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  1. #16
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    Looks great Bob.
    The door is especially interesting- they give no end of trouble. We expect them to move and expect the brittle refractory to last.
    you'' have heaps of fun with it. I've been using a Corin special this last few weekends at a friends place; did i say i love furnaces?!

    Andrew.
    'Waratah' spring hammer by Hands & Scott c.1911- 20, 'Duffy, Todd & Williams' spring hammer c.1920, Premo lathe- 1953, Premo filing machine.

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  3. #17
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    Quote Originally Posted by AndrewOC View Post
    Looks great Bob.
    The door is especially interesting- they give no end of trouble. We expect them to move and expect the brittle refractory to last.
    The door is a copy of a door on an electric furnace I used a fair bit where I used to work and it worked for years for me without any problems. The door on my furnace worked well up until this evening when I noticed the frame width had expanded so that the refractory bricks (which was already a loose fit) was starting to wander out of the frame. I think I can easily fix this and then I think it will be fine. I wish I had moved the counter weight over just another cm or two as it gets fairly warm so I think I will add a length of wire to the existing cable so that the counter weight rises and falls below the level of the door way so then it won't get hot. lowering the counter weight will also make the whole this a bit more stable.

    you'' have heaps of fun with it. I've been using a Corin special this last few weekends at a friends place; did i say i love furnaces?!
    Andrew.
    I can certainly see a lot of possibilities opening up. I have to keep reminding myself that I primarily put this together for my tool making process but I can see some distractions heading my way.

    I played around with the flame this evening and realized I do not have enough air going to the torches to blow them out so they could probably use more air.

    Here is night time pick of the torch flames
    Nighlights.jpg

  4. #18
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    Still waiting for a bit of time to put in my gas line to my shed but mean time I decide to pimp my Anvil stump.

    I added a tool rack and some levelling legs.
    Not many tools as you can see because I will be making my own.
    The legs only level the stump on the concrete floor - the majority of the weight is still taken direct by the stump, the legs just stop the stump from rocking
    Building a natural gas forge - WIP-img_3847-jpg

    Building a natural gas forge - WIP-img_3846-jpg
    Attached Images Attached Images

  5. #19
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    I finally got some dedicated me time and last week I installed 22 m of 19 mm diam copper underground to the shed which was a bit of a drama in itself. So I can now run my forge inside my shed. I have also upgraded my fume hood ventilation to a i300 cfm unit so that I won't gas myself.

    In the mean time I modified the forge gas plumbing to make it 19 mm plumbing all the way from the meter to the T piece on the forge where the gas line switches to 1/2" diam plumbing to each torch. The previous arrangement was all over the place. 19 mm to within about 2m of the back veranda gas bayonet, then 1/2" to the bayonet, the a 10 mm flexi hose to the forge, the to a 1/2" T piece and finally through gas taps with a 7.2 mm orifice so the net effect was I was gas flow limited. The other reason for going 19mm was that my gas supply is very low pressure and 22m of line could serious slow down the flow rate.

    Nothing much to see really, I took away the idler circuit because it wasn't working properly and I need to rejig it.
    The electronics on the gas supply post is a new starter. Previously I had a push button BBQ starter but I have switched that for a battery powered starter from a hot water system - more details below.
    Anyway I fired it up briefly and got to 1100ºC with just one torch and the gas valve opened about 3/4 of the way so still have a lot to play with.
    Building a natural gas forge - WIP-newforge-jpg

    Here is a close up of the starter. The HV unit from the HWS has a number of sensor inputs which are basically relays that can be short circuited except for one that is wired to a switch.
    Throwing the switch sends a fat spark across the spark unit with a frequency of about 2 sparks per second so it lights a bit more assuredly than the push button BBQ starter.
    Building a natural gas forge - WIP-starter-jpg

    I heated up and belted around a bit of hot metal but it was 8:30 pm so I could not go for long.
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  6. #20
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    Haven't had time to experiment much today but I discovered a couple of things.

