Ioneater's Model12 Construction

Discussion in 'Pitts Model 12' started by ioneater, Jun 24, 2017.

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  1. Mar 6, 2018 #201

    navybipe

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    it works great with OA also. puddle just flows down the valley and little risk of "burning" the exposed edge.
     
  2. Mar 17, 2018 #202

    ioneater

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    Up in Shreveport this weekend and meet up with Jeremy. Pegasus is even more spectacular in person. Here he is paying homage to the radial gods.

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  3. Mar 18, 2018 #203

    Ryan Mactaggart

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    How’s it ride? ;)
     
  4. Mar 29, 2018 #204

    ioneater

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    Finished the remaining bell crank. It went much smoother than the first one a few weeks ago. Still a long way to go before I have any consistency from bead to bead. It rings like a bell! Next up, start attaching fairleads and additional brackets to the fuse.

    The fuse currently has 2-part epoxy primer applied. What is the best method for removing and preventing any residual primer from messing with the weld? I'm thinking a scotchbrite to white metal followed by acetone?

    IMG_20180328_183928.jpg
     
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  5. Mar 29, 2018 #205

    ioneater

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    It's set up for solo so.......Jeremy was tweaking his new spades and seemed to be happy with the latest adjustment. One of these days I hope to get a ride in somebody's. Of course, I'll pay for the gas!!! The one I know of in Mississippi is going up for sale according to the owner. Had no interest in giving a ride after several polite requests and a flight physical with his office.
     
  6. Apr 2, 2018 #206

    ioneater

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    The last of 6 fairleads and this happened in a shower of blue-green quicker than I could react to....... I think there must have been a little dab of primer or some other contaminant on the metal that I missed during the prep. Crap!

    IMG_20180402_102411.jpg
     
  7. Apr 2, 2018 #207

    cwilliamrose

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    Looks like the tube was sealed and it blew the puddle out when the tube heated up. That's a common problem when welding tubes that are not vented. If you can drill a small vent hole where the weld will eventually cover it and save that part of the weld for last the tube can't pressurize. Or let the cluster cool before finishing the last part of the weld, then finish the weld quickly so the tube can't heat up and blow the puddle out again.
     
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  8. Apr 2, 2018 #208

    Knight Twister

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    When I get a fuselage to work on thats already welded up I drill vent holes anyway. I usually drill them on the outside so they won't be seen welded up under the topcoat. I use a #50 bit in my sioux drill. Unless you know the builder and they told you they vented the structure its a good idea to vent since welding up a blowout is no fun.
     
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  9. Apr 2, 2018 #209

    ioneater

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    You guys are probably right, hell I don't know what else it could be. That's the weird part. Acted like there was no argon but there is good flow and I also had aluminum foil behind the welded area for a gas dam. I also do a pre-flow before striking the arc on every weld and ensure there is no draft (close the garage door). Did 5 of these yesterday no issues with venting, and one of them on the same tube as this one. Started with a cold (70F) structure this morning and kapow. I've got a vent hole drilled now and am cleaning around the hole. This is going to be tricky.....er fun, lol.
     
  10. Apr 2, 2018 #210

    wzm

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    If you don't have full penetration of the closed chamber with the weld, it won't be able to blow out, as you have a solid bit of metal in between. If you have a full weld, but you move quickly, the air inside the closed chamber still might not expand enough to blow out the weld. Small tubes seem to be more prone to this issue then large tubes, as they have a MUCH smaller volume of air to heat up.

    Once it's blown, you need to decide if you want to grind it out and start over (which might be the easiest solution, given where that fairlead is, and how little weld is complete), or try and reweld the contamination until all the air pockets are gone. Rewelding requires that you get close with the tungsten, back off on current, and just work the contaminated bit until it quits popping; each pop will be a contaminated pocket expanding and blowing out, but as they do that, they can create new voids that need to be addressed.

    Grinding it out can compromise the underlying tube if you are too aggressive, so be careful. On the other hand, you can be sure you've gotten all the voids if you grind the contamination out.
     
