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29 November 2024 00:33
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Question |
| Asked by: |
Blaze |
| Subject: |
Explanation of what causes an overhung gyro to precess (why the spinning mass moves) |
| Question: |
Let me start off by saying that if you want to determine if there are any forces or movements in a gyro that can useful for your purposes, it would be really helpful to know all the “hows and whys” of gyroscopic movements, what makes a gyroscope “tick”. If you don’t know that, then any experiments you do will just be “stumbling around in the dark”. Now, don’t get me wrong, I am not knocking that approach. A lot of very useful and interesting things have been discovered by “stumbling around in the dark” experiments, but, one of the first things to realize about gyroscopes is that there is no “magic” here. This is really a fairly simple mechanical device. It is just a spinning wheel that is moving around a pivot (if there is any magic in that, then I must be living in a different universe than everyone else, and yes, I have been accused of that once or twice). Keeping in mind that this is a relatively simple mechanical device, I will try to explain why the spinning mass of an overhung gyro will precess.
It will help greatly if you look at the diagram I posted earlier (or the explanation that follows won’t make any sense to you, of course, it still may not make any sense to you even if you do look at the diagram). Here is the link again.
http://i.minus.com/idHlM3teKCxZn.PNG
When I use the term “diagram” in the following explanation, I am referring to the entire image you see when you go to the link above.
I will go through the top right hand box in the diagram (Left Side View or LSV for short) with a more detailed explanation as it is the key to understanding what is happening.
In the LSV box the view you are seeing is edge on from the 270 degree point on the wheel (left side in End View of diagram). This means the Precession Axis appears as a point (yellow circle). Gravity is attempting to pull the wheel down. Because the shaft is supported at the pivot, this downward movement will twist the wheel around the Precession Axis (very much exaggerated in LSV box). Of course the shaft would also be angled downwards but that is NOT shown in the diagram. I am just trying to keep it simple so it is easier to understand. I am not putting in all the nuances that would really be there as they would only change the magnitude of the effect and would not change the fact that there is an effect.
We are only going to look at the movement of a particle from the 270 degree point (from the Precession Axis) to the top of the wheel which is the 0 degrees point (ie: we are looking at 90 degrees of movement clockwise from the End View in the diagram). This would be the upper left Precession Quadrant in the End View of the diagram.
The red dot represents a particle of matter on the surface of the wheel. If the wheel were not being pulled down and twisted around the Precession Axis by gravity, the particle would move “straight upwards” in the LSV box (really it is rotating from 270 degrees towards 360 degrees but it looks straight up in the two dimensional view of the LSV box). Gravity is trying to twist the wheel around the Precession Axis but because the wheel is spinning, this twisting action will try to force the particle to move at an angle upwards and to the right in the LSV box but the inertia of the particle resists this movement. The only way the particle can go “straight up” like it “wants” to (because of its inertia), is to rotate the entire wheel around the Lift Axis which is an “out of the page” curving motion towards the viewer (curving because the other end of the shaft is attached to the pivot, this is a clockwise movement when viewed from above). If the curving motion is carried far enough clockwise (when viewed from above) the red dot that is represented on the “angled” wheel will be superimposed on the red dot that is on the vertical wheel in the LSV box. The distance that the wheel moves in a clockwise direction (when viewed from above) to keep the particle moving in the direction it “wants” to go due to its inertia is the amount of precession that will take place. Of course the only reason this works at all is because the wheel CAN move around the pivot. If the precession movement was blocked then the gravity would simply pull the wheel down until it rested on some horizontal object (like a table top or floor) or the downward movement was arrested by some other means.
This explanation only looks at one particle of matter in one Precession Quadrant but all particles in both Precession Quadrants contribute to the total effect (with the particles in the other Precession Quadrant moving as in a mirror image). The same explanation with some minor variations would also explain why a gimbaled gyroscope precesses.
And that ladies and gentlemen, is the simplest explanation. If you want to look at all the other factors that exist then the explanation would likely get quite a bit more complicated. Even the simple explanation will likely take some fairly good spatial relation ability to really understand it but once you do understand it, it is really not that difficult.
