Does One's Hemisphere Effect the Direction of a Bullet's Spin?

Aussiviking,

The weak local effects of the Coriolis Effect would have no bearing on the direction of spin on a bullet. To put it another way, the direction of spin will have no bearing on whether the bullet is affected by the Coriolis Effect, nor would the hemisphere it is fired in.

However, the rotation of the earth does effect the striking point of bullets slightly, and longer range projectiles more, if they are fired in anything other than an east or west direction. This is a factor of the tangential velocity of points on the earth decreasing between the equator and the poles. This becomes a major consideration with targeting parameters for missiles.

Regards, Greg

I was under the impression the reason toilets flushed in that manner south of the equator is because they are made that way, not because of the hemisphere they are in. Am I wrong? Sorry to vear off topic...

Hi aussiviking, you wrote: "... i wonder this because in the southern hemisphere the water flows down the hole in a left to right vortex but i believe in the norther hemisphere it travels the other way..."

This particular view is an urban legend. It is only on the large scales of weather systems that the Coriolis effect causes a distinct difference in rotation direction. On the small scales of water down a hole, it depends on the surroundings of the hole and other disturbances of the water.

Regards, Jorrie

The spin of a bullet is determained by the rifleing not the hemisphere. Water on the other hand goes down the drain clockwise above the equator and counter clockwise below.

Water on the other hand goes down the drain clockwise above the equator and counter clockwise below.

We have just gone through this in the Aeroplanes and Water Down the Drain thread and as Jorrie said it is an urban legend and the rotation of the earth has nothing to do with the way water swirls as it goes down a drain.

MASU- I have been working on our "water down the drain" problem and am finding out that to produce accurate results, I/we need to build test apparatus to exact specs. A suitable container needs to be built to tight specs. so as to not influence the outcome. I will get back with you later. James

Hi James,

I was afraid we were going to need to build something with great accuracy.. I am moving house from Adelaide to Sydney which is about a 1,500 Km move. I had to get rid of my lathe and most of the heavy equipment that I had in my workshop last week. I hadn't use it for some time and I just knew that the minute I got rid of it I was going to need it. I do plan to get another lathe but is going to take a while before I can look for and get one.

I have complete machine shop available, including CNC (though regretably no 4th or 5th axes). My problem is finding the time... I'll see what I can do.

I still haven't found an editor toolbar...

Dick

Hi Dick,

You should be seeing something like this when you enter the text for you post.

Are you getting something like this or is it completely different?

Thanks for the image.

No, there is no toolbar on my screen.

Instead, at the bottom of my screen is a list of Formatting Tags Instructions for Linking:,Formatting:, and Images:

I don't know how to use the Images for files on my own computer. I wish we could just cut and paste...

Dick

Ah ha I think I know what is going on. What you are seeing is the old CR4 editor and web page, it was replace some six months ago with a new look and more powerful editor that has the toolbar.

What is happening is you web browser is using a cached version of the page from either on a proxy server or you machine. It has never bothered to update the page since you first visited the CR4 post editor page and hence when it sees the URL for the CR4 editor web page it uses the cached version which was replace all that time ago.

There must be some way to force your web browser to go and get a new copy of the page from the CR4 web site rather than using the cached version. Have a look at your browser options and see if you can turn off the proxy server and caching options for a while and then see what you get. Once you have downloaded the new web page and editor you can turn them on again.

There is also a property of web pages that tells browsers to reload if the cached version is over certain age. The CR4 editor obviously has that set to zero which means that the page never times out and forces a reload. If you are still having problems after turning of the caching post it here and I will get in touch with Chris and see if he can help.

This could be causing you problems on other sites as well. Have you noticed that pages you visit regularly that should change or be updated regularly, like TV programs and weather reports, aren't updating?

Hi

If you are seeing the formatting instructions then you do not have javascript enabled or this is some other problem affecting javascript. Please email me at cr4admin@globalspec.com and we can discuss this is more detail.

Thanks,

Mark

Re: Does One's Hemisphere Effect the Direction of a Bullet's Spin? 03/12/2007 12:24 PM

Thanks for the image.

No, there is no toolbar on my screen.

