Gahh.... there is a lot to catch up with. I'm not going to be able to comment yet on the various spreadsheets and calcs above; I've been busy with an experiment of my own, on a feature of the Inverted Travis Effect and virtual water.

I think there is some relevance to the Zed topic under discussion here, in some way. I have just started thinking about this today, really, and it needs some time to "sink" in.... no pun intended. Anyhow, there is a definite difference between restraining your pod by locking it down internally to the chamber, and restraining it by holding it under with some kind of externally applied mechanical stop or force. The key to the ITE and virtual water appears to be that you must have your pod restrained or pushed down externally by something that isn't attached to the chamber holding the water that is surrounding the pod. The "virtual water" effect corresponds to the buoyancy force expected from the volume (displacement) and weight of the Floater.
I think. Maybe.

Here's the video of the experiment. Kind of long. In the "description" on the YT page I give the complete experimental report with the numbers measured and calculated, such as they are.
http://www.youtube.com/watch?v=1iijUjtkV-E

Quote from: fletcher on September 13, 2012, 08:55:04 AM
Hi .. I think you'll find your answers in the attached pic I made - it is a representation, & I used 'g' at 10 m/s^2 just for ease of calculations readability.

In essence it's a tortoise & hare race story - lifting slowly & surely with very little fall gradient uses least/minimum Work Done Joules by you to give the system PE J's - quick is costly because you have to lift higher to get fast transfer.

NOTE that the system cannot gain PE without a minimum of the SAME expenditure of Work energy it took to raise the system PE - SLOW is the most optimal & efficient method to achieve this efficiency, IMO.

So, in the last diagram, I'm not sure which value to take, so I'll do both.

The correct one I think is to do the Sum of PE's with Pod = 352.5 J, starting from 70.5 J. So minimum work done would be 255 J.

For completeness Sum of PE's without pod = 168.6 J from 70.5 J = 98.1 J work done, but this seems incorrect as we don't have to lift Bluey so high so I'll stick to "with pod" above.

My calculation for the average buoyancy force was incorrect in my last post, if we assume no extra water was being introduced. I had assumed "totally submerged" to ".2m not submerged", however, that doesn't actually mean the pod was raised by 0.2m.

So the average buoyancy force over .2m is "totally submerged" to "not submerged at all". Essentially I'm thinking initial buoyancy force of 367.9 J / 2 = 183.9.

Annoyingly this still leaves us short (In: 255 J, Out: 183.9 J) , so I'm going to get in to MT's spreadsheet next and see if more improvements can be made.

Quote from: fletcher on September 13, 2012, 09:07:39 AM
Sounds like its time to get your hands wet.

Yeah I should do, I've been trying various things with pint pots and tubing in the vain hope that I don't post anything too foolish! 

Amo

Quote from: MT on September 13, 2012, 03:40:14 PM
Hi guys,
attached is updated spreadsheet v2.1. Before opening it, rename file extension to xlsx so it opens correctly. Checked but could not find further errors in it. Still getting COP>1, see for yourself. COP>1 is not just for a specific dimensions of cylinder and pod, dims can be in certain range and still be over 100%. How is the work calculated is described in my previous post.

Interesting (also a bit ironic after spending quite some hours in Excel) was that when I finished checking the sheet I realized we can compute work done on pump water much easier.
Using the dimensions of cylinder and pod as in the sheet:
Precharge step needs 28 liters raised up to 0.9m
Stroke step needs 78 liters raised up to 0.1m + we need to lift the precharge 28 volume 0.1m


precharge work = m*g*h = 28 * 10* 0.9 = 252
stroke part 1 = 78 * 10 * 0.1 = 78
stroke part 2 = 28 * 10 * 0.1 = 28

total work 252 + 78 +28 = 358
Guess what that 358 is the same work that is relatively complicatedly computed in spreadsheet, cell F84.

respect,
Marcel

Argghh..

