Venturi Forge Build Part II - Burners

Continued from Part I Here

The first things I wanted to build were the burners. This is the only part that really needs to be precise. Namely, the drilling of the orifice where the propane enters the pipe to the forge. There are two basic types of burners, Venturi and Blown burners. Blown burners use a fan to mix the fuel and air and propel it into the forge. They are great, but I prefer to avoid the limitation of needing a power source. Venturi burners use the nature of gas exiting a small hole in a stream to create a vacuum which draws atmospheric air with it down the burner into the forge. They might not be considered to be as efficient or controllable as blown burners, but they are completely self sufficient as long as there is a gaseous fuel source being pushed out of the orifice.

So, to begin the build.

This is the layout for a simple venturi burner. The propane will flow in through the T fitting in the top middle, exiting through holes that will be drilled in the brass pipes. The gas will then shoot down the 3/4 to 1 1/4 bell into the black iron pipes (3/4") into the forge, drawing with it the air. All you really need to do this is a drill and a bit of patience.

First I marked the holes to drill in the bells for the brass pipe to sit. The hole will go all the way through both sides so the cap can seal off the outside ends of the brass. There are several variations on how actually to build a venturi burner, but this is how I will be doing mine.

Pilot holes drilled, an arbitrary size that had a sharp drill bit. I held these to the platen of the drill press by sliding a dowel rod through the bell and clamping that down. I had to support the 3/4" end of the bell so it was not at an angle.

Drilled to the final size. This was where the first snag hit. The largest drill bit the chuck could hold was just under the outer diameter of the brass pipe, so I had to file it out by hand until I could fit the pipe through it.

I have learned the hard way that it is important to always fit things as they will be when at the final state of assembly, else there will be errors and shortcomings. Here I fitted the caps to the pipe and slid the lot through the two holes I drilled in the bells. This is a good representation of where they will be when all assembled, so I marked the centre of the 3/4" hole on the bell where the orifice will point.

As marked, I centre punched the pipe so I can drill it without wobble. This is critical because the drill bit is so small (size #57) and would easily break if forced onto the convex surface. If nowhere else, this is the place to take your time.

I held the pipe in place with a piece of scrap lumber sawed in half and clamped to the platen. By minute adjustments I aligned it just so.

And in the final stages of the second hole, the bit snapped inside the hole. This is why I bought two of the bits. A few minutes of surgical extraction later and I had the bit freed. Fortunately the damage was contained and I was able to eliminate its effects within the radius of the finished hole.

Now onto assembly. It is necessary to ensure a tight fit of all the fittings, so I used nylon plumbers tape to wrap the threads. You could solder them or use some sort of liquid binder, but I had neither of those around and I used this on my old forge with no problems. A combination of the tape and tightening them to death seems to do the trick. However, ALWAYS check fittings for leaks when working with flammable/explosive gasses. One good way to do that is take a spray bottle and fill it with soapy water. Turn on the gas and spray all the connections. If you see bubbles from the joints, there is a leak.

Before I sealed the ends, I took a full round file and removed the burrs from where I drilled the orifice. Flow is a touchy thing, and those burrs could be enough to make the stream out of the orifice more turbulent than strictly necessary. At this stage I also took a hammer and slightly dented the pipes just before where they would enter the inside (non capped) side of the bell. I did this because it will prevent the bells from rotating around the brass pipes, which is not a good thing (the orifice needs to be pointed as close to down the centre of the black iron pipe as possible).

Together the two bells join with the T fitting, again sealed nice and tight. It is critical that you check to see the orifice is still pointing down the centre of the 3/4" (smaller) side of the bell. If not, just be careful to tighten one of the pipes or fittings until they are aligned with the bell that the two bells are aligned with one another.

Because I could not find a gas rated 1/4" valve that had male connections on both side, I had to join the T to the valve and the valve to the hose with two 1/4" male-male pipe fittings. An extra step but not catastrophic. Just be sure to seal the fittings!

