Long Range Hunting Online Magazine Coriolis effect
 Home LRH Store Forums Long Range Rifles Articles Reviews Group Hunts Shooting Classes G7 Ballistics Calculator Rules & FAQ Register Search Today's Posts Mark Forums Read

 Rifles, Bullets, Barrels & Ballistics

# Coriolis effect

#36
03-15-2007, 03:35 PM
 Silver Member Join Date: Jun 2007 Location: Buenos Aires, ARGENTINA Posts: 131
Re: Coriolis effect

[ QUOTE ]
I'm sitting here reading this and wondering if I am smart enough to even shoot a gun. [img]/ubbthreads/images/graemlins/smile.gif[/img] I thought the coriolis effect was the (urban legend) reason why the water in the bathtub swirled when you let the drain out.

[/ QUOTE ]

Yes...I know it's off topic but couldn't resist [img]/ubbthreads/images/graemlins/smirk.gif[/img]

Compared to the rotations that one usually sees the rotation of the Earth is very small: only one rotation per day.

The water in a sink might make a rotation in a few seconds and so have a rotation rate ten thousand times higher than that of the Earth.

It should not be surprising, therefore, to learn that the Coriolis force is orders of magnitude smaller than any of the forces involved in these everyday spinning things.

The Coriolis force is so small, that it plays no role in determining the direction of rotation of a draining sink anymore than it does the direction of a spinning CD.

The direction of rotation of a draining sink is determined by the way it was filled, or by vortices introduced while washing.

The magnitude of these rotations may be small, but they are nevertheless much greater by comparison to the rotation of the Earth.

The direction of rotation of a draining toilet is determined by the way the water just under the rim is squirted into the bowl when it is flushed.
__________________
regards, Gus

http://www.patagoniaballistics.com
#37
03-15-2007, 04:45 PM
 Gold Member Join Date: Sep 2003 Location: Blighty Posts: 637
Re: Coriolis effect

Gustavo,

Wow, taking a 3.5year old thread out of suspended animation and straight back to full throttle must rate for an award of some sort!! [img]/ubbthreads/images/graemlins/smile.gif[/img] [img]/ubbthreads/images/graemlins/smile.gif[/img]

[ QUOTE ]
As Brown Dog said, this drift could be cancelled by other factors, like wind. But the sole notion of an arithmetic cancellation is not a good excuse to not account for it...

[/ QUOTE ]

...wind would not have been a 'cancelling' or 'adding' factor that I had had in mind. I meant the cumulative effects of the other factors that maybe grouped under the title 'Effects of the rotation of the Earth'.

In Dave's N to S hemisphere 120mile shot example (Dave, have you bought your own ATACMS now? [img]/ubbthreads/images/graemlins/smile.gif[/img]); I would suspect that coriolis would cancel out (although even starting to think about zone to zone shooting makes my brain ache [img]/ubbthreads/images/graemlins/smile.gif[/img]) and projectile lag would, by a long stretch, be the dominant 'Effect of the rotation of the Earth' and the shot would show a calculatable error to the right. Were the shot to be reversed S to N, the projectile lag error would be to the left. The cumulative effect of the 'movement of the Earth's surface in space' to these left and right projectile lag drifts(ie both are Westerly and the calculated projectile lag would be reduced as the Earth 'rises' to meet the round) would be negligible.
#38
03-15-2007, 08:43 PM
 Silver Member Join Date: Jun 2007 Location: Buenos Aires, ARGENTINA Posts: 131
Re: Coriolis effect

Brown Dog,

And you were right, sorry if I misunderstood your original post! however my point still remains the same, as wind can easily mask this and other effects.

Of course other factors relating to the Earth rotation, could have a cancelling effect to the Coriolis acceleration...for example the Eötvös effect might appear in place.

Regarding Dave's example I agree on the general notion of a final negligible error to account for, but as you stated right, it could depend mostly on azimuth to target.

PS: give me a date and time to collect the prize! [img]/ubbthreads/images/graemlins/wink.gif[/img]
__________________
regards, Gus

http://www.patagoniaballistics.com
#39
03-16-2007, 01:59 AM
 Gold Member Join Date: Sep 2003 Location: Blighty Posts: 637
Re: Coriolis effect

[ QUOTE ]
Of course other factors relating to the Earth rotation, could have a cancelling effect to the Coriolis acceleration...for example the Eötvös effect might appear in place.

[/ QUOTE ]

Eötvös'll be playing it's theoretical part in the 'Earth's rotation' error budget, but I suspect the induced E/W weight changes of fractions of one percent will be less than the projectile manufacturer's round to round weight variance! [img]/ubbthreads/images/graemlins/smile.gif[/img] (eg a 'standard' weight 155 shell is within tolerance at +0.7 to -0.7% of standard, a 165gr bullet at +/- 0.5gr is +/- 0.3%)
#40
03-16-2007, 03:06 AM
 Silver Member Join Date: Jun 2007 Location: Buenos Aires, ARGENTINA Posts: 131
Re: Coriolis effect

[ QUOTE ]
[ QUOTE ]
Of course other factors relating to the Earth rotation, could have a cancelling effect to the Coriolis acceleration...for example the Eötvös effect might appear in place.

[/ QUOTE ]

Eötvös'll be playing it's theoretical part in the 'Earth's rotation' error budget, but I suspect the induced E/W weight changes of fractions of one percent will be less than the projectile manufacturer's round to round weight variance! [img]/ubbthreads/images/graemlins/smile.gif[/img] (eg a 'standard' weight 155 shell is within tolerance at +0.7 to -0.7% of standard, a 165gr bullet at +/- 0.5gr is +/- 0.3%)

[/ QUOTE ]

Brown Dog,

You hit the nail this time, right once again!

I'm worried that if we continue to agree the purpose of this post will be nill...like the post itself! [img]/ubbthreads/images/graemlins/confused.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img]
__________________
regards, Gus

http://www.patagoniaballistics.com
#41
03-16-2007, 11:10 AM
 Silver Member Join Date: Jan 2007 Location: Great Falls, MT Posts: 203
Re: Coriolis effect

Buffalobob,
THANKS, now I can't even go fishing! [img]/ubbthreads/images/graemlins/smile.gif[/img] HEHE

Gustavo, I'm just being lighthearted...I completely understand most of this, however I didn't even feel the wind from some of it as it went right over my head.
__________________
Genises 27-3: Now therefore take, I pray thee, thy weapons, thy quiver and thy bow, and go out to the field, and take me some venison...
#42
03-16-2007, 01:28 PM
 Gold Member Join Date: Sep 2003 Location: Blighty Posts: 637
Re: Coriolis effect

[ QUOTE ]
I completely understand most of this, however I didn't even feel the wind from some of it as it went right over my head.

[/ QUOTE ]
..well, unfortunately from my perspective, understanding it doesn't make me shoot any better! [img]/ubbthreads/images/graemlins/smile.gif[/img] [img]/ubbthreads/images/graemlins/smile.gif[/img]

 Bookmarks

 Thread Tools Display Modes Linear Mode

 Similar Threads for: Coriolis effect Thread Thread Starter Forum Replies Last Post rem Long Range Hunting & Shooting 41 05-19-2014 11:34 AM lisagrantb Long Range Hunting & Shooting 21 04-02-2011 01:22 PM jmason Rifles, Bullets, Barrels & Ballistics 15 12-13-2010 07:11 PM justgoto Long Range Hunting & Shooting 17 08-03-2010 12:37 AM Brent Rifles, Bullets, Barrels & Ballistics 2 12-26-2002 05:27 PM

All times are GMT -5. The time now is 12:49 PM.