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Can I drill a 2" hole in a 5" C Frame?

Discussion in 'The Hokey Ass Message Board' started by DirtyDave, Oct 23, 2013.

  1. Giovanni
    Joined: Jan 21, 2010
    Posts: 173

    Giovanni
    Member

    I think the only real solution here is to sell the truck ;-P
    If the hole is centered in the frame (height) it will have the least effect on strength. I would weld a section of tube inside the hole to give it a little more strength. I would not box it however. If the plate used to box the frame was square, you would have stress concentrations at the corners which could lead to cracking. especially on an old C channel truck frame with riveted in cross members. The frame has some give in it, and a stiffer than the rest section could crack as the whole thing twists.
    As far as above the axle not having the most stress... the axle is supported by the leaf springs. The shear force should be greatest at the spring mounts, the bending moment will be greatest in the middle of the span, or above the rear axle. This is why you will see some I beams with a web that gets thicker as it approaches the middle of the span. Pushing the flanges further apart greatly increases the resistance to a bending moment. It has no effect on the shear strength tho, so having a tall I beam at the ends of the span is a waste of steel. For this reason, it would be safer to drill a hole than to notch. Notching effectively brings the flanges closer together which exponentially reduces the resistance to a bending moment where it is most needed. I know it has been done, but plenty of people have built cars with no front brakes. Doesn't mean its a good idea.
     
    Last edited: Oct 25, 2013
  2. Ok I think I have it, drill the hole, weld in a pipe, rerun the fuel fill, and sell the truck.
    Thanks as always
    :)
    Probably wont sell it on The HAMB now that this is out there.
     
    Last edited: Oct 25, 2013
  3. NoSurf
    Joined: Jul 26, 2002
    Posts: 4,176

    NoSurf
    Member

    This is why these "Structural Engineering" questions always turn into a shitstorm.

    "Structural engineering is the art of molding materials we do not wholly understand into shapes we cannot precisely analyze, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance."


    'Nuff said.
     
  4. pitman
    Joined: May 14, 2006
    Posts: 5,096

    pitman

    No Surf! That is the poetry, altogether true. And then we best-estimate, what the structure should provide, in terms of wise material use.
    One fact of engineering is; we realize 'at times', just how little we know.
     
  5. Don't forget to shoot the engineer, so you can start production.
     
  6. Google Tacoma Narrows bridge! Sometimes they guess wrong.
     
  7. NoSurf
    Joined: Jul 26, 2002
    Posts: 4,176

    NoSurf
    Member

    LOL. I am a structural engineer PE. But I do know I don't always have all the best answers.

    My wagon parked in the 480' truss bay here at work:

    [​IMG]
     
  8. [​IMG]
     
  9. I really don't believe the shit on here sometimes ? ? ?
    Argue with a fence post ...
    And to think my trailer ramp thread got deleted HAA
     
  10. 1950merc
    Joined: Jun 26, 2007
    Posts: 161

    1950merc
    Member
    from Butler, PA

    I thought that was scary, too. I'm not a mechanical engineer, so who knows. I saved this link for future reference though. I though it was interesting. I don't mean to highjack the thread.

    http://67-72chevytrucks.com/vboard/showthread.php?t=457037


     
  11. Giovanni
    Joined: Jan 21, 2010
    Posts: 173

    Giovanni
    Member

    why are all of the pedestrians and the cathedral leaning to the left? :p
     
  12. cayager
    Joined: Feb 10, 2012
    Posts: 293

    cayager
    Member

    belled hole. sometimes you can find a dimple die used. kind of like an electricians knockout punch that puts the flare in the hole for strength. 2" hole in frame is no big deal.
     
  13. I would really be impressed if those trusses ran North/South instead of East/West! LOL
     
  14. blowby
    Joined: Dec 27, 2012
    Posts: 7,889

    blowby
    Member
    from Nicasio Ca

    Wouldn't it take some serious heat to get much bell out of a hole like that without cracking?
     