Instead, at the bottom of my screen is a list of Formatting Tags Instructions for Linking:,Formatting:, and Images:

I don't know how to use the Images for files on my own computer. I wish we could just cut and paste...

Dick

Its good you have a machine shop available. I will help you in any way I can! I think MASU would like to be kept up to date as to what we do also. I was thinking along the lines of a clear plexiglas tank so the results could be filmed from the outside. The hole in the bottom of the tank would need to be in the exact center of the tank. The tank size should be at least 10x10x20high( flat bottom) Everything would need to be LEVEL. Tap water not allowed. Clean bottled water only. Tank mounted where there is no outside vibration. What we are measuring here is the angle of the vortex. It should vary wherever you are in the world. James

Hi James,

It sounds good, perhaps a slight tapering of the base towards the drain in the center would be helpful and maybe adding a drop of dye to the water or perhaps some KMnO₄ gingerly placed on the bottom would show any rotation up more clearly.

A slight tapering would be acceptable. Your suggestion of a "marker" dye should work.

I have potassium permanganate crystals on hand! James suggested 10x10x20 (I presume inches). A square container will significantly limit any vortex. I believe a cylinder would be better. How about a 5 gallon polycarbonate water bottle upside down, with the bottom cut off, and a valve system carefully centered in the original mouth? We would need to make a stand with leveling, etc.

Dick

I thought of a 5 gallon water container but rejected that idea because sometimes they are rough and uneven on the inside. They also have some mould marks. Square container would work IF it was big enough so as to not obstruct the vortex. A round acrylic clear pipe (12 inch dia) would be ideal. I am working up prices on which way to go. I got a stand worked out for both tanks. The reason for a clear container so we can viedotape the vortex. After videotaping results, ship the container to , lets say MASU in Australia and let him do the same. If we get 4-6 people from around the world, we should get a good idea of the effects the coriolis has at their location. James

Hi James, Dick and others,

I have been having a think about how the coriolis effect could be demonstrated if indeed it is actually causing any rotation and there are two factors that control the effect.

Firstly there is the north-south component of any motion. The longer the north-south motion is the greater the deflection due to the earths rotation. This means the lower the height to width ratio the better.

Secondly there is the time factor, the longer anything takes to move in a north-south direction the greater the deflection will be from the earths rotation. This means we want the container to drain as slow as possible.

Put these together and it gives us a shallow, round container that has a slight slope of the base, towards a central drain. I thought about it being transparent but believe making it out of some light coloured plastic, that was translucent and could be illuminated from either below or above, to give maximum contrast against any dye that is used in the water.

If the device is turned or machined on a lathe we need to be careful because the turning process may leave microscopic variations in the surface. These variations being circular may impart a rotational force on the liquid as it flows over the surface overwhelming the coriolis effect.

So how about this for the specifications.

Diameter 500 mm

Depth 20 mm

Slope of base to drain 1 mm

Drain diameter 2 mm or less

To be machined out of a solid piece of some light translucent plastic material, using a milling machine rather than a lathe, with some sort of leveling mechanism and level measuring as in my earlier post plus a compass to check the alignment

I think this would give the best chance of the coriolis effect imparting any rotation while keeping it a simple and light as possible and keeping the shipping cheap and simple.

How dose that sound? Has anybody got any further thoughts on it?

MASU-thanks for getting back so soon. I will look at these dimensions and see what I can come up with. James

"If the device is turned or machined on a lathe we need to be careful because the turning process may leave microscopic variations in the surface. These variations being circular may impart a rotational force on the liquid as it flows over the surface overwhelming the coriolis effect."

To machine the shallow cone on a CNC mill would require a custom cutter with the correct angle on the cutter end. Even a large diameter ball end mill would leave a series of ridges or a single spiral ridge, depending on how it was programmed.

On a lathe we can grind a tool and set it to the correct angle, and also easily round the inside and outside corners. Especially in plastic, we could go through several steps of polishing, using opposite directions of rotation for alternate steps.

My little lathe at home can only handle 240mm diameter; in San Diego I can turn nearly a meter. I have on hand some teflon cylinders that are about 160mm diameter and about 40mm thick; I agree that is small, but they're free! They are the standard white teflon, which is only a little translucent.

