Talk:Gyroscope

Template:WP1.0 I have just completed Eric Laithwaite who was obviously just plain wrong. However, when I read accounts from experts about the nature of his mistake I'm none the wiser. They talk about fast tops and slow tops and are obviously refering to a body of knowledge that I've never managed to find. Can we have some more content here? An account of where Eric Laithwaite went wrong would be really useful Cutler 12:24, 11 Feb 2004 (UTC)

I've been adding stuff to the Eric Laithwaite article today. One of the external links may help. DFH 21:56:00, 2005-09-08 (UTC)

Are flywheels gyroscopes?

This article claims that momentum wheels and flywheels are gyroscopes. Is this true? The definitions I have read state that gyroscopes are devices designed to resist rotation of the spin axis, which is not the purpose of the devices I just mentioned. Obviously, they have this property as a side-effect, but this is not enough to make them gyroscopes. -- Heron 21:29, 25 Jul 2004 (UTC)

image accuracy

I'm not an expert at this, but I do believe that the image stating that aerobic bicycle is possible due to gyroscopes is incorrect as the wheels really aren't spinning fast enough to really provide any resistance that would aid in the balancing.

Writing Too Technical: Need For Lay Explanations, Also Description of Gyroscopic Inertia Should be More Prominent

Wikipedia is not a science journal it is a public use encyclopedia. Therefore all science terms should include reasonably easy to understand lay descriptions.

75.252.224.147 (talk) 08:15, 18 May 2009 (UTC)

Confused

I don't understand much of this entry. Can someone write an easy to understand version? Gyroscopes explained so a kid can understand?

How about the following introductory paragraph?

A gyroscope is a wheel spinning on an axle, mounted in a frame which allows the axle to be pointed in different directions. When the wheel spins, its rotating mass causes the axle to point in a fixed direction, and to resist any attempts to change its direction. This makes it useful for navigation, balancing of machinery, and demonstrations in physics classes.

Please tell me if this is detailed enough, or too simple. --Heron 08:23, 7 Sep 2004 (UTC)

I like it. That will make a good intro. StuRat 02:19, 28 October 2005 (UTC)

Would it be possible to pick an image with a lighter background to display? It's rather hard to read the names of the parts of the gyroscope with the current green-backed image. -- Guest, 23 Apr, 2005

Inertia

Moved to talk:inertia

Proposal for change

I propose that the heading History be changed to Properties. Really, only the first sentence is actually about the history of the gyroscope. The rest is a very good description of how a gyroscope behaves, complete with a correct description of how a gyroscope can hang off the end of a table (the description matches the one given in "Feynman Lectures on Physics.").

what reference frame for rigidity?

With respect to what reference frame does a gyroscope have a tendency to remain rigid in space? I.e. In what reference frame does the plane of the gyroscope remain constant? The surface of the earth? A celestial reference frame?

Gyroscopic rigidity and precession affect the attitude indicator and heading indicator of an aircraft, but there are 2 different gyroscopes for these 2 instruments. It may be necessary periodically to reset these gyroscopes because they can drift, usually due to to friction in the mechanism or other physics in the construction of the gyroscope that makes it deviate from it's theoretical ideal performance.

But one flight instructor told me that the heading indicator in particular drifts at a certain pace in a certain direction (and generally needs to be reset every 15-30 minutes or so) because the earth is rotating and the gyroscope, being rigid in space, is then not rigid w.r.t. the earth's surface. This theory is consistent with my experience as a pilot, but I can't say with certainty that this is what's happening.

Thus far, I have not found a satisfactory answer to this question. 142.103.14.11 22:56, 7 March 2006 (UTC)

I agree here, I think the gyro is already rotating w.r.t to the earth when put into the airframe. likewise when the airplane banks, and does a loop, the gyro itself is already subject to the forces due to the loop, is it not? —Preceding unsigned comment added by Alokdube (talk • contribs) 06:44, 16 February 2009 (UTC)

Gyroscopic inertia

In the intro it says "this is also known as gyroscopic inertia or rigidity in space."

