Overunity (what is it?)

[TechStuf]

I won't ask any more and if you don't provide evidence the readers of the thread can draw their own conclusions.

Time will tell.  And as for the readers of the thread,  I'm fairly certain that a goodly number of them are capable of using the "search" function on this site to find further information, as the topic has been re-visited "once or twice".

You're too jaded, you must be communist Chinese.

See, I can make leaps in logic while ignoring evidence too.

I think it obvious that my "vice" is FE.  As for your use of "Hoe", that "cracked" me up.

I'll tell you what.  Think instead about having ssex with a 1974 Sylvie Kristel in bathroom of an airplane during a long transatlantic flight.

Wow.  With delusional fantasy skills like that....Umm....who needs drugs?





TS

[MileHigh]

I'll make an appeal to the readers of this thread:

If anybody can provide some links that back up TechStuf's claims about cavitation I would be happy to have a look at them.

[TechStuf]

 
Well, it seems obvious that you have fingers....


Perhaps use them for typing a few bits in the search field.


As a wise man once said,  "These aren't fart bubbles in the tub we're talking about here".  (I paraphrase)



TS

[MileHigh]

Webby1:

Just for "fun" I tried to look up the tensile strength of water.  It was one of those cases where the search was frustratingly difficult.  Finally I found what looked like a credible link that stated it can vary between one and 25 megapascals.  It depends on things like impurities in the water.  So let's say for argument's sake it's two megapascals.  Converting that to psi gives you the tensile strength of water being 290 psi.

Air pressure is 14.7 psi.   Let's imagine you have a metal cylinder with a closed end and an open end.  It's filled with water and the cross-sectional area of the inner cylinder is five square inches.  So if you have a piston in the cylinder and a machine pulling on the piston and slowly ratcheting up the pulling force, the machine has to pull with about 1450 pounds of force before the "break" happens and the water cavitates.  After the cavitation, then you are only pulling against the outside air pressure, which would be about 73.5 pounds.

So as you can see in this thought experiment, imagine the pulling pressure from the machine slowly increases to the point where it hits 1450 pounds of pulling force.  During this whole time the piston is barely moving.  Then, all of a sudden, the situation changes and the machine is pulling with 1450 pounds of force, but the resistance to the pulling has suddenly dropped to 73.5 pounds.  So the piston will suddenly fly off in the direction of the pulling force.

Now relate that back to the story of the pump speeding up and the power consumption dropping when the cavitation starts.  Obviously they are not directly comparable situations, but at least you get a sense of the dynamics at play.

MileHigh

[Farmhand]

@MH
Im not sure how it would work in the drum setup with the holes drilled in it,but with any other water pump,once it cavitates,the load come's off the motor-meaning it draws less current.This we seen all the time in the mine's,with both the water pump's and hydrolic power packs.We found this out when trying to figure out why the surge breakers kept tripping.So myself and the sparky sat there and would watch the amp meters on the motor's.The pump would cavitate ,and the current draw would drop.But when the pump grabed again while running flat out,it would draw a shit load of current in one hit,and throw the breakers.
So from my experiance,cavitation reduces the load on the prime mover. The same applies for boat.When in my youth,and racing formula 3 tunnel boat's,once you trimed up to high,the prop would cavitate,and RPM would go sky high. That was also the end of the prop aswell-high carbon S/S melted in a flash. Now that takes some heat.

But like i said at the start,i dont know if this would be the same in the drum setup?.

I haven't got far reading this thread yet, but it seems to have gone off topic where I am at, anyway about the cavitation.

How about this theory, the water gains most of it's heat before cavitation begins. The in-out measurements should begin when the device is first turned on and continue for some period after cavitation has been going.

I know what cavitation does when it happens with a prop on a boat, suddenly the engine screams with less load and the boat slows, usually an operator with any sense will reduce the applied power to stop it as quick as possible. In a boat the heat created before cavitation occurs is left behind, with the drum heater I'm guessing the heat remains local.

Cheers

P.S. most boat motors that have cavitation issues usually have an anti cavitation plate or surface which would seem to increase the water pressure around the propeller at a cost of more drag.