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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; Originally Posted by jcw ......ok Don't go under... 50mm=1.96" 1.2mm=0.047" May not need to go over 75mm=2.95" 2.0mm=0.078" The thicknesses sound about right... I almost ...

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  1. #21
    Member jordan's Avatar
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    Quote Originally Posted by jcw View Post
    ......ok

    Don't go under...
    50mm=1.96"
    1.2mm=0.047"

    May not need to go over
    75mm=2.95"
    2.0mm=0.078"

    The thicknesses sound about right... I almost always use 16g tubing which is 065. occasionaly 18g tubing for subframes or bracing which is 049.

    084 is 14g, 095 is 13g. Like Teazer said those typically are not in the realm of sport chassis building.


    Harley's maybe...

    but whatever, nobody comes here to listen anyway...



    I meant comparing a thinner walled tubing at one larger size diameter.

    Okay thanks for clarifying, i didn’t understand, i haven’t run the tests with thinner walled tubing yet.

    I will run it with the .065 wall and see what it looks like.
    Maybe with the weight savings of using the .065 the frame can be triangulated from the outside of the pivot up to the neck. Although this probably won’t be necessary.
    Thanks for the advice.

  2. #22
    Junior Member themotoworks's Avatar
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    1400ft/lbs really isn't that much, I simulated frame designs using a solid rod extending to the contact patch and put 500lbf inline with travel and perpindicular to it, basically as a reference, you shoudn't in my opinion, see anything close to your safety factor anywhere on the frame with those loads, if you do, I would redesign. while it's unlikely a bike would experience that kind of loading continuously, you have to realize that those loads can easily by experienced periodically, leading to fatigue and failure

  3. #23
    Member jordan's Avatar
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    Quote Originally Posted by themotoworks View Post
    1400ft/lbs really isn't that much, I simulated frame designs using a solid rod extending to the contact patch and put 500lbf inline with travel and perpindicular to it, basically as a reference, you shoudn't in my opinion, see anything close to your safety factor anywhere on the frame with those loads, if you do, I would redesign. while it's unlikely a bike would experience that kind of loading continuously, you have to realize that those loads can easily by experienced periodically, leading to fatigue and failure
    Likewise i loaded 750lbs on the front axle and the frame displaced the axle by a whole 42mm
    That means the spin twisted 3.6 degrees
    I think once the engine is bolted in, it will help strengthen this dimension.
    Other than that, the lateral flexing 12mm is easy to correct with a minimum of triangulation from the exterior of the pivots to the neck.

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  5. #24
    Senior Member XB33BSA's Avatar
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    none of those foale basckbone frames use the engine as a stressed member
    the engine is basic aly just hanging and gives zero added structural ridgidity

  6. #25
    Senior Member XB33BSA's Avatar
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    ii seel this myth often,in forum discussions,that the rear shock loading is going to the stearing head
    with the mono shock pointed at the seerring head
    complete horseshit
    the loading that the shock/spring impasrts to the frame is all going into the swinger pivot

  7. #26
    Member jordan's Avatar
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    Foale Frame designs

    Quote Originally Posted by XB33BSA View Post
    ii seel this myth often,in forum discussions,that the rear shock loading is going to the stearing head
    with the mono shock pointed at the seerring head
    complete horseshit
    the loading that the shock/spring impasrts to the frame is all going into the swinger pivot
    That may be true, but you know as well i that every action has an equal and opposite reaction. You can angle the rear shock appropriately so that the upper shock mount and SA pivot are facing equal magnitude forces with opposing directions.
    So if the sa pivot is perfectly in line with the backbone, it is purely under tensile stress. The upper shock mount however will need to be placed higher up on the backbone and will be at a steeper angle to the spine.

    When you try to bend a pipe, do you push on it end to end to compress it until it bows out?
    No, you push at 90 degrees to it. Well here i want to minimize the flexing, so the forces must be directed along the spine.

    The goal is to align the forces along the spine as best as possible because would be a purely compression and tensile stress. This is not possible with a standard SA rear suspension as the shock mount of the SA would need to be as close as possible to the pivot, so compromises must be made.

    I never claimed i was aiming the forces from the rear to the steering head, i said i wanted to have them aimed as close to parallel with the spine as possible to minimize the strain of the spine.

  8. #27
    Member jordan's Avatar
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    Quote Originally Posted by XB33BSA View Post
    none of those foale basckbone frames use the engine as a stressed member
    the engine is basic aly just hanging and gives zero added structural ridgidity
    I had assumed as much, which is why they were not included in the simulations.

  9. #28
    Senior Member Geeto67's Avatar
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    Quote Originally Posted by jordan View Post
    I had assumed as much, which is why they were not included in the simulations.
    I don't buy that, the rear mounts connect to the pivot, and the front mounts connect to the neck. I'll give you that they probably don't add a lot, but I'd be damned if they don't add something - even in a cradle frame the engine adds some rigidity.
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  10. #29
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    Quote Originally Posted by Geeto67 View Post
    I don't buy that, the rear mounts connect to the pivot, and the front mounts connect to the neck. I'll give you that they probably don't add a lot, but I'd be damned if they don't add something - even in a cradle frame the engine adds some rigidity.
    In the original frame designs the front mounts were just bolted to the spine.

    It will do little to reduce the torsional strain as they are mounted so close to the axis of rotation in comparison to the length of the forks. I would rather not rely on it for rigidity, but if it adds any that will be a bonus.

    For the lateral strain it may help, but the mount on the engine is about 18” below the spine. That means i am asking the front motor mount and the down tubes to resist a significant amount of torsional stress.

    It might help the longitudinal strain, but even in that case the spine only bowed by 1.3mm so it’s not really a concern.

    The best bet would be some additional triangulation from SA to neck

  11. #30
    Senior Member XB33BSA's Avatar
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    Quote Originally Posted by Geeto67 View Post
    I don't buy that, the rear mounts connect to the pivot, and the front mounts connect to the neck. I'll give you that they probably don't add a lot, but I'd be damned if they don't add something - even in a cradle frame the engine adds some rigidity.
    the weight of the front of the engine is hanging from a non structural flexing mount
    the rear of the engine indeed it can add to thAt areras strength so me say zero was wrong
    i am only joining in here to ad what i fead in foales book ,but its obvious to a designers eye what is happening or not
    in his book he states the front tubes support the weight of the engine
    and no more mention of it and he certainly would mention if it did contruibute
    in oreder for them to add structural and tuie the engine into that kit needs to be aan actual structutral type of design ,needing substancial triangullation and a substational mount up at the neck
    thats all i like the frames
    Last edited by XB33BSA; 03-14-2018 at 10:26 AM.

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