tank of gas blew the bottom out with a fireball!

Now an atomizing sprayer that can run waste vegetable and waste motor oil through simple burner arrangement would be the thing! Most oil burners I see designs for use cumbersome burn chambers.

Phil

[junker]

would the fuel rail off of a car work? or even off of a diesel. i know the cummins diesel in particular (only used the example because i know it best, i am in no way advertising) uses reduculously high pressures in it's fuel pump (in diesel's this is on the side of the engine the pump that is in the tank is called a lift pump) maybe use the fuel rail and fuel pump off of a small diesel engine to spray the fuel (gass or oil) for the forge. maybe drill a tiny hole in each injector so that they continuously spray? would a carbourator with a turbocharger (or it's electronically powered equivelent) on top of it to force air through and then just use the normal fuel ports in the carb to deliver the fuel?

[pkrankow]

I don't know about diesels, but cars have one fuel pump...in the gas tank.

Fuel injectors are solonoids, normally closed IIRC, and when proper voltage is applied they open and the spray forms a very fine mist, ideal in fact for mixing and burning, so why mess with it? It is nice to have an "off" switch that is quicker than pressure running down.

Don't forget the fuel pressure regulator on the return end of the injector rail with a recirculating line back to the tank.

This is suddenly feeling like a "tab A into Slot A" kinda thing. Once you have a good blower, good fuel pump, good fuel injector, and the proper voltages to run everything it should be easy. Just need to cobble together a manifold...No reason it won't work.

In fact it is seeming almost scary easy.

Pay mind to leaks before even thinking about lighting a fire. I have seen a pinhole in a high pressure fuel hose throw a stream of fuel over 10 feet.

If I had free run of a bone yard I might consider this even.

Phil

[Glenn]

Let me throw in a word of CAUTION here. Pressurized and flammable fuels do not play well with open flames or ignition sources. Put them in a closed container and it adds another level of excitement.

The nonsense about gasoline and dynamite
A lot of times, it is the rate at which the energy is transferred or released that is more important than the amount of energy. There is an often repeated statement that a cup of gasoline is the same as 16 sticks of dynamite. Are they talking about the energy or the power (rate of release)? First off, energy probably isn't an appropriate comparison. After all, the energy in that cup of gas (around 8MJ) is the same as the energy in about a pound and a quarter of wood, which clearly isn't really comparable. Anyway, on an energy basis, the cup is more like 4 pounds worth of high explosive(8 MJ for the cup of gas, 2 MJ for the pound of HE).

More significant though, is that the explosive releases all of the energy in around 4 microseconds: a rate of 2000 GigaWatts. The gas-air mixture takes 2 or 3 milliseconds to explode (the combustion wave is limited to the speed of sound), for a power of around 3 GW. And of course, the wood takes several minutes to burn, for a power of around 30 kW.

For an interesting exercise compare this to a small nuclear explosion of 20 kilotons (= 80 Tera Joules = 8E13 Joules), where virtually all the energy release takes place in about a microsecond for a power of almost 10 to the 19 watts. 80 TJ is a bunch of energy (about what a 1000 MW power plant puts out in a day), but it is the phenomenally high rate that makes nuclear explosives really different.


Calculation background:
Gasoline has an combustion energy of about 47.4 MJ/kg, so a simple calculation will show that the cup (170g) will release about 8MJ when burned. When vaporized and mixed with air at the optimum ratio (stoichiometric), the mixture will occupy about 2100 liters, or a sphere some 0.80 m in radius. Assuming the mixture is ignited at the center of the sphere, it will take about 2.5 milliseconds for the flame front to propagate to the outer edge. This makes the assumptions that the flame front moves at the speed of sound (probably reasonable), and that the sphere of mixture doesn't expand appreciably due to the heating in the middle (probably very optimistic). So, 8 MJ in .0025 seconds is 3200 MW, or 3.2 GW

The detonation wave in most high explosives moves at around 4500 m/sec, substantially above the speed of sound (which is what makes it a detonation, and not just burning fast). That 4 pounds of explosive would be a cylinder about 5 cm in diameter and 20 cm long. At 4500 m/sec, it takes about 4 microseconds for the detonation wave to move through the entire amount. 8 MJ in 4 microseconds is 2000 GW. Reference

They no longer make pressurized out board motor fuel containers, plumbers blow torches, and several other gasoline related items for a reason. Please, use caution and play safe.

[pkrankow]

Let me throw in a word of CAUTION here. Pressurized and flammable fuels do not play well with open flames or ignition sources. Put them in a closed container and it adds another level of excitement.

After reading what Glenn has to say, Yes, Scary easy.

Phil

[junker]

I don't know about diesels, but cars have one fuel pump...in the gas tank.