When what is happening in the diagram and the LSV box is fully understood, it can also explain why a larger diameter wheel will precess more slowly than a smaller diameter wheel and why a higher wheel rpm will cause slower precession, but that explanation is for another thread.
Blaze
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| Date: |
6 May 2012
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Answers (Ordered by Date)
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| Answer: |
Blaze - 07/05/2012 00:04:31
| | | by the way, I should add that I don't care if there is or is not a reaction force at the pivot, it doesn't really matter to the explanation, the wheel precesses around the pivot and for the purposes of the explanation above, that is accepted as normal.
Blaze
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| Answer: |
Glenn Hawkins - 07/05/2012 00:31:24
| | | The problem is not that you are not being understood, but that you are being understood.
Why the tilting wheel twist down on the pivot, therefore holding itself aloft, has been explained and yes you are right again. Very Good. Read through my old post if you question that.
I am sorry, but your idea that the forward to precession top quadrants coupled with the rear lower quadrant causes precession. . . is not true. When the correct reasons will be explained, they must be presented as a series of causes and effects and not simpler because-statements. Incidentally I once mistakenly believed exactly the same thing about those two quadrants. So you have been hard at it trying out to reasoning the great unexplained question, except that your conclusion is wrong. The quadrants only help the complete top and bottom to torque down on the pivot, and nothing more. I say again, precession is so complicated and your are not close. I know. An Angel gave me the understanding. This is the God honest truth.
I suppose you will be ticked off and I am so very sorry for that. At least maybe you now know you are understood. Blaze, you are a very sharp cookie and I never lie. You know it and I know it.
Cordially yours with much kind intentions,
Glenn,
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| Answer: |
Glenn Hawkins - 07/05/2012 01:15:23
| | | I have to say more. I have to leave you with something. I am finishing up my posting here to build and live. What you think and what I once thought may provide a tiny boost, but not much if any.
Look at your watch this way. The hands are rotating clockwise like our wheel, consider our position is the pivot and we pivot as we swivel in our chair always watching the face with the wheel. As the top falls outward, deflections at 10:30 o’clock apply force back toward us, we the pivot. That would precess the wheel, however this inward front movement would tend to twist the rear of the wheel at 1:30 o’clock outwards away us. So whatever gain you got in the front top to precess, would be taken away in the rear top. This same vertical twisting would occur at the bottom, but oppositely at 4:30 toward us and 7:30 o’clock away from us. Any attempt to precess caused by your description would cause a counter effect. I hope I can be understood. Good luck.
Bye now,
Glenn
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| Answer: |
Blaze - 07/05/2012 02:02:50
| | | Bam, bam, bam
Hi Glenn. I am not ticked off and if I was it would be at myself for making a stupid mistake, not at you for pointing it out. I do understand your second post to this. Thank you, it helped. I am preparing a response (could be a while) as I am still not sure that I am wrong (or completely wrong anyway). I am not say that I am not wrong, just that I am not sure that I am wrong (is there enough "nots" in there for you?).
B^3
Blaze
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| Answer: |
Glenn Hawkins - 07/05/2012 18:27:27
| | | Hi Blaze,
This might help.
The pivot it is not given force and tendency to rotate around the gyro.
I see the reason for asking about it. You thought the gyro was caused to twisted itself vertically by deflection around the pivot and that this should by practical logic also cause the pivot to try to rotated around the wheel.
Imagine looking down from the top view at a busy gyro and freeze-frame all motion. Reach down and twist the gyro while it is frozen motionless in place. That twist would cause precession, however in order for that to happen the shaft would have to apply force horizontally against the pivot.
The pivot to withstand, would have to be anchored to the fulcrum and fulsome anchored to the floor for equal opposite reaction support. Otherwise the wheel weighing thousands of times more the pivot nodule would never precess. Instead, the pivot would always rotate around the wheel only and it would not be possible to have overhung precession.
This is what happens:
The wheel pulls itself in the exact circumference in which it precess'. It creates this path by it’s own reactions and without putting any horizontal effect against the pivot.
