Here is a head scratcher:

Lets say a lead box sinks to the bottom of a water tank.

In doing so, the potential energy (PE) of the system (water in tank + lead box)
decreases as the PE of the lead box decreases more than the increased
PE of the water being lifted to replace it.

Where does the "lost energy " go?


Maybe The Zed is tapping into this reservoir of lost energy?




for my answer, scroll down....









In air, a falling lead box converts its PE to kinetic energy (.5 * m * v).
This is lost by air resistance, and when the box hits the ground it deforms
the ground and itself which heats up itself and the ground.  Or if that is insufficient
then it bounces and the cycle repeats until all energy converted to heat.

I guess in water it is the same, but the "water resistance" dominates.  So the
water must be heating up.

I think the problem with all these pressures is that they only act over a relatively short distance. Start with the risers/pod assembly all the way down, with your pressure distribution in the nested cylinder "pistons" of air. Then release the things so they can be pushed up by the pressure. As soon as they start to move, the water level in the pod chamber will drop a lot as water rushes into the space below the pod. This will immediately reduce the pressure in the innermost chamber and also allow all the other pressures to reduce by pushing back thru the "U"s. As the pod/risers go up the pressure drop is greater, and I think the assembly only needs to move a short stroke before all the pressures are back to normal. In fact if it "bounces" above this point it will actually be sucked back down by the water and airpressure in the "U"s. I think.

I'm just imagining here, and also going by what I see in my single-layer pod/riser in the enhanced PerPump with TinselZed.
So the answer is, no, because by the time you get to the top of the stroke, or by the time you reset, the pressure multiplication effect is gone so there's nothing that can be used anywhere else, it all got used lifting or sloshing water around.

Quote from: webby1 on September 16, 2012, 02:42:54 PM
So just like the "demo" videos where the lift is of a short value.

In the pod chamber I can still add more fluid to continue with the lift but the others I can not.  I suppose that the added fluid in the pod chamber can still influence the other parts to help mitigate those pressure drops.

This then explains why the initial part of the lift is much higher and then falls off so if I set my lift value to the final stroke pressure at end of stroke, I can take more out in the beginning and why it works better when I do use a higher resistance to lift and then allow it to reduce to the final value,, all those pressure shifts happen a little later in the stroke.

As I pointed out in my previous posts: As the pod starts to move up the air pocket expands quickly.  This reduces the air pressure and the lift force.  If the stroke is too far, it can even go to negative air pressure, where you would be better off venting the air instead of creating suction -- best not to go there.  The optimal stroke is short, but the details are different depending on the geometry and starting pressure preloads.

I should know more as the sim improves.

Quote from: webby1 on September 16, 2012, 03:55:12 PM
Well this helps to bring Waynes comment on how much lift resistance to use into a new light, if you have a max value of lift and use 3\4 of that value you are building in room for more.  I was kind of thinking that it was just to leave some saftey room against blowing a skirt.

So at 3\4 lift value to max then the water is 3\4 the way up the side of the pod, so as lift happens and the other risers start to loose that pressure then more of the force is directed against the pod, retarding its lift so now the water will flow up past the sides of the pod and re-balance the pressure under the other risers until you have reached the full stroke value, then the pod chamber is full to the top and all lift resistance is balanced by the pressure held within the system.

Then on sink you have the full pressure value but only over a small volume of fluid, when that starts to vent the pressure will drop off quickly allowing the other risers to "push" down by not being able to hold against the mass that is left on top,, focusing more of that force into the pod chamber and slightly increasing the amount of pressure you can get back out,, and then the mass left on the risers reduces the difference between the rest pressure and the lift pressure which reduces the extra cost value.

Correct, good discussions going on here, now my spreadsheet may be more understandable.

Note the Pod Ret. water height before Rise (Full Pre-Charge)  and after rise while the force remains the same. Less than 3/4 water levels can be reached by lowering the water level in the pod retainer and adding air pressure to bring the water head back up to where it was before the water level reduction or 3/4 of max.

The initial setup goal should be to have the Pod sunk at start of Initial Pre-Charge. Actually, that is the reason for the 'Minus Pod' value and is only usefull at Initial Pre-Charge settings.

Regards, Larry   

I'd been doing pretty good at staying dry until I started looking for greater differentials in this 1U.
With 20+ lbs total load a blown skirt makes a pretty good splash... 
Dale