    1) Don't disconnect an air hose for one torch back back at at the blower when the forge is running on the other torch. The hot exhaust gasses inside the forge will go back down the unconnected air hose and melt it very quickly! It's OK not to be running the torch but the air hose must be connected and blocked off. I was wondering what the hot plasticky smell was

    2) Make sure the air hoses are firmly connected. If an air hose comes off when the forge is at full operating gas/air the reduction in air flow to the torch generates a huge yellow flame out of the forge doorway. Before this happened I had just jammed the hoses onto their respective fitting but since then I have clamped them down firmly with hose clamps.

    3) I lit the second burner and without much tuning I got the temp of a bit of steel up to 1250ºC as measured by a pyrometer. Two burners puts out a fair bit of exhaust heat and heated the whole shed up very quickly. I wondered why the ventilation fan was not coping and then realized I had the shed doors closed - it cooled a little once I opened the main shed door but its not good for the neighbours to hear me belting steel - guess it's going to be a daytime only operation.

    If this sounds a bit nerve wracking - it is a little.
    One certainly has to concentrate and not take things for granted - I certainly wouldn't be doing this without good ventilation.
    Just for the record I also do have two fire extinguishers on hand.

  7. #21
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    Bob - I'm sure you will be perfectly fine - muscled, bare-chested and sweating ... hammering away lit only in the light of a roaring furnace and the occasional solar flare.

    If you did it in slo-mo it'd be like the blacksmithing version of Baywatch (complete with explosions)

    ... "SmithWatch" ? "Forgery" ? "Irony" ? "Hot Metal" ? "Striker & Hardy" ??

    Do we now have to refer to you as 'Smitty'?

    Cheers,
    Paul

  8. #22
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    Quote Originally Posted by pmcgee View Post
    Bob - I'm sure you will be perfectly fine - muscled, bare-chested and sweating ... hammering away lit only in the light of a roaring furnace and the occasional solar flare.
    If you did it in slo-mo it'd be like the blacksmithing version of Baywatch (complete with explosions)
    ... "SmithWatch" ? "Forgery" ? "Irony" ? "Hot Metal" ? "Striker & Hardy" ??
    Do we now have to refer to you as 'Smitty'?
    Cheers,
    Paul
    Sweating - definitely, muscled -hardly , swearing - you bet . . . . .. I'll be taking a lot of shortcuts and my grinders and linshier will be working overtime to correct my mistakes.

    Do we now have to refer to you as 'Smitty'?
    FWIW my Italian grandad on my mums side was a blacksmith - her maiden can loosely be translated into smithy.

  9. #23
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    I haven't done anything with the forge because I was waiting for a kosher 19 mm gas hose to arrive.
    It looks like a fire hose compared to the standard 1/2" hose
    Building a natural gas forge - WIP-hose-jpg
    Now I just need to get a couple of fittings and I'll be all set.
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  10. #24
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    One of the reasons I have not done anything for a while with my forge is because I realized it badly needed some safety features.

    The major problem was that being a blown gas forge, if for whatever reason the forced air supply was to stop, the small blue blown flame would immediately turn into a very large yellow fireball.
    The fireball would be so big it would engulf the forge and I could not hope to get near the manual gas taps either on the forge itself or the stopcock on the wall behind the forge. Then I would have to run some 20m to the next stopcock back up near the house.

    The air flow could stop for any number of reasons e.g. blower failure, mains power failure or I could just put a red hot piece of metal through one of the plastic air supply hoses.

    After much mucking about, this is what I came up with to automatically turn off the gas on air flow failure.

    It all starts with the psuedo Pitot tube.
    One copper tube points into the air stream and the other is perpendicular to the air stream which generates a small but measurable pressure differential under air flow
    Pitotube.jpg

    The pitot tube is mounted in a 3/4" BSP T fitting so that the ends of the copper tubes are in the middle of the air stream passing through the forge torch
    Pitotube2.jpg

    The pitot tubes are connected to this air flow switch ($20 from fleabay) using 2 pieces of black irrigation tubing - sorry its so hard to seeing being all black
    The two blue taps are air pressure bypass monitors that I can attach to an air pressure meter to set the switch triggering point.
    The switch is adjustable from 0.1 to 10" of WC.
    AirflowSwitch.jpg

    I have set it so that when the air pressure falls below about 0.2" of WC the air flow switch opens removing power from this 24V solenoid valve.
    Solenoid.jpg
    Interestingly got the solenoid valve out of a skip at work. The valve was part of a water cooling control panel for a vacuum furnace. Tis indeed amazing what is thrown out.
    The fancy looking ex-CPU fan and heat sink have been added to cool the solenoid which gets quite hot as it really meant for use use with water which would carry the solenoid heat away.

