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Suicide front suspension materials, strong enough??

Discussion in 'The Hokey Ass Message Board' started by jkeckss, Jul 26, 2012.

  1. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,211

    gimpyshotrods
    ALLIANCE MEMBER

    Per-square-inch, every square inch. Can pipe do that?

    D.O.M. is a sound investment.
     
  2. Rootie Kazoootie
    Joined: Nov 27, 2006
    Posts: 8,134

    Rootie Kazoootie
    Member
    from Colorado

    Certainly. Steel is steel and it's really stupid, it doesn't know if it's being made into a pipe or a tube. Assuming the grade of steel and the forming process is the same, pipe will be essentially the same stength as tubing, just sized differently. Compare the specs on sch. 40 pipe to the specs on tubing:
     

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  3. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,211

    gimpyshotrods
    ALLIANCE MEMBER

    Okay:

    D.O.M.:
    TS: 80Kpsi
    YS: 70Kpsi

    Pipe:
    TS: 60Kpsi
    YS: 35Kpsi

    1/2 the yield strength. Enough said.
     
  4. Rootie Kazoootie
    Joined: Nov 27, 2006
    Posts: 8,134

    Rootie Kazoootie
    Member
    from Colorado

    Yeah, and Chrome molly would be even stronger and Titanium would probably be even stronger than that, whats your point?. Do you think your biggest problem is going to be your front crossmember when you exceed 35 thou. psi yield point? really?
     
  5. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,211

    gimpyshotrods
    ALLIANCE MEMBER

    As a Master Mechanical Engineer, certified welder, and a professional car builder, I can say, yes, 35Kpsi yield on a suicide spring crossmember is not enough overhead.

    Given the cost difference between the two alternatives, it is irresponsible to suggest going with the inferior material.
     
    Last edited: Jul 28, 2012
  6. BCCHOPIT
    Joined: Aug 10, 2008
    Posts: 2,601

    BCCHOPIT
    Member





    Some cool pics you found thanks for the info.
     
  7. Rootie Kazoootie
    Joined: Nov 27, 2006
    Posts: 8,134

    Rootie Kazoootie
    Member
    from Colorado

    o. K. :)
     
  8. Rootie Kazoootie
    Joined: Nov 27, 2006
    Posts: 8,134

    Rootie Kazoootie
    Member
    from Colorado

    FWIW- a couple more. If you've ever wondered how pipe/tube is formed, the first pic shows the decending series of rollers the flat stock goes through to turn it into a tube. The second shows how true seamless tube/pipe is made.
     

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  9. BCCHOPIT
    Joined: Aug 10, 2008
    Posts: 2,601

    BCCHOPIT
    Member

    It is hard to find USA made DOM. and 4130 And it cost a lot more then the china shit.
    If you are working on something like a Front Axle or a roll cage make shore you ask where it's made. I just got some 4130 2" .250 wall $700 for one stick shipped with a pile of other other DOM stock and steel bar stock to help soak up the the shipping cost.
     
  10. Rootie Kazoootie
    Joined: Nov 27, 2006
    Posts: 8,134

    Rootie Kazoootie
    Member
    from Colorado

    I've heard that the China C/M is a little 'suspect.' I really don't mess with or concern myself with that stuff nowdays, so I don't have any personal experience. Years ago, though, Newport Steel was about the most prolific supplier/producer of C/M and it was always top quality. Don't know if they still make it there or if they're even in business anymore, for that matter.
     
  11. VoodooTwin
    Joined: Jul 13, 2011
    Posts: 3,453

    VoodooTwin
    Member
    from Noo Yawk

    The forces required to fail a 24-inch long Schedule 40 steel pipe set up in a suicide front suspension would likely fail everything else on that car way before the pipe fails. I'd run it, no problem.
     
  12. bobscogin
    Joined: Feb 8, 2007
    Posts: 1,768

    bobscogin
    Member

    No argument which is stronger on a per square inch basis, but is pipe strong enough? That's an engineering question that transcends a simple comparison of mechanical properties. Depends on the pipe. Pipe could be used if the wall thickness is sufficient. Not arguing in favor of pipe, just saying that there's more to the choice than mechanical property comparisons.

    Bob
     
  13. What about ERW tubing. Twice as thick friendlier to weld.
     
  14. Is the new crossmember going in a original model A frame? If so all this talk about yeild is kind of silly since the frame probably isn't up to A36. If it ever gets hit it will seperate from the frame.
     
  15. Rootie Kazoootie
    Joined: Nov 27, 2006
    Posts: 8,134

    Rootie Kazoootie
    Member
    from Colorado

    And who sez "common sense ain't common anymore"?We ain't building Space Shuttles. You, sir, get it!:D:D:D
     
  16. hipkatgreaser
    Joined: Aug 29, 2007
    Posts: 164

    hipkatgreaser
    Member

    For one if you use pipe instead of tubing your welds will be pourus due to the high carbon content in the pipe and the welds will fail because of the tiny pinholes in the weld due to the contaminants in the metal.
     
  17. Should we be worried that pipe lines and buildings will start failing?
     
  18. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,211

    gimpyshotrods
    ALLIANCE MEMBER

    2' pipe: $46.20.

    2' D.O.M.: $69.60

    Your call. Save $23.40, or don't. For my money, and my customers money, I am going with D.O.M. Then again, what do I know.
     
