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  1. #1
    Join Date
    Aug 2011
    Location
    Palmetto, Georgia USA
    Posts
    19

    Lincoln tombstone tig

    Hi all,
    so my project that im working on is converting a lincoln ac 225 stick welder to a dc tig welder. a lot of you are probably saying " hey you big dummy go buy a real tig welder and stop being cheap?!" i see you point and and raise you an answer im taking circuit analysis next semester and what a fantastic semester project. so with the confusion out of the way here is what i have so far. to convert it to dc ive got a rectifier unit from a miller thunderbolt


    A IRKT91 SCR module to control the current of the incoming AC with a 600 watt dimmer here is the module. im waiting on a 680 pF 2kV cap to complete the control.



    I plan on using this skinner valve to control the shielding gas flow. its a 24 volt unit i would like to use a cap that would discharge and act as postflow timer..... i hope that's fees able.


    now onto the high voltage. im lost as to how im going to get this NST to work as an arc starter. i dont know how i can get the arc to jump the gap between the tungsten and work rather than across the rectifier rendering it useless and toast


    please brutally point out every problem with this project. all constructive input is valued

  2. #2
    Join Date
    May 2005
    Location
    Richmond, Virginia
    Posts
    6,020
    Stop messing with that NST until you figure out what's going on! Playing with a 10-15 kV transformer that can deliver 15-25 mA can easily be LETHAL. It looks like you have one of the fairly big ones.

    Go ask a TIG welder how much the HF tickles. Or ask someone what it feels like to test a lawnmower ignition for spark when you don't have a plug.
    --- RJL ----------------------------------------------

    Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
    -------------------------
    DialArc 250 (1974), Idealarc 250 (1971), SyncroWave 250 w/Coolmate 3, SP-175+, TA 161STL,
    Lincwelder AC180C (circa 1952), Victor & Smith's O/A, Dayton (Miller) spot welder, 1200 sq.ft. of garage filled with crap and a kid that can actually run the stuff +++

  3. #3
    Join Date
    Aug 2011
    Location
    Palmetto, Georgia USA
    Posts
    19
    thank you for the concern. yes i plan to avoid the NST until i'm certain it can scratch start and all the other features are working ie. gas flow foot control

  4. #4
    Join Date
    May 2005
    Location
    Richmond, Virginia
    Posts
    6,020
    We have a France NST ("Franceformer") that we have used to make a Jacob's Ladder. Very scary, maybe 20 mA at 15 kV. We had a pair of lineman's rubber gloves and other safety precautions and never got too close to it. It was fascinating to see how the arc would cut through a piece of paper as if it wasn't even there.

    One "learning tool" is to go to the local farm store and buy a cheap low-powered electric fence energizer. They are great fun at parties when you get folks to grab hold of it. They are nothing like what will hit you if you get bit by a NST.

    Do read up on high voltage insulation - you don't just string any old wire over and around your components, the bench and inside the welder.
    --- RJL ----------------------------------------------

    Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
    -------------------------
    DialArc 250 (1974), Idealarc 250 (1971), SyncroWave 250 w/Coolmate 3, SP-175+, TA 161STL,
    Lincwelder AC180C (circa 1952), Victor & Smith's O/A, Dayton (Miller) spot welder, 1200 sq.ft. of garage filled with crap and a kid that can actually run the stuff +++

  5. #5
    Join Date
    Aug 2011
    Location
    Palmetto, Georgia USA
    Posts
    19
    Ive had a couple years experience in the high voltage field. Ive worked with my good friend operating the worlds smallest IEC Fusion Reactor. 4.6 million neutrons per second and 20kV. deuterium was the fuel (heavy hydrogen) theres a lot more like them http://www.fusor.net i want to use this welder to weld up so SS vacuum flanges
    heres a deuterium plasma at 10keV

    i also had an opportunity to play with a 1 megawatt jacobs ladder

  6. #6
    Join Date
    May 2005
    Location
    Richmond, Virginia
    Posts
    6,020
    Well, then, you should have introduced yourself as a distinguished expert instead of wasting our time as a rank amatuer who we'd read about in the newspaper. I don't mind an expert getting snuffed, but I'm really nervous about the kids. Although you should set a good example. Really.
    --- RJL ----------------------------------------------

    Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
    -------------------------
    DialArc 250 (1974), Idealarc 250 (1971), SyncroWave 250 w/Coolmate 3, SP-175+, TA 161STL,
    Lincwelder AC180C (circa 1952), Victor & Smith's O/A, Dayton (Miller) spot welder, 1200 sq.ft. of garage filled with crap and a kid that can actually run the stuff +++

  7. #7
    Join Date
    Aug 2011
    Location
    Palmetto, Georgia USA
    Posts
    19
    ive had experience with a little high voltage, welding (high current) is new to me. i appreciate your concern i would like to live a long life so i take as many precautions as possible including avoiding it haha. i dont like fooling with the high voltage with current in close proximity. i would like to have an arc starter however i dont like the track marks left behind when you scratch.

    Curiosity is the driving force for innovation. I aim to prove you can be curious and safe
    Last edited by Steven Shaw; 08-14-2011 at 06:17 PM.

  8. #8
    Join Date
    Apr 2009
    Location
    houston pa
    Posts
    1,508
    how dumb was it of me to bring wiz into this thread! i retract.
    Last edited by mikecwik; 08-15-2011 at 10:14 PM.

  9. #9
    Join Date
    Aug 2011
    Location
    Palmetto, Georgia USA
    Posts
    19
    Back to the subject at hand any comments, concerns, queries?

  10. #10
    Join Date
    May 2011
    Location
    The Boonies of Texas
    Posts
    13
    Steven check your PM's

    Thurmond
    Miller Bobcat 3 Phase,
    26 series gas cooled TIG torch, setup for quick connect to Bobcat.
    Miller Suitcase X-Treme 12VS
    SuperCut 50P plasma cutter returned after issues for EVERLAST PowerUltra 205P
    Hobart Handler 187 Mig / Flux Core
    Standard Oxygen / Acetylene Cutting, Welding setup.

  11. #11
    Join Date
    Aug 2011
    Location
    Palmetto, Georgia USA
    Posts
    19
    you ve been pm'd

  12. #12
    Join Date
    May 2005
    Location
    Richmond, Virginia
    Posts
    6,020
    Steven, I counted eight I's in your replies. Get over yourself and don't get electrocuted, please. We'd like to see what you come up with, just go easy.
    --- RJL ----------------------------------------------

    Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
    -------------------------
    DialArc 250 (1974), Idealarc 250 (1971), SyncroWave 250 w/Coolmate 3, SP-175+, TA 161STL,
    Lincwelder AC180C (circa 1952), Victor & Smith's O/A, Dayton (Miller) spot welder, 1200 sq.ft. of garage filled with crap and a kid that can actually run the stuff +++

  13. #13
    Join Date
    Aug 2011
    Location
    Palmetto, Georgia USA
    Posts
    19
    my b. whether or not the first person is used is irrelevant. Me shall keep that and mind though thank you

  14. #14
    Join Date
    Aug 2011
    Location
    Palmetto, Georgia USA
    Posts
    19
    good deal tritium! me shall give it a go

  15. #15
    Join Date
    Apr 2009
    Location
    houston pa
    Posts
    1,508
    it wasnt irrelevant, it was the start of a blueprint.

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