Sidecar Design Formula - IMPORTANT!

Discussion in 'Hacks' started by Get Back, May 25, 2009.

  1. davebig

    davebig Another Angry Hun !

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    Nobody else would ever get away with that :fpalm
  2. High Octane

    High Octane Long timer Supporter

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    I could do that.
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  3. claude stanley

    claude stanley Claude

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    subframe gs 2.jpg
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  4. claude stanley

    claude stanley Claude

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  5. High Octane

    High Octane Long timer Supporter

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    Thanks for the post Claude. I have the pic already and it’s given me some ideas.
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  6. arbalest

    arbalest Been here awhile

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  7. davebig

    davebig Another Angry Hun !

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    That's Claudes design for 1150gs
  8. arbalest

    arbalest Been here awhile

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    I like that.
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  9. GerardW

    GerardW Adventurer

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    IMG_8433.JPG Holy mackerel, what did I is the past months. Here is the subframe for my 1150 pulling a 130kg rolling chassis. Why the need for such a heavy subframe ?
  10. davebig

    davebig Another Angry Hun !

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    That's easy there are plenty of folk who feel the rear subframe on the 1150 gs is too light to just clamp too, tying both sides of the tug together can't hurt and it appears you used rose or heim joints in the two lower points Claude uses mounts that bolt up solidly.
    Underbuilt or overbuilt.
  11. GerardW

    GerardW Adventurer

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    Thanks. I'm also one for over engineering. Mine just came out like that because I knew nothing and copied PowderMonkey's build. I did use rose joints. Here is how I engineered the rear top of the stabilizer mounting point spreading the load off the subframe.


    IMG_8448.JPG
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  12. GerardW

    GerardW Adventurer

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    Here is my whole to-bike mounting set-up. Criticism is welcome. In the meantime I have strengthened mounting of the the brace to the front of the subframe to the crashbar mount under the tank and re-mounted the stabilisers perpendicular to the car.
    IMG_8585.JPG
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  13. High Octane

    High Octane Long timer Supporter

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    Just remember when u fly the chair u have a 4ft lever trying to bend the crap out of everything.
    Like a tool designer once told me when I was working for him “We don’t engineer anything we just make it as strong as we can and hope it doesn’t break”.
    But I do agree with your thoughts, when is heavier just extra weight without the need? I dunno. When I was designing my upper rear mount I calculated the flex on an unsupported cantilevered 1 1/4”!tube, anchored on the lower subframe but not supported at the top. The calculated deflection was scary. I didn’t think the bike rear subframe was designed to transfer the load back to the engine mounts either so I went all in and built an exoskeleton frame to do the job. Overbuilt? I hope so. I don’t have the engineering tools to do a proper analysis so I default to: “We don’t engineer anything we just make it as strong as we can and hope it doesn’t break”.

    Mine. It weighs 47lbs.

    74EA9E4E-1A0C-415A-AEC9-D810B7B6AB04.jpeg
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  14. GerardW

    GerardW Adventurer

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    I trust the Germans followed that same engineering philosophy. But does the subframe not in fact bear on that rear engine mount ? I'm busy with a second sidecar to 1150 so still doing some R&D.
  15. davebig

    davebig Another Angry Hun !

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    The rear sub frame on a stock 1150gs, holds up the seat and muffler,bags if you run them. It's not overbuilt.
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  16. High Octane

    High Octane Long timer Supporter

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    The frame failure I’ve seen ( google search) look to be cracks in the relatively thin tubing. I think the frame is designed to support vertical forces but not so much horizontal. I picked up the same engine mount, transmission mount (at the foot peg bracket) but add in the lower subframe. On both sides of the bike. But the biggest deal is its 1” diameter steel tubing with an 1/8” sidewall, If the welds are good I don’t think it will break. But who really knows.
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  17. davebig

    davebig Another Angry Hun !

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    Part of the trouble is when designing something to sell the bean counters get the final say not the engineers, things are built to a price point.
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  18. GearHeadGrrrl

    GearHeadGrrrl Long timer

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    That's why so many modern bikes make the engine do double duty as the main frame- It's not better engineering, it's just cheaper that way!
  19. Prmurat

    Prmurat Long timer

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    And Phil Vincent just turned in his grave... View attachment 2370441
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  20. davebig

    davebig Another Angry Hun !

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    As did Dr T from Ducati.