Yes, the renaming allowed me to open it with no problems.
BUT

NO. Whenever I see false precision......  ten digits after the decimal point ... I pretty much go blind !! Come on..... all that means is that the number is WRONG. I mean, if you say you have 3.456789236 ounces of something.... and it turns out that you "really" have 3.456789235 ounces or any other number than that precise billionth of an ounce value.... then you were wrong, weren't you.
But since your input measurements cannot possibly be more accurate than, say, the tenth of an ounce, you should really only use two or three sig digs at the most. You say "3.46" ounces.... and you will still be right if the true value is from 3.455 to 3.465 ounces, which is within the limit of precision and accuracy of your measurement.

I still haven't analyzed it to see where your error is, if there is one.... I'm going to have to get over my horror and loathing of false precision first. But thanks for the work, anyway....  but next time, please only list digits that mean something, in your answers.

Quote from: TinselKoala on September 13, 2012, 07:00:13 PM

Gahh.... there is a lot to catch up with. I'm not going to be able to comment yet on the various spreadsheets and calcs above; I've been busy with an experiment of my own, on a feature of the Inverted Travis Effect and virtual water.

I think there is some relevance to the Zed topic under discussion here, in some way. I have just started thinking about this today, really, and it needs some time to "sink" in.... no pun intended. Anyhow, there is a definite difference between restraining your pod by locking it down internally to the chamber, and restraining it by holding it under with some kind of externally applied mechanical stop or force. The key to the ITE and virtual water appears to be that you must have your pod restrained or pushed down externally by something that isn't attached to the chamber holding the water that is surrounding the pod. The "virtual water" effect corresponds to the buoyancy force expected from the volume (displacement) and weight of the Floater.
I think. Maybe.

Here's the video of the experiment. Kind of long. In the "description" on the YT page I give the complete experimental report with the numbers measured and calculated, such as they are.
http://www.youtube.com/watch?v=1iijUjtkV-E

Great vid.

FWIW, IMO, when the Pod is restrained at its highest position [although still completely submerged] the system is in equilibrium, although you had to put Work in to depress the Pod & raise the water level internally initially - [I bet if you did that on a scale it would also read an extra 200 gms or so as you pushed the Pod under] - when it is against the stops the system parts have no potential or ability to move in any direction except together i.e. the forces are there, they just can't be used to do Work because no further displacement is possible.

When you depress the plunger you do more Work on the system again - the system wants to find new equilibrium because you've added the extra Work into it - because the two main players are not 'hard connected' i.e. they are separate entities for this part of the exercise, then the system will try to establish new equilibrium of forces - so the scale [a calibrated Pressure meter] registers the force you put into holding down the Pod, because the parts are not bound by being locked together as one & effectively try [but do not succeed] to move apart, registering as wt force on the scale - but force with no distance is not Work.

I would predict that if you locked down the Pod again at the new lower level [just a split pin or something] then the scale would go back to 1035 gms thereabouts or whatever the combined weights of all the parts was.

Well, that's my take anyway - it will be interesting to see what you or others conclude.

P.S. your timing was impeccable - just this morning I started drawing up some pics looking at similar things with a question for see3d & his sim, related to them - maybe on the weekend I'll finish them.

........

EDIT: If you wanted to check whether pressure wasn't linear I guess you could make up a kit to measure apparent weight of a submerged mass more dense than water - i.e. the water filled beaker on a surface, a mass suspended in it to a balance beam scale - vary the depth the mass is submerged to see if there is any difference in the apparent weight with depth ?

Just a suggestion.

@fletcher.... heh.... if the geometry of the dense object is irregular there won't be a smooth relationship between the simple depth of lowering into the water and the buoyancy force, but once it's completely submerged, if it's rigid and sealed, there should be no change in the force with depth.
Yesterday I made up some crude drawings to see where the "opinions" lay on this issue of non-linear pressure changes with water height.
As I've said before, I think that I saw the effect of a "step" in the pressure function in my PerPump 2.0 with functioning TinselZed, as the pump output pressure was increased during the time the riser was free to float, and then dropped abruptly when normal filling of the lower chamber resumed. Some people would call this a non-linear pressure change.

Anyhow, here are the sketch "koans" for meditation. In each case the outer chamber is sealed and you are injecting water at a _volume regulated_  constant rate at whatever pressure is required (you have a magic pump), and you are asked to predict the rough shape of the resulting gas pressure vs time function as the chamber geometry fills and the water level rises.