Gyroscope - I just don't get it.

[Creator]

Creator, I re read your post. My response about lifting the rope was inadequate

As the spinning wheel precesses around your hand it moves into a horizontal position and you can lift it easily, but if the wheel is not spinning you must lift its weight which is unchanged AND twist the wheel into the horizontal position. the force on your wrist due to the very small leverage provided by the axle stub would in my opinion make it appear as though the wheel weighed a lot more.

Is this what you are getting at?

Yes; Eric Laithwaite, prominant electrical engineer, caused quite a stir at (and was rejected by) the Royal Society by showing he could circumvent Newton's laws by taking 50 lb. gyroscope which could barely be lifted by one hand, and yet with it spinning he could easily lift it over his head.
He went on to develop a device using a gyroscope that could provide propulsion using no external thrust.

Here's a little background: http://search.msn.com/results.aspx?FORM=SMCRT&q=laithwaite and gyroscopes

 

[futb0l]

You should try and spin a top. It is similar to a gyroscope.

 

[Creator]

oops,. I put the wrong reference... Here's a correct one for Eric Laithwaite:...
http://www.alternativescience.com/eric-laithwaite.htm

 

[gerben]

http://www.gyroscopes.org/1974lecture.asp

 

[quasar987]

Fantastic lectures, thanks a millon m8!

 

[skeptic]

Eric Laithwaite was one of those most dangerous creatures: a career-crackpot who managed (I blame it on a shortage of university manpower after WWII) to get himself into a position of academic power. The gyroscope affair was only the tip of the iceberg. He also fancied that he was an expert on moths, and maintained a ludicrous theory (radio) for their communication even when the relevant pheromone (the true explanation) could be bought 'over-the-counter'. He did not even invent the linear induction motor, for which he is often credited. It was invented by Wheatstone. He also did not invent Maglev: an experimental levitated railway was already in operation when Laithwaite was a child. He did not develop a gyroscopic propulsion device; he got patents for several. This means nothing. The patent office is a joke, and let's any nonsense go by (they get their fees regardless). One of the leading free-energy (perpetual motion) promoters is a former patent-agent! I call Laithwaite dangerous because he has seemingly infected thousands of people with the idea that gyroscopes have anomalous properties and, more importantly, he has made acceptable the performance of sloppy experiments, and grandstanding for the benefit of journalists. His name should rightfully become a pejorative term among scientists; like Quisling is among politicians.

 

[qetuol]

My question is:

which forces are present in the case of precessing gyroscope?
I have drawn a simple picture of the situation. The red force is the gravitational force. Is there a centripetal force -green? I think there must be since the mass is rotating. With the green force is easy to get why the mass is not falling. Or the green force is just fictional?

 

[rcgldr]

What is included in the articles but not clearly stated in this thread is that the gyroscope "reacts" to a torque about 90 degrees out of phase. On an obect spinning about the vertical axis, a torque along the roll axis results in pitch reaction, and vice versa. This is how helicopters are controlled, roll and pitch torques at the rotor blades result in pitch and roll reactions respectively, so the control inputs are shifted in the "cyclic" 90 degrees out of phase so the control input stick corresponds to the anticipated reaction.

In the case of a gyroscope aligned so it's primary axis is horizontal, then a roll torque results in a yaw reaction, except that since one end of the gyroscope is fixed at a point, the yaw reaction is resisted. The result is that the gyroscope will react with both roll and yaw until it's rate of yaw matches the precession speed. If there is no dampening (a frictionless base), then the gyrosope rate of yaw, and direction of it's primary axis would cycle.

If the frame supporting the gyroscope were placed on a scale, then the scale would show a lower "weight" when the gygroscopes center of mass was accelerating downwards and a higher weight during upwards acceleration, as the gyroscope rate of yaw and primary axis direction cycles. If the initial condition is such that the rate of yaw is the same as the "precession" speed, the torques cancels and the rate of yaw and direction of primary axis remain constant (assuming no frictional losses), there would be no component of vertical acceleration and the weight shown on the scale would be constant and equal to the weight of gyroscope and supporting frame.

 

[jetboy11]

This gentlemen, is exactly the point<

everything here revolves around centifugal force of an object that is balanced and spinning, now we know that this balanced spinning object has a center line, eg a center line that the object spins around,
Now if you introduce, every action has an opposite and equal action against it we can see how the the top maintains its centre point, and weight.

Introduce another balanced spinning object around the first object using the same center(plane), then you have a gyro that balances itself by offsetting one weight against the other in diff directions

 

[Cleonis]

I don't understand why a rotating gyroscope whose rotation axis is inclined with respect to a vertical axis does not fall to the ground dues to gravity as fast as the non-rotating giroscope.

The answer to that has two stages. First the physics of gyroscopic precesssion.

This section from the http://en.wikipedia.org/wiki/Precession#Torque-induced" explains with a picture why gyroscopic precession occurs in the first place.

In the following post here on physics forums
https://www.physicsforums.com/showpost.php?p=2375054&postcount=3
I discuss the classroom demonstration of a spinning bicycle wheel, with horizontal axis, supported on only one axle end. Ultimately gyroscopic precession accounts for the chain of events that makes the gyroscope not topple over immediately.

Cleonis

 

[fluidistic]

To Cleonis : The question you've just answered has been asked in 2004, November.
The asker also understood the answers he got in the thread, clearing his initial doubt.