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Author Topic: Cadman’s Hydrostatic Displacement Engine  (Read 27817 times)

Offline Cadman

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #30 on: June 25, 2019, 05:34:04 AM »
Hi Brad,

You may have a point. This is going to require an experiment to sort out.

If you took a 6” ID tube 5 ft tall closed at the bottom, filled it with 7” of water, and dropped a 5.95” x 40” 17 lb slug into it, I just can’t believe that the slug would float and not sink to the bottom of the bucket even if the slug had a 1.5” hole in it.

Ahh, I think I may have it. We are not taking atmospheric pressure into account.?
Well, we’ll see what’s what. The proof is in the pudding, eh?

Regards,
Cadman

Offline tinman

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #31 on: June 25, 2019, 06:21:39 AM »
Hi Brad,

You may have a point. This is going to require an experiment to sort out.

If you took a 6” ID tube 5 ft tall closed at the bottom, filled it with 7” of water, and dropped a 5.95” x 40” 17 lb slug into it, I just can’t believe that the slug would float and not sink to the bottom of the bucket even if the slug had a 1.5” hole in it.

Ahh, I think I may have it. We are not taking atmospheric pressure into account.?
Well, we’ll see what’s what. The proof is in the pudding, eh?

Regards,
Cadman

Your pipe inside a pipe is a good test.
I think you will be surprised at the result.

Like you say,absolute answers are found by testing the actual device.


Brad

Offline Grumage

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #32 on: June 25, 2019, 09:17:01 PM »

Offline citfta

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #33 on: June 25, 2019, 10:06:22 PM »
Thank you Graham!!



Offline lumen

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #34 on: June 26, 2019, 01:20:11 AM »
If the volume of the displacement tube weights more than the equal volume in water (it sinks in a tub full of water) then it works …… Only it don't work with that much weight because the displacement tube could just be water instead!

Offline tinman

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #35 on: June 26, 2019, 03:30:59 AM »
Thank you Graham!!

Graham made an error in his calculations-but easy to make.

Brad

Offline Grumage

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #36 on: June 26, 2019, 12:14:47 PM »
Graham made an error in his calculations-but easy to make.

Brad

Thanks Brad, indeed there was.

The bore diameter is 3/4" in the video equating to 8:1 ratio. So the piston length should have been 6".

Cheers Graham.

Offline Cadman

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #37 on: June 26, 2019, 04:21:37 PM »
For your entertainment.   :)

https://www.youtube.com/watch?v=aTOJpDBS1Bw

Thank you very much Graham!

As happy as I am to see that, I believe there is an error, but one that could easily be correted.

This is how I figure it: and please someone correct me if this is wrong
area of your 3/4” piston with a 1/8” hole is 0.4295 sq in
area of my 6” piston with a 3/4” rod is 26.4126 sq in
that gives a ratio of 61.4962 to 1
the scaled piston assembly weight would be 0.2764 lbs or 125.39 grams. (17 / 61.4962)
I get 5” piston length at 1:8 scale. (40 /8)

And BTW, you don’t need to grease the rod, that just adds resistance. It will either displace the water or not.

If my figures are correct, would it be too much to ask for you to drill partial holes around your center hole in your rod until it weighs 125 grams, then rerun your test?

It would be very appreciated and save me a lot of work if you can.

Regards,
Cadman

PS steel weighs 0.283 lbs per cu in. or 128.37 g


Offline lumen

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #38 on: June 26, 2019, 06:21:33 PM »
The answer is very simple. The displacer is exactly what it must do (in this case ) displace water.
In the vertical position it will sink (displace water) only until the water it displaces equals the weight of the displacer.

Not hard to understand.
To displace water for the entire length of the displacer would require it to weight as much as it's exact volume in water.
If it does not, it will sink only to a point where the water it displaces is equal in weight to the displacer.

I think this will be a problem unless it can be done in an additional step just to raise the displacer.

Offline Grumage

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #39 on: June 26, 2019, 06:26:35 PM »
Thank you very much Graham!

As happy as I am to see that, I believe there is an error, but one that could easily be correted.

This is how I figure it: and please someone correct me if this is wrong
area of your 3/4” piston with a 1/8” hole is 0.4295 sq in
area of my 6” piston with a 3/4” rod is 26.4126 sq in
that gives a ratio of 61.4962 to 1
the scaled piston assembly weight would be 0.2764 lbs or 125.39 grams. (17 / 61.4962)
I get 5” piston length at 1:8 scale. (40 /8)

And BTW, you don’t need to grease the rod, that just adds resistance. It will either displace the water or not.

If my figures are correct, would it be too much to ask for you to drill partial holes around your center hole in your rod until it weighs 125 grams, then rerun your test?

It would be very appreciated and save me a lot of work if you can.

Regards,
Cadman

PS steel weighs 0.283 lbs per cu in. or 128.37 g

You're most welcome.   :)

Brad and I have been in conversation about the issue already.

So the piston needs to be 5" long and approximately 125 g in weight?

Cheers Graham.

Offline Cadman

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #40 on: June 26, 2019, 06:41:30 PM »
5" for 1:8 scale. The 125 g is according to my figures trying to scale the piston weight so the psi under the piston would be scaled.

I think my figures are right but would appreciate a confirmation. My head is quite foggy today.

Respectfully
Cadman

Offline Grumage

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #41 on: June 26, 2019, 06:47:46 PM »
Post script.

Aren't we forgetting about the fact that the displacer piston is attached to the power piston assembly?

Wasn't the figure of 20 Lbs mentioned?

Cheers Graham.

Offline Cadman

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #42 on: June 26, 2019, 08:06:24 PM »
In the analysis I posted, 17 lbs included the whole assembly.
If you want to use 20 lbs, that's OK at this point.
Maybe that's what it needs to be. It's a work in progress.

Cheers
Cadman

PS. We want to use the lightest piston assembly that will do the job. The lighter it is, the more power we'll have on the up stroke.

Floor

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #43 on: June 26, 2019, 10:34:23 PM »
Just an Idea, as an aside, not to distract from the good progress.

In the drawing the fluid is flowing down from the reservoir  to the power piston
it would then lift the displacement piston represented as the weight.  Don't know how
it would then reverse.

Offline tinman

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Re: Cadman’s Hydrostatic Displacement Engine
« Reply #44 on: June 27, 2019, 05:16:29 AM »
The answer is very simple. The displacer is exactly what it must do (in this case ) displace water.
In the vertical position it will sink (displace water) only until the water it displaces equals the weight of the displacer.

Not hard to understand.
To displace water for the entire length of the displacer would require it to weight as much as it's exact volume in water.
If it does not, it will sink only to a point where the water it displaces is equal in weight to the displacer.

I think this will be a problem unless it can be done in an additional step just to raise the displacer.

That is not correct.

Here we are dealing with hydraulic pressures and forces,not buoyancy forces.


Brad