DIY AN665-20 threaded clevis's?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by skeeter_ca, Jan 31, 2017.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Jan 31, 2017 #1

    skeeter_ca

    skeeter_ca

    skeeter_ca

    Well-Known Member

    Joined:
    Jun 29, 2005
    Messages:
    1,026
    Likes Received:
    50
    Location:
    Yucaipa, Ca
    Has anyone or would anyone build your own clevis's? On my build I am looking at buying 32 AN665-20L/R clevis's for the drag/anti-drag wires in the wing. Just the fittings alone will set me back $406! Would, could or has someone cut their own out of 4130 solid rod, slot, drill and thread it to the same size? Could you expect the same strength as store bought ones even if you had to oversized it? Is this a reasonable idea?

    skeeter
     
  2. Jan 31, 2017 #2

    Victor Bravo

    Victor Bravo

    Victor Bravo

    Well-Known Member

    Joined:
    Jul 30, 2014
    Messages:
    5,986
    Likes Received:
    4,795
    Location:
    KWHP, Los Angeles CA, USA
    edit: never mind I thought you were talking about male threads....
     
  3. Feb 1, 2017 #3

    Matt G.

    Matt G.

    Matt G.

    Well-Known Member

    Joined:
    Nov 16, 2011
    Messages:
    1,241
    Likes Received:
    468
    Location:
    Kansas, USA
    Could you? Sure. Will they meet all of the requirements that the commercially-available item does? Who knows. You'd have to test them. And then make more after destructively testing your first batch. What is your time worth? $400 for 32 fittings is not a great deal of money in the grand scheme of things...
     
  4. Feb 1, 2017 #4

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    11,849
    Likes Received:
    2,251
    Location:
    Port Townsend WA
  5. Feb 1, 2017 #5

    Dana

    Dana

    Dana

    Super Moderator

    Joined:
    Apr 4, 2007
    Messages:
    8,548
    Likes Received:
    2,963
    Location:
    CT, USA
    The AN parts are almost certainly forged to the basic shape before final machining, which gives much better grain structure than a part machined from bar stock.. As such, any homemade substitute would probably not be as strong unless made larger (and heavier).

    Dana
     
    Matt G. and wsimpso1 like this.
  6. Feb 1, 2017 #6

    BJC

    BJC

    BJC

    Well-Known Member

    Joined:
    Oct 7, 2013
    Messages:
    9,499
    Likes Received:
    6,256
    Location:
    97FL, Florida, USA
    Could the Pitts approach be adapted to your wing? BTW, what are you building?

    The Pitts uses wires that go through the spars and are tensioned with nuts on each end. Light, simple, low parts count, strong.


    BJC
     
    BoKu likes this.
  7. Feb 1, 2017 #7

    lr27

    lr27

    lr27

    Well-Known Member

    Joined:
    Nov 3, 2007
    Messages:
    3,216
    Likes Received:
    465
    I'm pretty sure you can find all the required specs. If they look doable, and you're a good machinist, I'd say go for it.
    AN665 can be found here, though I don't see a -20:
    http://www.abbottaerospace.com/wpdm-package/an665-terminal-threaded-clevis-type-tie-rod
    Judging by a quick look at the drawing, it looks pretty simple, and overbuilt. The part looks like it uses unnecessary material. I doubt if the thread spec is anything special, but I guess it might be worth looking up.
    material and plating spec:
    http://miscellaneoushardware.emilspec.com/MIL-DTL-5683/index.html
    Note that you have a choice of number of alloys, and that it's supposed to be hardened. If I was making one of these, I'd consider leaving a smooth, gradual bump on the outside around the area where the threads end to reduce stress concentration at the sharp inside corner. Just a little one. Sharp inside corners are generally a bad idea, as the stress gets much higher there. I don't know if it's going to be worth your time, unless you have some kind of automation.

    On the other hand, you might be able to get something a bit less expensive that will safely do the job. I'd check the plans of other reputable airplanes. Does anyone know if the Baby Ace kept this size of tie rod end:
    baby ace tie rod end detail.jpg
    This doesn't look like a great design to me, but the Baby Ace has a good reputation, doesn't it? I don't really like the inside corners bent into that strap.
     
  8. Feb 1, 2017 #8

    lr27

    lr27

    lr27

    Well-Known Member

    Joined:
    Nov 3, 2007
    Messages:
    3,216
    Likes Received:
    465
    Wouldn't they say that it had to be forged in the specs? I don't see it. The spec does say it has to hold at least 2,760 lbs. So just hang your car from it. If it holds, it's good. ;-) It only has to be stronger than the tie rod itself. The minor diameter of a male 10/32 thread is around .150". So at the nominal 2400 lbs, that would be about 136,000 psi, neglecting the stress concentration. The clevis will need to have significantly more than 75,000 psi strength, though one could beef up certain areas without making it much heavier. Say, a bit thicker right around the hole for the pin, and a bit thicker over the threaded section. I'll admit I haven't looked into the properties of the various alloys allowed.
     
  9. Feb 1, 2017 #9

    cluttonfred

    cluttonfred

    cluttonfred

    Well-Known Member

    Joined:
    Feb 13, 2010
    Messages:
    6,353
    Likes Received:
    2,224
    Location:
    World traveler
    PerhPs you could find a source for surplus milspec items rather than making your own?
     
  10. Feb 1, 2017 #10

    Pops

    Pops

    Pops

    Well-Known Member

    Joined:
    Jan 1, 2013
    Messages:
    7,022
    Likes Received:
    5,916
    Location:
    USA.
    I made the tail wires on the JMR just like the Baby Ace wire ends. Even made the nipples on the lathe. Its called homebuilding and I do as much as I can. No, I buy my props, some things are beyond my job title.
     
  11. Feb 1, 2017 #11

    skeeter_ca

    skeeter_ca

    skeeter_ca

    Well-Known Member

    Joined:
    Jun 29, 2005
    Messages:
    1,026
    Likes Received:
    50
    Location:
    Yucaipa, Ca
    I had considered that but for some reason I dismissed it. I'll have to recheck that option.

    I am building a Volmer VJ-22.

    skeeter
     
    BJC likes this.
  12. Feb 2, 2017 #12

    lr27

    lr27

    lr27

    Well-Known Member

    Joined:
    Nov 3, 2007
    Messages:
    3,216
    Likes Received:
    465
    Why are props beyond your job title? Seems like, in the past, people often used to make their own. Might be handy if you need to change pitch or something. Of course you'd have to be careful about the grade of wood you used.
     

Share This Page

arrow_white