Hi Dick,

Can you hold your thoughts for a day or so. I am absolutely swamped at the moment, it just turned 05:00 Wednesday morning and I have just cleared all the thread updates. I havn't even looked at the new threads from yesterdays mail out yet. I have done some calculation on the sort of deflection we can expect from the coriolis effect so we have an idea of what we are dealing with. I believe it may be possible to actually demonstrate the coriolis effect but it's going to be tricky.

I will start a new thread, under my blog, for the experiment, with a collation all the ideas that have been put forward in the two threads that are currently discussing the coriolis effect plus ask who is interested in taking part. I will try and get it done before the next newsletter but if not it will be in the following one.

By the way have you been able to get the new CR4 editor to download to you system yet or are you still stuck using the old one?

Dick-I was just about to order some clear acrylic (24"x24"x1.25 thick) Thats big enough for MASU measurements. (his is in metric) Acrylic can be polished to get out any cutting head scratches. I dont mind buying the plastic ($175 dollars!) If you can mill it to his specs. let me know for sure if you want to do it. James

James

That size block of acrylic is only $158 (plus tax & shipping) at McMaster-Carr. Let me check my local (30+ miles to Sacramento) plastics store to see what they have & how much. I think I can go down tomorrow. No sense shipping it from the east coast if I can get the same or better price locally.

I just got home, so it will be at least a week & a half before I can get to a big enough lathe to do the job.

Dick

dkwarner-If you are going to do the machine work, thats fine. I can at least pay for the acyrlic . Just let me know, I will send a money order to your street address. James

James

Sounds good. I'm about to go down to Sacramento to look at plastic, but I'll probaly not actually buy it until I return to San Diego in a week or so (so I don't have to lug it down on the plane). That will also provide time for others to contribute ideas to Masu's new thread before I start machining.

Speaking of threads, I plan on drilling three threaded holes near the outside edge, so threaded legs can be screwed in or out to assemble and level. Also smaller holes to mount spirit levels and perhaps a camera mount.

Dick

When I was in High School and College, they did not have video tape, but rather 16 mm movies shown with a projector. They were usually fun to watch. I remember one where they demonstrated the coriolis effect. They used a large circular tank filled with water several feet deep with a small hole in the center of the bottom. The test was in the northern hemisphere and the water would drain counter clockwise, after a while.

That's strange. Have you ever looked at the direction toilet water flows down the drain? I live in the northern US. I have three commodes in my houe. Two flow counter-clockwise and one flows clockwise.

Joe Coriolis

yea, I live in Tennessee, USA, and just got back from spending a month in New Zealand- I was watching in particular for vortex rotation in every sink/toilet/etc. while I was down there, and I saw vorticies rotate both directions, but counterclockwise seemed to be predominant (I didn't keep a written record, so I have no precise numbers). Observations back home show similar results (CCW predominant). My (less than scientific, yes, but still consistently observed) results seem to show that drain configuration is by far the dominating trait to determine vortex rotation.

I would say this myth is busted :)

Ah, yes, and I forgot to include- bullet spin is determined by the rifling (sp?) of the barrel, as stated in other posts.

Also, as a bullet should be (assuming you arent shooting into the ground or straight up- neither a good idea, imo) rotating on an axis horizontal to the ground (rather than a vertical axis, such as a vortex) I would presume that the effect would not figure in, even if such a phenomenon did have significant effect.

Actually you have busted it in more ways than you realize. In the southern hemisphere the coriolis effect cause a clockwise rotation and in the northern hemisphere a counterclockwise rotation.

Well aussiviking friend down under,

Jorrie says water going down a drain counterclockwise south of the equator is an urban legend.

Up here in the north If I stopper a sink and fill with water, shut off the water then pull the stopper, the water drains clockwise.

Kindly perform the same test and report back, Thanks

Sail4ever- Read my post directly above yours. The coriolis force is weak when it comes to draining of water down a sink! I have seen it drain both ways in different sinks. To have a totally accurate result, I believe a tank needs to be designed to rigid specs. Tank would need to be level, etc. James

Hi Sail4ever,

Up here in the north If I stopper a sink and fill with water, shut off the water then pull the stopper, the water drains clockwise.

