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Thread: Introducing a J-4 project

  1. #281

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    Quote Originally Posted by tempdoug View Post
    so for the elevator it will be a solid linkage with no cables?
    Push-pull under floor to a horizontally mounted bellcrank under baggage area. Cables run back half way under floor allowing for long baggage space, then rise as needed to get to elevator.
    The control sticks and all bellcranks mount on ball bearings and cable ends utilize aviation REP bearings so there is very little chance of friction.
    The control surfaces themselves are also hinged on ball bearings.
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  2. #282
    RVBottomly's Avatar
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    Quote Originally Posted by CharlieN View Post
    The control sticks and all bellcranks mount on ball bearings and cable ends utilize aviation REP bearings so there is very little chance of friction.
    The control surfaces themselves are also hinged on ball bearings.
    Looks good Charlie--

    I'm really interested in these various bearings. I searched REP bearings and couldn't find anything. And I'm wondering how the control surface bearings mount. Last I recall (long ago--I know) you were talking strap hinges.

    Vic

  3. #283
    Gordon Misch's Avatar
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    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)
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  4. #284
    RVBottomly's Avatar
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    Quote Originally Posted by Gordon Misch View Post

    Thanks! That looks like it. I don't know why I couldn't find it before.

  5. #285

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    Yes my original intention was to utilize strap hinges. I made the spars for the elevator in stainless to reduce the chance of corrosion within the hinge area. And with the greater selection of low friction engineering plastics as well as the ability now to 3D print extremely complex shapes strap hinges are of great interest.

    But I also like ball bearings, no stiction, yup a tough word for me to spell but low static friction, the break free force in low movement pivots.
    I had already designed ball bearings in the early parts I made. I have not taken any pictures of the bearings installed, primarily since they go against the grain in some circles, I will get some shots.

    What I do have,
    Control stick pivot, there are bearings inside the relay rod as well.
    IMG_0202.JPG

    I will take pictures of the mounts for the torque tube since they have bearings inserted as well.

    Bottom of rudder, the control horn has two bearings inserted, these are 3/8 ID flanged bearings, the lower sets over a stainless pivot pin, the upper is primarily there for support but prevents the rudder from lifting off the upper or lower pivot pins.
    IMG_6370.JPG IMG_6371.JPG

    The control cables will have threaded ends swaged in place that will be fitted into FAFNIR REP3 Bearings. There are many different sizes available, I am now over $1500 of these bearings in this project alone. The elevator horns to the left have these bearings in place.
    IMG_6375.JPG
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  6. #286

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    Thank you Gordon for that link above.

    My control torque tube rides on these these thin wall bearings, they are available in assorted sizes.

    IMG_7439.JPG
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  7. #287

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    I am getting some welding done once again. I am welding inside structure in the aft section of the fuselage. This used to be pretty easy when I was young and did not need glasses to focus on the arc. Frustrating part is depending on the reader I wear I can get a near perfect view of the weld, but only within a few inch depth of view.
    Trying to get one's helmeted head partially withing the structure allowing for the proper viewing angle and distance while allowing both arms to be positioned as needed with the precision to weld at the very low power that .028 and .035 wall tube requires.

    Dang this is kind of slow going one might say.
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  8. #288
    RVBottomly's Avatar
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    Quote Originally Posted by CharlieN View Post
    I am getting some welding done once again. I am welding inside structure in the aft section of the fuselage. This used to be pretty easy when I was young and did not need glasses to focus on the arc. Frustrating part is depending on the reader I wear I can get a near perfect view of the weld, but only within a few inch depth of view.Trying to get one's helmeted head partially withing the structure allowing for the proper viewing angle and distance while allowing both arms to be positioned as needed with the precision to weld at the very low power that .028 and .035 wall tube requires.Dang this is kind of slow going one might say.
    I feel for you, Charlie! I'm using gas, but I have three different drug-store readers for whichever task is at hand. I'm using a face shield after a few times of bumping my cheek with a hot rod tip while contorting through the airframe. It also makes it a little easier to change glasses.
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  9. #289

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    Thinking about the glasses, I stack the readers Kind of sounds stupid but I tend to wear a pair of very large lens general distance glass that works well at 3 to 8 feet or so, about a 1.5 for me. These would be considered the safety glasses. Then I slip closeup glasses under these, under as in from the top between the general ones and my eyes. This combination my focal length is 8" to a foot or so.

    But yes, when you blast a hole through a tube or burn back an edge, it does not matter what torch was in your hand, ya still got to fix it.

    I think back, I have not done much torch work in recent years but I have some to do, my go to torch is a set of Purox 200 "aircraft" torches my dad brought home from work when I turned 14. They still run well now fifty years after I got them used.

    There are times the softer flame is easier to work than the higher energy of the TIG rig.
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  10. #290
    Larry G's Avatar
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    I get the lenses for my welding helmet then I don't have to where glasses
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  11. #291

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    Quote Originally Posted by Larry G View Post
    I get the lenses for my welding helmet then I don't have to where glasses
    I have not had luck fitting corrective lenses with the newest auto dimming helmets. I should probably revisit them.

  12. #292

  13. #293

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  14. #294

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    Interesting, a friend of mine lives 6 miles from his listed location. There is another rafter rat hanging on Bob's Island near here as well.
    In many ways, for the money it would not be worth my time to finish the rebuild of my original one.

    But scrolling down that FB listing the Swift at $26K caught my eye.

  15. #295

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    As I am picking away at the small hard to get to welds, when I step back I keep getting an illusion something just Ain't right.