Thats very ambiguous, it sounds as if its saying gyroscipic inertia is another name for gyroscope. More reasonably it would mean that its a synonym to angular momentum. If thats the case, it should NOT link to this page, it should NOT be bolded on this page, and it should be much less ambiguous. Please someone either change it, or answer me so *I* can change it. Thanks. Fresheneesz 22:21, 15 March 2006 (UTC)

I still don't understand why......

a gyroscope spins faster when force is applied. I think it's due to the conservation of energy law, i.e. that the energy i apply to overcome the resistance to spin must show itself somewhere, but I have tried and tried to think how, using Newtonian laws of motion, the result is an increase in the spin speed. How is the force transferred in this direction, when the only direct physical connection between me and the gyro is my hand on the housing which hold the gyro's axle? I wonder if there is something non-Newtonian going on, but that seems a bit far fetched to me. I'd be very grateful for an answer. -142.103.14.11 14:52, 28 April 2006

I'm not sure I know exactly what applied force you mean, but in case you are refering to something like the Dynabee, the answer, as posted there, is a lot less mysterious than you theorize above:

"The axis of the gyroscope in the gyro powerball is fixed to the spinning mass and it rests in a little groove inside the wrist exerciser device, which almost completely covers the gyroscope inside it, except for a small round opening on top of it, which is where you can manually start the gyroscope. Once the gyro is spinning, tipping the device will cause the gyroscope to start precessing, with its axis slipping around in the groove in a circular fashion. The groove inside the device, is a little wider than the axis, and the gyroscope's evasive action towards the externally applied force will cause one end of the axis to push against the upper rim of the groove, while the other end of the axis pushes against the lower rim of the groove. While the axis is slipping around inside the groove, the friction between the axis and the groove rims will accelerate or brake the spinning gyroscope, with a maximum effect when the axis starts "rolling" inside the groove. Since this friction force is essential for the device's operation, the groove must not be lubricated. The acceleration of the gyroscope is best when the precession of the gyroscope is supported and amplified by wrist motion."

-AndrewDressel 19:12, 12 October 2006 (UTC)

Right-hand rule

Added reference to right-hand rule and brief description of how it applies. AndrewDressel 12:13, 16 May 2006 (UTC)

Motorcycles

"Examples of some free-output-gimbal devices ... the front wheel of a motorcycle. Countersteering is how motorcycles turn corners using the gyroscopic roll reaction of the spinning front wheel."

Any references for this claim that have actually done the experiement or the math? My understanding from reading the liturature (Jones, David E. H. (1970). "The stability of the bicycle" (PDF). Physics Today. 23 (4): 34–40. Retrieved 2006-08-04. and Gromer, Cliff (February 1, 2001). "STEER GEAR So how do you actually turn a motorcycle?". Popular Mechanics. Retrieved 2006-08-07., etc.) is that countersteering is simply a technique for causing a motorcycle to lean and that gyroscopic effects are not necessary. -AndrewDressel 02:27, 15 August 2006 (UTC)

None found, so I've taken it out. -AndrewDressel 14:32, 15 August 2006 (UTC)

New images and diagrams

Well, I made a few new images for the article, including an animation showing how the gyroscope wheel works. They were originally made with a left-handed spin, so I flipped them horizontally to fix it. ☢ Ҡi∊ff⌇↯ 20:00, 4 October 2006 (UTC)

 Switching the left hand spin seems to have switched the input and output axes.  A quick check of (input) cross (spin) = (output) shows correct orientation.  Dan  —Preceding unsigned comment added by 128.253.139.199 (talk) 14:00, 1 November 2007 (UTC) 

Is my hard drive defying physics?

I'm really confused about how a hard disk can be a gyroscope and still work when it's being moved around. See my entry on the hard disk talk page here. Twilight Realm 19:19, 29 October 2006 (UTC)

If your hard drive is spinning on a vertical axis, you can lift your computer vertically no problem, and you can slide it around the floor no problem either. But if you tilt the computer, the hard disc will "try" very hard to tilt in a plane at 90* to the axis of your tilt. It will be restrained by its bearings, but will stress the bearings, so best not to wobble it about too much.

I think.

So do computers aboard ship tend to wear their bearings out?

Richard

Still Not Quite Understanding...

I guess I'm just an idiot, but I'm having a hard time understanding the whole bicycle wheel/rotating stool thing. Could someone explain it for me please? --SuperCow 05:37, 21 February 2007 (UTC)

Never mind, I've figured it out. I am an idiot. --SuperCow 14:47, 6 March 2007 (UTC)

Serson 0 - Laplace 1

I just added John Serson to the History section, then deleted him again, then added Laplace. I ought to explain.