Congratulations you have just shown that it is not coriolis or the Earths rotation that is causing the rotation. If it were the rotation would be counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.

Sail4ever-Oops-sorry, I forgot to log in! James

I can probably answer your question by informing you that water doesn't flow in any one direction in either hemisphere due to anything other than its initial easiest path dictating a clockwise or anticlockwise vortex forming. If that wasn't the case logically no vortex would form on the equator ;) Regards, JD London

Wow! If it made a difference, then you would need a different rifle to shoot, depending on if you were shooting north, south, east or west. Not to mention all the angles in between. And how far north or south you were.

What about baseball pitchers? All lefties maybe they would do better if they only pitched south of the equator (depending on which way the pitchers mound was orientated compared to the home plate!

Even it made a difference it would be far less than the beat of your heart.

ANYTHING thrown, fired out of a gun, projected into the air, is influenced by the spin of the earth. On a small scale such as you throwing a ball, the coriolis force would be very small. However, when a missle is launched, the coriolis force has a big outcome as to the accuracy of the missle. James

To the "thing" being shot at, it does not matter if it is drilled thru the heart that the bullet was a micro millimeter to the left or the right of the point aimed at, it is still dead!!

One must look at these things from a "reality accurate" point of view!! Not theoretical!

As another keen shooter: No.

NO

The spiral groove in the barrel determine the direction of rotation.

This can be tested without an apparatus. Just remember to remove the cartridge from the chamber first.

Note that a shotgun do not have grooves because rotation will make the particles move apart and kill the whole neighborhood.

Remember we are not even talking about whether the shot passes thru the left ventricle or the right ventricle......for a good shooter there is then a difference.

What we are talking about is "its the same ventricle!" With something like a 0.0001cm difference. None of the target hole test plugs I ever saw would note such a difference....you would probably need a good microscope with a built in measuring gauge!!!!

Talk about being pedantic and a hair splitter.......a hair is a lot thicker anyway than what we are talking about....

I maintain that the differences, albeit there, are too small to worry about and are probably several magnitudes less than the differences between normal good quality rounds fired thru a good quality barrel.....by a top marks-person.

The British SAS have some very good marksmen, none of the ones I knew years ago would have worried about this effect, but wind, temperature, air pressure (with height) and elevation differences (to name but a few) have much greater effects on long distance accurate shooting than this hemisphere problem.....

Andy,

That all makes a lot of sense, rifling was invented in the Northern Hemisphere and has worked fine even in Antarctica.

To Masu and the experimental crew, while a lovely super machined device transported around the globe sounds like a controlled experiment, it isn't.

1. Not enough samples.
2. No control over transit effects
3. Skill level. (even the best of us old folks do it differently).
4. Daily climate changes.

As well as the super job (not instead of) how about a whole heap of experiments that are conducted over a time period using run "what you brung" and semi known objects that are rotated from site to site. We will maybe need to fund raise to keep this going for long enough to make real judgements.

I wanna be in, but can't make a perfect object.

I disagree and agree.

A controlled experiment is simply one where as many variables as possible are reduced or eliminated, so the variable(s) being studied can be picked out from the noise. I think its safe to say there is no experiment where all variables but one are completely eliminated. We all know (or should know) that no machining is perfect, and certainly not mine, although due to a generous supply of patience I believe I will do a better job than many might. Still, using the exact same apparatus in diverse locations eliminates quite a few variables, making this a useful experiment.

Your 'what you brung' idea is also a good one. Although soda bottles are not exactly the same size and shape worldwide, they are probably the most universally available container that can be cut to reasonably consistant dimensions. Why don't you write up a set of instructions on how to cut, mount, fill, wait, release, observe, etc. that we all could follow to be as consistent as possible. We could then all send our results to you (or perhaps to Globalspec) and all the data could be put on a spreadsheet and correlated?

Dick

Good plan!

I'll be in touch.

Maybe A10 tins or even A4 tins would be a good run what you brung as can manufacture is controlled to tight tolerances and are made to international standards.