Fuel injectors are solonoids, normally closed IIRC, and when proper voltage is applied they open and the spray forms a very fine mist, ideal in fact for mixing and burning, so why mess with it? It is nice to have an "off" switch that is quicker than pressure running down.

Don't forget the fuel pressure regulator on the return end of the injector rail with a recirculating line back to the tank.

This is suddenly feeling like a "tab A into Slot A" kinda thing. Once you have a good blower, good fuel pump, good fuel injector, and the proper voltages to run everything it should be easy. Just need to cobble together a manifold...No reason it won't work.

In fact it is seeming almost scary easy.

Pay mind to leaks before even thinking about lighting a fire. I have seen a pinhole in a high pressure fuel hose throw a stream of fuel over 10 feet.

If I had free run of a bone yard I might consider this even.

Phil

in a gas engine the injectors are solinoids. but in a diesel the game is about pop- pressure. when enough pressure is behind it it opens. remember, any fuel going into the cylinder in a diesel is forcing it's way past the compression in that cylinder at it's highest point. (probably why the fuel pump in a diesel is so redicuoulsy high pressure)where as a gas engine is essentially being sucked in on the downstroke (or just sprayed in at the lowest point of the piston) so i have no clue which would be better. if any1 has any ideas im open lols. but i wonder it the carborator with a high pressure fan on top would be the better bet. it would atomize the fuel with the incoming air and then you could set it up on a nozzle like a normal propane forge. sorry if this sounds moronic to anyone but im just throwing out ideas. and don't worry glen ill be carefull. lols and if i blow myself up ill make sure not to let IFI slip in any way :P

[Glenn]

Phil, I looked into (pun intended) using waste oils as a fuel source, first for heating and then with the intent to develop it into a forge. Got the design from a "known source" and built the prototype. There was a small design flaw in the plans and the combustion flamed out. As I looked into the open air intake, the thing re-ignited blowing 4 feet of flame out every opening and orifice available. I can tell you with certainty how long it takes for eyebrows to grow back.

Design #2 was built with a more compact burn chamber, MUCH thicker metal (1/4 inch plate steel) and included an explosion proof design. This (design 2) is a manually operated system that MUST have constant attention and adjustment. The design is still being tweeked.

Would I try to run it on gasoline - NO !!
The Darwin awards are still taking applications and I do not want my name on the list.

[pkrankow]

Last thoughts on this. In a modern fuel injected car fuel is metered by how long the injector is open, so if pressure is constant you would need a pulse generator to run the injector, not just an on/off switch.

Now, even if I go to a bone yard and start asking for parts at a "pull yourself" yard the used parts are hundreds of dollars (I have bought most of this stuff for a car before, both new and used) so it is back to the cost vs benefit.

I checked, the explosive limits for propane is similar to gasoline. It is simply way easier to get too much gasoline in the system than propane (being liquid and all). Propane has about 75% the energy of gasoline per unit volume.

I'm going to leave this alone for now since Glenn is prodding so much.

Phil

[Glenn]

I'm going to leave this alone for now since Glenn is prodding so much.

IForgeIron has always pushed safety first.

There are some devices that use gasoline as a fuel source, and power source, but you need to know ALL there is to know in order to use them safely. I am just trying to provide some knowledge on things that can go wrong, how wrong, and how fast.

Personal safety is just that, YOUR taking the responsibility to keep YOU safe.
(steps down from the soap box making room for someone else.)

[pkrankow]

. but i wonder it the carborator with a high pressure fan on top would be the better bet. it would atomize the fuel with the incoming air and then you could set it up on a nozzle like a normal propane forge. sorry if this sounds moronic to anyone but im just throwing out ideas. and don't worry glen ill be carefull. lols and if i blow myself up ill make sure not to let IFI slip in any way

Sounds as simple as it gets. Get a 1 or 2 barrel carburetor and go for it! You already have a fuel metering scheme set to approximately the correct ratio. Build a plate like an intake manifold so the carburetor operates as it should, run directly to the burner.

I don't know what volume of forge to attach it to though.
Phil

[junker]

all i need is a small knife forge, something with a removable back so i can work longer pieces. but i'd like to be able to forge weld billets in it. i'd like to try it with a small carb first just to check if it works (and for safety's sake)

[pkrankow]

OK, dumb thought for a carburetor... how do you turn it off? What about electric power loss?

With a propane forge you turn the fuel off and it is good. With a blown propane forge how dangerous is loosing power? If you just cut air wouldn't the carburetor "backfire" if there was fuel left in it? With propane a gas solenoid can be used to cut fuel if power is lost, but with a carburetor, what about fuel remaining in the float bowl?

I know some carburetors do not use float bowls, but would a lawnmower carb be big enough to fire a small forge? That lawnmower does not use a float bowl because the entire fuel tank is hanging off the bottom...but they backfire without further headache at least...

Phil

[cckemm]

My father has an older army gasoline burner meant for large portable kitchens so I did a quick search on the net and came up with this.

