Anomalous movement resistance in a spinning gyroscope
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From: top9 on 12 Apr 2006 07:05 Yes, it is a "memory" efects in a disc of rotor and spindle.
From: top9 on 12 Apr 2006 15:32 From: Physical Review Letters <prl(a)ridge.aps.org> >Date: Tue, 22 Oct 2002 14:04:22 UT >To: jk18(a)cam.ac.uk >Subject: Your_manuscript LW8007 mazur >Status: > >Re: LW8007 > Anomalous ``memory'' effects in a spinning top > by Jerzy Mazur, Joanna Spalinska-Mazur, and Jacek Klinowski > >Dr. J. Klinowski >Dept. of Chemistry >Univ. of Cambridge >Lensfield Rd. >Cambridge CB2 1EW >UNITED KINGDOM > > >Dear Dr. Klinowski: > >The above manuscript has been reviewed by one of our referees. > >On the basis of the resulting report, it is our judgment that the >paper is unsuitable for publication in Physical Review Letters. We >enclose comments from the criticism that led to our decision. > > >Yours sincerely, > >Jane Throwe >Assistant Editor >Physical Review Letters >Email: prl(a)aps.org >Fax: 631-591-4141 >http://prl.aps.org/ > > >---------------------------------------------------------------------------- >Report of Referee A -- LW8007/Mazur >---------------------------------------------------------------------------- > >This manuscript reports on the dependence of friction in a >mechanically fixed spinning top on the history of spinning direction. >It describes a simple experiment, provides insufficient data analyses, >and by drawing no conclusion suggests mysterious effects in a simple >mechanical system. It is by no means suitable to be published in any >scientific journal. > >If the authors are really interested in understanding their results, >they should come up with a model describing the temporal development >of the spinning frequency. The authors argue that "bearing wear would >reduce the rotation times". This is wrong, the opposite is the case >and is called "run in"-effects in tribology. Probably these effects >explain the whole set of experiments.
From: shevek4@yahoo.com on 12 Apr 2006 17:32 realist wrote: > http://www.oswirus.krakow.pl/cat_14/gyroscope/ > > Memory effect in its rotor? Thanks for bringing this to our attention. Allow me to quote from the discussion in the paper: "Given the results of the experiments described above, we believe that although friction is responsible for the gyroscope ultimately coming to a stop, frictional e?ects cannot be responsible for the e?ects observed. First, to a stop, frictional e?ects cannot be re- sponsible for the e?ects observed. First, they would depend on the type of material of the spinning disk, spindle or bearing. Second, needle bearing wear would reduce the rotation times (the spindle's top is being rubbed away which causes the moment of friction to rise) and not lengthen them, while surface rearrangement would not favour alternate directions of rotation, but would a?ect all the results equally. " How do you arrive at that conclusion? I don't see why a surface rearrangement couldn't favor one direction over another.. there are plenty of examples of surfaces that do have anisotropic friction coefficients, though perhaps yours could be the first example on such a small scale. "For the same reason, our findings cannot be explained in terms of these frictional (microscopic irregu-larities) force, because such forces would lead to a constant di?erence between rotations in the anticlockwise and in the clockwise directions, which is clearly not the case." That's the same statement again. And again, I don't see why we can assume such forces would be constand for different directions. Picture a surface such as: ______ ___/ | ---/ |------------- A portion of the needle sliding across this surface from left to right will see less friction than if the needle portion were sliding from right to left. "Ad-ditionally, the time di?erences for the anticlockwise and clockwise rotations are large at the beginning of measurements, they decrease as the time of gyroscope's movement rises i.e. in the subsequent experimental runs. It seems to be obvious that the bearing's microscopic irregularities would generate an opposite e?ect." Forgive my ignorance.. how is that obvious? Another consideration: friction due to air resistance. Comments? Cheers - shevek
