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Suicide Front End.. Now I know what they meant

Discussion in 'The Hokey Ass Message Board' started by orphaneddie, Apr 15, 2008.

  1. 27 Tall T
    Joined: Dec 16, 2005
    Posts: 333

    27 Tall T
    Member
    from Butler Pa.

    more pics , how many miles on the build?
     
  2. OLLIN
    Joined: Aug 25, 2006
    Posts: 3,150

    OLLIN
    Member

    was that car on ebay earlier this year? How many miles before it broke?

    pleeeeeeeeeeease more pics and closeups too. Looks kinda similar to my car.
     
  3. thunderbirdesq
    Joined: Feb 15, 2006
    Posts: 7,091

    thunderbirdesq
    Member

    Definitely looks a little small but it's hard to tell from that pic for sure. What it looks like is it's loose! That bolt shouldn't be sticking out like that...:eek: More pics needed, stat!
     
  4. Unkl Ian
    Joined: Mar 29, 2001
    Posts: 13,509

    Unkl Ian

    Close up pics of both sides would be helpful.
     
  5. orphaneddie
    Joined: Jul 1, 2007
    Posts: 120

    orphaneddie
    Member

    I got the car on ebay about a year ago.. not too many miles on it before it broke, and NO freeway miles. The perch bolt snapped clean off.. and the bolt looked really thin in diameter. I need to look for more upclose pics to see... but it was definitely too small of a diameter to be driven, I should have changed it when I got it. Definitely attached to the bones. and not too sure how well the weld was.....

    Gotta get home and get more pics loaded up.. Im still at work
     
  6. MercMan1951
    Joined: Feb 24, 2003
    Posts: 2,654

    MercMan1951
    Member

    I hope you're not the victim of :

    "Let's throw a bunch of this **** together real quick and sell it on eBay..."
     
  7. scottybaccus
    Joined: Mar 13, 2006
    Posts: 4,109

    scottybaccus
    Member

    I just love all the speculation and conclusions founded on two photos that don't illustrate any detail at all.

    Designs like this must take into account a mul***ude of forces like sheer, tensile and torsional stress. Only a mechanical engineer has the capacity to say what is best with any certainty. The rest of us can only guess at what might be better than something else. How about opening your minds to learn instead of jumping out front with hasty opinions?

    Any one that thinks they KNOW what happened here is a fool. Anyone wondering what happened here without jumping to a conclusion on so little information can be confident in their own judgment.

    Eddie,
    I hope you'll respond to Kevin's questions and provide some additional photos. Don't be concerned about any that would p*** judgment. You have an opportunity to share what you find out and we all appreciate it.

    I will reserve my opinion until I know more.
    It doesn't matter what it was welded with, but how well it was welded. It doesn't matter what country made the materials, but rather if there was an unseen flaw before, or unknown damage after, construction.

    All you experts with your conjecture need to get over yourselves.
     
  8. Clark
    Joined: Jan 14, 2001
    Posts: 5,132

    Clark
    Member

    Scotty...well said!!
    Clark
     
  9. orphaneddie
    Joined: Jul 1, 2007
    Posts: 120

    orphaneddie
    Member

    Well here we go.. I could only find a few pics from when I got it.. Now I really wish I had taken more of the "before" stuff. But what I can remember off memory was.... The tube was welded to the bone... the perch was screwed through the bone and a cap was welded over the nut. there was about a quarter inch gap between the tube and the perch, and now that I think about it... my spring was at maximum with no bounce. Must have been stretched as far as it could go.
    [​IMG]

    [​IMG]

    I know they dont show much.. but maybe that will help.

    her is a pic of the broken perch and the one that survived
    [​IMG]
     
  10. orphaneddie
    Joined: Jul 1, 2007
    Posts: 120

    orphaneddie
    Member

    [​IMG]one more if it on the flatbed




    and what we did to fix it
    [​IMG]
     
  11. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,676

    Kevin Lee
    Super Moderator
    Staff Member

    Woah... those look like they could be T-bucket style spring hangers made to fit onto one of those generic batwing bits usually welded to a tube axle?

