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  • airweld
    replied
    B.E.V.

    I've had problems with the arc switching off when in AC mode. It will restart normally every time but will just snap off for no reason every once in a while. I don't use AC all that much so it's been just an annoyance so far. Very intermittent so hard to nail down. Other than that I really like the machine. I use a water cooled torch with a CK hand amptrol. Works for me. Scott.

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  • BugEyedValiant
    replied
    Hey airweld,

    What kind of problems are you having with your Lincoln 205? Just curious because I havent heard much about them.

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  • Slagman
    replied
    Actually a preheat is not needed for tubing of this size, but what needs to be done is just a quick heat in the range of 120 degrees or so, to get the "moisture" out of the base material. The head tube is the same size as the rest of the frame, .035. There is an insert that gets put in the headtube that will accept the fork. The bottom brackets are the thickest pieces, and the front seat post is actually thinner than .035", it tapers down to an .024". Post weld heat treatment is not needed, but stress relieving the joints is needed.

    Slagman

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  • chip hayden
    replied
    i agree but, i might consider preheat and/or pwht where the tubing is welded to the bottom bracket or the headset. just because of the difference in mass might cause the welded area to cool too rapidly. chip.

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  • Slagman
    replied
    I don't see 30 amps as being a problem. I've welded .035 4130 in that heat range, only with a Lincoln Squarewave 175. It was a tandem bike to be exact. The only thing was, I was using the foot control, and I had the amps set to not go over 60. Never had a problem with going over that, but I was using an .040 tungsten with a lense. Skip on over to the projects page and I'll post a picture of the bike in the next day or 2, (assuming I can post it right.)

    Slagman

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  • airweld
    replied
    Aircraft Welding

    Chip and Ed2
    I have an airframe repair and modification shop, so you have some confidence that I have some experience to base my opinions on, not that I believe my opinions are any better than anyone elses. I have a new Lincoln 205 AC/DC inverter that works great in DC mode with all the latest waveform controls but I am having a problem in AC that I haven't resolved yet, so if anyone else has this machine, I'd love to hear from them. I have a ThermalArc 140 DC inverter that I use for fieldwork. I started with a Lincoln Squarewave 175 that performed flawlessly for years. I would recommend it as a solid basic machine. If I wanted an AC/DC inverter I would wait to see what Miller is coming out with shortly.
    As for post weld heat treatment of airframes, I know a lot of ink has been devoted to the subject and and each side of the issue has it's defenders, but all I can tell you is that I use TIG mostly(some MIG) and I do not PWHT. I don't know of any OEM's or aftermarket airframe makers who PWHT either. For an amateur built airframe gas welding is the cheapest way to go and was used for more airframes than electric I would guess. But a good TIG machine would be my first choice. Hope you find this useful and if you have any questions, I'll do my best. Scott.

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  • Hobart Expert Rock
    Guest replied
    HI BOB..........BELIEVE IT OR NOT MY SCANNER IS BROKEN, LET'S TRY THE MILLER WEBSITE AND I JUST PICKED A MANUAL ONE THAT I LOOKED AT WAS THE BLUE STAR 2E, PAGE 4, AM AND DC VOLT AMP CURVES THE DC IS KINDA COUNFUESING IT SHOWS RHEOSTATE MIN, MID WAY, AND MAX. BUT YOU CAN SEE A GOOD CURVE ON THE AC. LOOK AT THE FIRST 3 RANGES THE AMPS PRETTY MUCH DROP OFF AND GO 45 AMPS, 58 AMPS, AND 95 AMPS........... YES I WILL GET THE SCANNER FIXED......... ROCK
    [email protected]

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  • Pin Head
    replied
    Originally posted by Phil
    The question is: does the Econotig read the output voltage to determine if the arc is established (for gas flow control or hi-freq start, etc). If it does, then you have a problem because of the series resistor, the Econotig will "see" arc volts added to the voltage dropped by the resistor.

    Regards,

    Philippe
    They typically monitor the voltage and current, but only within a broad range to tell whether the arc is struck or the circuit is shorted. The arc voltage is largely determined by the ionization potential of the shielding gas. Argon is approx 16V, while Helium is about 25V (which is why He is "hotter"), and the machines don't care if you are using Ar or He.

