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Eric James ----- |
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The undiscovered truth... |
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Forum groupies,
Behold! I shall ask a leading question for which it is your privledge to ponder...
Before I do, I should note that I haven't seen this addressed in any analysis of gyros during my research, so I think I may have thunk it first. Or, maybe I've just missed it amongst all the "vector here, vector there, vector everywhere" analysis I've studied.
Sandy, if you want to patent something.... well, I don't think this is patentable. It's really just an observation.
Let's think on it like Luis' and Glenn's puzzles...
Ready?
Behold! The Great Ubavontuba asks:
Is the speed of a precessing gyro's mass constant?
Behold! The question has been asked! Minds ponder, lights flicker, illumination ensues!
Okay, way too dramatic, but it's all in fun.
Enjoy!
Eric
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| Date: |
11 May 2005
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Answers (Ordered by Date)
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Victor Geere - 11/05/2005 09:12:45
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| | No. Since a precessing gyro is turning backwards (like a car moving forward with it's wheels in reverse), the lower part spins in the direction of precession, while the top part spins away from precession. The lower part is thus moving faster than the top part.
The velocity (as oposed to speed) is another interesting one.
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Sandy Kidd - 11/05/2005 10:14:55
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| | Eric
It depends what you mean?
I hope this is what you mean?
I also take it that this is in a passive system?
It’s a bit like a helicopter.
The blade moving forward into the direction of flight generates most lift.
Similarly a gyroscope moving forwards in the direction into which it has been forced develops an increase in accelerated mass in the forward moving sector of the gyroscope (not the leading edge of the gyroscope)
Gyroscopic rim angular velocity, plus forward moving angular velocity, which is an added acceleration.
The gyro itself will not change speed, but there will be an increase in the accelerated mass in the forward moving sector of the gyroscope, and that accelerated mass will be swept from forward moving sector, to forward moving sector, as the gyroscope changes direction during nutation.
As can easily be seen, precession direction depends purely on which way the gyro is rotating, when it drops.
Can only count 3 directional changes in nutation, should there be 4?
Any offers for 3 and a bit?
That would mean the increase in mass would sweep up and down in the gyroscope in a shape resembling an inverted bucket.
So the speed of the gyroscopic is constant the speed of the mass isn’t.
And not a couple in sight.
Sandy.
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Victor Geere - 11/05/2005 13:44:41
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| | Couple does not apply to motion. Motion is caused by an unbalanced force.
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Sandy Kidd - 11/05/2005 14:07:02
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| | Victor,
Where does gyroscopic couple come into the picture then?
Please explain?
Tell me how it is created?
I made a comment, now you explain the rest.
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Victor Geere - 11/05/2005 16:30:18
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| | Sandy
You made three comments:
1. "Eric ... when it drops." You answer Eric's question and I agree with you on this.
2. "Can only count 3 ... speed of the mass isn't." I don't understand this, mainly because I don't understand what nutation is. I have asked if it is wobble, but haven't had an answer yet.
3. "And not a couple in sight." See Glen's first answer to your question about : Gyroscopic Couple . Essentially I agree that there is no couple, and my explanation for this is that this is not an action + reaction = rest situation, it is a rest + unbalanced force = motion situation.
Regards
Victor
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Nitro MacMad - 11/05/2005 18:04:11
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| | Dear Victor,
Unbalanced force = acceleration - not motion as such.
Kind regards
NM
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Eric James ----- - 11/05/2005 18:37:53
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| | Forum,
Anyone else get the fox, chicken and corn thing yet?
Remember, only 3 trips!
Eric
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Glenn Hawkins - 12/05/2005 04:35:03
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| | Eric,
Lot of good answers here. I learned a couple of new things from Sandy’s helicopter. There are other things I have to digest.
My friend, you knew this was not so simple as it seems. Remember, some of us don’t think precession is possible in either a vertical curve, or horizontal curve unless a 90 o force is causing it and that that causing force must itself be constantly changing. That is to say a gravity-powered gyro will not precess unless it also drops. Consider that a gyro is angled upward over its pivot on a tower. As the gyro descends to a horizontal alignment, and next continues it’s decent to become angled toward the floor, its path downward has been a spiral. At the top angle the precession orbit is small. Looking down at it, the diameter of the descending precession orbit grow larger until it is in horizontal alignment with the floor, then the spiraling path grows smaller as it angles to the floor. NOW THE QUESTION IS and I don’t know the answer— do the RPMs of precession orbit remain the same during the downward spirals, or do they decrease in speed as the gyros drops to vertical alignment because the orbital paths grow larger, and then increase in RPMs as the angle drops toward the floor?