A gyroscope is an inertial propulsion device in and of itself alone. If fact, I predict if a ring were magnetically suspended while spinning in a vacuum chamber and magnetic forces pushed the top of it’s face inward and pushed the bottom of it outward, the gyro would precess in a large circle without a shaft and pivot.
“This is very different from how the gyro twist down against the pedestal for support”
Now to consider friction: Between the tiny area of two hard services, a pivot setting in a concave seat, (apply one weight viscosity oil if you like) the drag from friction would be so minute as to be near immeasurable. Such little drag would have near zero effect by caparison against such large mass in motion.
If we need more evidence consider a gyro suspended from 14 feet. You know the gyro will pull the string outward from the top anchor in its circumference of precession. But have you ever tried to sight the gyro and string to line them up vertically from the center spot from wherein the gyro precess'? Or from the outside? The string never leans to the right and it never leans left. It would if the pivot even so much as hinted it wanted to circle the gyro. The pivot is the 14 foot above tie-off. The string and gyro do not advance, or lag behind precession. There is just no sideways force at all applied to the ends of the arms of the gyroscope or the pivot.
Well, It appears we have all conquered another dead horse. We all win again.
Bye fellows. Take care,
Glenn
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| Answer: |
Blaze - 08/05/2012 03:17:15
| | | Thanks for taking the time to understand where I am coming from Glenn. The last post helped.
I get what you said about the quadrant theory, but I was just wondering, have you ever done any actual math on it? I thought it over again and realized there are some non-symmetries that I didn't take into account that are interesting. It will likely turn out to be nothing but I am going to do some math on this one, well geometry anyway with maybe a little geotrig thrown in for good measure. Like I said, probably nothing, but it doesn't hurt to check it out. If nothing else I will eliminate something else and that in itself is worth something. If the math reveals anything, I will post again on this topic.
Thanks again
Blaze
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| Answer: |
Glenn Hawkins - 08/05/2012 04:44:05
| | | I want to forget the geometry, trigonometry and logarithms I learned at Air Defense Artillery And Missile School in Fort Sill Oklahoma and I don't care to try to remember much of what I learned at the University of Maryland concerning numbers, but good luck to you. Have at it.
I did however apply some numbers in discounting my good professor’s claims in his part 6 video. Burp! Too much chilly to night. Burp!
Blaze, just concentrate on the mechanics. You are good at that and I admire your for it. The mechanics will give you the answers. The numbers come after you know how it works.
Glenn,
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| Answer: |
Glenn Hawkins - 08/05/2012 05:05:27
| | | Please excuse me. This math was used to kill people in Vet Nam in my service time before the event of the computer. But I know it wasn't the math to blame. Math is good.
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| Answer: |
Blaze - 08/05/2012 05:09:53
| | | Well... I have been going at it since my last post and the initial geometry looks promising. I want to make sure that I haven't made a mistake before I say that there is anything there. It is more complicated than I expected (so much for SMS eh?). I think my calculator is getting hot ;-)
By the way, isn't the quadrant theory sort of the mechanics? Or did you mean the actual physical mechanics?
I will have to look at video 6 to see what you mean about the good professor. Was that video link you posted in your Fallacies and Verifications?
Blaze
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Blaze - 09/05/2012 19:58:55
| | | I took last night off to give my brain a break. However I can say that the quadrant theory actually does have some merit but it is NOT complete as was explained here. All motions have to be taken into account (big surprise, huh?) to explain why a gyro does what it does. That was not done in the explanation above but the explanation is closer than you might think. I still have to confirm a few things but can say quite comfortably that I now believe I understand why and can explain how at least two counter intuitive movements of the gyro happen, 1) why a larger wheel will precess more slowly, and 2) why a wheel with higher rpm will precess more slowly (not just that it does that, but I can explain what causes it to do that). I believe that the quadrant theory may even explain why the gyro precesses around the pivot with no horozontal reaction at the pivot, but that is yet to be confirmed (so you can throw point 2 in the notes section of the link out the window as it was always wrong, but of course, you already knew that). More work and confirmation to be done before I can say more.
Blaze
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