    Unfortunately nothing is quite as simple as what I have described above as lighting the flame requires no forced air but some gas, so the air flow sensor needs to be temporarily bypassed while the flame is being lit.
    So I made up this control box (grey box in middle of photo) that has a few bells and whistles to enable a safety aware startup to take place
    COntrol.jpg
    A small switch temporarily bypasses the the airflow sensor. At the same time the bypass displays a red LED and sounds a piezo buzzer to warn the operator that the airflow switch has been bypassed.
    The operator can then manually open the gas line just a whisker to light the gas (this generates a yellow smokey flame about 150 mm long)
    The the air supply is turned on just enough to get the flame approaching a green colour.
    Then the gas is turned up some more, the air some more, and this is repeated until a satisfactory flame is generated.
    At this point the air flow is sufficient to keep the air flow switch closed so the bypass switch can be turned off.
    This also switches off the red LED and the buzzer, and also switches on an orange LED
    If the power fails at anytime during start up the solenoid will still active and turn the gas off and the orange.

    The control box contains the 240/24V AC transformer and the rectification circuits for the LEDs and Buzzer.

    I can't use the forge for blacksmithing for another 4 or so weeks due to some surgery I had a recently but I will at least fire it up tomorrow and do some testing with small flames .

    I also got myself a CO and mains gas sensor/alarm so that I don't gas myself in the process.
    Attached Images Attached Images

  11. #25
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    I finally fired up the forge with the new safety features and the upgraded plumbing.


    The safety cut outs all work fine which I am very happy about.


    Previously my gas plumbing was a bit of a mess with some section of the plumbing as narrow as 5/16" in diam.

    Now I have 3/4" pipe all the way from the main line to where the gas line splits into 2 x 1/2" pipes to each of the torches.

    I only measured the gas consumption for the front torch and it consumes nearly the same as the two torches together did previously.



    I'm still working out optimum settings but it got a piece of metal up to 1200ºC using just the front torch and then my pyrometer started playing up so I couldn't measure any higher than this

    It must have got quite a bit hotter because the forge doorway surround started to glowed hot.


    I had some minor surgery a couple of weeks ago but I'm not allowed to lift anything heavier than 5 lb or engage in anything strenuous for another 3 weeks!


  12. #26
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    How is the forge holding up 12mths on?

    Has it had much use?

    What was the gas tank that you started with? It looks like it is gal plated. Does it get hot as gal off gases toxic fumes I'm told.

    Enjoyed the read thanks for sharing.
    …..Live a Quiet Life & Work with your Hands

  13. #27
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    Quote Originally Posted by DSEL74 View Post
    How is the forge holding up 12mths on?
    Has it had much use?
    I still haven't done much blacksmithing with it (too many distractions like mens sheds and playing with motors & VFDs). I've used it mainly to heat pieces of steel so I could bend them, and heat treated a few bits of tool steel.
    Another reason for this is my shed is too small and crowded for the radiant heat out put of this forge. In summer/autumn I can't use it for more than about 30 minutes because even with significant forced ventilation of my shed the forge heats up the whole shed to over 50º. Cool down time is outside air temp dependent but on a hot day it takes couple of hours to reach outside air temp. If it's 40º outside I really can't use it at all. On a cold winters day I can run for about a hour or so - cool down time is also much quicker, so I can use it 3-4 times during a cold winters day.
    I did not use enough rigidizer so the insulation needs some repair. The white silica bricks are a bit fragile and can't handle repeated heating/cooling so I should find something more robust. I should probably reline it and use more rigidizer.

    What was the gas tank that you started with? It looks like it is gal plated. Does it get hot as gal off gases toxic fumes I'm told.
    It was a galvanised tank, from a fork lift. I was not worried about welding the galv as I have a well ventilated (2600 cfm) welding booth. Some galv around the opening did oxidise slowly during the initial couple of firings but I run the forge next to the welding booth so any fumes are very quickly ventilated out of the shed. The bulk of the tank does not get that hot so the galv is still intact.