  19. lostforawhile
    Joined: Mar 23, 2008
    Posts: 4,160

    lostforawhile
    Member

    isn't it better to use something you know for sure what it is, vs. something someone is giving you that may or may not be what they think it is?
     
  20. BCCHOPIT
    Joined: Aug 10, 2008
    Posts: 2,601

    BCCHOPIT
    Member

    The mount that holds the spring will fail before any 3/16 thick tube or pipe will fail.
    Then I hope he is not going to weld it all up with a 110 mig with a long cord on a 20 amp breaker.
     
  21. jkeckss
    Joined: Dec 1, 2011
    Posts: 21

    jkeckss
    Member

    Haha no, my dad is a pipeline welder. Has been for 30 years, his welds are regularly x-rayed for quality control and any imperfections are not acceptable. He will be doing the frame welding for me to ensure it is of the proper quality. Safety first, right? :)
    Aside from that, not to change the topic completely.. but would a quarter elliptical front suspension system be a safer option to the suicide style? I imagine it would significantly lessen the stresses on the front end, especially since it spreads the load over 2 points vs the one center point.

    http://www.jalopyjournal.com/forum/showthread.php?t=433843
     
  22. BCCHOPIT
    Joined: Aug 10, 2008
    Posts: 2,601

    BCCHOPIT
    Member

    Why ask us when you have a Pro at home.
    I think you should do the welding and have your dad school you and check your work.

    My dad gave me the tools and a place to work and made me do all the work. Now I can out do him at most things and he has me fix his toys. I will do the same with my two boys
     
  23. jkeckss
    Joined: Dec 1, 2011
    Posts: 21

    jkeckss
    Member

    My dad isn't into building much and doesn't have the depth of knowledge related to the details of building. I have been giving him the "teach a man to fish" speech for a while. I am going to do most of the welding myself, but I don't trust my welding enough as a beginner, to do the frame safely. I am getting him to do the structural stuff, so mostly frame rails and cross members.

    He is not as willing as your dad was to foster the hobby, I will be more so when I have kids for sure!
     
  24. VoodooTwin
    Joined: Jul 13, 2011
    Posts: 3,453

    VoodooTwin
    Member
    from Noo Yawk

    3/16" steel pipe is 3/16" steel pipe. Anyone have any pictures of a failed suicide front suspension built from 3/16" steel pipe? Post em up.
     
  25. Rootie Kazoootie
    Joined: Nov 27, 2006
    Posts: 8,134

    Rootie Kazoootie
    Member
    from Colorado

    O.K. now ya got me curious. What exactly do you indend to use this rig for? Offroad racing? A wheelstander or something? Seriously, you seem to be (imo) overly concerned/obssessed with your front end falling off for some reason. I mean at what point are you going to feel "safe"? There's no point building something if you're going to be paranoid (real or imagined) driving it. If a quarter-eliptic suspension is more to your comfort level then, by all means, go that route.
     
  26. pitman
    Joined: May 14, 2006
    Posts: 5,148

    pitman

    Quarter elliptic looks unusual, and can be made to work just fine. Henry was clever, in that the center portion of his transverse spring, was "working-both-sides". A quarter elliptic has the center multi-leaf region 2 times. So you got more weight, and separate side spring tuning possible.
     
    Last edited: Jul 30, 2012
  27. jkeckss
    Joined: Dec 1, 2011
    Posts: 21

    jkeckss
    Member

    Haha in all honesty I will just be happy to see progress at this point. This is my first build so I am attempting to make is simple-ish, but I want it to be safe.. really its just going to be a street car, though I am going to have about 400 hp. I suppose as far as safety goes its a bit ironic, cuz no matter how I build the car I am still going to have more protection than riding my motorcycle. I just want to make sure I am not going to be driving down the road and have a catastrophic failure resulting in a fiery crash! :eek:

    I am really a newbie to all of it, my knowledge basically has come from reading every scrap of info I can find thus far.
     
  28. Ever do an endo on a bike? In a car it is worse because you are strapped in and have to ride it out. When a " suicide" front end fails at speed you should plan on doing an endo. But it is a very cool thing to ad to your resume I suppose. ;)

    You do what you are comfortable with, I don't run water pipe or gas pipe on my cars because I know better. But if you are comfortable with it then go for it. Maybe you'll be just fine and maybe you won't.
     
  29. I have a great deal of respect for the information you provide here on a regular basis but I must take exception to your statement. I deal with this every day and pipe has a structural rating just like all other steel. This idea that DOM is better is misplaced. It's just different. I may be completely out of line here and I may find out you are a PE. In that case I apologize. Saying "you know better" should be based on some specific knowledge. I not trying to kick up dust here but this is serious stuff.
     
  30. You don't have to be a PE to know better than to advise someone to risk their kneck on water pipe. I actually suggested mechanical tubing and not necessarily DOM.

    I suppose that I know more than any other reason because I have building and racing cars and bikes for over 40 years. I have made mistakes in judgment and I have seen more than one weld tear out of a piece of water/gas pipe not because of a faulty weld but because the pipe is not made to take the pressure of a structural piece.

    He wants to use the piece in a situation where it is not only getting pounded thousands of times in a single trip but als getting flexed thousands of times in a single trip. The moment loads alone are going to be more than the pipe is designed to take. It is water pipe or we are makig the judgement that it is water pipe as the builder does not know what it is just that it is free.
     

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