One of two things must happen. For there to be no change in the speed of mass transfer, either the RPMs of precession are not constant during the drop, or the downward speed of the spiraling path is not constant. If there is a change in the speed of precession, which of the above chances, RPMs, or the speed of the drop, or do both conditions change, yet remain out of balance to one another? I expect no replies, because I barely know myself what I’ve said. Sorry. This is tough stuff.
As to your question, I lean heavily in my guess that all is in balance, and the world turns on a greased axel you know. That is, when all things are in balance with one another, there should be no change in any of them. Except for a bit of friction to slow rotation and lessen angular momentum, the speed you speak of should remain constant…I’m pretty sure.
Glenn Hawkins,
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Eric James ----- - 12/05/2005 06:18:49
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| | Victor,
A couple (in regards to angular momentum) is two equal but opposite forces acting in parallel lines.
Basically, this defines the forces that cause pure angular momentum without incurring any linear momentum.
If the forces are not equal, both angular and linear momentum will occur.
Eric
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Eric James ----- - 12/05/2005 07:31:14
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| | Sandy!
I just discovered that you recently brought up this very question in regards to Aurthur Dent's description of gyroscopic couples! Why didn't you say so?
More:
Anyway, let's consider a smooth running system and ignore nutation for the moment.
As you have clearly identified, the gyro's mass moving into the direction of precession is moving faster than that moving opposite the direction of rotation.
Obviously, this constitutes a change in momentum in each point mass of the gyro as it revolves. It is either accelerating or deccelerating (technically a form of acceleration).
As I have alluded to in previous posts, according to the laws of Newton, acceleration requires force.
There is a lot of acceleration (in both directions) going on. Where is all of the force coming from that is causing this?
Interestingly, If you were to consider two parallel planes of rotation wherein point masses were moving at the rate of the rotating masses at the top and bottom of the gyro, the bottom would rotate significantly faster.
If you took this difference in angular momentum of the two planes and modeled it by stopping one rotation (say the top) and just demonstrated the difference in rotating the bottom, you'd realize a rotation that is twice that of the original precession.
Imagining a ball caught between these two planes, you see the ball rotates as a result of a couple!
So, there is the couple you were asking about.
This couple represents forces acting on the gyro. As can plainly be imagined now, the couple is not equal and oposite, so "linear" momentum is incurred.
Since the gyro is anchored at the pivot, this linear momentum is converted into angular momentum.
And there you have the reason a gyro precesses. It precesses due to an unequal couple.
More later...
Eric
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Sandy Kidd - 12/05/2005 07:44:22
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| | For any interested party
Hope this helps.
We have 2 different systems to play with here.
Passive systems and active systems.
For the moment I shall steer well clear of the active systems or systems subjected to radial acceleration. They operate differently.
Without nutation we cannot have precession, that is basically what it is all about.
The motion I described previously occurs in all passive gyroscopic systems.
In a passive system with considerable energy nutation, whilst always present is not easily seen.
The faster a gyroscope rotates the slower the precession speed will be and the nutation ripple very small appearing almost non existent, but it will always be there.
As the energy in the gyroscope diminishes the nutation ripple will decrease in frequency, and each ripple will increase in depth and length.
The gyroscope appears to precess very smoothly, whilst in effect it is tracing out a path like an inverted bucket or UUUUUUUUUUU continuously.
I did say when a gyroscope is “dropped”.
In a high energy system, it is very doubtful if it drops very far before the first nutation direction change takes place.
We all know a gyroscope reacts at right angles to an applied force.
Immediately it is “dropped” (gravitational acceleration) the gyroscope due to the increase in accelerated mass on the forward moving sector of the gyroscope (not the front of the gyroscope) the gyroscope is immediately turned at right angles to the downward or vertical motion of the gyroscope.
