Talk:Gyrocompass

message: Rather than go far afield into discussions of paramagnetic and diamagnetic materials I removed the technically incomplete "nonferrous wires with current" digression.  —Preceding unsigned comment added by 67.101.101.98 (talk) 22:51, 3 October 2008 (UTC)
thread_title:  "ferrous metals" 

message: I don't really feel I can change the article itself but I do have a slight issue with the wording of one part.  I have done a fair bit of work at university on the gyrocompass, and I think that to cite friction as the "crucial ingredient" is misleading.  The actual "crucial ingredient" is the combination of an applied torque and the rotation it causes (it can also be a rotation and a resulting torque, the two are both linked).  Friction may be one method of applying this torque but I have not yet come across it.
In its simplest and most effective form, a gyrocompass is a gyroscope in which the gimbals (or mountings) are modified to force the rotor axis to remain horizontal relative to the earth's surface.  The components of rotation caused by the spin of the earth mean that the rotor must align itself with the true meridian in order to obey the law of conservation of angular momentum.
Other, more practical gyrocompasses use gravity to keep the rotor horizontal/apply the torque.  This is necessary on a pitching and rolling ship, where horizontal is not the same as the floor!
James
Nosrednax 15:54, 28 September 2005 (UTC)
replies: text: I didn't know anything about gyrocompasses before reading this article, but I've tried anyway to apply James's advice to the article.  Feel free to correct me if I've done so incorrectly, and please add sources if you know of any.  --Allen 05:59, 9 October 2006 (UTC)
thread_title:  "Crucial ingredient" 

message: Changed the link of Magnetic North to http://en.wikipedia.org/wiki/Magnetic_North_Pole#North_Geomagnetic_Pole because it was instead linking to an album by Hopefall: http://en.wikipedia.org/wiki/Magnetic_North.--M-w-b 09:39, 20 July 2007 (UTC)
thread_title:  Forgot to add the reason for my change. 

message: It migth also be mentioned the gyrocompass is used is satellite stabilization.  In combination with a horizion sensor, this is how early American and Soviet spy satelites maintained 3-axis orientation.
With regard to history, the discussion of Kaempfe vs. Sperry seems to imply that Sperry just stole someone's ideas.  Kaempfe was an art major who stumbled on the gyrocompass concept while trying to convince the navy to fund a submarine expedition.  Sperry did independant work on gyroscopes, and his engineers dominated the research and development of many gyroscopic-based servomechanisms over a period of years (ship stabilizers, autopilots, etc).  What I'm saying is, Kaempfe was first, but Sperry (and Minorsky and others) were really more important, not just someone who stole an idea from someone else.   A good book to look at is Bennett's history of control engineering. DonPMitchell (talk) 22:32, 19 May 2008 (UTC)
replies: text: This article is WAY too hard to understand. If you don't know how a gyroscopic compass works before you read it, you wn'
t know afterwards either.
80.169.162.100 (talk) 14:31, 10 February 2010 (UTC)
thread_title:  Satellites and History 

message: Should we not include at least a short reference to Hermann  Anschütz-Kaempfe and his 1904 patent on the theoretical workings of a gyrocompass? I strongly feel that the current article is woefully incomplete without mentioning that.
(Cyberroach (talk) 14:12, 25 January 2011 (UTC)
replies: text: Hi Cyberroach: yes, a subsection on his works would be commendable. There are currently Wikipedia articles on Mr. Anschütz-Kaempfe in six languages, but the English article is a very brief stub that only mentions gyrocompasses in passing.  Can you provide the explanation of his works relative to this device?  Best: HarryZilber (talk) 20:13, 25 January 2011 (UTC)
replies: text: Anschütz invent the world first self north adjusting gyrocompass. It's maybe for interest Sperry infringe the Anschütz patent. Sperry lost 1915 the patent lawsuit. The lawsuit consultant was Albert Einstein and Anschütz win 1915 this lawsuit.
  --HDP (talk) 11:03, 26 January 2011 (UTC)
replies: text: Fixed. --Kubanczyk (talk) 20:39, 1 November 2011 (UTC)
thread_title:  History - Hermann Anschütz-Kaempfe 

message: I think a mathematical description of a gyrocompass is useful, for students and for general people. I tried to add a section, but it was erased at once without discussing even this topic.  — Preceding unsigned comment added by Antoniuspisa (talk • contribs) 05:27, 23 November 2013 (UTC)
thread_title:  Mathematical description of a gyrocompass 

