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Thread: Torsion Bar Autopsy...

  1. #1
    Junior Member
    Join Date:  Jan 2019

    Location:  Central Georgia

    Posts:    26

    My VIN:    3880

    Torsion Bar Autopsy...

    Torsion_Broke.jpg

    While I have absolutely no doubt that a scratch could, and probably will create a stress riser that will eventually cause a failure, close inspection of the actual break of the failed passengers side bar from 3880 shows that these things apparently are tougher than one might think. Check the picture out. This bar has had a DEEP crack in it for quite a while before it finally failed. This thing was stored for 15 years in a shop bay. It hadn't seen a drop of water in 15 years. Yet the picture clearly shows that it had been cracked about 1/4 of the way through for quite some time. You can plainly see rust in the initial fracture. That crack had to have been that way for quite a while for rust to develop in there. I opened and closed that door many time before it finally snapped, and it had to have been already cracked about 1/4 of the way through the whole time. I was really a bit shocked by that. Note the center of rotation when it sheered... about 1/3 of the way in on the opposite side of the rusted fracture. Makes perfect sense. At any rate, the replacement (and the drivers side original) got 3/8" plastic wire loom over their entire length to prevent any scratching in the future. Just thought you guys might find this interesting.

  2. #2
    Owner since 2007 Farrar's Avatar
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    Fascinating! Thanks!
    3.0L, automatic, carbureted

  3. #3
    Senior Member Rich's Avatar
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    Location:  San Francisco Bay Area, Calif.

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    Thanks for the post-mortem on the fracture.

    Sorry to hear of another one gone.

    Care to tell us how close to the rear hinge this failure occurred?
    March '81, 5-speed, black interior

  4. #4
    Junior Member
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    Location:  Central Georgia

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    It broke on that end roughly 4-5 inches from the splines, but it broke under the stainless. You couldn't see the break holding the door up. So it didn't break AT the hinge, but near it. Wound up working late tonight and the shop is a couple of miles down the road, so I can't check it this evening, but I'll make measurements and more photos tomorrow evening and post them.
    Last edited by TGGreene; 03-27-2019 at 08:44 PM.

  5. #5
    Junior Member
    Join Date:  Jan 2019

    Location:  Central Georgia

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    My VIN:    3880

    D-Roof-Bar.jpg

    I very carefully measured and placed the bar exactly in line with where it lays end to end in the box. The chisel is about the same width as the hinge and is laid exactly in line with the hinge. As you can see, the bar snapped about an inch and a half behind the hinge, so it wasn't scratches from the hinge that started the failure.

  6. #6
    Senior Member
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    Location:  Richmond Va.

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    tggreen what are you replacing with. Just asking for future reference.

    Steve

  7. #7
    Junior Member
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    Location:  Central Georgia

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    Quote Originally Posted by steve View Post
    tggreen what are you replacing with. Just asking for future reference.
    A bar from DMC (delorean.com). $910 plus shipping, which is the actual postage - pretty cheap. At least they don't rape you on the shipping too. I guess they've already been "satisfied". I wish there were other options, but I couldn't find one. DMC has a stock of passengers side bars, but not the drivers side bars. http://www.dmoco.com/Torsion.html has the drivers side bars, but not the passengers side. Same price.

  8. #8
    Senior Member Patrick C's Avatar
    Join Date:  May 2011

    Location:  Northern Michigan

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    Quote Originally Posted by TGGreene View Post
    A bar from DMC (delorean.com). $910 plus shipping, which is the actual postage - pretty cheap. At least they don't rape you on the shipping too. I guess they've already been "satisfied". I wish there were other options, but I couldn't find one. DMC has a stock of passengers side bars, but not the drivers side bars. http://www.dmoco.com/Torsion.html has the drivers side bars, but not the passengers side. Same price.
    DMC sells the DMOCO bars, correct?
    Patrick C.
    VIN 1880
    Modifications done to my car can be seen in this video: https://youtu.be/ncMjW2pI2e4

  9. #9
    Senior Member Rich's Avatar
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    Location:  San Francisco Bay Area, Calif.

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    Club(s):   (NCDMC) (DCUK)

    Quote Originally Posted by TGGreene View Post
    D-Roof-Bar.jpg

    I very carefully measured and placed the bar exactly in line with where it lays end to end in the box. The chisel is about the same width as the hinge and is laid exactly in line with the hinge. As you can see, the bar snapped about an inch and a half behind the hinge, so it wasn't scratches from the hinge that started the failure.
    Thanks for the detailed follow-up on that.

    Given that location there is the possibility that the root cause of that bar's failure was wear on the bar due to contact with the edge of the hole in the roof or body tub, the forward edge of which is about 1.5 in. behind the back of the hinge.

    It's the first time I've heard of a bar failing there until now. I wonder if others have seen failures there.

    Setting aside theories about why it happened at that location you may wish to check to see if your new bar is clear of at least the front of that hole all around. With the door open just grab the bar (by hand, not with a tool) near the rear hinge and push it about 1mm in all directions. I'm making that number up. The bar should move easily without touching the hole.

    More common is a bar rubbing against its respective rear hinge, as you know. And then breaking someday at or near the rubbing point. Just a reminder to the rest of the community.
    March '81, 5-speed, black interior

  10. #10
    Senior Member
    Join Date:  Aug 2018

    Location:  Virginia

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    My VIN:    1623

    Is DMOCO still around? Their website has pages that haven’t been updated in more than 10 years.

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