It is now moving at right angles to the force that accelerated it, but now, the lower sector of the gyroscope, sensing this increase in acceleration, moves at right angles to this new found mass increase, and tries its best to climb vertically back up the hill, from whence it came.
The gyroscope now runs out of steam, and the cycle starts again.
So this explains, I hope precession (following), precession direction and what creates them.
For some weird reason nutation is very rarely mentioned, which unfortunately, and understandably allows folks to think gyroscopes just do what they do automatically.
As I have said before there is no magic in gyroscopes, just lack of understanding.
Sandy
PS Before someone mentions it, there is of course a decrease in accelerated mass on the rearward moving sector of the gyroscope, during nutation.
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Eric James ----- - 12/05/2005 08:21:02
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| | Sandy,
Wow, you're really sold on nutation. I doubt we'll be able to see eye to eye here, but I'll try anyway.
Nutation is a wobble. That's all it is.
A "dropped" gyro will experience nutation due to a collision of forces. Basically, it oscillates between the force of gravity and the forces of precession. It adds nothing to the precession.
This is easily demonstrated by spinning up a gyro horizontally supported on both sides of the axis and then very gently removing one support. Precession starts, but nutation doesn't.
Often, due to uneven surface charatersitics of the pivot point of a mounted gyro, nutation will devleop, but hanging gyros generally do not experience nutation until the gyro's rpms drop to a point where it is difficult to sustain precession.
If what you say were true, at this point precession rpm should increase! It doesn't. Action increases due to the nutation motions, but overall precession doesn't.
Eventually the gyro will not be able to sustain precession and it will drop and then transfer angular momentum into a spin-up of the whole system.
Another example is to simply hold a gyro out while standing on a turntable and experience the precession as it spins you around. Next, start the gyro bouncing in a nutation. You'll note that your rotation speeds up as the gyro falls and slows down as it rises. Your average rotational speed can actually decrease!
Eric
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Sandy Kidd - 12/05/2005 11:57:45
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| | Dear Eric,
No we are not going to agree on this one.
It is a fundamental issue as to why a gyroscope is a gyroscope.
You will not be able to give me a reason why a gyroscope should precess in the first place, and to call nutation an uncontrolled wobble. Well?
How does the gravitational acceleration keep a gyroscope moving otherwise.
It is the only acceleration available.
Whether you like it or not all passive gyros nutate, and for good reason.
I did not invent this stuff.
Also as a precessing gyro loses speed, and as I said previously precession speed will increase quite dramatically before it falls over.
Sandy.
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Victor Geere - 12/05/2005 12:18:59
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| | You are right Nitro, hence the equation
[a mass in] rest + unbalanced force = motion
or
[a mass in] rest + acceleration = motion
Sandy,
You say:
>>"And not a couple in sight."
>>"Where does gyroscopic couple come into the picture then?"
So is there couple or isn't there?
Eric,
To make a long story short, is that the answer? ... that the bottom part is moving faster than the top part?
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Victor Geere - 12/05/2005 12:53:37
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| | I can see Sandy's point about notation, because the gyroscope has to be able to fall in order to precess. If it was supported on both sides of the axis it would not precess.
I am not so sure that this potential notation actually realizes, because it certainly isn't visible.
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Sandy Kidd - 12/05/2005 13:07:08
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| | Eric,
Enjoyed your input so far.
However, I do not know if you have gathered that I tend to specialise in accelerated systems, basically because I personally do not think that passive systems have much to offer in the search for inertial drive
They are much simpler to understand and much easier to manipulate.
Nutation and precession do not exist in accelerated systems, making the whole issue much easier to control.
The following I have broken down for all to follow, so Eric please do not feel insulted by my simplistic descriptions
Consider:-
A gyroscope being rotated at high speed, and the gyroscope being itself rotated in a circular path at considerable speed.
This constitutes a simple accelerated system.
The upwards and downwards (leading & trailing) sectors of the gyroscope will be subject to the same radial acceleration and will produce no net turning moment.
The rearward moving (upper) sector will experience less acceleration effectively due to its reversed rotation direction.
The forward moving (lower) sector will experience the lion’s share of the acceleration effectively due to the common forward movement or put it this way that sector of the gyroscope and the direction of its advance are parallel.
