For the fans of Archimedes only

[path_finder]

Remember this former link: http://lectureonline.cl.msu.edu/~mmp/applist/f/f.htm
(Catch and drag the red top of the spring with your mouse)
Just a though: by acting down the spring, the diver goes down, but what about the COG of the water? IMHO it goes down also.
So far let's suspend this assembly at a ferris wheel, and then move the spring in opposed manner on the both sides of the rotation: you win!...
What is wrong in this concept?

edited:
may be the scissor in the MT138 is acting remotely on the bellow and therefore on the COG, the workers toy mechanism assuming the alternate control.

[greendoor]

The way I see it, when you apply Force via the spring to the water, the COG of the water goes UP (not down). The volume of the trapped air gets smaller - and the only way for that to happen is if the water rises up to displace it.

This is just a variation on buoyancy schemes - and there is no free lift from buoyancy. It's just the inverse of lifting solid mass. The "less than solid" objects are squeezed upwards by the heavier surrounding fluid mass falling around them. Ultimately - mass falls down under gravity attraction. The apparant upward force of buoyancy is just the effect of a much greater attraction going on around the object - and upward movement only happens if mass is allowed to fall down to replace it.

[path_finder]

Dear greendoor,
One time again your comment was pertinent.
I confirm your explanation by the drawing hereafter showing the COG compensation of the two volumes.
The both displaced volumes are identical (same mass) and therefore this container has the same weight before and after the spring actuation.
Obviously the global weight did not change, but a question is remaining: what about the COG relocation?
The COG of the upper volume #1 falls down with a distance shorter than the COG of the lower volume #2, wich moved about twice this distance (depending of the radius ratio of the container and the diver).
If this is true the weight don't change, but the COG is relocated.
This is here the particular condition used in the Tesla patent (a variable COG position inside the same assembly of weights).
Where is the mistake?

edited: grimmer changed to greendoor

[greendoor]

Hi pathfinder - i'm greendoor, not grimmer nor Grimer. But I think you are right - I had neglected to consider that the 'diver' then falls, so I can see that the COG of the water really does fall.

This is achieved at a cost - the Force acting downwards is in addition to gravity, and is almost acting like an increase in gravity or water head.

Your picture can't be to scale. I agree that the total mass of water has to be the same in both drawings. However - air is compressible and water is not. Therefore, as the volume of air in the 'squeezed' drawing is clearly smaller, the volume of water must remain the same, and therefore the Level of this water must go down.

I believe if you drew these accurately, it would be clearer that the COG doesn't change as much as you are suggesting. The level of water would drop at the top, which represents the COG of water falling, which would compensate for the fact that the bubble of air has moved downwards, which represents the COG of water rising.

[greendoor]

IMO, applying pressure via the water is pretty much the same as forcing a buoyant object down into the water by applying force with a stick. This is similar to applying tension to a mass suspended by a spring. When the force is removed, the float or the mass goes back to it's initial position. I can't see that we are achieving anything special.

[path_finder]

dear greendoor,
I apologize for the avatar confusion.
This is NOT my drawing, and I cannot certify its accuracy.
It could be useful to verify this point, but based on a Java program, I'm pretty sure that applet has a chance to be exact.
I do not contest the unvariance of the mass, but I still ask to verify the position of the COG before and after the spring actuation.

edited:
During the falling down motion of the diver, the pressure is constant therefore the air volume, and by the way the main COG of the assembly is moving.

[Tarsier79]

Gday pathfinder

Yes the Cog does drop, and by the amount shown. When the diving weight is floating, the density of the diver is less than the water, and is at the top. When compressed enough to sink, the diver is the heavier than the density of water, and sinks to the bottom.

If the spring, and actuator were located at the bottom of the piston, then the COG would remain fairly consistent.

Unfortunately, as Greendor says, the amount of energy to achieve this motion, makes a wheel using this mechanism unlikely.


Cheers

Kaine

[path_finder]

Dear Tarsier79

the amount of energy to achieve this motion, makes a wheel using this mechanism unlikely

Respectfully, don't throw the baby with the water of the bath.

First we need to know the exact value of the force needed for the motion of the diver.
This point is not obvious, the atmospheric pressure playing a role in this calculation.

Then when the equilibrium is obtained (at the end of the first string's compression phase) the diver moves with a very low additional force.

And at least (and not the last) if the phenomenon is reversible (who knows) we can link two opposite containers with a seesaw. In that case the summary of the energy for actuating the both opposite springs will be null, but we win because the main purpose was not an unbalance, but a dynamical relocation of the two opposite COGs, one accelerating and the other slowing.
as you know a variation of the COG speed can be an excellent source of PM

I'm not a fanatic of the buoyancy, but IMHO this story of weight, keeping the same mass, but with a moving COG, has to be learnt deeper.

[Tarsier79]

Just because one spring is compressed, and the other uncompressed doesn't mean it doesn't take energy keep the see-saw in one direction or the other. Childrens see-saws with springs are in many playgrounds, and oscillation is fairly easy, but is quite rapid.

Are you looking for the diver to move? or just have a change in density. I don't see the diver moving that quickly. Nor do I think the change in COG will be enough. There will also be considerable friction at the piston.

Apart from making the piston airtight, the rest of the mechanism should be easy to make, so don't let my opinion cloud your enthusiasm. As there has been no working model presented, the experiment would at least show you one way or the other if this is the path to pursue.

Cheers


Kaine

[path_finder]

Remaining on the same concept (fixed mass but moving COG):
The diver actuated by a remote pressure variation (like above) can be replaced by a more efficient mechanism, with a displacement speed more quicker:
imagine an hollow cylinder with a sliding weight inside
For introducing an unbalance, fill the cylinder with some oil, drill a calibrated hole into the weight, and insert a valve on the hole.
You are now very close from an hydraulic shock absorber (see here: http://en.wikipedia.org/wiki/Shock_absorber)
Solder two pins in the middle of your cylinder where you attach a rope for a link with the inner rim of the wheel.
The wheel is always balanced (if all cylinder are identical and suspended at same mutual distance).
But the variable COG (because the shift of the weights inside the cylinders) can be used for create a desynchronization between the two sides of the wheel (by a clutch per example on the two suspension pins).
Just a suggestion to be analysed more deeper.

Note this could explain the presence of the handkerchief around the weights during the Bessler presentation.
May be the grease was here for a better shift of the masses inside the cylinder.
May be also the view of a weight would have show the lost of oil from the cylinder.