At first, I saw Serson on gyroscopes.org and thought that he had a prior claim to Bohnenberger, so I added Serson to this article. I also created an article on Serson. I then found that Serson's design was merely a spinning top and didn't really deserve to be called a gyroscope, so I removed him again. I then found the article at the Institute of Navigation that explained the link from Bohnenberger via Laplace to Foucault, which I thought was much more interesting, so I added that the the article. Now we have an accurate history, and a new article on John Serson, so everybody wins, I hope. --Heron 14:53, 2 June 2007 (UTC)

Gyroscopes in Fiction

Needs expanding so as to provide a brief description of where gyroscopes appear in these fictional texts 124.182.230.53 11:50, 29 July 2007 (UTC)

Agreed, this section is completely useless as it is now. Either this section should be expanded to include the way in which gyroscopes are used in those fictional texts or it should be removed. However even an extended section would IMO not make much sense here. A gyroscope is not by itself something fictionary nor does it play a major part in any of these fictional texts. So I don't really see why it is relevant to have this section in this article. Hadoriel 11:06, 13 August 2007 (UTC)

Gyroscopes in modern technology

Today gyroscopes are used in dozens of different technological machines from the International Space Station to modern aircrafts and even in underwater torpedos. However there is virtually no mention of this in the article. I think a paragraph about this should be added as this is the main use of gyroscopes today. Hadoriel 11:11, 13 August 2007 (UTC)

opening sentence is inaccurate

I'm new to wikipedia, so forgive me if I'm speaking out of turn. I work with, and lecture on, all sorts of things to do with gyroscopes and I am pretty comfortable with them. I've created lots of videos on things to do with spin (see http://www2.eng.cam.ac.uk/~hemh/movies.htm ) and I've got a page devoted to gyroscopes and boomerangs ( http://www2.eng.cam.ac.uk/~hemh/gyroscopes.htm ). We've also set out to reproduce all of Laithwaites experiments - see http://www2.eng.cam.ac.uk/~hemh/gyroscopes/htmlgyroscopes.html . I'd be happy to help out with the gyro page and if appropriate it may be thought appropriate to include links to our work.

But my main reason for writing gere is to say that the opening sentence of the Wiki Gyroscope page is not correct. It reads:

"A gyroscope is a device for measuring or maintaining orientation, based on the principle of conservation of angular momentum."

But a gyroscope would be useless if angular momentum were to be conserved. The whole point is that a gyro exhibits precession and this requires the imposition of an external couple, thereby changing the direction of its angular momentum - being a vector quantity. Is there any chance of changing this sentence to read:

"A gyroscope is a device for measuring or maintaining orientation, based on the principles angular momentum."

Hughhunt 19:52, 23 September 2007 (UTC)

I agree. The phrase "tends to resist changes to its orientation" should also be changed. Perhaps something like "moves in a direction perpendicular to the applied torques and at a rate inversely proportional to its rate of spin" would work. -AndrewDressel 13:39, 25 September 2007 (UTC)

I'm not sure I see the problem. Angular momentum IS conserved--if the external torque is zero, the angular momentum doesn't change. The usefulness of a gyroscope for measuring orientation derives from the fact that in practice, even with gimbals it is impossible to eliminate torque entirely--if it weren't, you could put a stationary carton of milk (or whatever) in gimbals, and it would maintain its orientation. The orientation of the axis of a gyroscope changes less in response to a given torque than does the "axis" of a stationary carton of milk with the same moment of inertia. The gimbals minimize the torque, and the spin of the gyroscope minimizes the change in orientation produced by whatever torque manages to get through. So I certainly wouldn't go so far as to say the opening sentence is incorrect. On the other hand, it would probably be good to point out that, aside from precession, there is no such thing as "gyroscopic stability" a misconception many people seem to hold. Rracecarr 13:59, 25 September 2007 (UTC)

Surely if the external torque is zero (and hence angular momentum is conserved) then a gyroscope can no longer be used for "measuring or maintaining orientation"? To actually make a measurement you need that torque. --The Great Apple 15:18, 16 November 2007 (UTC)

Thanks for modifying the opening sentence, but the opening paragraph still describes a GYROSTAT not a GYROSCOPE (eg with the words "its orientation remains nearly fixed"). Is this the intention? Besides this there is a lot more that could do with fixing on the page. I'm happy to help if you're interested. Many of my students here in Cambridge are now aware of the shortcomings of the article and I've set them an exercise to produce improvements. When they're ready I will put them on my own web pages ( http://www2.eng.cam.ac.uk/~hemh/gyroscopes.htm ) -- Hughhunt (talk) 21:30, 16 November 2007 (UTC)

I note with dismay that the opening paragraph has gone back to the very-much-incorrect "A gyroscope is a device for measuring or maintaining orientation, based on the principle of conservation of angular momentum." As noted above this is incorrect and misleading and entirely inappropriate for a reputable article in Wikipedia. A "rate gyro" is a perfect example of a gyroscope whose orientation changes in normal operation. It is the most common device used to measure angular motion. And its orientation changes therefore angular momentum is NOT conserved. Also I would appreciate if those commenting above would identify their credentials. It appears to me that Rracecarr, for instance, does not understand gyroscopes by saying such unscientific things as "The gimbals minimize the torque, and the spin of the gyroscope minimizes the change in orientation produced by whatever torque manages to get through." many thanks Hugh Hunt, Cambridge University Hughhunt (talk) 21:59, 15 January 2008 (UTC)

