IanJ's Marquart Charger build thread

Discussion in 'Marquart Charger' started by IanJ, May 4, 2017.

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  1. Jun 9, 2018 #581

    taff

    taff

    taff

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    Making my I struts.
    For this weld, I started by tacking the sides and then start at the front making my way back. And the deep crotch was the last area I welded.
    I had and kept a good clean point to the tungsten (so that the arc wouldn't wander away from the target).
    I had about 1 1/2" of tungsten sticking out of the gas lens, to be able to reach up close.

    DSC_8351 (800x536)[1].jpg
     
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  2. Jun 9, 2018 #582

    Larry Lyons

    Larry Lyons

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    Nice looking bead Eric
     
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  3. Jun 9, 2018 #583

    IanJ

    IanJ

    IanJ

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    Well, that answers the question of how you jam a gas lens into a space that tight. :D

    I tried TIG in my welding class, and didn't enjoy it. The gas torch made way more sense to me, so I'm going to stick with it until I run across a job where TIG is clearly a better choice. Then I'll have some pondering to do, and will be back with questions about TIG.
     
  4. Jun 9, 2018 #584

    Randy

    Randy

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    IanJ, I am with you on being comfortable with gas welding. A couple years after learning to gas weld I bought a Tig on sale at Oshkosh, used it for about two hours and sold it. I learned to gas weld in the welding workshop at Oshkosh in the 70's. I told the instructor I wanted to go home knowing how to gas weld. He asked what that was worth to me, I said I would buy his breakfast every morning, he said count his wife in and I had a deal. So for 5 days I bought breakfast for 3 at 7am. By 7:45 we were in the weld tent with the flaps down and I got over an hour of undivided, individual attention. When the workshop opened at 9am I would just practice for a couple hours and again an hour or so in the afternoon. At the end of 5 days my instructor handed me a folded piece of paper, "Thank you for breakfast. You get an A+ for the class, see you next year." Best 15 breakfasts I ever bought :)
    You have taken welding classes so you probably already know most of this but for any others who don't here are some of the basic things I learned -
    1) If the flame is oxy. rich it will burn the carbon out of the steel causing it to be brittle.
    2) If the flame is Acet. rich it will add carbon to the steel making it soft.
    The solution is to set the flame so you can just barely see the acet. burning at the tip of the flame, better the steel is very slightly softer than brittle. If you cannot see this "soft" tip you do not know where you are and could be way oxy. rich.
    3) The torch tip should just 'whisper' as you weld. If you are turning the gas up past the 'whisper' point to get more heat you need to go to a bigger tip.
    4) If your tip is "popping" during the weld it is because the tip is to hot and you are igniting the gas inside the tip. Need bigger tip so the tip can be moved further away from the weld. "Popping" does two bad things, it can splatter liquid metal, which hurts like H-LL and sets clothes on fire or it can blow a hole through the tube - both are bad.
    Looking at your photo in post #570 the way I would weld it is to tack the tubes together in 4-6 spots. For me this works better than trying to jig the parts together. Weld up each side of the joint, welding thru the tack's, as far as you can and keep a good looking weld. Then connect these two welds across the top. My Oshkosh instructor taught me to weld up the sides to the point of being able to lay a piece of welding rod from one side of the joint to the other while it just touches the two angled tubes. Tack the rod to one side of the bridge then bend the rod down until it touches the other side of the bridge and burn it off. This plugs that deep chasm that all your heat goes into when trying to weld across. At this point you will need to go to the next diameter rod to reach from one tube, across the small dia. weld rod and into the tube on the other side but it will weld much easier. It also helps to use a larger tip just to preheat the cluster then switch back to the tip needed for welding. My wife is very adept at holding a handheld propane torch on cluster welds to give me the extra heat I need.
    When welding shorter tubes, the final closure weld will usually result in blowing a hole in the tube from the heated, pressurized air inside the tube. The way to prevent this is to drill a very small hole in the tube before closure. Finish welding the tube closed. After it cools you can go back and weld the small hole closed quickly enough that the air pressure does not reach 'blow thru' stage.
    As far as selecting the correct tip, that will come with experience. You will see how long it is taking to preheat your weld area and just know you need to go larger or smaller.
    And last but not least, whenever you finish a weld pull the heat away slowly, maybe 5 seconds or so before you take the heat totally away. This lets the weld normalize.