    IMG_7513.JPG

    My mind playing tricks on me since the fuse is hanging upside down from the ceiling, but the curve of the longerons looks like it is upright, but missing the vertical spar.
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  16. #296
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    Charlie, Looking forward there is a horizontal tube which ends. It looks like a mid partial longeron and is the same on both sides. Above that end cutoff there is a vertical which goes to the bottom longeron, top of picture. Why is one of these verticals bent in the middle and the opposite one not bent?
    N1PA

  17. #297

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    Good eye Pete,
    Not sure I really like this mid longeron but I wanted substantial shoulder height structure to mount the shoulder belts too. The structure adds allot of torsional strength which just may not be needed. I am used to the cars I have built where each one is stiffer than 10,000 Ft-Lbs in torsion. The plane has no need to be but it is hard for me to back down.
    I have yet to measure this frame in torsion or bending since there are a number of critical diagonals in the last bay near the tail that are not installed yet.

    This mid structure also imitates the original J-4 shelf behind the seats.

    The asymmetry you see is where on one side is a lower baggage door with upper on the other side.
    The bent tubes are where a mid stringer will terminate while eliminating the need for additional tin work around the door openings.
    Intention is the fabric will directly wrap the tubes around openings with either V or D seal gaskets on the door edges. Simple with fewer parts and especially greatly reduced cavities for rust to start.
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  18. #298
    Southern Aero's Avatar
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    Charlie

    Dunno if you have ever seen these or not but great for gas welding, you put whatever "cheater" lens in that you need and don't have to stack your glasses.

    Wouldn't help RV from poking himself with a hot filler rod tho!


    Spits.jpg

    https://www.ebay.com/itm/MAGWELD-IR5....c100010.m2109


    A friend turned me on to them years ago................ work great. I still have to use 2.5 cheaters for tig work. The glasses seem to work better for me than the inserts for the helmet
    ......... It doesn't cost any more to go first class! You just can't stay as long.

  19. #299
    RVBottomly's Avatar
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    Quote Originally Posted by Southern Aero View Post

    Wouldn't help RV from poking himself with a hot filler rod tho!
    There is no help for me. If I weld long enough my hand goes numb and I can't feel what direction the rod is heading after I stop. People at work have started looking for the latest interesting brand marks on me. The face shield helps a lot!

  20. #300

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    Those glasses look allot better than the glasses/goggles of the past. I have had clear wrap arounds that technically had correction but either I did not know how much correction I needed at the time since I grew up as a hawkeye, the transition to lenses took me some time.
    And I have burnt my cheek more than once.
    Heck a few decades ago I was doing some torchwork, hot summer day wearing shorts. I was one of those muscle bound weight lifter types that wore short shorts.
    I fumbled and dropped the torch, tip went down right into my inner leg, that mark is still there.
    Vic, I now have a new to me pinched nerve in my neck, makes my left arm and hand go numb. I have motor control but the full arm tingles. Not every weld but is a half dozen times a day. I am going to have to give in and go for PT.

  21. #301

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    Almost a step forward, I first attempted to tack the mounts of the control sticks onto the fuse, but could not get them to stabilize at all. With everything mounted on ball bearings it just could not be made to sit in place.
    So I used a piece of 1 X 4, mounted on the milling machine and made a jig for locating the control stick mounts. Last night I set the mounts in place then walked away happy.
    So this morning I went down, fired up the Tig and did the initial welds for the mounts, now I am happy again.

    IMG_7520.JPG IMG_7521.JPG IMG_7522.JPG

    Cool, now I can mount the sticks for the first time, granted the fuselage is upside down and hanging from the rafters I can not sit and fiddle,

    IMG_7527.JPG IMG_7528.JPG

    But now, and only now I find I made the mounts such the the torque tube is a half inch or so too low. The top of the tube was to be just a touch below the floor level which allows proper geometry of the aileron cables and clearance to other systems. Oh well, cut it apart and make things right.
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  22. #302

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    I decided the mounts for the control stick will be fine as they are, not sure I intended the torque tube to be where it is but there is technically nothing wrong with it.

    I got back to making parts. This entailed doing some detail drawings, machining a few bits and the welding.
    What I am concentrating on now is making the mounting points for the pedal assembly. Since the seats are fixed I have chosen to make the pedals adjustable. It comes down to adjustable pedals are less of a weight gain or safety hazard than a movable seat that does not have proper crush structure under it.

    These few parts have quite a few hours in them but they are a start.
    IMG_7536.JPG IMG_7538.JPG

    Now I have the fuselage sitting upside down on the shop floor. The lift eyes on top of the front spar are nice since they are threaded into the structure and allow for leveling.
    Basically the parts made today are the rectangular tube along the centerline, the two dowels seen up front are for the center mount for the brake torque tube. Aft of that the pin hanging down is the center pivot where the pedal structure will be mounted. Next will be to make some tooling to align the outer pedal mounts, then to fabricate that structure.
    The pedal assembly will be a L&R cradle mounted on Delrin bushings. These will locate the pedals which will utilize ball bearings for all pivots.
    I have yet to decide if the pedals will be fabricated in stainless or if I will spring for all Titanium tubing. That might be decided if I am buying a new camera for Oshkosh this year or not.
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  23. #303

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    Here is a screenshot of the pedal assembly as being built. Lots and lots of little parts to be made.

    June2019 FrontLow1.jpg

    I got a few hours in on this making parts and doing minor but needed revisions, basically updating where I left off on these parts drawings a few years back.

  24. #304

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    Another screenshot,

    June2019A.jpg

    Looks like the image gets scaled in reverse with the rudder being proportionally big with the engine being way too small. Damn software.

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