Gyroscopic Stabilization of a Discus

Precession of a gyroscope

I am interested in the flight of a discus which maintains stability even though it retains an axis which is not vertical; ie the spin is not aligned with the gravity vector. Indeed it can fly in a stable manner with as much as 35deg to the horizontal and yet not settle into precession. You cannot make a gyroscope spin at a fixed angle to the vertical without the onset of precession. What's so special about a discus. Any ideas? Thanks Colin Coli.white (talk) 01:11, 19 August 2008 (UTC)

If by "gyroscope" you mean the toy that spins like a top, as shown in this picture, then the reason it precesses when its axis is not vertical is that the couple of gravity acting on the center of mass and the ground reaction create a torque. I don't know where the center of lift is on a discus, but perhaps it is close enough to the center of mass so that the two do not create significant torque. -AndrewDressel (talk) 03:10, 19 August 2008 (UTC)

Yes I think you are right. The way I look at it is that unlike the gyroscope, there are two external forces on the discus, gravity and drag. The resultant of these two is a force vector at an angle back from the vertical which the spinning discus can align to for stability. I think we are saying the same thing - maybe. Thank you.Coli.white (talk) 00:59, 20 August 2008 (UTC)

Hmmm. I think we're getting closer, but we're not quite there yet.

1. There are two main external forces on the spinning gyroscope: a) the force of gravity acting on the center of mass, and b) the ground reaction at the point of contact. Together, if they are not perfectly colinear, these two forces are a couple that create a torque and so cause precession.
2. There are also two main external forces on the flying discus: a) the force of gravity acting on the center of mass, b) the resultant aerodynamic force (combination of lift and drag) acting at the center of pressure. Together, these may or may not generate a torque.

It would seem that if a discus were flying smoothly, without precession, then these two force must not be generating a torque, but I'm not an aerodynamicist. You might check out the Physics of flying discs article.-AndrewDressel

(talk) 01:32, 20 August 2008 (UTC)

Yep. I got it! Also read the 'Physics of Flying discs' article. It puts much emphasis on the difference in drag in the two planes and this largely accounts for the flight path. Comparing with the discus though the difference in drag in the two planes will be minimal a) because of the weight of the discus (drag to weight ratio will be low in both cases), and b) the vertical velocity component is low compared with the horizontal and assuming drag is α to velocity squared, I think the vertical and horizontal drags would be similar and minimal.So what keeps the discus up is aerodynamics, what keeps the frisbee up is both aerodynamics and drag. Do you agree? Coli.white (talk) 00:10, 21 August 2008 (UTC)

I'm not sure. I don't get the distinction you are making between "aerodynamics" and "drag". "Drag" is just a name for the component of "aerodynamic" forces that resists motion. Drag and lift will effect both frisbees and discuses to varying degrees. However, since this discussion is no longer about gyroscopes, we probably should stop here. Perhaps you can continue it on the Discus throw talk page. -AndrewDressel (talk) 02:12, 21 August 2008 (UTC)

Error in Section:properties

In this section, the line: " perpendicular to both the gravitational torque (downwards)" implies that there is downwards (wrt the model system described) torque. This is, in fact, an error: there gravitational force is downwards, but the torque is not. Consider that t = r x f, where t = torque, and r is the distance from the centre of rotation that the force, f, is applied. In the described system, if we take the attached end of the gyroscope as the origin, and the free end of the gyroscope as (l,0,0), where l is the length of the thing, we end up with t = r x f = (l,0,0) x (0,0,g), where g is the force of gravity, which is downward in the z direction). Therefore, the torque is in the y direction. 129.128.128.32 (talk) 01:05, 26 August 2008 (UTC)

Good catch on this one. Yes, the torque due to gravity is not "downwards". I believe I have corrected the text. -AndrewDressel (talk) 14:21, 26 August 2008 (UTC)

This error is also shown earlier in the section: "It follows from this that a torque, t, applied perpendicular to the axis of rotation, and therefore perpendicular to L, results in a motion perpendicular to both t and L" There is again a confusion between torque and the force of gravity, an important feature as these are 90 degrees from each other. The motion induced is perpendicular to f and L, not t and L as written (the motion induced is in the direction of the torque). 129.128.128.32 (talk) 01:05, 26 August 2008 (UTC) regards, demon master 72

Not sure about this one, perhaps because "motion" is ambiguous to me. I've replaced it with "rotation about an axis". The axis of precession ${\boldsymbol {\Omega }}_{P}$ is perpendicular to both the axis of applied torque ${\boldsymbol {\tau }}$ and the axis of rotation ${\boldsymbol {\omega }}$. -AndrewDressel (talk) 14:21, 26 August 2008 (UTC)

Cancellation?

