Suggestions for small pressure pump?

Hi,
This is my first post here, so please excuse if its off topic.
I am building a model submarine capable of deep submerging, and to provide
its buoyancy control I need a pump capable of operating at a pressure of up
to 100 million Pascals, (= 1000 atmospheres, ~ 14,700 psi).
It has to push ~0.1 litres of a selected fluid (I get to choose this -
probably a non-compressible oil?) in under 15 min.
The power source is not a concern, but the design of such a pump is a little
tricky to my non-expert mind.
My inital idea was a simple piston, with a 1mm^2 bore area, running at 10
pumps per second, driven by a cog and hinged shaft, with a stroke length of
20 mm. ( A 1mm^2 area at 14700psi gives10Kg, or ~22 LBS weight force.).
Valves would control the flow direction.
The cog would be driven by worm drive, with possibly one gear reduction in
between.
Im trying to conserve energy, so need to minimise # of gears.
My concern with this is the compression stresses on the stroke shafts, and
the resulting frcture potential, and so I started wondering if a "pulling "
pump would be better, so as to put the shaft(s) in tension. Im thinking a
very high strrength steel, like lathing back a long 1.6mm dia. drill bit,
might be the simplest way to go, but a witha disimilar bore metal, I may
run into thermal expansion coeff probs....
Anyway, my questions are...
1. Is a piston pump, the best way to go, for simplicity, and practicality?
2. Is there any other pump designs (eg turbine, worm?) that could be a
better choice?
3. For a piston - type, is my initial idea roughly on the right track?
4. What kind of source metals should I use? ( I dont have a foundry or
anything fancy... so its hardware stores, and maybe some hobbyist lathes /
tools to get the job done).
Any comments would be appreciated.
TIA.
Dave Merrett,
Salisbury, South Australia.
Reply to
Simone Merrett
Loading thread data ...
Just x-posted to a more appropriate group.
And have you visited the sub-committee site?
It's probably the best place to start.
Cheers, Gary B-)
Reply to
Gary R. Schmidt
This is way off-topic for u.r.m.r., but it does sound interesting! You might be better off posting to a model boats newsgroup. Are you quite sure about the pressures involved?
On 12/02/2006 08:23, Simone Merrett said,
Reply to
Paul Boyd
Anyone who doesn't already know the answer to the question isn't qualified to be around pressure vessels.
Just who is going to see your model at 30,000 feet, how will you control it, and do you have enough mega money for trips to one of the ocean trenches to run it? Somehow, something seems terribly wrong here. Wrong newsgroups, wrong question, impractical concept.
IIRC, ultra-high pressure pumps are staged, anyway.
Reply to
3D
Without wishing to dampen your enthusiasm, to compress any fluid to those pressures you will have to be sure of the purity and cleanliness of them. Air at 6000 psig holds dangers of dieselling, so pressure release has to be gentle and controlled. Newtonian fluids such as oil and water do not compress but can flash off to gas - each having its own unique temperature. The forces involved are going to be high and I doubt if a reciprocator could be provided with crank bearings sufficiently strong.
Regards
Peter A Montarlot France
Reply to
peter abraham
Hi, This is my first post here, so please excuse if its off topic. I am building a model of a Trident submarine capable of firing off miniature missiles while submerged, and to provide its propulsion, I need a working nuclear reactor capable of fitting in a submarine about one meter long.
The power source is not a concern, as I have access to a ready supply of enriched uranium, but the design of such a reactor is a little tricky to my non-expert mind.
My inital idea was a simple PWR, with an output of 32 gigawatts, etc
My concern with this is the compression stresses on the turbine shafts, and the resulting frcture potential, and so I started wondering if an AGR would be better, so as to put the shaft(s) in tension. Im thinking a very high strrength steel, like lathing back a long 1.6mm dia. drill bit, might be the simplest way to go, but a witha disimilar bore metal, I may run into thermal expansion coeff probs....
Do you think if I make my own whitemetal bits and use traditional solder, that will be any good for the reactor containment vessel?
Also, does anyone know whether Hornby still supply the Trident missiles with working 2 megaton warheads from the "Thomas the Tank goes Nuclear on Hogwarts" range, or will I have to make my own from brass etches?
Any comments would be appreciated. TIA.
Steve, Rampton, England
Reply to
Steve W
You are going to have problems with flow past the piston. A bore of 20mm and a stroke of 1mm would be easier ;-) 1000 atmospheres pressure is extremely dangerous and is way beyond you if you're having to ask questions of us! Think more in terms of one-three atmospheres pressure to be practical.
You may run into problems a 1-3 atmospheres pressure!
At the scale you're working in, a pump is probably the only workable way to go.
No, clearances would reduce efficiency to nearly zero.
Think in terms of clearances in proportion to bore - you can't make a 1mm bore pump. Consider the load on the big end bearings at the pressures you're considering - that's a BIG bearing area! You might as well go for the big bore/small stroke. Consider the pressure on the "head" of the pump - you will need either to make the head and bore in one piece or you're going to need some big bolts!
At 14,700lb/sq.in most available metals will leak! You can't connect the pump to anything - it will have to be part of a fixed circuit built in solid metal!
Regards, Greg.P.
Reply to
Greg Procter
Absolutely - I suggest that a suitable dry test spot would be any underground railway station where any component failure would be relatively confined.
Reply to
Greg Procter
Don't be daft, Greg. There is a London Transport bye-law specifically forbidding spitting, smoking, drinking, or the conveyance of thermo-nuclear assemblies or any other device likely to cause a public nuisance on any Underground train.
Cheers, Steve
Reply to
Steve W
if you plan to test it in a public place then shouldnt you consider lead free solder ?
Cheers, Simon
Reply to
simon
Don't you be daft as well, Simon! If I was to use lead-free solder, then we'd have radiation leaking out all over the place through the joints, wouldn't we? And that would be the end of the W family line.
Let's just stay practical here.
Cheers, Steve
Reply to
Steve W
Bit selfish if you dont mind me saying. It was of that line that I was thinking and the darwin award that would surely be yours.
Cheers, Simon
Reply to
simon
I'm curious about something here. How exactly does this pump system control buoyancy? It would seem that simply moving fluid from place to place doesn't change the average density of the overall machine much--if a small volume of water exterior to the hull is replaced by this fluid, is that going to be enough? I'd have thought that a better bet would be to have a cylinder filled with gas (maybe even air, but there's probably some reason why a gas would work better) and then use a piston worked from inside the hull to change its volume.
If the difference in mass of 0.1 litres of the fluid versus the same amount of water would do the job, think how little volume change of the gas would do the same. What would count here would be the specific gravity of the fluid/gas (want something either much larger or much smaller than 1--or some other figure if it's salt water, which presumably it is since the depth is so great), and I'd have thought a gas would be a better choice. Unless the fluid is mercury, maybe.
Oh hell, now I'm thinking of something even more stupid. Why not just control buoyancy by extruding a solid bar through the wall of the hull? A 0.1 litre volume change ought to be easy to achieve.
Or even warp the hull by jacking the sides apart. 100 ccs of volume change, how hard could that be? Solve all your pressure-sealing problems right there.
Reply to
jpurbric
I have nasty feeling that you rotten pommy bastards are not taking this question seriously and are mocking this chap - or is the boot on the other foot or even hidden in his anarok?
Reply to
peter abraham
"peter abraham" wrote
Hey, you're a pom yourself, living in France doesn't negate that! ;-)
If I wanted to find our about pressure pumps would I post to three model railway groups - on each in the UK, USA and Australia or would I find a group which was more appropriate?
John.
Reply to
John Turner

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