I was thinking use an A10 with a 6mm (trial and error may be needed to get a decent vortex), firstly in the centre and then at varying offsets.

Your thoughts?

I looked around, but did not find any of what I believe we simply call a #10 can (tin). As I recall they are around 150mm in diameter and maybe 180-200mm tall. Is that the one you are referring to as an A10?

6mm is a good choice for the hole; most people in the US (including myself, for now) don't have metric drills, but a 15/64 inch drill bit is within 0.2% of the size of a 6.0mm drill bit. If Masu decides a smaller hole is better, then a 4.0mm is another good choice; a 5/32 inch drill is just over 0.1% smaller than 4mm, and a #22 drill is essentially identical to 4mm.

Dick

I think we are on the same page, from what I remember the A will be for American. The A10 holds 3kg to 7lbs and the A4 850g to 2lbs.

Drill size won't be much problem we use both.

My god,

Are the people posting on this thread actually engineers?

Does One's Hemisphere Effect.... Shouldn't that be 'affect'?

Now we can start all over.

That's an interesting point. I looked up affect and effect in the Encyclopedia Britannica and got the following, which you can hopefully read.

However after checking at Dictionary dot com on the meaning of affect and effect and checking with others the only thing I can conclude is that I am now even more confused about the use of either that I was initially.

Affect is an action to introduce some sort of feeling or emotion.

It would be great if a force could affect a bullet. It might decide to miss a target or return to sender.

Hi masu and everyone,

Here's a better description of the difference between affect and effect:

http://www.grammartips.homestead.com/affect.html

I never had problems with using these two words as long as I used them thus, affect is a verb and effect is a noun. There are some uses where they can be used in reverse but I try to avoid that. 'Keeps things clearer.

Regards to everyone.

No the hemisphere you live in DO NOT and CAN NOT effect the direction of spin of a bullet.

The simple because a rifle is specifically made with a spiral groove to introduce a spin. The spin is required to prevent any other rotation (for example back over front)that may be caused by air Resistance. (Remember the bicycle wheel experiment)

The direction of the spin is immaterial. The rotation of the earth is also to slow to change the trajectory.

Wind speed and direction will have a much bigger effect.

I suppose the word rifleing means the spiral groove. (Not to sure of all words)

To avoid embarrassment for a bad shot you may however blame it on the hemisphere. and you may add that the decision by the cr4 team was indecisive and that the experiment must first be designed.

I just had a thought of how the hemisphere and direction one is shooting may have an effect on the motion of a bullet but it has nothing to do with coriolis.

If you move a conductor at any speed or rotate it in the presence of a magnetic field you will induce a current in the conductor. This current will then interact in a destructive way with the magnetic field and oppose the motion. The direction of the magnetic field varies depending on you location on earth so the effect that it is going to have is going to vary according to your location, the speed of the projectile, the conductivity of the projectile and the direction the projectile is traveling.

Having said all that, I have no idea what sort of effect this would have and have serious doubts that it would be significant when compared to atmospheric fluctuations and disturbances.

In 1851 Faucault invented an experiment to prove that the earth is turning.

A large metal ball on a thin wire - pendulum.

The direction of the swing rotated as the earth was turning.

He had problems in explaining the lack of results at the equator.

Here at 26 degrees south my plumbing conforms to specifications and rotates vigorously clock wise. Even overcoming a slight ccw stir.

Could it be that the effect is less at 40 degrees?

Hi Hendrik,

If you read my post about the coriolis effect you will see that for you location the sort of deflection you will see in the flow path, is around 32 μms^-1m^-1. That means that for something like a toilet bowl you will have a vortex forming in the center with a diameter of less than 3 μm. I am sorry but I don't care how much you spent on your toilet it is not manufactured with tolerances less than 3 μm so the asymmetries in the container and filling are going to completely overwhelm the coriolis effect.

The flow in the cistern part follow the rules.

The flow is designed to flush all parts of the bowl (above water level) and therefore the water must be spread around the perimeter. a slight uneven distribution of flow or delay will induce unbalanced flows and currents.

The shape of the contents and skid marks may also have an effect.

