Register now to get rid of these ads!

model a frame twist tolerances

Discussion in 'The Hokey Ass Message Board' started by ADReese, Sep 16, 2012.

  1. ADReese
    Joined: Aug 28, 2009
    Posts: 119

    ADReese
    Member
    from spokane

    Im working on a car with a new aftermarket model a style frame. It is rec tube and has a tubular k member. It has a .25" twist in the frame from the front to rear. It doesnt seem like alot, but it can be seen by the naked eye and sits cocked with the rear coilover suspension. The K member makes it so ridgid that the twist does not come out with the weight of the drivetrain and body. Is this within acceptable tolerances or should it be considered an issue? It bugs me, but Im also extremely picky. Please let me know what your opinions are.
     
  2. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    What's the tolerance of the road that the car is going to be operated on?

    Heat up the k-member in strategic places to remove the twist. If that does not work, a relief cut, or two may be necessary.
     
  3. ADReese
    Joined: Aug 28, 2009
    Posts: 119

    ADReese
    Member
    from spokane

    Good point :) The frame has a 2" sweep and a 6" kick so its tough to determine just what is off. I think its the culmination of all of the weld joints adding up to the .25" discrepancy. Keep the opinions coming
     
  4. 66gmc
    Joined: Dec 4, 2005
    Posts: 603

    66gmc
    Member

    if its a new frame i dont think it should be out more than an 1/8" max
    Trying to bolt the body to a twisted frame could start causing issues with panel alignment, or cause doors to not latch properly.
     

  5. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Quarter-inch is what Ford allowed on the assembly line when new. Shims were used to compensate of any discrepancy.

    You're just keeping up the legacy.
     
  6. chaddilac
    Joined: Mar 21, 2006
    Posts: 14,021

    chaddilac
    Member

    Mine is .125... and I just left it! Small angle shim in the rear spring straighten it all up for me.
     
  7. fordor41
    Joined: Jul 2, 2008
    Posts: 1,011

    fordor41
    Member

    I don't know how old that would be. I've never seen any shims in a 30-40's Ford. Watch a video of the fords ass'y line. The bodies were slammed onto the frame and bolted down and I mean slammed. No one was checking the gaps on anything.
     
  8. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Model A, circa '28-'31.
     
  9. ADReese
    Joined: Aug 28, 2009
    Posts: 119

    ADReese
    Member
    from spokane

    Im used to shimming the body for gaps, thats a non issue. I guess I mainly dont like having to modify the coilover mounting position to make up for a twisted frame. When the coilovers are attached, equally adjusted and at the same angle, the rear crossmember becomes parallel with the ground and the twist shows itself in the front.
     
  10. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    It can be corrected, but it will take a bit of work. Know any frame guys in your area?

    If you can get it into a jig and throw some heat on it, it should dial right out.
     
  11. henry29
    Joined: Sep 5, 2007
    Posts: 2,872

    henry29
    Member

    Most factories have a panel and body alignment step further down the line.
     
  12. ADReese
    Joined: Aug 28, 2009
    Posts: 119

    ADReese
    Member
    from spokane

    Ya, there are a couple of frame shops in the the area. I worked in a collision shop for four years, so Im familiar with the frame rack procedures. I just wanted to know if I was being too anal for this era of car. I like to over analyze things ;)
     
  13. Don's Hot Rods
    Joined: Oct 7, 2005
    Posts: 8,319

    Don's Hot Rods
    Member
    from florida

    A quarter of an inch isn't horrible, but if it is a brand new frame have you talked to the builder ? That twist could be taken out with some creative jacking and binding, plus a little heat. But I bet if a lot of our frames were put under a microscope they would be out more than that.

    Don
     
  14. ADReese
    Joined: Aug 28, 2009
    Posts: 119

    ADReese
    Member
    from spokane

    I did drop a note to the builder tonight just to inquire further about his build tolerances. The frame itself is absolutely beautiful, so this really caught me off guard.
     
  15. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Have you moved the whole deal to a different spot on the floor? We have this argument with my boss at the shop all of the time. No floor is perfect, either.
     
  16. I wouldn't live with it. I'd be measuring it every way possible. If the builder let that slide, Id be concerned.
     
  17. fiftyv8
    Joined: Mar 11, 2007
    Posts: 5,394

    fiftyv8
    Member
    from CO & WA

    If you have any doubts, fix it now as it is the easiest time to do so.
    If left it will annoy the crap out of you forever and a day.
    If you can't do it yourself, I am sure as others have said, it would be a fairly easy fix for folks who do this work daily.
     
  18. ADReese
    Joined: Aug 28, 2009
    Posts: 119

    ADReese
    Member
    from spokane

    Its actually up on jackstands right now. I didnt trust the floor either so I leveled it out with a 6 foot builders level and my digital degree finder for extra measure. Sadly it makes the twist even more obvious this way...
     
  19. fordcragar
    Joined: Dec 28, 2005
    Posts: 3,198

    fordcragar
    Member
    from Yakima WA.

    I'd probably put some frame gauges on it, to figure out where the problem is. You might not be happy with it, until it is a little closer.
     
  20. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Fix it. Have it done. You'll be happier. It won't cost that much.
     
  21. ADReese
    Joined: Aug 28, 2009
    Posts: 119

    ADReese
    Member
    from spokane

    Sounds good guys, I appreciate the advice. I feel slightly less ocd now :)
     
  22. Good, the floor doesn't matter. level the center section, X check it, and work from there.
     
  23. 117harv
    Joined: Nov 12, 2009
    Posts: 6,589

    117harv
    Member

    Post some pics so we can see it and how/where you are measuring. How are you measuring it, diagonal? If so a 1/4" is nothing to worry about that is a 1/8" in the middle. A model A body is probably more than twice that.
     
  24. ADReese
    Joined: Aug 28, 2009
    Posts: 119

    ADReese
    Member
    from spokane

    Dont have pics on hand, but if I level the frame at the front crossmember there is a quarter inch height difference in the height of the rear rails at the rear crossmember. And vise versa if you level the rear crossmember.
     
  25. This should give you 4 places across the frame and both main rails to level. That also should give 3 separate planes plus an over all- and all 4 should be square.

    I wouldn't use coil overs to gauge the squareness, there are too many variables, too many brackets involved, and they are adjustable.


    Levels can be off, and subject to the angle of sight. be sure to check again with spinning the level .

    You could stand the frame on its side and use the plumb sight to see whats twisted where.

    I'd like to see what kind of k member is so stiff that adds that much torsional rigidity.
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.