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Thread: Coriolis effects explaned

  1. #1
    Member 199p's Avatar
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    Coriolis effects explaned

    Was flicking around on the internet as you do when as work and found this gem of a video.
    I have had it explained a few times but never this simply so thought i would share

    https://www.youtube.com/watch?v=jX7dcl_ERNs

  2. #2
    Member Uplandstalker's Avatar
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    Yup, a heading of either north or south with effect our windage too. Bullet leave the barrel and the rifle and target continue to spin with the earth and the bullet slows(relative to the earths rotation) as it travels toward where the target once was.

    Also, is you ask any survey if the effect of gravity is the same all over the world, you might be surprised by the answer. Some of you will not believe me, but even here in New Zealand, water can run up hill due to differing geoid model and these difference gravitational forces. This is worst in areas where the flat land rapidly changes to very steep and high mountains. Couple of examples are areas like Kapiti, most of the coast of the south island and where the Canterbury plains meet the Southern Alps. So it's possible to have water flow "up hill" across the Canterbury plains by up to 12 meter or more. How this actually affects the flight of a bullet is not signifcant at the distances we shoot, even at extreme long range.

    Just useless information to pass on.

  3. #3
    OCD Gravity Test Specialist kiwi39's Avatar
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    great share - very well presented vid.

    Thanks

  4. #4
    Member marky123's Avatar
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    Latest thing-Gunwerks coriolis effect turrets.We don't know what it is,but $500 a set!

  5. #5
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    Interesting, I would have thought that since the round is in the chamber moving at the same speed as the target as the earth spins then when it is fired it would continue at that speed. Sort of along the same lines as dropping peanuts on the plane doesnt make them shoot to the back. Very interesting, I will have to read up on this.

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    Toby knows all about this shit, there is a thread about 3 weeks long on the subject
    dskd likes this.
    Boom, cough,cough,cough

  7. #7
    Member Savage1's Avatar
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    I imagine the effect is completely negated by any type of wind. Shouldn't it be directly relative to the latitude of your location and bearing of your shot? If it had anymore than a negligible effect then I would have thought that you would be able to I put those figures into the shooting apps.
    gadgetman likes this.

  8. #8
    Almost literate. veitnamcam's Avatar
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    Shooter accounts for it savage
    BRADS likes this.
    "Hunting and fishing" fucking over licenced firearms owners since ages ago.

  9. #9
    Member Uplandstalker's Avatar
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    This would be true if shooting in a vacuum. But the effect of air pressure and humility slows the projectile down.
    kiwi39 likes this.

  10. #10
    Semper excretia Ryan's Avatar
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    Quote Originally Posted by Uplandstalker View Post
    This would be true if shooting in a vacuum. But the effect of air pressure and humidity slows the projectile down.
    Fixed it for ya.
    "I would rather suffer under imperfect freedom, than languish under perfect control".

  11. #11
    Member Puffin's Avatar
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    Worth resurrecting I thought as @JRW87's comment deserves another attempt at an answer.

    Quote Originally Posted by JRW87 View Post
    Interesting, I would have thought that since the round is in the chamber moving at the same speed as the target as the earth spins then when it is fired it would continue at that speed. Sort of along the same lines as dropping peanuts on the plane doesnt make them shoot to the back. Very interesting, I will have to read up on this.
    In all cases the bullet in flight (other influences neglected) does maintain the same eastward component of motion as the rifle it was fired from, just like the peanut in the plane example. The shooter and target travel at the same angular velocity, but if they are at different latitudes - as they would be for shots taken to the north or south – they would not be moving at the same linear speed since the radii to the axis of rotation will differ. It is this difference that makes the target move ahead (shooting towards the equator) or lag behind (away from equator) the bullet's path.

    For directly east/west shots, where the linear speed is the same, then the reason for there also being left/right movement comes from the imbalance to original centripetal acceleration where bullets shot eastwards drop less than expected, and those to the west more. This movement is at right angles to the axis of rotation, so is not actually normal to the earth’s surface except at the equator, so skewed. This can be split into two components acting at right-angles, one which does act in the same axis as gravity - the Eotvos or vertical deviation from the expected gravity-based trajectory - and a horizontal component. Bullets shot to the east drift towards the equator from this horizontal component. The reverse applies for shots taken west.

    All shots away from the cardinal compass points are influenced by a mix of both effects, but they all deliver left drift in the southern hemisphere. The difference in the size of deflection with direction affects long range trajectories. I've read that treating all directions the same is acceptable for shooting out to a kilometre or two. An interesting effect even if the resulting variations in POI are small enough to disregard.
    Last edited by Puffin; 06-04-2017 at 03:35 PM.

  12. #12
    Member zimmer's Avatar
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    Only recently refreshed my brain by reading Brian Litz's excellent paper on spin drift and coriolis effect - his bottom line on spin drift, don't worry too much about it, the wind will deal to you mostly.

    http://appliedballisticsllc.com/ball...rces/articles/

    About the 9th article down. Lotsa other good stuff there as well to read n bed at night.
    Last edited by zimmer; 06-04-2017 at 03:45 PM.

 

 

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