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What Did You Do To Your Jeep Today?

Discussion in 'Builds and Fabricators Forum' started by Focker, Jul 23, 2016.

  1. Nov 12, 2022
    Stakebed

    Stakebed Member

    Lake Co....
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    Thank you guys.
    Can't quote both of you because you're on different pages using my cell phone. I'll shout out @timsresort .

    I have photo proof Yj has 28" of articulation. I wonder what it's RTI would be? Inquiring minds want to know. :D:D
     
    FinoCJ likes this.
  2. Nov 12, 2022
    timsresort

    timsresort Active Member 2023 Sponsor 2022 Sponsor

    South Lake Tahoe CA
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    All you have to do is figure out how long the hypotenuse is of a right triangle with a vertical leg of 28", and angle of 30 degrees, then divide by your wheelbase. Don't ask me, I hate geometry.
     
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  3. Nov 12, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    there is more than just front end articulation - the rear end provides additional flex for more travel up the ramp, and these old jeeps have a bit of frame flex etc. But if we use 28in as the minimum height the jeep can achieve on the ramp, using some trig (28/sin30*) = 56 inches of travel up the ramp. intermediate cj5 has wb of 84, so (56/84) X 1000 is 667.
     
    Last edited: Nov 12, 2022
    Ol Fogie, Stakebed and timsresort like this.
  4. Nov 12, 2022
    timsresort

    timsresort Active Member 2023 Sponsor 2022 Sponsor

    South Lake Tahoe CA
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    There, see, easy. Thanks James
     
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  5. Nov 12, 2022
    Cj5dale

    Cj5dale Member 2023 Sponsor 2022 Sponsor

    Knoxville, Tn
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    So to put this in context for me, what would a stock CJ5 score?
     
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  6. Nov 12, 2022
    Stakebed

    Stakebed Member

    Lake Co....
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    While @timsresort and @FinoCJ were typing, I was online elsewhere trying to remember soh cah toa from high school. Fino beat me to posting.
    Someday I'll have to play on one of those ramps.
    Thanks to @Buildflycrash and @dnb5853 for piqueing my interest.
     
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  7. Nov 12, 2022
    timsresort

    timsresort Active Member 2023 Sponsor 2022 Sponsor

    South Lake Tahoe CA
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    Boy, we're an exciting bunch. Saturday night trying to remember HS geometry. Our local club has a ramp that I borrow when I want to flex something. It's in a photo in my tux build, I believe. It's a ton of fun if you get a bunch of jeeps together.
     
  8. Nov 12, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Guess here a bit, but probably around 500? If so, that would mean it would travel 40 inches up the ramp, to a height of 20 inches - can't imagine it would be any more than that....
     
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  9. Nov 12, 2022
    Buildflycrash

    Buildflycrash More or Less in Line. 2024 Sponsor 2022 Sponsor

    Gulf Breeze FL...
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    Has was in the bed. But the bumper is not a bad idea!
     
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  10. Nov 12, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    true - but I am a physics teacher (well up until 2 years ago). one nice thing about a 30 degree ramp is the relationship between height and distance along the ramp (the hypotenuse) is 1:2.
    Sin30 = 1/2
     
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  11. Nov 12, 2022
    timsresort

    timsresort Active Member 2023 Sponsor 2022 Sponsor

    South Lake Tahoe CA
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    Ok, so I'll ask a dumb question, but in all seriousness. If 45* is 100% slope- 1:1, why isn't half of that-22.5* 1:2?
     
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  12. Nov 12, 2022
    dnb71R2

    dnb71R2 SuperDave 2023 Sponsor

    Grand Mesa, CO
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    One thing to remember, ALL FOUR TIRES must remain in contact with the ground. As soon as one lifts, the judge will stop you and take a measurement.
    If I ever do this again, I'll air down.
     
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  13. Nov 12, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    first and foremost, remember that slope is a ratio of the two 'legs' of the triangles, and %grade is based on a tan relationship. But more to the point, that is why there is so much value in the unit circle...remember that for a constant radius of one ('unit' in the unit circle), the two sides represent the distance on x and y axis....the relationship between the angle and the leg lengths are not linear...In the fig shown, the 3 triangles are increasing in angle by 15 degrees each. as the angle increases from 30 to 45, you can see how much shorter the horizontal side gets....then go another 15 degrees to 60 and you can see for the same amount of angle change, the horizontal leg got shorter by a larger amount than it did previously. If this relationship was linear, the distance between the right angles at the bottom would be the same - but they are not. Its not linear.....turns out the relationship is what we call cosine. If we did the triangle along the vertical leg on the y-axis, the relationship would be similar, and is the sine function. Another way to thing about it, as the radius arm sweep through an arc, it changes more along one axis than it does along the other.
    [​IMG]
     
    Last edited: Nov 13, 2022
  14. Nov 12, 2022
    timsresort

    timsresort Active Member 2023 Sponsor 2022 Sponsor

    South Lake Tahoe CA
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    Thanks for the explanation. Now I see it.
     
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  15. Nov 12, 2022
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    RTI ramps are fun and can be useful for checking suspension clearances and whatnot, but ultimately the only thing that matters is how the vehicle works on the terrain you are traversing. High RTI ramp scores do not necessarily relate to trail performance.
     
  16. Nov 12, 2022
    Cj5dale

    Cj5dale Member 2023 Sponsor 2022 Sponsor

    Knoxville, Tn
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    This is the first explanation of this I have ever really understood. Thanks for taking the time to explain it!
     
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  17. Nov 13, 2022
    dozerjim

    dozerjim Member

    western New York
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    :confused:......:study:........:shrug:
     
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  18. Nov 13, 2022
    Stakebed

    Stakebed Member

    Lake Co....
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    Who wudda thunk? One forum offers Jeep and trigonometry advice. All in one place.

    For his next trick, @FinoCJ will walk us thru home physics experiments. Maybe a centrifuge built from discarded Jeep parts.
     
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  19. Nov 13, 2022
    timsresort

    timsresort Active Member 2023 Sponsor 2022 Sponsor

    South Lake Tahoe CA
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    We found that the judge can usually be bought with as little as a beer.
     
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  20. Nov 13, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    having flashbacks to remote teaching....i am sure there is a math teacher out there cringing at my overly simplified physicist (well, even worse, geologist) interpretation. Like many things we learn when young, we focused on things like memorizing the unit circle, or only applying trig concepts to random triangles, or even just blatant application. But the true value is much more complex and subtle (and even beautiful in its existence) - like the relationship between a radius of curvature and the amount the distance along each axis changes as a relationship - that we don't truly value during our schooling years (or even thereafter). The beauty to me of these topics isn't truly viewable at a surface level, and reveals itself only through years of devotion - just like the beauty of a master-craftsman's work reflects that commitment as well.

    now back to regularly scheduled programming....if only all that trig could help me weld triangles on the transmission cover
     
    Last edited: Nov 13, 2022
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