    I'm ***uming the two short lengths of tubing which were welded to the wishbone were threaded and these hangers were just screwed in up to the end of the threads?
     
  12. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,676

    Kevin Lee
    Super Moderator
    Staff Member

    And if I'm being completely honest... your fix kind of spooks me out too. There are some really good ideas in the Tech forum. Sorry, but I had to say it.
     
  13. Speedway T bucket type perches. with them welded solid, you simply tore the bolt off at the end of the cut threads like Bruce L stated. If they would have been bolted through the bone in a bung and allowed to pivot ever so slightly it prob would have been fine. Your suspension simply "worked" on the threaded part til it let go.
     
  14. scootermcrad
    Joined: Sep 20, 2005
    Posts: 12,383

    scootermcrad
    Member

    SHEARED off right at the shoulder portion... totally as expected!! I've been waiting to see this EXACT picture for while. Hard to tell if it was pure sheer or if there was some torsional "twist" fracturing there from your picture, but I suspect a little of both in this case. The base threaded portion was WAAAAY too small in diameter (obviously) the location of step/shoulder was really the worst part of it though. You are very lucky!

    I would rather see people mount their perches solid like Paul shows in the tech section and mount the crossmember at the correct angle to provide minimum binding. The spring will allow some twist.

    Another similar way to yours was to actually weld a thru-tube into the bone transversely through the tallest face and then bush it so the perch is allowed to rotate. Again though... those spring perches are not really designed to be loaded like that and still could potentially fail if the pure bulk of the perch doesn't support the side loading.

    I don't think people should be discouraged from mounting their spring to the bones AS LONG AS IT'S DONE CORRECTLY WITH GOOD WELDING PRACTICES. Also, some bones will NOT take the side stresses of this type spring loaded. Some are thicker walled than others.

    Maybe someone can dig up Pauls spring shackle mounts as well as some good examples of the "pivoting" type using spring perches.

    Scotty rules! Well stated man! :D
     
  15. toddc
    Joined: Nov 25, 2007
    Posts: 976

    toddc
    Member

    Are those perches really supposed to be left "loose"?:eek: If the bolt is not tight ( properly tight ) the constant movement will lead to a breakage every time, given enough miles.
     
  16. chaddilac
    Joined: Mar 21, 2006
    Posts: 14,077

    chaddilac
    Member

    well said scooter!
     
  17. toddc
    Joined: Nov 25, 2007
    Posts: 976

    toddc
    Member


    I agree with everything except this bit. Bad welding is not the main problem with most of the failures presented on the hamb. **** design, and most often ridiculously undersized parts are to blame. The welds that are shown to have failed, in most cases have failed due to inappropriate placement, and improper materials selection.

    I'm not directly having a go at you , scooter. But it seems that whenever there is a failure, its soon followed by a chorus of people crying about MIG welders.
    :confused::confused:
     
  18. scottybaccus
    Joined: Mar 13, 2006
    Posts: 4,109

    scottybaccus
    Member

    Thanks Eddie. I'll put my .02 in now. It appears to be a tensile failure, likely from your spring being too short, as you stated above. I think you'd do well to seek out the tech Kevin mentions. You really want the suspension to bottom out with extra length still available in the spring and shackles. The angle of the shackels through the suspension travel is very important.
    I applaud you for sharing. Too many people play down any issues on their car. Thanks to you, we all learned a bit.
     
  19. chaddilac
    Joined: Mar 21, 2006
    Posts: 14,077

    chaddilac
    Member

    But a lot of the time failure can be from the welding skills or the lack there of... seriously we've all seen the bubble gum displays on other threads, which is not the case for this car but you have to agree it's probably split 50/50 for **** design and bad welding. At least I think it is.
     
