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Thread: How can I check my frame is straight

  1. #11
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    Thank you, Eric!

    Its self-leveling.

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  2. #12
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    Quote Originally Posted by T. Cotten View Post
    Folks,

    The inspection method detailed in H-D service manuals can be adapted to other marques, with appropriate straight edges and common sense.

    This Hen was fun.

    ....Cotten
    PS: I finally found the 340 print courtesy of http://virtualindian.org/
    It still will not tell you if a frame is "straight", or not...
    Looks like your "Frame Table" has a little sag. :-)
    Be sure to visit;
    http://www.vintageamericanmotorcycles.com/main.php
    Be sure to register at the site so you can see large images.
    Also be sure to visit http://www.caimag.com/forum/

  3. #13
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    That's how it leveled out, Chris!

    Actually Folks, my "frame table" is the big I beam, used creatively in the rear of the Hen.

    Most frames retain their "memory", and want to be massaged square and true.
    As long as the rear wheel follows the front, it doesn't matter much in between.

    Framework is very satisfying.

    ....Cotten
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    Last edited by T. Cotten; 07-18-2017 at 01:20 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  4. #14
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    Folks, If I can really help at all..

    The whole gist of the HD manuals' procedure is easy to miss.

    Basically, a long straight-edge rod must be installed into the headstock. Math lets you correct for diameter, as it will for the centerline straightedge.

    Then, a vertical support is set up on the rear of the frame, with appropriate diameter, so that it will guide another long straightedge rod parallel to the centerline of the powerplant-bearing chassis, usually held against the seatpost tube, hopefully spaced out enough from the headstock rod that it "sweeps" with a visible clearance, when moved in an arc.

    A changing gap indicates the headstock is skewed from the chassis centerline.

    Hope that helps the H-D Service manual make sense...


    ....Cotten
    Last edited by T. Cotten; 07-18-2017 at 05:52 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  5. #15
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    Quote Originally Posted by T. Cotten View Post
    Most frames retain their "memory", and want to be massaged square and true.
    As long as the rear wheel follows the front, it doesn't matter much in between.

    Framework is very satisfying.

    ....Cotten
    I agree 100%, Tom. Every motorcycle frame I have had, and had the awareness to check, has been mangled, bent, or just tweeked, but still out of spec. I agree that frames seem to have a memory, and are partial to returning to their original shape. However, both of my Hendersons had traumatic damage, and from my forensic research; they had been seriously hit in the right rear. It's remarkable how much stress is transferred to the (seemingly) undamaged areas.
    Eric Smith
    AMCA #886

  6. #16
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    Quote Originally Posted by exeric View Post
    I agree 100%, Tom. Every motorcycle frame I have had, and had the awareness to check, has been mangled, bent, or just tweeked, but still out of spec. I agree that frames seem to have a memory, and are partial to returning to their original shape. However, both of my Hendersons had traumatic damage, and from my forensic research; they had been seriously hit in the right rear. It's remarkable how much stress is transferred to the (seemingly) undamaged areas.
    So.... ..

    Did you fix them?


    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  7. #17
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    This topic is a favorite of mine, and I've straightened (by my own definition) about a half dozen Chief frames and several Sport Scout frames. A few concepts can guide you through the inspection, and help explain the end result your after.
    First concept, by my reasoning, is that the center planes of the wheels and the neck should all lie in a common plane. This apparently speaks for the parting lines of the engines too, although they are less critical to the handling of the bike. When working with a bare frame, of course, you have to know axle dimensions so you can transfer the center lines to the appropriate frame parts or references, i.e. the slippers in the rear, or the centers of the forks. The forks should be managed separately anyway so you can work with the neck.
    Concept #2 is left-to-right symmetry. If you have a common center plane the slippers should be the same distance from that plane, and the centers top and bottom should show this. The neck can be referenced with a framing square if you have a table and a center-line, and the lower portion of the frame is in a fixture that centers it on the center-line. Finally, a shaft that projects through the neck's bearing centers should also project through the centerline on the table.
    If the language of the involved geometry is confusing try to find a book with some diagrams. We are relying on definition of the plane, and the line, and symmetry. My work all happens on a 4' x 12' x 3/8" table slab, and I've used a variety of large "persuaders" to move things to where they belong. My fixtures secure the frame in the front motor mounts and the base of the lower casting on the seat post. ... and I've used 10' long steel tubing to move the slippers, so that requires some pretty firm fixtures. Slippers are easier than the neck, imo,.. I've only used heat when straightening collision bends, or to relieve stress to limit that "memory".

    Wish I had pix.

  8. #18
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    Filibuster!

    I agree but.. the "parting lines" on a Milwaukee machine can lead you astray.

    That's probably why they ignored them in the Service Manual.

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  9. #19
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    Quote Originally Posted by T. Cotten View Post
    So.... ..

    Did you fix them?


    ....Cotten
    I did fix the Henderson frames, but they were pre Deluxe and not as stout as the double down tube frames; hence easier to move. I have done a few H-D frames and there is more to be mindful of to achieve orthagonality, and dimensional correctness. I have not done an Indian slipper frame, but they look like they would be more difficult than an H-D frame. My Excelsior frame, and Merkel frame were the easiest to move as they are both very light, and minimalist. I think you can assume that any frame that uses the motor as a stressed member will be bent like a noodle. If I ever get a title for this mid-70s Honda that I have, I will be curious to see if the frame is bent. I'm betting it's not as I think Honda put a lot of engineering into making it strong; albeit, kind of ugly
    Eric Smith
    AMCA #886

  10. #20
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    Big Twin H-D frames were almost fun, Eric!

    Until the steel turned to mud by '84 or so.

    But I never attempted a single-down-tube model, and I don't know how I would hold onto one. (Never a sportster either of course.)

    My Chief frame experience, beyond weld repairs (couldn't find a pro..), was only to straighten bowed sections of frame members using the grate at the bottom of my framing tools photo.
    As with Milwaukee machines, straightening individual members in the best, often intuitive, order brings the entire assembly back to harmony.

    Missed my chance at a REAL table once, for a song.
    But it would have been impossible for me to transport or handle, and no place to put it.. ... . *sigh*

    .....Cotten
    Last edited by T. Cotten; 07-19-2017 at 12:19 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

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