Now whilst the rearward moving (upper) sector is experiencing much less acceleration than the forward moving (lower) sector it is still subject to angular acceleration and therefore could not be described as part of a couple.
The upper sector is still experiencing acceleration even if of a lesser amount.
There is no inward turning force present in this sector at all.
It is this imbalance which allows the gyroscope to generate thrust in the vertical plane.
To call this a couple would really be stretching the imagination.
Sandy.
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Nitro MacMad - 12/05/2005 19:46:40
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| | Dear all,
I am sorry to bring another branch of science into this again but the similarity between the output of an operational amplifier and some of the functions of a gyro are almost too coincidental to remain unremarked upon.
The bounce or nutation (will you Americans with flashy automatic spelling correctors switch them off so we don’t have to worry how a gyro might “notate”) of a gyro suddenly released to precess around the almost compulsory Eiffel tower very much mirrors the output of an op. amp. fed with a square wave input. With an op.amp. (gyro): the greater the negative feedback (gyro spin speed) the less output overshoot (nutation) there will be for a given switch speed of the square wave shoulder (mass/pivot length). Thus, given sufficient spin speed of a gyro of a given mass/pivot length, nutation will become disapearingly small.
Incidentally a gyro does not need nutation or, as mentioned before, any reduction of spin speed to “drive” precession any more than an op. amp. needs overshoot or higher inefficiency to make negative feedback cause better input signal to output signal fidelity.
Kind regards
NM
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Sandy Kidd - 13/05/2005 07:12:31
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| | NM
Don’t know about the reduction in spin speed to drive precession. Not my thought. But I must disagree with your statement relating to the fact that there is no need for nutation to be present for a gyroscope to go into precession.
Sandy.
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Victor Geere - 13/05/2005 08:56:39
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| | Nitro, do you know if a gyroscope's spin speed is affected by precession? Positively or negatively? If it makes any difference, I am particularly interested in a gyro precessing around it's centre of mass.
Victor
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Nitro MacMad - 13/05/2005 19:53:42
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| | Dear all again,
The experiments I carried out to answer my own questioning of my opinions about the (then to me) illogical actions of a precessed gyro were done so long ago that I may be wrong to repeat my opinions here for fear of misleading you all with (what may now be defective) memory.
What the hell (Can we still say “hell” here? Someone said before “what the hay”!), I may get hit by a lorry (“truck” for you Yanks) tomorrow (no cheering Dr. David F and or Mr. Dent, or you Yanks!) so bear with me while I try to find words to describe effects that don’t have words, because they have not been looked into by enough people that matter in our society to have found a consensus to describe them.
Nutation can be, slightly, compared to the bounce of a dropped ball. I say “slightly”, because there are numerous other forces and reactions to those starting forces when applied to precession. However, it is a reasonable starting point, because the initial drop of the spinning mass of a gyro takes a finite time (which reduces with increasing gyro spin speed in relation to its mass) to react between the effects of gravity and the effects of precession. Nutation is thus, not driving precession, merely an effect resulting from precession!
That a gyro spin speed is only loaded by bearing load and not precessional load I believe I checked against an increased precessional load by putting a weight on the gyro’s outer shaft to increase the precessional load then compared this against a matched load on the pivot bearing. Perhaps someone else could check this for me.
The question of the rotation of the centre of mass can, without the complication and cost of an air bed, be checked with a gyro and a long string (or any suitable thread) pendulum. Far from centring its mass it will be found, instead, to rotate its centre of mass increasingly outward. This instantly challenges both Newton and some, at least, of the conservation ideas.
That the above suggestions are only my opinions based on (very old) memories I regret and offer my apologies for any dead end paths that are followed because of them.
Kind regards
NM
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Eric James ----- - 14/05/2005 00:42:35
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| | Victor,
In answer to your question, the couple I represented can be considered to be "why" a gyro precesses, but rather more accurately depicts the uneven force acting on/with a gyro that describes its precession.
The next question should be to wonder where the couple comes from...
Nitro, even hanging from a string the gyro rotates around the string. This is because the string is attached to a frame that is atached to the earth. You still have to count the whole mass of the Earth as being part of the support!