  20. scootermcrad
    Joined: Sep 20, 2005
    Posts: 12,383

    scootermcrad
    Member

    I fully agree and that's what I was trying to get at with the "done correctly" part. :D:cool:
     
  21. Ductile steel doesn't fail all at once. The crack started some time ago, and worked its way through the bolt. The failure could have happened on any bump, it just happened to be this bump.

    The original design was built and had enough strength, but did not account for the fatigue loading. Putting those perches in a bending load (shear loading is not a failure mode in this case) on the treaded portion was a **** design and was going to fail sooner of later. The valley of the threads magnified the bending stress and began crack propagation. If that bolt was an inch in diameter, it still would have failed, and actually wouldn't have lasted much longer.

    Welding them on will work for now, however, you are leaving a place for crack initiation in the middle of the welded area. Given enough time, this setup will also fail, but this might be far past the life of the rest of the car, but we don't have enough information to know. I'd like to see a better perch stuck all the way though a hole drilled in the bone and bolted or welded in. Don't give cracks a place to start and they won't start.
    David
     
  22. scootermcrad
    Joined: Sep 20, 2005
    Posts: 12,383

    scootermcrad
    Member

    Seems in this case it could be a combination of things, proably not welding but quality, parts selection (as Scotty-B mentioned) and sizing of the components to boot.
     
  23. scootermcrad
    Joined: Sep 20, 2005
    Posts: 12,383

    scootermcrad
    Member

    Another well put answer!

    Great things have come out of this thread!
     
  24. lowsquire
    Joined: Feb 21, 2002
    Posts: 2,567

    lowsquire
    Member
    from Austin, TX

    I use forged perches, and a thickwall tube with a taper to match the top of the perch put right through the bone and tig welded in, then you ***mble the front end and with car at ride height, Torque the perchpin nuts, to set the angle correctly without preloading the spring.no way would I leave it loose,'bushed' or not. any angle change is almost immeasurable, and will be absorbed in the spring pack.
    I started reading this thread with trepidation about my methods..but seeing the tiny and poorly designed perch pin that failed, im no longer worried about my stuff.
    Oh and im glad your ok..:)
     
  25. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,676

    Kevin Lee
    Super Moderator
    Staff Member

    Paul's idea ruled. It's my opinion that there is no "good example" of this so-called pivoting mount. Every example I've seen has basically taken something that was never designed to pivot, left it loose, then suggested there was some sort of self aligning movement going on - when in reality it probably just rattles around a bit each time the suspension tops out.

    I think it just complicates something that should be simple. Now if someone can show me a production car that uses a perch designed like that... I'll still think it's lame. :)
     
  26. orphaneddie
    Joined: Jul 1, 2007
    Posts: 120

    orphaneddie
    Member

    Thanks for all the input guys! Time to do some research and get it done right.
     
  27. zibo
    Joined: Mar 17, 2002
    Posts: 2,361

    zibo
    Member
    from dago ca

    fukn eddie...
    glad your ok now after lookin at the pics!
    raise that friggin steering box and engine and make a real scrub line!
    TP
    now thats material for a new Luck of the Draw song!!
     
  28. ROADRAT EDDIE
    Joined: Apr 17, 2005
    Posts: 1,349

    ROADRAT EDDIE
    Member
    from New york

  29. Unkl Ian
    Joined: Mar 29, 2001
    Posts: 13,509

    Unkl Ian

    The perch should have been installed tightly against the tube,
    so the bolt is loaded in tension,and the shoulder distributes
    the bending loads.Stronger,and will last longer that way.

    The spring was too short,so you had no suspension travel.
    All the suspension loads were concentrated on the bolts.
    The weakest link.Sooner or later,they had to break.

    Shackles should be at 45 degrees.

    Any binding will break parts,sooner or later.
     
  30. Weasel
    Joined: Dec 30, 2007
    Posts: 6,696

    Weasel
    Member

    Aaah, finally a voice of reason in an ocean of stupidity....
     

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