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thread_title:  External links modified 

message: I don't want to make large-scale changes here without feedback or discussion.
==="We consider a gyrocompass as a gyroscope which is free to rotate about one of its symmetry axes"===
the WP definition of a Gyroscope is a spinning disk with two gimbals.  I think we should cleary distinguish between the spinning disk (the rotor) and a gyroscope mechanism (with two gimbals).  The expression "rotate about one of its symmetry axes" appears many times, couldn't we just say rotor spin axis as per Gyroscope.
==="Therefore there are two independent local rotations"===
* Confusing!  Is this the two gimbals of a Gyroscope or is it the spin axis and one rotation about the local vertical?
"We establish cartesian coordinates (X1,Y1,Z1)"
* cartesian should be capitalised
* it's not clear what X1,Y1,Z1 are.  Later it looks like these are used like elements of a point coordinate vector.  We should talk about establishing a local coordinate frame, often written as {1}.
==="First time-dependent rotation"===
* (X1,Y1,Z1) looks like the coordinate vector for a point expressed with respect to frame {1} which is being transformed to a coordinate vector with respect to frame {2}.  
* this is simply a rigid body rotation from frame {1} to frame {2}.  It is written as a point transformation which is the transpose of the rigid body transformation.  I know there are strong feelings about whether to use rigid-body transformations or point transformations, I prefer the former, but at the very least the article should clearly describe what it is using.
==="Fourth time-dependent rotation"===
* Is this the orientation of the rotor's spin axis with respect to true north (TN)?
* Should state explicitly that the x-axis of frame {6} points to TN.
==="Last time-dependent rotation"===
* "The last rotation is a rotation on the axis", normally we speak of a rotation being about or around an axis, not on an axis.
* Is this the rotation of the rotor about its axis?  ie. is \dot{\psi} the angular velocity of the robot disk.  For a gyrocompass we assume its axis is always in the horizontal plane?  Why is there no t in this equation as there is for the first time-dependent rotation?
* "The last rotation is a rotation on the axis", be clearer about where this new frame {7} is located.  It looks like it is attached to the barycentre of the spinning rotor disk.
==="Dynamics of the system===
* \vec{\omega} is not actually defined.  From the definition of the kinetic energy it must be the total angular velocity of the rotor due to rotor and Earth rotation.
* "On the other hand, tThe tensor of the rotor's inertia is given by"
* The big expression for \vec{\omega} has a × symbol which is confusing, there is no cross product here, it is matrix-matrix multiplication.
* There should be an explicit mention of why the translation from frame {4} to {5} is ignored.
* When the expression for \ddot{\alpha} is discussed it should be in the context of an oscillation about zero (ie. pointing to TN).
* "is the part of the Lagrangian responsible for the dynamics of the system of the rotor axis pointing direction α."
* "where the angular velocityfrequency (in radians) of this harmonic motion of the rotor axis of symmetry of the gyrocompass about the north-south line is given by"
===References===
* I couldn't find where this derivation came from
* [4] is a broken link.
Peter.corke (talk) 01:55, 28 December 2018 (UTC)
thread_title:  Multiple problems with "Mathematical model" section 

message: * I couldn't find where this derivation came from
* [4] is a broken link.
Peter.corke (talk) 01:55, 28 December 2018 (UTC)
thread_title: References

message: This angle is undefined in the section on second and third fixed angles
 of rotation.
Burressd (talk) 15:24, 24 March 2023 (UTC)
thread_title:  Please define phi.