"Isolation" is often misunderstood in regards to the laws of motion. This is what tripped up Professor Laithwaite in regards to the Alex Jones invention. Even an air table only isolates in two dimensions. It isn't true isolation.
Anyway, there is an online video clip of a precessing gyro hanging from a string that I'll have to find for you guys. Wikipedia had a good one a while back, but someone deleted it.
Sandy, please explain to me how you think nutation transfers its oscillating motion into the angular motion of the preceesion. Also, please explain why gyros with no apparent nutation precess smoothly and steadily and not unusually slowly (presuming the energy level of the nutation is in correlation to precessional speed).
Eric
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Nitro Macmad - 14/05/2005 09:20:24
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| | Dear Eric,
The gyro on the string was not supposed to be held up as a demonstration of precession “in isolation” but to show that a precessing gyro does not rotate around its centre of mass but around a point at or close to its pivot. This, as usual, is due to the effects of “Nitro’s first law”.
Although Alex Jones device being gravity driven needs something fairly large (the Earth) to operate, simple mechanics can produce a motor as the input power source and matched contra rotating sprung masses to “push against”. Oh! It would be wise to ignore the word “simple”.
You may wish to look up John Harrison’s H1 to H5 for some clues to “force balancing”. He was a British inventor. It took him forty years to come up with an answer that now, of course, seems obvious to everyone so I forgive myself for the time it is taking me to answer my simple problem.
Kind regards
NM
PS John Harrison, after succeeding, was humiliated and called a fraud and then shafted and cheated by that wonderful body who’s job it is to promote science; the Royal Society (acting for the Longitude Board). We can obviously rely on such vanguards of science to lead the way to – er – humiliating anyone who dares to tread new paths until they succeed, then helping steal the idea without full payment, if Harrison’s experience is anything to go by.
It is so encouraging to remember that more recently that other bastion of forward thinking: the Royal Institution followed this same technique of “support” for, not nutters in sheds who have come to expect it but, its own member Eric Laithwaite. The Royal Society felt obliged to join in the mindless destruction, and his humiliation was completed by the removal of his nomination to this “hallowed seat of learning” – sometimes nowadays pronounced “gang of crap heads”. Luckily (?) for poor Eric he hadn’t quite got there so he didn’t have to suffer any stealing part of this “support”.
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Eric James ----- - 15/05/2005 02:18:28
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| | Nitro,
I guess I havn't been clear or something. The center of mass for a precessing gyro system that is not isolated from the Earth is essentially the pivot point of the precession.
This is why gyros seem so magical. They seem to precess in a fashion that defeats the normal understanding of Newtonian mechanics. They don't though, you just need to understand where the center of mass really is.
Eric
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Glenn Hawkins - 15/05/2005 03:12:37
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| | You might find additional explanations to the several given here.
You could try: Hawkins - 11/01/2005 02:46:52
A SCIENTIFIC STUDY OF GYROSCOPIC BEHAVEIOR PARTICULARILY TO DO WITH NUTATION
If you do, please be kind enough to ignore some smartassed remarks I was silly enough to make and now am ashamed of.
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Nitro MacMad - 15/05/2005 15:11:44
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| | Dear Eric,
Pray tell where that "centre of Mass" is
Kind regards
NM
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Glenn Hawkins - 22/05/2005 15:10:56
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| | Dear Nitro,
I can tell you where the center of mass is. It is exactly where you know it is.
Eric has a great deal of knowledge and an extraordinary insight. It appears here he was protecting ‘book’ physics a bit too much and then again he may have had a bad dinner and was a bit sleepy too. We’ll have to let him slide on this one. He really is an otherwise brilliant fellow who gets it right.
Incidentally, your Law is perfect and I use it a great deal.
Best regards,
Glenn Hawkins
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phase - 05/07/2005 19:19:16
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| | The mass is constant;
and the center of mass has nothing to do with the actions of the gyroscope
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Nitro MacMad - 05/07/2005 19:58:05
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| | Dear Phase,
The mass "should" be constant. The centre of mass "should" have nothing to do with the action of a gyroscope.
A quick check with a toy gyro will help you see, however, that that aint what a gyro does do.