  15. That is what I was thinking. while I love that idea I am fairly confident I cant produce that. I suspect the right dies on a hydraulic punch setup would produce that.

    An alternative would be to weld a pipe on the hole.
     
  16. saltflats
    Joined: Aug 14, 2007
    Posts: 10,904

    saltflats
    Member
    from Missouri

    How about you drill the hole and make a diamond shape plate with a hole in it to weld around the hole.
    Hay I have been to the top of that leaning tower.
     
  17. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    HOLY SHIT! I wouldn't park MY car under that! LOOKIT those HOLES in those trusses!!!:rolleyes::eek:
     
  18. Probably shouldn't ask if I can drill 17 or so 1" holes in a 2" axle then should I?

    So how many things are wrong with this ?
    Lets see:
    The area between the spring mounts is most critical. We know where the spring mounts are on this right ? Oops
    % taken out doesn't equate to the % left oops
    To close to the flange
    Too far out of the neutral axis
    Too many holes too close together
    No reinforcements
    No pipes
    No boxing
    No holed fish plates
    No no no

    This seems to defy every single reason or counter offered on this thread.
     

    Attached Files:

    Last edited: Oct 25, 2013
  19. pitman
    Joined: May 14, 2006
    Posts: 5,096

    pitman

    Hey, is that Squirrel out in the middle taking measurements? :eek:
     
  20. VoodooTwin
    Joined: Jul 13, 2011
    Posts: 3,455

    VoodooTwin
    Member
    from Noo Yawk

    Wow, I didn't know that the frame in question was made of forged steel. In that case, just load up the 12 gauge and pump a few rounds where you want the hole. You'll achieve the dimple, no problemmo. The removed steel is over rated. :p:)

    Comparing a hole drilled into a frame by a hobbyist to an ENGINEERED truss system is hilarious. The better comparison would be to go remove one of the chords of that truss, and ask the design engineer to approve it. And let's not even go near the aircraft comparison.....what mechanic in his right mind would dare to drill a 2 inch hole into the structure of a wing? Funny stuff, dudes!

    I tend to care about my family and other motorists, so I tend to build with some safety in mind. You are free to do whatever you want, of course.
     
    Last edited: Oct 25, 2013
  21. 49ratfink
    Joined: Feb 8, 2004
    Posts: 18,100

    49ratfink
    Member
    from California

    an I beam has a lot more strength than a C channel.... with that being said I would drill my 2" hole in the frame and not worry about it.
     
  22. blowby
    Joined: Dec 27, 2012
    Posts: 7,889

    blowby
    Member
    from Nicasio Ca

    This thread should have a poll.
     
  23. 2racer
    Joined: Sep 1, 2011
    Posts: 960

    2racer
    Member

    maybe a disclaimer would be better....
     
  24. agree
    I shoulda gone to the vote
    thought of that somewhere late in page 2
     
  25. It's all about the moment of inertia
     
  26. blowby
    Joined: Dec 27, 2012
    Posts: 7,889

    blowby
    Member
    from Nicasio Ca

    I think you still can, go to thread tools at the top.
     
  27. Jack E/NJ
    Joined: Mar 5, 2011
    Posts: 670

    Jack E/NJ
    Member
    from NJ

    blowby>>>This thread should have a poll.>>>

    Just say no to big gasholes!

    Jack E/NJ
     

  28. Stress=Mc/I
    Ever hear of this one?
     
  29. stealthcruiser
    Joined: Dec 24, 2002
    Posts: 3,748

    stealthcruiser
    Member



    No resonant frequency effects? :eek:
     
  30. 117harv
    Joined: Nov 12, 2009
    Posts: 6,590

    117harv
    Member

    Pipe, boxing, heat, belled, sleeved, fish plate, do it, don't do it, trusses, wing spars, girders, Narrows bridge, leaning tower of Pizza...my head hurts...Im off to the shop to cut, shorten and weld my pitman arm:)
     

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