And here it is with the hose and regulator attached. I scavenged the regulator from my old forge's burner, as I could not find them locally and didn't want to wait to order one. The regulator allow you to control the pressure of the gas as it enters the orifices. Since there are two, each will theoretically receive half the pressure. That means I would need to burn twice the amount of gas for the same intensity flame as my old forge, but I have faith that this one will be better insulated so it will not need to run at as high a pressure to hold a temperature.

Next step, building the housing.

Continued in Part III Here

Venturi Forge Build Part I - Design

The initial design of this forge was inspired by my small one burner venturi forge being too small and thermally efficient for many of the projects I want to pursue. Some of the main design considerations were having two burners for a larger interior chamber size, a door on the side to allow larger pieces to be inserted (crucibles, armour work, etc.), and a much greater thermal efficiency. A good deal of the aesthetic design has changed due to tooling limitations, but the functionality remains essentially the same.

Above is the original design that I sketched one night on a red eye flight. Although I never actually measured anything or referred to it during construction, I held mostly true to it.


As life presents me with an ever changing outlook on the nature of possession, I have begun tending towards a state of mind where I want to be inspired by the objects around me, my tools, my workplace, where I live. And for it, I decided to start drawing a design that I would later hammer into the housing of the forge much like I did with this armguard.

This is the original design I started drawing that same night as the forge body, but it never really took me. So I started over, similar in concept but different enough that I was able to make something of it.

Over the course of the next several weeks, I started accumulating parts and materials for the construction, but then as fate would have it I fractured my finger right as the last pieces arrived. Unable to begin working on the forge, I had to content myself to the half truth that I would be better off waiting until I could hold tools again.

A good many weeks later, I am finally able to start the build. Below is a list of all the parts I have gathered and used, everything from the sheet metal to the rivets. More to come soon.


Parts List:


-Forge body-

.06" Sheet, 24"x36" -- for use as the shell
.06" Sheet, 12"x12", x2 -- for the two end faces
5/16" rod, 3' long -- to use as a handle/tool/firebrick shelf outside the working end
1/4" rod, 3' long -- to cut and make rivets out of, holding the body together
1/8"x1/2" rectangular bar, 6' long -- various structural reinforcements, around circumference of ends and on side door, and legs
1/8"x2" rectangular bar, 1' long -- brackets to reinforce where the burners meet the housing
Heat resistant black paint -- didn't get this one yet as the shipping would be at hazmat costs so I'm seeing if I can find it local. Used to paint the outside of the forge to give it a uniform, matte, rust resistant finish. After looking around I found this at the local hardware store marketed for stovepipes and grills.
3/4" Flange and accompanying bolts -- to connect burners to shell
Hinges -- For the door on the side. I was going to make these myself but decided not to...
3/16" rod, 3' long -- assorted rivets that the 1/4" was too large for
1"x3/32" rectangular bar -- to seal off the sides and bottom of the door to prevent flame seepage and cover the tool marks of cutting it out


-Burners-

3/4" Black steel pipe, 8" long, x2 -- shaft of the burner
3/4 to 1 1/4 bell reducer -- Flare at the top of the burner to hold nozzle and for air intake
1/4"x4 1/2" Brass pipe, x2 -- gas pipe line that will be drilled for the venturi nozzle
1/4" inner diameter brass pipe cap, x2 -- closes the non feed end of the nozzle pipe
1/4" inner diameter brass T fitting -- joins the two brass pipes and connects them to the gas line
#57 drill bit -- For drilling the pipes for the venturi nozzle (I ordered 2 in case one breaks)
1/4" Ball Valve -- (Female coupling on both sides) Last line of defence for the propane line, quick shut off if needed. Male coupling on both ends preferred, but none were available.
1/4" Pipe nipple, x2 -- For joining the valve to the burners and the hose to the valve
1/4" Propane hose -- To attach the burners to the propane tank. I was going to use the one from my old forge but decided to salvage only the regulator.
Propane regulator -- To join the hose with the propane tank and to regulate the propane PSI as it enters the burners. Using my old one, as I could not find any with a readout and throttle.