From: shevek4@yahoo.com on 12 Apr 2006 17:48 realist wrote: > http://www.oswirus.krakow.pl/cat_14/gyroscope/ > > Memory effect in its rotor? Thanks for bringing this to our attention. Allow me to quote from the discussion in the paper: "Given the results of the experiments described above, we believe that although friction is responsible for the gyroscope ultimately coming to a stop, frictional e?ects cannot be responsible for the e?ects observed. First, to a stop, frictional e?ects cannot be re- sponsible for the e?ects observed. First, they would depend on the type of material of the spinning disk, spindle or bearing. Second, needle bearing wear would reduce the rotation times (the spindle's top is being rubbed away which causes the moment of friction to rise) and not lengthen them, while surface rearrangement would not favour alternate directions of rotation, but would a?ect all the results equally. " How do you arrive at that conclusion? I don't see why a surface rearrangement couldn't favor one direction over another.. there are plenty of examples of surfaces that do have anisotropic friction coefficients, though perhaps yours could be the first example on such a small scale. "For the same reason, our findings cannot be explained in terms of these frictional (microscopic irregu-larities) force, because such forces would lead to a constant di?erence between rotations in the anticlockwise and in the clockwise directions, which is clearly not the case." That's the same statement again. And again, I don't see why we can assume such forces would be constand for different directions. Picture a surface such as: ______ ___/ | ---/ |------------- A portion of the needle sliding across this surface from left to right will see less friction than if the needle portion were sliding from right to left. "Ad-ditionally, the time di?erences for the anticlockwise and clockwise rotations are large at the beginning of measurements, they decrease as the time of gyroscope's movement rises i.e. in the subsequent experimental runs. It seems to be obvious that the bearing's microscopic irregularities would generate an opposite e?ect." Forgive my ignorance.. how is that obvious? Another consideration: friction due to air resistance. Comments? Cheers - shevek
From: Roy L. Fuchs on 12 Apr 2006 20:40
On 12 Apr 2006 14:48:23 -0700, "shevek4(a)yahoo.com" <shevek4(a)yahoo.com> Gave us: > >realist wrote: >> http://www.oswirus.krakow.pl/cat_14/gyroscope/ >> >> Memory effect in its rotor? > >Thanks for bringing this to our attention. Allow me to quote from the >discussion in the paper: > >"Given the results of the experiments described above, we believe that >although friction >is responsible for the gyroscope ultimately coming to a stop, >frictional e?ects cannot >be responsible for the e?ects observed. First, to a stop, frictional >e?ects cannot be re- >sponsible for the e?ects observed. First, they would depend on the type >of material of >the spinning disk, spindle or bearing. Second, needle bearing wear >would reduce the >rotation times (the spindle's top is being rubbed away which causes >the moment of >friction to rise) and not lengthen them, while surface rearrangement >would not favour >alternate directions of rotation, but would a?ect all the results >equally. " > >How do you arrive at that conclusion? I don't see why a surface >rearrangement couldn't favor one direction over another.. there are >plenty of examples of surfaces that do have anisotropic friction >coefficients, though perhaps yours could be the first example on such >a small scale. > >"For the same reason, our findings cannot be explained in terms of >these frictional (microscopic irregu-larities) force, because such >forces would lead to a constant di?erence between rotations in the >anticlockwise and in the clockwise directions, which is clearly not the >case." > >That's the same statement again. And again, I don't see why we can >assume such forces would be constand for different directions. Picture >a surface such as: > > ______ > ___/ | >---/ |------------- > >A portion of the needle sliding across this surface from left to right >will see less friction than if the needle portion were sliding from >right to left. > > > "Ad-ditionally, the time di?erences for the anticlockwise and >clockwise rotations are large at the beginning of measurements, they >decrease as the time of gyroscope's movement rises i.e. in the >subsequent experimental runs. It seems to be obvious that the >bearing's microscopic irregularities would generate an opposite >e?ect." > >Forgive my ignorance.. how is that obvious? > >Another consideration: friction due to air resistance. Comments? > >Cheers - shevek Yes, yours is a bit more technically stated, but my response was also to the effect that whatever bearings are being used, there would be a surface reorientation, as you describe that would lend to rotation in one direction being favored up to the point that opposite rotational periods lead to a surface reorientation that favors the new direction. I would call it "seasoning". Even disk brake operational observations show some of these tendencies. In fact, they prove it to be true. It is just a micro scale, whereas the disc brake scenario is a more macro scale of the same effect. |