Cadman’s Hydrostatic Displacement Engine

[Grumage]

Good morning All.

Wait, there's more....

My PC keyboard has developed a form of Dyslexia, adding extra letters to typed text so I was unable add to yesterday's post.

Just before my son and I filmed the demonstration we needed to add an extra bit of length to the plastic ball point pen ink tube. My son decided to try the assembly with the whole length of additional tubing. A whole " Foot ( 12" ) " was allowed to sink down the cylinder. For a brief moment we saw the piston sink and stop at a point where the pressure had equalised. The Buoyancy point!

Cheers Graham.

[tinman]

Hi Brad,
No, I think all the hydraulic math is good and works but the displacer weight (buoyancy problem) was never correctly accounted for.
Like a 3000 ton ship will displace 3000 tons of water to stay afloat. The problem is worked in reverse to find the required weight for the displacer to sink.
What is the weight of the water your displacing......so the displacer must weight that much or more to sink, or it will float.

I agree mostly.

Hydrostatic Force is the force due to the pressure of fluid at rest. Whereas
buoyant force is the upward force exerted by any fluid upon a body placed in it.
Hydraulics also incur frictional forces,where as the buoyant force dose not-other that water surface tension.

But as you say,if we use the buoyant force,we can make accurate calculations.

Cadmans piston weighs 5lb.
It is 6 inches in diameter,and 40 inches high--so lets do the math 

Cadmans piston has a volume of 1130.97 cubic inches minus the displacement tube,which has a volume of 70.68 cubic inches. The total volume is 1060.29 cubic inches.
There is 60 cubic inches in a liter,so Cadmans displacer piston will displace 17.67 liters of water.
This is very close to 17.67 kg's or 38.95 pounds.
From that we subtract the 5 pounds for the pistons weight,and we are left with 33.95 pounds.
He had 17 pounds in total,and from that we subtract our 5 pounds we have already accounted for. This leaves us with 12 pounds of gravitational force.
Once again,we seem to be short 21.95 pounds.

Now,if you have a look at my calculations i posted before in this thread ,in the pic below,using hydraulic force calculation's,you will note that i came to a short fall in weight of 22 pounds.
Hows that for close enough 


Brad

[citfta]

Here is a reply I made to Brad at OUR.

Sorry Brad, but you are overlooking a very simple thing that Cadman pointed out at OU.com.  The pressure on the bottom of the piston is going to push the water up the tube just like Graham's video shows.  And that is going to allow the piston to sink because the density of the piston is greater than the density of the water as Graham has hinted at in the thread at OU.com.  I guess only a full scale test will prove this but common sense says that a solid object with a density greater than the density of water will sink if the water can somehow get past the object.  And if I recall correctly Cadman has said he intends to put more than one tube up through the displacement piston.  So that would also change the calculations in favor of the piston sinking.

Respectfully,
Carroll 

[Cadman]

Brad

Only have a minute for a quick post.
Actually the engine is only displacing a column of water 6" high, which weighs 6.26 lbs. Even if you add in the 1.5" x 40" column in the piston it would only be 9.2 lbs.

Cheers
Cadman

[lumen]

Wait, there's more....

Decided to try the assembly with the whole length of additional tubing. A whole " Foot ( 12" ) " was allowed to sink down the cylinder. For a brief moment we saw the piston sink and stop at a point where the pressure had equalised. The Buoyancy point!

Cheers Graham.

Thanks Graham,

Now you can see the problem showing up.
It's not just a sinking weight, it's displacing water and causing pressure to build and stop it from displacing additional water.

tinman,
Thanks for doing the math. I think we both knew that the result was the same calculating pressure or buoyancy.