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  • chip hayden
    replied
    hello airweld and Ed2,
    i believe i'm about to "open a hornets nest" but i have to ask; do you find it necessary to post weld heat-treat these relatively thin sections of 4130?
    over the years i've had this discussion and never reached a definitive answer.
    some feel oxyfuel is the preferred method because the heat of the flame and the relatively slow welding process [ofw] allows the weld to pwht. most of the early cr/mo airframes were welded this way and "never had an arc struck on them".
    others i have discussed this with say gtaw is the only way to fly. they believe such thin sections don't need pwht. even in tube clusters and attach ends where forgings are welded to the tubes. an example would be the airworthiness directive to replace the tailboom support strut end fittings on the schweizer/hughes helicopter.
    i've read that anything less than 1/2" doesn't need pwht[in 4130]. other literature says 1/8" max thickness. i personally feel all bets are off when welds are in close proximity[like in a cluster or on a forging with a relatively large mass welded to thin wall tubing].
    what do you guys think? and how have you addressed this situation. thanks, chip.

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  • Ed2
    replied
    Airweld

    Scott:

    I have been involved in aircraft maintenance for many years. I am seriously considering construction of an amateur built. Since I plan to fabricate only one aircraft at this time, I am trying to minimize my cost therefore the econotig appeared to be a potential candidate.

    What welder do you use and are you happy with its performance for this type of work?

    Ed

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  • Ed2
    replied
    Thanks to everyone for all your input. Sounds like the econotig is not the machine I need for this job. I have two other Hobart welders (small mig and AC/DC stick) that I am very happy with. I am considering a tig for thin wall 4130 tube.

    Thanks again,

    Ed2

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  • airweld
    replied
    I had someone monitor the readout and it was between 30 and 35 amps while welding .035 4130 tubing. I have always heard a rule of thumb was 1 amp per 1 thousandth inch material thickness and it appears to be in the ballpark. I weld 4130 airframes, what are you welding on Ed2? Scott.

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  • Bob
    replied
    Hobart Expert Rock (S Scott??).

    A few posts back you described a VA curve verbally. From your description this curve sounds quite different than the one Phil posted. Can you post your curve if it is not the same one.

    Hobart Expert Dave described the 100A, drops to 80A with long cables .... and you have to turn the machine up to get back to the 100A needed. Please understand I do believe Dave and that this does actually happen with a typical garden variety stick welder.

    A true constant current device could be thought of as automatically and electronically turning it self up to keep that 100A flowing. As in "the current stays constant".

    Having said that, it seems like that might be a useful characteristic for a stick welding machine, to automatically sustain a give current in spite of longer cables.

    Not sure the econotig lives up to that, but from Rocks input it sounds like it comes close.

    Ah aint science grand! Actually I am enjoying the heck out of this site. It is a welcome diversion to my day job in electronics, which is kinda a hectic nightmare lately.
    I just might be able to set up and take pix of the suggested lab experiment ... but I have a road trip to do this weekend so it will be a while.

    Bob

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  • Phil
    replied
    The second file illustrates at what output voltage the current would equal 10A, assuming you would introduce a series resistor between your power source and your TIG torch. This would be the voltage at the output of the Econotig (that is an important point later on), and would be equal to the arc volts added to the voltage dropped by the resistor. You will see that the volts axis is crossed at about 60 volts. Assuming 15 arc volts, leaves 45 volts dropped by the resistor. At 10A, that resistor would have to equal 4.5 ohms and would dissipate 450W (read: hot).

    In theory, this would work to obtain 10A output. The question is: does the Econotig read the output voltage to determine if the arc is established (for gas flow control or hi-freq start, etc). If it does, then you have a problem because of the series resistor, the Econotig will "see" arc volts added to the voltage dropped by the resistor.

    Regards,

    Philippe

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  • Phil
    replied
    Originally posted by Phil
    Bob, you are quite right. Constant Current welding power sources are not perfect as shown in VA curves. I have attached 2 files edited from the Econotig manual VA curves. The first called Econotig VA curve rated min is exactly that. Note that the rated min is 30A at 15 arc volts. This is shown in red. The volts axis indicates 15, the amps axis 30 (makes sense that is what the unit is rated at).
    Sorry here is the first file

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