Nobody can have conclusive results by looking at a toilet, rather use it for what it was intended for - Thinking chair.

The point that everyone is missing is that this effect is the same as moving a gyro in a specific direction. The result is a 90 degree deflection. The earth is spinning so an object moving towards the earth will have a tendancy to deflect in a specific direction.

The northern semisphere direction would be opposite of the southern hemisphere in the same way that tightening a bolt direction seems opposite if you are tightening from the top or the bottom.

The movement is constant from west to east for both north and south locations, however, the spin would seem opposite in that a person would see the spin in the south as righty tighty,(clockwise) while the person in the north would see the spin as lefty loosey (counterclockwise). If both perceived the motion from North to south (water down in the north and water up in the south) the rotation deflection would be the same.

Your point about the vertical motion may have a slight influence on bullets, but should have no effect on water going down a drain, since the water on all sides has the same vertical motion. Theoretically this should cause a slight sideways force on the drain, but I don't believe that would cause a vortex. This tendency to curve would be with respect to a vertical line, while the Coriolis force acts horizontally (tangential to earth's surface), and oppositely for water flowing in opposite directions on opposite sides of the drain.

As to the original question, assuming that you are shooting on level ground. and the target would be at the same elevation as the weapon, the answer is no, it would not make a difference since the total deflection up and down of the bullets trajectory is equal.

If however the target was at a different elevation an error would be introduced to one side in the north and the opposite side in the south. To change the rifling to the opposite direction would only correct for the direction of error, it would not eliminate the error. The problem here is that you now have a different weapon, and the change in weapon and sights would introduce more error than would be gained.

The important thing to know is that if you offset your aim for an elevated or depressed shot in the south, the offset will be the opposite in the north. The greator the lattitude, the greator the offset.

Hi Thecno,

"The important thing to know is that if you offset your aim for an elevated or depressed shot in the south, the offset will be the opposite in the north. The greator the lattitude, the greator the offset."

I disagree completely with you conclusion about the deflection from a bullet's path having anything whatsoever to do with the earths rotation.

A bullet is acting like a gyroscope and as you pointed out causes a translation of any force applied to it by 90°, dependant on the direction of rotation. Therefore while the bullet is in flight it is being acted upon by a force acting vertical, in other words gravity. Therefore, this would translate into a horizontal deflection to the right of left dependent solely on the rotation of the bullet. Changing hemispheres would have absolutely no affect on the direction of deflection as gravity is still acting vertically.

For the earths rotation to have any effect your distance from the axis of rotation must change. The change in distance is what is going to have the affect and since the earth is only rotating very slowly either the duration of the motion or distance along the radial must be large. If you were at the north pole the sort of deflections we are talking about is around 72 μm per meter per second. So for a bullet that travels 1,000 m over about a second and a quarter we have a deflection of around 90 mm.

That's not a great deal and while detectable, I would hazard to say, that at a range of 1,000 m, most shooters would be happy with landing a bullet within 90 mm of where they were aiming.

I cannot believe that you are talking about 9 cm at 1000meters....So if I understood you fully, if I corrected my sights to take this into account and then turned around 180° and shot at a similar target also 1000meters away, I would miss my aiming point by 180mm? I think that you have miscalculated the effect by an order of magnitude, I could accept 18mm or less, but not 180mm!!

If you were correct, then every marksman would need to know the compass direction in relationship to when he sighted in his rifle and his distance from the pole/equator, before he could shoot!!! This effect would also be clearly described in all shooting manuals and not that I have read them all or or even any recently, but I remember nothing about this effect in any of them that I have read......but again, I am not an expert in this area, more an interested spectator!

Convince me please.....

I'm with you. And as long as I can break a plate at a 1000 and dot an I at 300, I am not going to take it in consideration.

Too many other variables, in a 1000 meters the wind speed may change, some times the direction, how hard my heart is beating, (some shooters use biofeedback to slow their heart beat), anyway I don't believe that in a 1000 meters the spin of the earth matters.

And as far as the rotation of water goes that has no correlation with either.

No one ever mentions that high and low pressure weather systems rotate opposite directions.