Gas Forge Blower

Much easier to use technology that already exists than to reinvent the wheel.

[poleframer]

Wonder if diesel would go through a gasoline fuel injection nozzle...would be less explosive, and a safer fuel I think.

[junker]

doesn't diesel have to be compressed to burn?

[Dragons lair]

doesn't diesel have to be compressed to burn?

Needs lots of compression to fire an engine(over 300psi in my garden tractor)
However an oil furnace burns with no compression(fine vapor). #2 heating oil is about the same as diesel. A lot of folks burn off road in the oil furnace.It is
about $.50 a gal cheaper.
Ken.

[junker]

the only problem is that using diesel would defeat the purpose of making it (gas cheaper than propane where i live)

[Dodge]

doesn't diesel have to be compressed to burn?

I'm not a diesel mechanic but my father was and this is the way I remember him explaining it: It doesn't have to be compressed to burn. It has to be heated closer to its flash point (gasoline has a very low flash point). Diesel's is higher than a spark plug and the compression of a normal gas engine can ignite. Therefore, a diesel runs at much higher compression and uses a glow plug instead of a spark plug. Diesel will burn out side the engine when it gets hot enough. Just like oil, it has to be preheated. That's what the glow plug inside a diesel engine does. It preheats the fuel so the compression will start the burn easier. Once the engine is running, the glow plug generally shuts off as it is no longer needed.
For a burner to run on diesel, it would need to be preheated just like a waste oil burner.

[Sweany]

Heck I drive a gasoline burner to work ever day.

Gasoline forge? check this out.

http://steampunkworkshop.com/foundry-furnace-part-4-gasoline-burner

[edge9001]

that seems to the the answer to thse question posed by this thread. only for a forge running soley off of gasoline, I recommend perhaps using an old car fuel tank instead of the urn. with a little enginuity(spelling??) you could also rig up the original fuel pump, float valves, and fuel gauges and have a safe way to monitor the fuel levels. if used indoors i would out it near a wall and mount the tank outside for safety.

just my 2 cents

[Dragons lair]

I'm not a diesel mechanic but my father was and this is the way I remember him explaining it: It doesn't have to be compressed to burn. It has to be heated closer to its flash point (gasoline has a very low flash point). Diesel's is higher than a spark plug and the compression of a normal gas engine can ignite. Therefore, a diesel runs at much higher compression and uses a glow plug instead of a spark plug. Diesel will burn out side the engine when it gets hot enough. Just like oil, it has to be preheated. That's what the glow plug inside a diesel engine does. It preheats the fuel so the compression will start the burn easier. Once the engine is running, the glow plug generally shuts off as it is no longer needed.
For a burner to run on diesel, it would need to be preheated just like a waste oil burner.

I have to disagree with a few points. Glow plugs do not preheat the fuel.On my tractor and trackhoe there is no fuel being pumped while the plugs are heating.
after running a while they will start without the plugs. Also I have no preheater in my oil furnace. Atomized oil is blown thru a transformer arc.
Ken.

[MattBower]

I've built an oil burner, although I no longer use it for a variety of reasons. I would think you could run gas in any of the oil burner designs with a little tweaking. In fact, the hardest part might be re-engineering them to prevent the gas from igniting too soon. But that's exactly what I like about oil vs. gasoline: oil is inherently safer. Its much higher flash point means oil is much harder to burn. Yes, that makes it more difficult to engineer the forge to sustain a burn. But it also makes it much less likely that something will go badly wrong. A small oil spill is no big deal. A small gasoline spill has the potential to very quickly become a big gasoline fire. (And as Grant pointed out, oil can often be had cheap or free. Gas costs good money.)

Just my $0.02.

[Dodge]

I have to disagree with a few points. Glow plugs do not preheat the fuel.On my tractor and trackhoe there is no fuel being pumped while the plugs are heating.
after running a while they will start without the plugs. Also I have no preheater in my oil furnace. Atomized oil is blown thru a transformer arc.
Ken.

Like said, I was just remembering what Dad told me. I'm older than he was when he told me , but that makes sense now that you mention it, Ken. But the fuel is being heated before the engine runs if "there is no fuel being pumped while the plugs are heating." I do know that without the fuel being warmed it won't ignite easily without compression or atomization. This is why the fuel in a jet engine burning JP5 (basically high grade fuel oil with a higher flash point than JP4) has to be heated before it is introduced to the already compressed air in the combustion stage and subsequent turbine. (Not a diesel mech but I was a jet mech)
I wasn't aware of the atomization of the thinner fuel oil in a (commercially made ?) furnace but I was mainly referring to a waste oil burner in a home made forge. Waste oil would be much thicker than fuel oil and difficult to atomize by the backyard forge builder. We're still talking forges right? Sorry for going too OT.
Scott :)