-Lining-

Kaowool, 1"x24"x5' -- synthetic wool lining, other brands are fine. I may have to order more of this, as it might not be enough to do 2"
Satanite Refractory Mortar, 3 Pounds -- seals the kaowool fibres and makes it a little more durable
ITC-100 Refractory Coating, 1/4 Pint -- IR coating, dramatically increases the efficiency of the forge. This will be placed over the satanite
Bubble Alumina Refractory Coating, 2.5 Pounds -- High flux resistance and rates over 3000 F, used for the floor lining (firebrick) and around the edges/burner inlet. This will be placed as an outer layer where applied
Firebrick, x3 -- 2 are for the floor of the forge, one in case one breaks/for a shelf outside the front

A Long Way Home

08 January, 2014

Dublin

0603 Greenwich time

Some of the worst winter storms in recent memory have swept the United States, grounding thousands of flights because of the high winds and extreme cold in excess of -30^oC. The flight back was scheduled to depart at 1130, arriving in the states at 1345 (Eastern Seaboard) after five time zone changes, to which I had a connecting flight to the Midwest at 1600. With more than two hours to move three gates down.  And then the first news came.

0930

We arrive at the Dublin airport and wait in line at the check in queue and there are people everywhere, baggage strewn about and airline agents frantically trying to deal with irate travellers. After some time, we learn that there have been hundreds of flight cancellations at JFK International Airport and across the US at large. The flight was delayed for a 1430 departure, to arrive at 1705 arrival.

1030

We are finally able to check in for the flight to JFK, and I hear that, because my connecting flight was not booked on the same itinerary, they would not be able to reschedule it until I arrived at JFK. Alright, worse things have happened. I would be able to find another one there.

1100

Security behind us, a final meal in Ireland eaten, past customs and the second security checkpoint, and we were waiting in the gate.

1400

The plane finally arrives and the previous passengers disembark. While the flight crew assembles and prepare for the 7 hour flight, we begin to form a line outside the gate.

1445

Takeoff. The seat is in the middle and my legs are long, but it is not the worst I have seen. Then I found the not-too-old gum stuck to the carpet right where I have to stick my feet so my knees are not wedged on the back of the seat in front of me. Alright. Stick the plastic of the in-flight headphones on it (which are the worst ever, if you have never had that pleasure) and forget about it. In-flight entertainment is down, but that is what books are for anyway.

1530

Movie time. Groovy.

JFK International Airport, USA

2205 [1705 EST]

Arrival at JFK. From the back of the plane (seat 40 of 41), it took a solid 30 minutes. By the time I was able to speak with the agent at the gate about possible flights, the last one for the day had left 10 minutes ago. After searching around, she found another at LaGuardia airport, about 15 minutes away from JFK that would depart in 2 hours, and it is the last flight of the night. Excellent. Down to baggage claim.

2250 [1750 EST]

Baggage arrives.

2300 [1800 EST]

Embark for LaGuardia. Traffic is clear at first, but the farther out of JFK we go, the worse it becomes. The 15 minute drive turns to 30.

2330 [1830 EST]

Arrive at LaGuardia. I have never been to this particular airport before, but the signs seem to be obvious enough. There is a single building with large letters on the top reading the name of the airline. After getting out and walking up to the windows, I see that it is only the arrivals. Perfect. The plane leaves in less than 45 minutes. So I make my way the only way there is to go, down towards the rest of the airport.

2340 [1840 EST]

I find the desks and get my ticket, check my bag, and make my way through security. On the other side I try and find my gate, but there are only C and D gates, but my ticket reads SH4. I have no idea what that means, and with less than 20 minutes to get to the flight, I find someone. The first security agent has no idea, and neither did the second. After a third, they concluded that it was in Terminal 4. Where was I and why did the ticketing agent not tell me I was in the complete wrong building? No time to think. They said there was an airport bus that would take me there, the A Line.

