Re: Uniform motion

"Phantom" <phantom@xxxxxxx> wrote in message
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"Greg Neill" <gneillREM@xxxxxxxxxxxxxxx> escreveu na mensagem
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"Phantom" <phantom@xxxxxxx> wrote in message
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"Greg Neill" <gneillREM@xxxxxxxxxxxxxxx> escreveu na mensagem
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"Phantom" <phantom@xxxxxxx> wrote in message
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So, Nutation and Precession are independent effects.
Nevertheless, conservation of energy requires that
both be related by the above equation.
Otherwise you'll have to tell where did the energy go.

Angular momentum is conserved, so momentum is
only exchanged. The bodies that are applying
the torques are the ones that are exchanging
momentum with the precessing and nutating one.

The associated with precession and that associated
with nutation do not have to be equal. The only
constraint is that the angular momentum of the
entire system (including the bodies responsible
for the torques) be conserved.

Yes, that's true.
You want the angular momentum of the entire
system to be conserved.

Not only do you want it, it *must* be so.

Right.

Also, you say that the bodies that are applying
the torques are the ones that are exchanging
momentum.

All of the bodies involved can exchange angular
momentum.

First you've said:
++The bodies that are applying the torques are
the ones that are exchanging momentum with the
precessing and nutating one.;;

Now you say "all bodies", including the gyroscope
himself.

In other words, I'm consistent. I simply restated the
fact in order to make sure that you were taking the
correct meaning.


Do you have any references saying that energy
or angular momentum of the gyroscope himself
changes anyhow?

How could it not if torques are applied? Simply
because the body is precessing and nutating it is
obvious that the angular momentum vector is
changing direction!


The book I've mentioned, from Harvard and
published by Cambridge, implicitly says the
gyroscope himself must be out.
Basically, in the gyroscope rotating frame of
reference (fixed to the body) no gyroscopic
change occurs.

This would only be true if it were defined to be
so for the sake of analysis, or if the moment of
inertia and angular momentum were so large that
any changes over the observed time would be
insignificant.


That's perfect to me, once the gyroscope
momentum I3w3 (or the energy 1/2*I3*w3^2)
doesn't change.

Why would it not change? It can move energy
or momentum to the other bodies.

The gyroscope is characterised by:
Angular momentum - I3 w3
Kinetic energy - 1/2 I3 w3^2

Since I3 (mass inertia moment) won't change,
only the gyroscope main angular velocity w3
can change.

The moment of inertia won't change with repsect to
a frame of reference attached to the body. But the
axis about which it is measured (or calculated) can
be reoriented in space. Certainly the angular
momentum vector will change with applied torques.


How do you think that is possible?
References?

Think about the absurd situation it will be.

It's as absurd as noting that an accelerated body
can change velocity, direction, and location --
perfectly reasonable in other words.




Look:
T1*w1 = -T2*w2 (like I said previously)

That equation does not necessarily hold!
Why would you think it does? The torques are
independent, the bodies involved are separate,
and they may have different masses, moments of
inertia, and distances.

You keep talking about external bodies when in
fact there are none.
On the nutation side, the usual mass under gravity
has been changed by a piston, tie-rod, crankshaft
system that applies torque over the gyroscope.
On the precession side I never said there was a
body there. On the precession side I've said there
are bearing (with friction) and now I include an
electrical generator or other means to take torque out.

Here, we have only:
1 - The torque T1 that causes precession w2.
2 - The gyroscope angular momentum I3*w3
3 - The torque T2 that causes nutation w1.

I've said the gyroscope is out of the energy
conservation balance. Hence I only have to
deal with variables: T1, T2, w1, w2.
You want to include the gyroscope angular
momentum in the balance of energy/angular
momentum change. You have to deal with
5 variables: T1, T2, w1, w2, w3

Fine, you've got a mechanical system rather than
a gravitationally coupled one. You've still got
the reaction torques to consider between the
gyroscope and the devices applying torques to it.
The system must include *all* of its couled
components.


My claim is that dw3/dt = 0
You claim is that dw3/dt is not zero.

You are wrong.

And why you are wrong?
You wrong because the only way you can
avoid *free energy* is that the gyroscope
must gain angular momentum by means of
increasing its angular velocity w3.

Nonsense. First, if there is precession and nutation
then the angular velocity vector *cannot* be constant.
Second, if there is an energy input it must be due to
the mechanical couplings pumping in energy from the
external machinery. Third, if there is frictional
losses in the gyroscope bearings then the angular
momentum must decrease over time, meaning that the
angular velocity will decrease over time. Any way
you slice it, your w3 is changing over time.


Maybe you are confused with the device
called *power-ball* which is a gyroscope
that one can spin up by hand movement.
First you got to know how a power-ball
works. The power-ball shaft rolls with friction
over a flat surface, so that when you move your
hand the surface friction causes the gyroscope
shaft to turn and torque is conveyed to the
gyroscope mass. Therefore, a third external
torque T3 exists that causes the gyroscope
to increase its energy/angular momentum.

On a conventional top/gyroscope we never
seen the gyroscope/top spinning up due to
external torque.

We see it spinning down due to bearing friction though.
This is a common enough experience that it is simple
to accept. We don't often see a device that can couple
a torque to a moving gyroscope in such a way as to
increase its spin rate.

How do you pretend to cause a dw3/dt to
be different from zero without introducing a
third torque T3?
How does w3 spin up without torque?
How does that spin up *magic* works?

You have *two* torques to play with already. They
already will form a resultant torque. Adding a third
torque won't buy you anything unless it's applied about
a different axis.

and:
L = T1/w2 = -T2/w1 (your total angular momentum).

No, the total angular momentum would be the sum of
individual agular momenta of all the bodies in the
system. You seem to want to pick and choose the
individual effects (precession, nutation) and declare
them to somehow be equivalent to the total angular
momentum -- I can't fathom why you'd think or do this.

Your angular momentum sounds logic (in theory).
But how do you put it into practice?
How do you convert torque (a higher dimension)
into angular momentum (a smaller dimension)?

You have two torques to play with. In order to change
the rate of spin of the gyroscope you'll want to have
some component of the resultant torque lie along the
angular velocity vector.


The facts are that Newton method and Lagrange
method causes torque T1 to be expressed by
four additive torque terms, and torque T2 to be
expressed by five addictive terms. Now you say
that w3 is not a constant. Hence you'll have one or
two more addictive terms both side o the equality.
You'll have to deal with an equality of around 11
to 13 terms.

I'm already in a big trouble to work with 9 terms
and I'm not sure if I can make it.
Your approach, with a variable w3, simply turns
the problem dependent on something else, which
of course you have no clue, nor I do.

I don't need your insults based on ignorance, so I'll
bow out and leave you to your own devices. Good bye.
.

Relevant Pages

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  • Re: Uniform motion
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