    P.S. I have done a fair amount of aircraft welding and have yet to find a place where Tig is a better choice for me. I think the reasons are, A) I know how to gas weld and B) I don't have a Tig welder :))
     
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  5. Jun 9, 2018 #585

    cwilliamrose

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    Your gas welding experience will help you if you ever decide to go the TIG route. I was a decent gas welder when I learned TIG and before I was anywhere near good enough at TIG I had already sworn off gas welding. TIG solved all the things I didn't like about gas welding mainly having to do with a lack of direct heat control. Hang in there....
     
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  6. Jun 9, 2018 #586

    wfrandy

    wfrandy

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    Actually, a neutral flame is what you should always shoot for. An oxidizing flame while burn the metal causing it to be porous and brittle. A carburizing flame will add carbon to the metal increasing its hardness, which also makes it brittle. In fact, a carburizing flames primary use was to apply hard facing back in the old days. So, for good quality welds you need to adjust the flame so it is neutral with just a barely perceptible lean toward carburizing at most. If their are a lot of sparks coming from the puddle it is probably oxidizing, if the puddle is bubbling without sparks, it is probably carburizing, neither is good. The advantages of Tig welding over Oxy-acetylene are, 1. more control 2. smaller heat effected zone 3. Inert gas shields the molten puddle from oxidation or absorption of impurities, such as carbon 4. and specifically for 4130 thin tubing, the ability to weld slower with less heat into the weld zone, while still achieving full penetration. One other tip, about filler rod, while you can gas weld 4130 tubing with 4130 filler rod, in fact, it is often specified for certification welds, do not use 4130 filler rod with Tig as the welds will be too brittle, use ER80S-D2 or ER70s-2 or equivalent instead. Personally, I would never use 4130 filler rod, unless it was for a part that was to be post weld heat treated, I personally use ER70s-6 rod when gas welding 4130.
     
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  7. Jun 10, 2018 #587

    IanJ

    IanJ

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    Thanks for all the tips! I knew some of them, am learning others, and didn't know a few. The bridging trick with welding rod is neat, I'll try that.

    I'm using R60 welding rod, which is what the welding shop said was the right thing for what I'm doing. Some destructive testing suggest that this is the case -- I generally rip the steel at the edge of the HAZ like you'd expect, and the welds have been solid.

    I finally had the correct brain spasm today: I can use 1018 steel for my compression tube bushings. This means I can machine them right now instead of waiting for the never-ending ACS order (my own fault, I keep adding to it). There's no need for a glorified nut-and-washer to be 4130. A fine use of my current downtime as I wait for more materials from afar.
     
  8. Jun 12, 2018 #588

    sdeldred

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    Hey IanJ


    Stumbled upon this thread, specifically about fuselage tubing and buying a kit.
    I'm just puting the finishing touches on my Charger, (covering wings, finishing up FWF).
    My brother has a Charger Project - Fuse, tail, landing gear even some wings, engine mount etc (no flying wires)
    Let me know if you want me to put you in contact with him - He lives in Springville Utah.
    Stevee
     
  9. Jun 12, 2018 #589

    IanJ

    IanJ

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    Thanks for the offer! I'm going to stick with my plan to build on my own for now. Give me a few more years to get really discouraged with my progress, then I'll probably start looking at projects. :D
     
  10. Jun 14, 2018 #590

    IanJ

    IanJ

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    Heh, I spent 2.4 hours working on the plane last night, and all but .5 was actually spent getting the lathe back into happy shape. The cross-slide was being finicky and sticking rather than sliding. All the bearing surfaces got a light polish, and once I had everything back together in the right orientation with the right oil (note to future self: Tri-Flow is not the right oil) it was... just about the same. Slightly better. Oh the joys of maintaining the toys. :D If I had more space, I'd consider upgrading to a bigger lathe just to have things like cross-slides be higher quality with human-sized handles.
     

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