Quote from: fletcher on September 14, 2012, 07:21:22 PM
These things relate directly to see3d's sim IMO where the piston raises the water volume around the locked down pod, so there is not just the work done to raise the water volume [weight] a height, but also a variable force input as the pod is partially submerging - he is contemplating using a counter balance mechanism for this effort required - IINM these experiments prove that the resistance will increase as pod is submerged, which needs to be factored into the sim as pgh calculation, and so a weight & lever counterbalancing approach [ f x d ] might be difficult to implement to get accurate results.

I am just trying to catch up with the videos and posts.  My main system drive failed this week, and I am just about back to normal again after having to hand make some mounting brackets to put a 2.5 inch drive where a 3.5 inch drive was meant to go in my Mac Pro... :-(

I hope I am understanding how these experiments relate to my sim.  When I counterbalance, it is just the lowest energy state that is zeroed out for the pod water weight and the riser weight.  The internal forces grow quickly as the water is raised around the pod, when it is held down.  When released, it will raise to equalize the forces.  My sim actually runs by just raising the top stop 1/1000 of the stroke at a time and recalculating all the forces again.  It keeps moving the riser up one increment until there is no more upward lift force.  It reduces the order of the equations by one to do it this way, and reduces the likelihood of a math error in the process. 

I obviously never have a case where the pod is completely submerged.  It is always partially out of the water.  For a zero layer system, the force seems to be linear with the height of the water column.

If i visualize a teeter-toter with two buckets on each side filled with water so that they are in balance and at the same level. how much force (or extra water) will it take to move one side down 10 degrees? 
The answer is not much.  That is my principle.

However, if suspended right at the waterline in each bucket is a water filled float (neutral buoyancy), taking up half the total water area and zero volume when level, then how will that change the amount of force required?

Quick note on my testing to date:
I've mostly been working on the basics during the very limited time I have to play with this thing; picked up a digital fish scale and a couple of measuring cups ( spouse gets twitchy when stuff disappears from the kitchen... ), rulers, stuff...

Made a larger diameter input cylinder - mounted the screw jack better - put a bottom on the 6.5" 'POD' ( crap!, it leaks a bit ) - vented the 1 riser currently installed - little stuff.

Anyway - it did prove one thing to me tonight, something that might be worth keeping in mind... GRAVITY is the force we're dealing with.

I tried setting up with just a 4lb ( rough measurement, this is a 3rd grade assessment, not grad school physics ) assembled riser / pod "plate". Lifting the unit with just water in the area around the pod was very straight forward, head in the input cylinder and around the pod followed real close and the weight needed to keep it sunk straight out of the textbooks.

Flooded the pod chamber and let the water flow into the first riser gap ( vented ) until I had about 6" in the gaps.

Lowered the input cylinder until the pod was back at the base and closed the vent.

Started the lift again and it behaved as expected; differential pressure caused the water in the "tank" to rise and the water in the retainer gap to sink even before there was any head around the pod, cool. The whole thing started to lift ( this is a single top plate - at this stage the pod is really riser 4 )

Brought it up about an inch and was going to measure the various heads and got surprised watching the system balance itself - the head around the pod kept increasing and the differential head in the 1U space kept shrinking to the point of being non-existent - CRAP! air leak....

No... I let it back down and Teflon taped the vent screw ( gotta be the leak, everything else has been tested ) - tried again with the same result then added a quart of ballast. The additional 2 lb load did the trick, 2.5 hours later the heads are still the same....

Initially, with a light load, while water was flowing in, a differential head appeared in the first riser but went away as soon as the system became static / stable. With more load the head differential remains....

Think I'm about done with 1U and will move on to 2

Dale

Quote from: neptune on September 14, 2012, 03:21:37 PM
@Webby1. I agree with every item on the "do you agree" list. You are doing great work.
@TK,regarding your video. I found it confusing initially to understand your concept of internal restraint and external restraint. Here is a way that I think I have grasped it, and would like to know if you think it is a valid way to consider it.
     Imagine we have a giant "G" clamp, that has no weight. We dispense with the lid , just keeping the jar and floater.
1. Internal restraint. we hold down the floater with the clamp, one end of the clamp fits on top of the floater rod, the other end fits between the bottom of the jar, and the platform of the scales.


2.External restraint. One end of the clamp fits on top of the floater rod, the other end fits between the base of the scales and the table.

Yes, I believe so. The internal restraint attaches or couples the floater to the chamber, requiring that they move, or stay motionless, together. The giant Gclamp clamping the floater to the chamber does this (with the "spring" of the buoyancy squeezed between the floater and the chamber floor). The external restraint decouples the motion of the chamber (which is moving up and down slightly on the scale) from the motion of the floater, which is either clamped to the external frame below the scale by your giant Gcramp, or is being pushed down by something that is also attached to the external, motionless frame like my body and hand. So the floater pod could be held in exactly the same relative position inside the chamber either way, but with internal restraint it can't move relative to the chamber. You can't pull yourself up by your own bootstraps.

@Wildew... that is indeed an interesting result. Any chance of a video showing the effect you describe? Are you sure your plugging of the leaks isn't responsible, rather than the increased load?

@fletcher: OK, we are in broad agreement then. I still can't see, from these simple demonstrations and experiments that I've been doing or that webby and wildew are reporting, see3d is simulating, where any work advantage is entering the system. Saying it comes from the other Zed isn't an answer, since the other Zed is getting its work advantage from the first one. So... keep the ideas coming. I just hope somebody hasn't mixed up the pieces of this jigsaw puzzle with some other random one.

@MT: So, has the large OU result in your spreadsheet sim gone away? I wasn't quite clear on your last posting if the error had been found and corrected.

We have seen some interesting experiments, with efficiencies as high as 80%. In the Zed, there are a surprising number of variables, and as we know, less than optimum values in these variables are not just additive, they multiply up. So optimisation is elusive, and not achievable overnight. See3d is our biggest hope of optimisation at this point. If 100% is achieved, then the big question becomes, how much of the energy in the exhaust can we utilise without bringing things to a stand still. Let us remember that it took Wayne four years to get to the point where he is at. And yes, I know that opinions differ as to just where that is.


It is refreshing to see that by and large, we are having sensible discussions and treating each other like gentlemen. That, in my opinion is fertile ground for growing the seeds of truth.


Regarding the breaking the bottom of the bottle out by pushing in the stopper. This should come as no surprise to anyone. All we have here is a standard hydraulic jack, with the slave cylinder arranged upside down.