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Technical To drill or not to drill.

Discussion in 'Traditional Hot Rods' started by reekie6, Oct 17, 2019.

  1. If you plan to use hair-pins or split bones, the I-beam becomes a torsion bar. Enter twist.

    If you drill holes in the web of an I-beam, the vertical yield point actually goes up, until it twists - just like in a monocoque assembly. Think Indy cars or Aircraft. Then it folds like a house of cards.

    Also, take note that NO ONE drills holes in their I-beam connecting rods to strengthen them, lighten them, or to make them look cool...

    But then, what do I know, I'm just a painter... ;)
  2. ... sure they did. Old school JD engine rods, with pistons, nearly 100 years old. Screenshot_20191019-042802_Google.jpg

    ... and still do.

    Blues4U, Jet96, mkebaird and 5 others like this.
  3. Interesting! I stand corrected... What are the newer rods for?
  4. Torsion (twisting) forces on an I-beam axle are not as severe as you might think. The majority of the torsion caused by braking is taken up in the leaf springs or wishbones/parallels. Even axles with drilled axle ends like kidcampbell71's are not in any trouble. The calcs show that the web does as little in the torsion stress arena as it does in the bending arena. Again the deformation is a function of the moment of inertia to which the web contributes precious little. Just has to be enuf web left to keep those flanges where they need to be. They do all the heavy lifting (pun intended)..
    Blues4U, Jet96 and gimpyshotrods like this.
  5. I can tell you one thing for absolute certain; they are for $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$!!

    Speed costs. How fast do you want to spend?
    Last edited: Oct 19, 2019
  6. v8flat44
    Joined: Nov 13, 2017
    Posts: 305


    Hole-ee Hotrods Batman ! Know that we know the hole story, maybe the Batmobile should.....nah, better not......
  7. porknbeaner
    Joined: Sep 12, 2003
    Posts: 41,384


    Unless your life in lived in .001 second and you are lightening everything else drilling your axle is for looks. If you like the look drill it. its not a 10 minute job but if it floats your boat its worth the labor.

    Here is the thought, my current project was first a land speed car then lived the rest if its life as a dragster. It does not have a drilled axle.
    Montana1 likes this.
  8. paintman27
    Joined: Apr 23, 2011
    Posts: 283

    from new jersey

    I remember going to World of Outlaw sprint races years ago and seeing steering wheels with holes drilled in them to lighten them up. So I guess if your as crazy as Steve Kinser, Doug Wolfgang, and Sammy Swindell I say go for.
  9. jimgoetz
    Joined: Sep 6, 2013
    Posts: 356


    Jet96 likes this.
  10. It would be Whislin' Dixie! :D
    jimgoetz and jaw22w like this.
  11. solidaxle
    Joined: Jan 6, 2011
    Posts: 419

    from Upstate,NY

    Interesting, nobody has claimed they have had one fail that was drilled.
  12. They shouldn't!
    pecker head likes this.
  13. akoutlaw
    Joined: May 13, 2010
    Posts: 770



    Attached Files:

    Jet96 and willys36 like this.
  14. bigdog
    Joined: Oct 30, 2002
    Posts: 496


    But the twisting force caused by the brakes is transferred to the hairpins, shouldn't apply any force to the center part of the axle.
  15. porknbeaner
    Joined: Sep 12, 2003
    Posts: 41,384


    That's cause those people are no longer with us. LOL
    Jet96 likes this.
  16. porknbeaner
    Joined: Sep 12, 2003
    Posts: 41,384


    In the '70s and '80s we used to drill the con-rods and the flywheels both. Light bike light lower end.
    kidcampbell71 likes this.
  17. solidaxle
    Joined: Jan 6, 2011
    Posts: 419

    from Upstate,NY

    So, to stir the pot again. No reported failures.
  18. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,343

    dirty old man

    I'll agree that the main purpose of drilling an axle on a street driven car is for looks, and it's a look that I like and have on my '31 "A" Hiboy.
    I'm guessing, but I suspect the first drilled I beam was on a car used in competition, and that it was just one of many things done to that car to lighten it up to the max. You do reach the point in lightening the car that every little bit added to other little bits adds up to lots of pounds.
    Then somebody saw this on the race car, liked the looks of it, and decided to copy it on their street driven car.
    There's another factor in this weight reduction no one has mentioned, and that's unsprung weight, which can be a major factor in tire adhesion on uneven surfaces. IMO. the biggest shortcoming of I beam front suspension is unsprung weight, and this drilling des, percentage wise, make a difference in unsprung weight.
    KJSR, kidcampbell71 and jimgoetz like this.
  19. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,500


    The engineers say not worry about it.

    Armchair quarterbacks say to not do it.

    Enough said.
  20. neverdun
    Joined: Oct 17, 2007
    Posts: 667

    1. Maryland HAMBers

    I've drilled every axle on every car I've built. Its a personal preference, I like the way it looks. I have a Superbell cast axle on my '32 and Posies called Superbell and asked if it could be drilled. Their answer was 3/4" holes 1 1/2" on center is the correct pattern with no reduction in strength of the axle. That is good enough for me. I don't paint my wheels red either, anything but.
    Jet96 likes this.
  21. OLSKOOL57
    Joined: Feb 14, 2019
    Posts: 389


    I hand drilled a 47-54 Chevy 1/2 ton truck axle for my ‘56 Chevy when contemplating a Gasser. Used a 1/2” drill with various size drill bits and step drill bits as well. Went to 3/4” diameter from center of web with 3/4” side to side width. I used a 4x4 post strapped to tailgate of my Chevy pickup, strapped the axle down on the 4x4. Started from center of web outward to the ends. Best I remember, (2016) it took 6-8 hrs, Looked great when finished, I was completely tired and sore. Did not build Gasser and if there is a next time I will have a heavy duty drill press.
    Last edited: Oct 30, 2019
    dirty old man and Cosmo49 like this.
  22. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,500


    The trick tool is a vertical mill, with a nice end mill.

    You can do an axle in about an hour.
    dirty old man likes this.
  23. Fortunateson
    Joined: Apr 30, 2012
    Posts: 2,697


  24. 41 GMC K-18
    Joined: Jun 27, 2019
    Posts: 534

    41 GMC K-18

    And I am sure you are correct, that being said, I shot the photographs, only to show what the car owner had done, the car isn't mine.
    neverdun likes this.
  25. pecker head
    Joined: Nov 8, 2006
    Posts: 3,619

    pecker head

  26. solidaxle
    Joined: Jan 6, 2011
    Posts: 419

    from Upstate,NY

    He didn't say why he did it. It's more of a look then a function. Personally I like it.
  27. Ralph Moore
    Joined: May 1, 2007
    Posts: 649

    Ralph Moore

    Drilled by a friend of mine. I like the extra holes, less wind resistance![​IMG]

    Sent from my iPhone using The H.A.M.B. mobile app
    neverdun likes this.
  28. goldmountain
    Joined: Jun 12, 2016
    Posts: 1,338


    While I'm in favor of holes, I Don't understand why you would drill holes in brake backing plates. Seems that would be detrimental for stopping when it rains.

    Sent from my SM-T350 using The H.A.M.B. mobile app
  29. 41woodie
    Joined: Mar 3, 2004
    Posts: 1,054


    My first thought...dead men tell no tales
    neverdun and porknbeaner like this.
  30. I'm an engineer and I agree. We tend to be very careful about what we put holes in and things like edge-distance comes up, read up on it.
    BJR and pecker head like this.

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