I have seen it claimed in various places that if two identical gyroscopes are mounted in the same gimbal and spun in opposite directions, they will cancel each other and produce no gyroscopic effect. This sounds illogical to me. I can see that they wouldn't precess, as they would each try to precess in opposite directions, but I would think they would still resist changing direction of their axis. I'm not an expert on this at all though, and would really appreciate it if someone that is could clarify this issue (and find a reference?). If it's a myth, I think this should be mentioned in the article. Of course, if it's true it should be mentioned too.--Dwane E Anderson (talk) 00:05, 25 February 2009 (UTC)

First, spinning gyroscopes do not "resist" changing direction of their axis; they precess in response to external torques instead of moving the way non-spinning masses do. Thus if two gyroscopes are connected and spinning in opposite directions so that the do not precess, then they will move in response to external torques exactly as equivalent non-spinning masses do.

Second, I doubt we will find a reference for exactly this derived result, but several bicycle dynamics researchers have used exactly this result to debunk long-standing theories that spinning wheels are what keeps bicycles up. They include:

• Dr. Richard Klein from the University of Illinois
• Dr. David Jones in Physics Today

-AndrewDressel (talk) 03:12, 25 February 2009 (UTC)

Thank you for the explanation. Please excuse my dumb question. I think this point should be mentioned in the article, as it does seem to come up in the real world. For example, I had heard that this cancellation of gyroscopic effect improves the handling in twin engine aircraft, which usually have counter-rotating engines to cancel torque.--Dwane E Anderson (talk) 21:53, 25 February 2009 (UTC)

Not a dumb question at all. Sorry if my response made it seem so. Yes, the twin engine aircraft example is a good one. I'll see where we can put that in. -AndrewDressel (talk) 23:21, 25 February 2009 (UTC)

not clear

I am not certain why a gyroscope would flip around if the earth rotates in 12 hours. I mean the person who mounted the gyroscope already had that movement, right? so the original wheel too already has inherited that rotational movement. Can someone help clarify? As far as I can see, the math simply says angular momentum is conserved, hence mass and MOI remaining constant, angular velocity w is conserved. i.e w=(r x v)/|r^2| , let r=xi + yj be the coordinates of a point on such a wheel (point mass) So x.dy/dt - y.dx/dt= constant for a 2 d plane rotation in the xy plane if w has to be constant. (given r is constant w.r.t time) assume an origin O as the pivot, x=r.cos(wt) , y=r.sin(wt) so the gyro will maintain its angular momentum w.r.t the original origin O and the above equation holds.

consider this object itself is rotating about another origin O` , the equation cannot be hence written can it? i mean typically such a rotation would be x= r1.cos(w1t)+r2.cos(kw1.t), y= r1.sin(w1t)+r2.sin(kw1.t) dx/dt = -(r1.w1.sin(w1t)+r2.k.w1.sin(k1w1.t)) dy/dt = r1.w1.cos(w1.t)+r2.k.w1.cos(kw1.t) .... obviously such a motion does not conserve angular momentum However, considering that the original person who placed the wheel and the point mass already possessed that motion w.r.t O`, how does one eliminate that consideration in a gyroscope? —Preceding unsigned comment added by Alokdube (talk • contribs) 08:43, 9 March 2009 (UTC)

gyroscopes

A mathematical error. The math description of the mechanics is totally incorrect. Author claims I is the moment of inertia! Which one? There are three principal values. The angular momentume vector is given by the dyadic prodcut of the principal moments of inertia and the principal angular velocites. From there on it's Newton, but using a rotating axis system, as is conventional, is complicated and tricky. Still an all there's no point in using equations that are blatantly incorrect. I recommend that they be removed. Also that this section be written by someone who has a professional knowledge of the dynamics of rotating bodies. —Preceding unsigned comment added by Polypuss (talk • contribs) 17:01, 18 April 2009 (UTC)

Bionic gyroscope

Can the bionic gyroscope developed by Dedy Wicaksono (TU Delft) be mentioned ? http://dedywicaksono.wordpress.com/2008/10/21/my-phd-research/