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### Author Topic: Cadman’s Hydrostatic Displacement Engine  (Read 35650 times)

#### lumen

• Hero Member
• Posts: 1388
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #45 on: June 27, 2019, 06:07:17 AM »
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.

#### Cadman

• Sr. Member
• Posts: 409
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #46 on: June 27, 2019, 10:36:48 AM »
You are both right. It finally came to me, how to say what makes the difference for the displacer, why the water will move upwards.

Pressure differential.

Both the piston and water column exert force and create the pressure. Less pressure above the piston means the lighter body, the water column through the displacer, will be forced up by the pressure below the displacer piston. This not the same situation as the water feeding the pressure piston.

Regards
Cadman

#### Grumage

• Hero Member
• Posts: 1113
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #47 on: June 27, 2019, 05:16:11 PM »
I'd like all readers to think about this word, I don't think its been mentioned as yet.

" DENSITY "

Cheers Graham.

#### Grumage

• Hero Member
• Posts: 1113
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #48 on: June 27, 2019, 09:47:38 PM »
More entertainment.

https://www.youtube.com/watch?v=gx0U0Wu9quQ

#### Cadman

• Sr. Member
• Posts: 409
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #49 on: June 28, 2019, 12:59:56 AM »
More entertainment.

https://www.youtube.com/watch?v=gx0U0Wu9quQ

That is great! I guess that puts that issue to rest.

Thank you sir!

#### Grumage

• Hero Member
• Posts: 1113
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #50 on: June 28, 2019, 12:21:33 PM »
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

• Hero Member
• Posts: 5365
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #51 on: June 28, 2019, 02:45:15 PM »
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

• Hero Member
• Posts: 1050
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #52 on: June 28, 2019, 04:31:58 PM »
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

• Sr. Member
• Posts: 409
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #53 on: June 28, 2019, 07:09:33 PM »
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

• Hero Member
• Posts: 1388
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #54 on: June 29, 2019, 04:39:20 AM »

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.

#### Grumage

• Hero Member
• Posts: 1113
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #55 on: June 29, 2019, 12:00:32 PM »
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.

Hi Lumen.

Yes indeed, we can see the problem. However that problem occurred at twice the value of the working parameters shown by Cadman.

As I see it the major problem will be the size chosen for a prototype. At small scale frictional losses will become its " Achilles heel " particularly with piston seals.

In this scenario " BIG " will definitely be " BETTER. "

Cheers Graham.

#### Floor

• Guest
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #56 on: June 30, 2019, 12:24:56 AM »
Been studying the design.

Here are some observations / opinions.

#### Floor

• Guest
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #57 on: June 30, 2019, 01:32:56 AM »
One more thing cadman,
congratulations

floor

#### Floor

• Guest
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #58 on: June 30, 2019, 01:59:22 AM »
One more, one more thing.

The check valve at the bottom of the displacement piston
needs to be simply closed / not functioning as a check valve during the
lifting of the displacement piston.

The device works because :

1. With that displacement piston valve closed, during the piston lifting
gravity is assisting that lifting.

2. Gravity does all of the work of lowering the displacement piston.

3. The combination of 1. and 2. is what enables the higher lifting of the fluid,
when the piston falls.

regards

#### Floor

• Guest
##### Re: Cadman’s Hydrostatic Displacement Engine
« Reply #59 on: June 30, 2019, 02:29:51 AM »
Another observation.

It is best that the valve at the bottom of the displacement piston, is closed upon
its arrival the bottom of its decent.  Other wise fluid will fall in the displacement
piston tube, while rising (due to hydro static pressure) in the supply tank .
An un needed waste.