2355 [1855 EST]

I find the bus stop, and the A Line bus is just pulling away. Bloody brilliant. Fortunately, it stops three feet later because of the traffic. As I run up to it, the bus driver looked at me and I asked through the door if it was the A Line. Of course it was. Then I asked if I could get on it. Of course not. The driver looked back to the road and drove away with me standing there in the -10^o winter without a jacket (in the checked bag, of course). Now I have nothing to do but to stand there like an idiot trying to think of a way to get to the other end of the airport. There is nothing for it but to go afoot, and so I did.

2405 [1905 EST]

I eventually forsake walking and get on one of the B Line busses which go about half way there. By now, it is too late to get on that flight, so I try and figure out what happened to my bag. I cannot go back to the original ticketing desk, as there is no one there to ask about baggage claim. The next bus should come in about 10 minutes, so I wait. 5, then 10, then 15, then 20, and still no bus. Over half an hour later one finally comes and I take it about 6km past the main airport to a small building with 4 terminals servicing AirFrance, some other airline, and the one I need that specifically handles flights to Chicago O'Hare. Nowhere in the airport signs does it mention that, or why it is that way.

2430 [1930 EST]

Inside the small outbuilding I went to the desk and inquired about flights out. No luck until the morning. The earliest flight was at 0615 EST. And of course, the airline was less than accommodating. The flight could not be transferred to another nearby airport, for whatever reason, despite this being the fourth flight since the ticketed one. Neither could they provide any transportation or lodging. Other than the wooden bench outside.

0010 [2010 EST]

I find that my bag never made it to the flight it was checked in for. Why? Who knows. It was flagged at being at the wrong deposit location but never touched again. I wish they would have told me that it was not the right location too, before I went through security. I asked if they could do anything to change it to my flight the following day. Of course not. But they would take care of it, they promised. And do I need to do anything? Absolutely not. And it will be on the plane tomorrow? Yes, because it is the airline's business now that it was not on the other flight. It would be taken there as soon as possible, which would be the flight I am ticketed to be on. And I do not need to do anything? No, they have it taken care of. They reassured me, despite everything else. Then they told me that the new flight I was booked for was cancelled. A few minutes later, they realized that it was the day's before that was cancelled, not mine.

0100 [2100 EST]

I find my way to the benches, and there is little more. The one store that was there is being closed down and there are no restaurants. The last meal I had was the in flight meal 11 hours ago. I pass a few hours reading amongst other things. The room is cold and the bench hard, and I need to be up at around in a few hours.

0845 [0345 EST]

Two hours or so of the worst sleep since hiking down from the summit of Mount Marcy in a 4 hour downpour, and I decide any more is fruitless. So I wake up and twiddle my thumbs and wait for the terminal to open. When I finally get through security for the fourth time of the day I can at last sit in a comfortable seat.

1100 [0600 EST]

The plane boards and leaves for the Midwest, for once smoothly.

1445 [0845 Central Time]

I arrive at O'Hare, and move towards baggage claim to see if they lived up to their end of the deal. 10 minutes, then 20, then 30 and I am alone with a sea of luggage with two other passengers who do not have their luggage.

1530 [0930 CT]

After wading through the lines I present the original baggage claim tag for the checked bag, and the lady behind the counter starts typing slowly on an ancient computer. And…the bag was never loaded on the plane. Nor would it be, as it was nowhere in the system to being processed.

1615 [1015 CT]

Finally, we come to find that the bag will be on a flight leaving LaGuardia at 1215 EST, so it will have to be shipped on arrival. Only, there are hundreds upon hundreds of other bags that need to be shipped, so it will take days. Sounds about right for the day.

1725 [1125 CT]

Finally, I am home. Exhausted, ravenously hungry, and in two day old clothes. It was an unforgettable end to a trip of a lifetime, and I am glad to have gotten here however long it took.