Sorry for the negative feedback - phase - feedback. Oh! All right, please yourself.
Kind regards
NM
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chris - 05/08/2005 16:48:13
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| | no it isn't
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d brown - 14/08/2005 13:20:01
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| | Things I accept:
1) Nothing is solid in the way we think of 2 things being bolted tightly together; no play, no gap; everything is vibrating. (except at absolute zero)
2) Coupled: Applied force and precessing force are coupled at 90 degrees. Well, as far as I've heard/read so far. But the precessing force can easily be countered, about 1/10 the applied force I've read, allowing the applied force to move the axis in the original applied direction.
3) Nutation: The not-usually visible effect of the interactions between the applied force, the precessing force, frictions... coming to equilibrium/balance; like the kinetic energy in a rubber ball coming to balance/rest with gravity, air friction, and the 'normal' force of what it is bouncing on.(normal force is used in explaining action - reaction.)
4) Applied force in our talks is always in the same perpendicular direction towards the center of the axis of spin. (meant to clarify, not confuse. Statement can be omitted.)
Seeing what is going on here:
a) In the 74-75 lecture videos there is, in my eyes, an exact representation of what is going on inside a so called 'solid' gyroscope; the gyroscope with balls on the end of wires. You can see the twist. All gyro.s would have this twist as there is space between atoms/molecules.
b) If the applied force is seen as a pool ball (mass and velocity represent size of force),
It and the atoms it comes into contact with will deflect from each other. use standard calculations. (remember the applied force is always renewed and we must use a new pool ball for each 'push' point in time(space/time), as the last one was deflected away.)
- remember the force is placed on axis point x, and must be conveyed to outer point y.
- in the ball-wire gyro, a nutation's energy would be seen/stored in a bending of each wire, and would be transfered in a way analogous to a whipping action,
-- and this energy would come from applying a force greater than the gyroscope's ability to precess in reaction.
--- What is preventing the gyroscop from precessing? Is it atmosphere dependant? Would the same happen in the gravitational middle of the gravity tunnel between Earth and the moon?
-- INTERESTING, I've not tried this:Try spinning a doughnut shaped magnet and putting the force directly on the outer edge of the spinning ring with an opposing magnet. What is the resulting nutation, if any?
:)
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d brown - 14/08/2005 15:27:54
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| | First, sorry if I repeat what others say, just getting up to speed. I came here with enthusiasm to communicate and not just read. :)
To comment on other points.
chicken, fox, corn... only 3 moves, really?
- my answer anyways: move chicken, move fox - move chicken back, move corn, get chicken.
3 directions for nutation? there are only 3 directions, the 4th would be space time, and isn't that happening too? hmmm.
- If nutation is a balancing, then the gyroscope does not have to keep falling if it's spin energy level keeps it in balance with the gravitational force, at the horizontal.(sorta seen in videos from here):
http://www.gyroscopes.org/movies.asp look at the last realplayer video.
Centrifugal force: Although the term is used to state that a gyroscope does not exert any, it should also be used to say that it experiences alot, from it's axis of rotation to it's outer ring. That is why an overly spun gyro WILL explode. Guess we found a bit of leverage on the weak??? force is it?
What would be the precession and nutation of 2 bars ------- spun about their center of gravity --------o------- in a clockwise direction, based on that view? What if it was 4 bars forming a plus? or an odd number of bars in balance?
Slowing spin, falling angle of axis, larger orbit, accelerating precession... But does the rpm remain the same? Is there something else trying to remain unchanged other than the angle of the axis?
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Momentus - 21/08/2005 12:16:27
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| | Regarding the rotating bar, this would be the same as an early two bladed aircraft propellor. Consider a plane doing a flat turn (wings Level). The Gyroscopic couple from this type of prop varies from a maximum when the blade is vertical to zero when the blade is horizontal. This caused a vibration on the engine bearings which led to the use of 3 bladed, or multibladed props.
3 is the least number of elements which will give a constant couple.
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Momentus - 21/08/2005 21:47:31
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| | Got my maxes mixed with my mins. The prop/bar would have minimum effect when vertical in a flat turn. Sorry.
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dave brown - 23/08/2005 16:19:58
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| | cool, thank you.
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