  11. Apr 2, 2018 #211

    ioneater

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    Bill, Kevin or Zach, if either of you have a moment for a phone call I could use some coaching before I make this even worse trying to fix it. My # 253-678-5608 or PM me with a number if you would like. Gracias!
     
  12. Apr 2, 2018 #212

    Randy

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    I have fixed many of these 'blow-outs' with A/O welding. Drill a small - #30 - hole in the tube for pressure relief then weld the blow-out hole shut. After the tube cools it is a quick, easy fix to weld the #30 hole shut without over heating the tube.
    Best way is as mentioned above - drill the #30 hole first then weld :)
     
  13. Apr 22, 2018 #213

    ioneater

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    First off, a belated thank you to Mr. Rose for the patience and encouraging advice on the phone a couple of weeks ago! I ended up cutting off the fairlead, grinding the tubing level around the hole and filling it in slowly. Worked like a champ! I've welded several more brackets, attachment points etc...... since and now drill vent holes in every tube I'm striking an arc on.

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  14. Apr 24, 2018 #214

    ioneater

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    Making these little buggers from scratch ate up a lot more time than I would ever have guessed.

    Hats off to those of you who have completed a plans built airplane!!

    IMG_20180424_140515.jpg

    IMG_20180424_152914.jpg
     
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  15. Apr 25, 2018 #215

    tdwrv8

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    It's a lot easier to cut them from a piece of rectangular 4130 tubing.
     
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  16. Jun 8, 2018 #216

    ioneater

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    Been a while since I've done anything meaningful. Crazy overtime schedule being short on pilots (thank you airlines!) Gave a friend a chunk of 304 stainless to fab for a step. It turned out very nice. Made a rough draft of the fittings for mounts. Need to tweak the fish-mouthing a bit more before welding them on at the correct angle.
    IMG_20180607_195539.jpg
     
    Last edited by a moderator: Jun 8, 2018
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  17. Jun 13, 2018 at 12:48 AM #217

    ioneater

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    IMG_20180612_122252.jpg IMG_20180612_173050.jpg IMG_20180612_173102.jpg Welded up the step fittings today. Went very smoothly using the step as a fixture. Came out at 11.5 degrees and looks level with earth when the fuse is at that angle. Next is drilling the holes in the fittings and step. Burnt primer stinks forever!
     
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  18. Jun 15, 2018 at 3:14 AM #218

    ioneater

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    IMG_20180614_090235.jpg IMG_20180614_120227.jpg IMG_20180614_191214.jpg Lessons learned drilling stainless... Have the vise tightly clamped to the press table so nothing can shift and start small with the bits. First hole ended up slightly off center. I was concerned with how this would look cosmetically but it turned out ok. Second hole I had a properly secured vise and started small, basically just like the tail stinger instructions. Much more gooder! Threw some junk bolts in for a test. Made a template for some firewall brackets.
     
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  19. Jun 15, 2018 at 12:04 PM #219

    kjkimball

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    Greg,

    Happy to help with the firewall tab info.

    On the steps we make, we made them from solid stainless rod and used an iron worker to bend the tight 90 bends so we didn't have to weld them at the corners. Yours looks good but I do suggest you add a few rows of weld bead tacks on the horizontal part of the step where the show will contact it. We put them on top and a row outboard and down from the top a bit. Helps stop the foot from slipping off.
     
  20. Jun 15, 2018 at 2:29 PM #220

    ioneater

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    Yes sir! Thank you very much for the coordinate info. It was easy to make a template with that.

    A little back story with the step...... IMG_20180607_200022.jpg

    Our base mechanic has some friends over at the TASMG (Theatre Aviation Sustainment Maintenance Group) on KGPT and offered to let them have a go at it. I submitted the drawing above and the stock to make it, expecting a stirrup bent up like yours. Surprisingly, they didn't have the tooling to make an accurate bend and went with the cut/weld option. And they polished it! I didn't know any of this until it arrived on my desk at work. I like the idea of the tacks on the steps, this thing is slippery.
     
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