Saturday, February 2, 2013

Experiment 10.4

Let us start by asking a few questions about experiment 10.3. 

Question A) When the two black motors driving the spinning of the wheels are both pointing in the same direction (i.e. up or down or to the left or right etc), the spin momentum of the two wheels 'line up' i.e. they reinforce each other so that the net spin of the entire unit is twice the spin momentum of a single wheel.

When the two black motors are pointing in opposite direction, (i.e., one points up and another points down or one points right and the other point left etc), then the net spin of the entire unit is zero (or nearly so).

So the question is:During the crucial phase of the experiment (i.e. when all the motors are active), why do the motors line up i.e. reinforce each others spin, giving a large net spin, only when they are horizontal?

Further the spins always arrange themselves so they cancel each other (point in opposite directions) when the motors are vertical?

We see that it is possible for them to choose any number of other configurations, for example:

1) They could always line up and reinforce each other.

2) They could always orient themselves so they cancel each other out.

3) They could always orient themselves so they are at 90 degrees to each other.

4) They could always orient themselves so they are 1 degree off from each other.

5) They could always orient themselves so they are 2 degrees off from each other.

etc etc

You get the point.

This question drove me crazy for 2-3 weeks. I repeated the experiment several times to cofirm that this is a pattern. 

The answer to this question must have to do with gravity. The black motors driving the wheels apply a torque upon the spinning wheels because they try to fall down vertically, in the earth's gravitational field (like everthing else on earth).  The horizontal position gives the most gravitational torque upon the spinning wheels due to the fact that it has the longest torque arm (and torque = force X torque arm). Thus it seems that gyroscopes seek out the maximum torque position, rather than try to avoid torque. 
Thats interesting!!! You might think that the arrangement might try to minimize its interactions however it seems it is maximizing its interactions with external forces. Its like the machine is actively seeking out the maximum force configuration!!!

Question B) The next question is a little more subtle. To understand it easily, I would suggest that we first review one of Eric Laithwaite's experiments - the experiment on the model Eiffel tower. You can observe this experiment by going to this website and downloading and watching experiment 4 in the list. 

http://www.youtube.com/watch?v=W-TOePv0Rig

The relevant portion of the experiment comes somewhat towards the end of the video, from time index 7 mins 10 seconds onwards.

Now, if you've watched the professor's experiment, you know that on the Eiffel tower for example that when a precessing gyro is pushed in the direction of its precession, it rises. Whereas, if its pushed in the opposite direction, it gives way.

In our experiment 10.3 too we see that the entire frame lifts about an edge when the Y-motor pushes along the direction of the precession and the spins line up in the H-plane.

That tallies.

The same Laithwaite's experiment also showed that trying to resist the precession of the gyro caused the gyros to give way.

So we'd expect that engaging the main motor in the  OPPOSITE direction to the one in 10.3 would cause the gyros to give up lifting when they are in the horizontal plane.

The interesting question might be:
Will the spins then orient so they cancel and the whole cage speed up? or will they continue to line up, just not lift, simply speed up the cage rotation and/or speed up/relieve the load on the sub-assembly rotation?)

If the spins orient so they cancel in the horizontal plane, then might we expect that the spins will line up when they are vertical? In which case, since there can be no precession when the imposed rotation is in the same plane as the spin of the wheels, we might expect a continuous speeding up fo the entire cage in a flash??

On the other hand, if the spins still line up in the H-plane, then we might expect that the wheels exprience a tilt up both in the clockwise and cc directions about the horizontal axis, which might  lead to a lift???


So to test this out, I performed another experiment, we can call it  experiment 10.4.  This experiment is essentially identical to experiment 10.3 except that in this experiment, the main motor that is on top rotates in the OPPOSITE direction to experiment 10.3 

(well, the other difference is that I increased the rate of rotation of the subassemblies to 1.5 seconds per revolution, instead of 3 seconds per revolution. I also synchronized the time period of the sinusoidal torque pulses applied on the cage to a 1.5 second waves. The experiment is therefore twice as fast as experiment 1.3, so it also lasts only half as long.)

Here is the sequence of events for experiment 10.4:

Time Index 8 seconds: The wheel motors are started

Time Index 58 seconds: The subassembly motors are started

Time Index 1 minute 50 seconds: The main motor is started


video

The results were also interesting, and different from the two scenarios I was wondering about. The wheels still behaved the same as 10.3, except instead of lifting the machine about an edge on the far side, they lifted the machine about an edge on the near side to the motors. A simple reversal, akin to the behavior of the gyro in Professor Laithwaite's experiment above.

I realized then that I had not understood the professors experiment properly and that if I had, I could have foreseen this third alternative.

Oh well! We live and learn.

I do have however another question now, one I have yet to test.

Question C) So far, we've synchronized the rotation rate of the subassemblies, and the time period of the sinusoidal torque applied to the cage. That is, in expt 10.3, both the subassemblies rotated at 1 revolution per 3 seconds as well, the time period of the sinusoidal torque applied on the cage had a time period of 3 seconds (remember that we applied 14 strokes of 3 seconds each).

In expt 10.4, we upped the speed of the subassemblies to 1 revolution for every 1.5 seconds and also adjusted the time period of the sinusoidal torque applied on the cage to 1.5 seconds.

What would happen if we changed that ratio? What would happen if for example, we rotated the subassemblies at 1 revolution per 3 seconds, but the cage itself was pushed around with a sinusoidal torque of time period 1.5 seconds? Further what would happen if we made that sinusoidal torque so that we switched its direction from clockwise to counterclockwise every 1.5 seconds?

My analysis says that this might force the spinning wheels to either switch the lifting from the far edge to the near edge as the direction of the sinusoidal torque changes. And if we synchronize this with the overal rotation rate of the cage, can we not make it so that the wheels always the machine about one side of the machine? So that way, instead of the whole machine see-sawing back and forth, would it not experience one consistent lift about one side of the machine???

I feel that my expectation might again be based on some flaw somewhere in my logic. That last experiment has made me more cautious. However, I can see past this proposition right now, so I am going to try that out next.


Note: You will notice that inspite of the addition of the capacitors, the two subassemblies do infact still defy the command to rotate at 1.5 seconds per revolution when their motors are initially engaged. This seems to be because they are encountering a very large load, much large than even the torque of the entire machine about its bottom edge. B.L. and I are currently trying to calculate the load coming on the wheels quantitatively. I will present the results of that as well, soon. There seems to be more than meets the eye there, however you will note that once the subassemblies start rotating at 1.5 seconds per revolution, they do not have any problem sustaining that rotation, unlike in 10.3, where they repeatedly stalled even during the experiment. It seems the start up load is amazingly high, atleast a 100 times what we expected. Curious!!



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