  14. #28
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    Quote Originally Posted by BobL View Post
    I still haven't done much blacksmithing with it (too many distractions like mens sheds and playing with motors & VFDs). I've used it mainly to heat pieces of steel so I could bend them, and heat treated a few bits of tool steel.
    Another reason for this is my shed is too small and crowded for the radiant heat out put of this forge. In summer/autumn I can't use it for more than about 30 minutes because even with significant forced ventilation of my shed the forge heats up the whole shed to over 50º. Cool down time is outside air temp dependent but on a hot day it takes couple of hours to reach outside air temp. If it's 40º outside I really can't use it at all. On a cold winters day I can run for about a hour or so - cool down time is also much quicker, so I can use it 3-4 times during a cold winters day.
    I did not use enough rigidizer so the insulation needs some repair. The white silica bricks are a bit fragile and can't handle repeated heating/cooling so I should find something more robust. I should probably reline it and use more rigidizer.


    It was a galvanised tank, from a fork lift. I was not worried about welding the galv as I have a well ventilated (2600 cfm) welding booth. Some galv around the opening did oxidise slowly during the initial couple of firings but I run the forge next to the welding booth so any fumes are very quickly ventilated out of the shed. The bulk of the tank does not get that hot so the galv is still intact.
    Thanks for the update.

    I was wondering not just about the welding but the Gal in use. I have been warned off using any gal components even gal pipes for air supply on in building my coke/coal forge due to the off gassing when heated.

    You could cover the the base with refractory cement. If you plan to forge weld the flux tends to damage it though.
    …..Live a Quiet Life & Work with your Hands

  15. #29
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    Quote Originally Posted by DSEL74 View Post
    Thanks for the update.
    I was wondering not just about the welding but the Gal in use. I have been warned off using any gal components even gal pipes for air supply on in building my coke/coal forge due to the off gassing when heated.
    There is a general misunderstanding of the toxicity of the fumes coming from Heated Galv in that most people think it is highly poisonous at any level which is just not so.

    Not many people realise that particularly urban dwellers already live is a soup of the same Zinc Oxide (ZnO) fumes which is present all around us from dust sources such as soil, Zn paint, corroding galvanised roofs and combustion products. The crucial difference is the concentration. These ongoing sources are always there but demonstrate that low level exposures don't have any long term health effects. Its only when the concentration gets too high that it starts affecting human health.

    After it has been fired a couple of times the Galv components used on a basic coal forge would simply not generate ZnO at a fast enough rate to lead to health problems.

    If you are at all worried about it, the way I would deal with it after a forge has been made would be to maximise shed ventilation, light the forge and walk away. come back every few minutes or so to add more fuel and let the forge get nice and hot. This will burn away the great majority of the galv that is likely to generate fumes. The subsequent amount of ZnO generate from running the forge will be tiny and just contribute to the general background of ZnO. The ventilation you should be providing for the forge and your self for any CO2 fumes should be more than sufficient to carry the small amount of ZnO away.

    This is not correct when welding or plasma/oxy cutting galv when a large pulse of ZnO is injected into the air around the operator and it can literally take your breath away. I have done this a couple of times so I am well aware of the effects and is why I installed a well ventilated welding booth in my shed.

    It's interesting to note that in terms of long term exposure the maximum recommended concentration of ZnO in air is 3 to 25 times higher than sawdust. Yet I see people squawking like headless chickens and wetting their pants over ZnO, but don't care if they are swimming in a shed full of sawdust.

    You could cover the the base with refractory cement. If you plan to forge weld the flux tends to damage it though.
    Yes I have thought of that

  16. #30
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    Bob
    Thankyou thankyou thankyou for that most clear perspective setting of The Zinc Issue!
    There has been much flapping about how murderous zinc is, with poor evidence in support. Often from fag sucking, gun toting, boozers (i.e. hypocrites).
    At work tomorrow I'll ask the Librarians for the research. What stuff have you come across? I would love to share it on other forums.
    A.
    'Waratah' spring hammer by Hands & Scott c.1911- 20, 'Duffy, Todd & Williams' spring hammer c.1920, Premo lathe- 1953, Premo filing machine.

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