It's said that special forces such as SAS can take someone out at 1600m. They'd be *****d if they didn't know about the 9/18 cm (personally I'd rather take it in the balls than the brain - before anybody says so yes I do talk out of my arse on occasion )

Hi Andy,

To start with the 90 mm deflection is the maximum deflection you would see if you were at the north or south geographic poles. It decreases by the sin of the angle you are from the equator.

Secondly if you were in the northern hemisphere the deflection is always to the right regardless of the direction you are shooting.

If the projectile were traveling south it would deflect to the west and since you are facing south the deflection is to the right. If the projectile were traveling north it would deflect to the east but you would now also be facing north so the deflection would also be to your right. While the absolute deflection is reversed the relative deflection is identical and since that is what is critical to aiming a rifle it will not affect your aim.

If you moved from one hemisphere to the other then perhaps you would be able to detect the results. Even so in such a case you would need to re-sight any rifle due to numerous other variables and would most likely not notice the change.

P.S. I vaguely remembering hearing of something like this back in my shooting days, but that was a long time ago and I cant recall the details.

The deflection due to drag against the spin is a bigger factor and of course it will be dependant on pitch and direction of the rifling as well as humidity, air pressure etc.

Also too long since I've done any serious shooting, damn the Jack booted one (Howard).

Dear everyone who has replied to my question reguarding bullet spin i feel humbled at the response and time that this has caused every one . it appears perhaps it does,or perhaps it doesn't but in any case it's a very small amount and may be not even be noticable .as for machineing a piece of gear to control and experiment around the world may be it would be better to get a standard sink and use that for the sink .

Too big to ship around economically, and then which shape of sink? In any event the construction of the test apparatus is well under way, although since I'm doing it in my spare time, it will probably be several weeks before it is finished...

Dick Warner

WHAT I DID NOTICE WAS WHEN I WAS DOWN SOUTH IN THE OTWAY RANGERS FROM ONCE I CAME THE SPINNING EFFECT OF THE WATER GOING DOWN THE HOLE WAS ALOT MORE THAN UP IN NORTH WESTERN AUS WHERE I AM LIVING NOW AND SOMTIMES IT WON'T FLOW EITHER WAY AND SOMTIMES ONE WAY OR THE OTHER.NOW I ALSO NOTICED THAT AT CERTAIN TIMES OF THE YEAR THE STARS ARE COMPLETELY A O BOUT AND I ENQUIRED ABOUT THIS TO FIND THAT LIVING AROUND THE TROPIC OF CAPRICORN WE ACTUALLY TRAVEL FROM ONESIDE OF THE EQUATOR TO THE OTHER. SO WHAT I AM GETTING AT IS THE FURTHER AWAY ONE GETS FROM THE EQUATOR THE MORE PROUNCED THIS EFFECT SEEMS TO BE .

Hi aussiviking,

I havn't conversed with you before so welcome to CR4.

The coriolis effect is indeed more pronounced as you get further from the equator but even so it is incredibly small.

There are three things that affect the deflection and they are your distance from the equator, the time that the object is in motion and the distance it travels. The maximum sort of deflection you can expect is around 80 μm s^-1 m^-1 so its going to be very difficult to get any sort of rotation going in a drain.

"LIVING AROUND THE TROPIC OF CAPRICORN WE ACTUALLY TRAVEL FROM ONESIDE OF THE EQUATOR TO THE OTHER."

You never actually move in relation to the equator, the axis of the earth and the equator do not move one inch over the year. What dose move is the apparent position of the Sun. Because the axis that the earth rotates around is not perpendicular to the plane that it goes around the Sun. As a result the sun will apparently move backwards and forwards across the equator as the earth goes round the Sun.

You may be interested in the experiment that a group of CR4 participants are setting up to actually test the coriolis effect. We are designing and constructing a test unit that will be shipped around the world to test the effect at each location. We are desperately in need of somebody that is close to the equator so if you are interested you can contact us through the Water Down the Drain & the Coriolis Effect thread.

PS You may not be aware of if but web etiquette equates typing a post in capital letters being analogous to shouting at the recipient. It doesn't bother me one iota but some people get offended by it and complain.