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Foale Frame designs

This is a discussion on Foale Frame designs within the Technical forums, part of the Caferacer.net Forums category; I was wondering what more experienced personnes think about the old backbone frames Tony Foale built in the 70’s They seem to be of extremely ...

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  1. #1
    Member jordan's Avatar
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    Foale Frame designs

    I was wondering what more experienced personnes think about the old backbone frames Tony Foale built in the 70’s





    They seem to be of extremely simple construction, lightweight, and from several simulations with autodesk’s frame analysis software seem to handle forces with minimal distortion.

    Tl;dr
    Want to have one made for a t500 engine, good idea or not?

  2. #2
    Senior Member Geeto67's Avatar
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    Here are my thoughts from a lifetime of being a motorcycle road race fanboi:

    The single spine frame design you posted above worked really well for light weight two strokes. Foale used that design for large race bikes as well as road bikes, but it quickly evolved into the wishbone style frames we know today, where as he was still building those single spine frames for competitive racers until 1978 for TZ250's and 350s.

    The biggest advantage is the direct connection between the swingarm pivot and the steering head. The only concern I have is that unless you pay special attention to the geometry and how the engine is used as a stressed member, you could end up with some frame twisting where the front wheel and rear wheel are moving out of alignment during cornering. If built properly and to his original specs it shouldn't be an issue, but it is something to consider. The heavier the bike and the more powerful it is the more likely you are to see those twisting forces - hence why the big bikes moved to wishbone frames and the smaller ones used the single spine for longer.

    A standard T500 is about 408 lbs dry. With the right equipment I could see you having a road bike in the low 300lb range wet (like about 325lbs) which would make the thing pretty spirited.
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    Senior Member Cyorg's Avatar
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    900 Honda
    Name:  IMG_0012.JPG
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Size:  3.74 MB
    "Non urinat in ventum"

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    Senior Member Geeto67's Avatar
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    cbx honda:

    Name:  Hon6_01.jpg
Views: 187
Size:  23.3 KB


    z1 900 frame:

    Name:  ne90y1417467883.jpg
Views: 214
Size:  27.3 KB

    Name:  moBzY1417467883.jpg
Views: 209
Size:  30.4 KB

    compared to the t500 frame, see how much wider the swingarm pivot supports are and how they attach further up the spine backbone?
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
    - Samuel Beckett
    A tool is just an opportunity with a handle
    - Kevin Kelly

  6. #5
    Member jordan's Avatar
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    Quote Originally Posted by Geeto67 View Post
    cbx honda:

    Name:  Hon6_01.jpg
Views: 187
Size:  23.3 KB


    z1 900 frame:

    Name:  ne90y1417467883.jpg
Views: 214
Size:  27.3 KB

    Name:  moBzY1417467883.jpg
Views: 209
Size:  30.4 KB

    compared to the t500 frame, see how much wider the swingarm pivot supports are and how they attach further up the spine backbone?
    I see it, it’s because the SA pivot is so far below the backbone. In order to deal with the force on the pivot having a larger inertial moment it required bracing. The advantage there is that the shock lies. Parallel to the backbone so the forces transferred are almost perfectly in line with the spine so there is little strain from that source.

    Interestingly, it was suggested here


    That the backbone frame may actually have more torsional stiffness than a triangulated wishbone style frame of similar weight.
    In terms of lateral stiffness however it is severely lacking by comparison.

    I was planning on using a 2.5” by 0.95” 4130 steel tube for the backbone. The image of the 500 frame i posted seems to indicate that he used used 2” diameter tubing, but to be certain in added and extra .5” to it.
    This page seems to indicate that he would have likely used thinner walls at 2mm than the 2.4mm i would use.


    I figured i could build it and see how it feels, and add a small tube on each side from the SA pivot up to the neck with minimal weight penalty. This would maximize both lateral and torsional strain.

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    Member jordan's Avatar
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    Unfortunately i won’t be able to have the pivot inline with the spine, it’s about 8” lower.
    This also makes designing the rear suspension in a way that gives a progressive rate geometry a little tougher as it limits the angles that it can be mounted at without mounting the shock under the spine. I’ve got a hunch about this one, but i’ll see how it mocks up in Inventor.

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    Senior Member CaTacL1sm's Avatar
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    I need that Z1 frame
    Quote Originally Posted by alwhite00 View Post
    Fuck all of you guys. Get into your little circle jerk and have fun. Thought this may be a pretty cool message board but damn, you guys are assholes.

  9. #8
    Senior Member Teazer's Avatar
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    .095" is pretty thick for a large diameter tube. Do the analysis with thinner gauge and see how much it changes the results.

    Can you rotate the T500 motor slightly forwards (nose down a little) to get a straighter run in the top tube?

  10. #9
    Senior Member Cyorg's Avatar
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    ...........

    Name:  IMG_0013.GIF
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    "Non urinat in ventum"

  11. #10
    Member jordan's Avatar
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    Foale Frame designs

    I know, i know cyorg.
    But i was hopeful that i could use a non linkage setup and still obtain a progressive rate. Far less complex, and a lot lighter.
    It’s easier to think harder now and build less later.
    I can do it with the overhead shock, but it means that the angle between the shock and frame increases as it compresses which i was hoping to avoid. If i can get the SA pivot to line up a bit closer it will be okay to mount on the top.

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