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# The physics of force transmission in air versus water pumping

Have you read anything of what was posted? Thanks.

Originally Posted by marinera
Great. We are addressing the key point finally. Stop here for a moment please: you are at 5hg in water. Which force the penis has to fight to expand? The compressive force of water, right? Which force the penis has to fight when pumping with air? The compressive force of air, right? What those who pump in water feel, is not more expansion, but more force : more compressive force on their penis, which has to fight an higher force to expand.

That’s why they say that, with the same level of force, they get less fluid build up with water pumping than air pumping. No explanation of less fluid build up with water pumping is satisfying, IMHO, other than this : penis, to reach expansion, has to fight more compressive force in water than in air. As an analogy, experienced pumpers do recommends to pump wrapped to minimize fluid build up (I think it was Gprent that gave this advice, could be wrong though).

Now the next stage: when pressure drops, you pump out more water; well, you could pump out more air when pumping with air, when pressure drops - and you’ll need less force than pumping out water. Air can expands means not that much: air will expand only where there is no penis. In the same perspective, penis will expand only where there is no water and will expand more where the water is less dense - at the top of the cylinder.

Giving that the pressure is higher at the bottom, when pumping with water (I know you believe this is a negligible factor, but I don’t believe that), together with the bouyancy force and the compressive force on the sides, you’ll have that, when pumping with water the penis is more pulled ‘ahead’, when pumping with air, penis is expanded in all directions - so, at the same level of total pulling force, you’ll have more girth expansion in air than in water.

Hope it is clear what I’m meaning. This is the picture that, so far, seems more to makes sense to me.

Fuck, it was a fatiguing post.

I get what you are saying Marinara, but its incorrect, as far as my knowledge goes. Perhaps others can chime in here to help sort this out.

Happiness begins where selfishness ends!

I’m right searching for a member with an operative knowledge of this field, Sparkyx, and with NO direct experience of pumping, so with no bias. Although I’m doubful a consensus will be achieved on the short term. I think thought on this has to, uh, ferment for a while, or otherwise saying, to cool down. Consciounsly or not, people who has tried water pumping will have a positive bias for this - if not for other reason, because they would suspect having thrown money buying a bathmate :) .

Fair enough.

Happiness begins where selfishness ends!

Not found the right guy who could help yet.

It seems the disagreement has narrowed, though, re-reading this :

Originally Posted by sparkyx
So, we remain at that an impasse. I get your position that the penis cannot expand into an incompressible medium (water), but I’m saying the penis doesn’t push the water out of the cylinder, it merely expands to fill the empty space when water is pumped out. IF YOU DON”T continue to pump additional water out, yes you are right, it cannot cont to expand.

The way I water pump when using a hand pump, is I bring it up to my vacuum level, lets say 5 in hg. As the penis expands, the vacuum level drops, so I pump it up to 5 again. This allows the penis to continue to expand at a force of 5 in hg. IF I didn’t pump the vacuum level up to 5 again, you are right, it would not cont to expand in that environmental, because it would have to push water out of the tube, and the valves of the pump will not allow it.

…..

Ok. Let’s say you pump to 5hg. Your penis fills the vacuum and pressure drops, let’s say to 3hg. If your penis is in water, the force which is acting on both water and penis is 3hg. This pressure is not enough to compress water; let’s assume (for simplicyt) the force required to both compress and expand water is 20hg (arbitrary number). You are saying doesn’t push water out of the cylinder; so the penis, to expand more at this stage (3hg) should be able to exert a force of 17hg: (20hg-3hg), force required to compress water.

With air, do the same: 5hg vacuum, which after a while drops to 3hg vacuum (because both air and penis have expanded). At this level, penis is expanded less than in water because some of the space will be filled by air, which is expandible where water is not.
But, being the penis denser than air, it will either move air or compress air. The force required either to compress or expand air is lower than 3hg - let’s say for simplicity it is 1hg. So, from this moment ahead, the penis will go expandin more - there is a positive expansive force of [3-1hg= 2hg) - where in water wouldn’t - to expand more in water, you have to pull out water, as we agreed. So, at a pressure that you read in the gauge, of 3hg, in water the penis isn’t expanding anymore, when in air it could be still expanding.

The respective neat total expansion is at this point hard to guess, but the point I’m seeing is that, at a given level of pressure, the penis could expand in air where couldn’t expand in water. What I’m missing here?

(I left out the distinctive effects on lenght or girth, for simplicity).

Originally Posted by midthigh
When you’re pumping you’re not using compressive force at all, whether it’s water or air. A vacuum is being created which is creating an extrusive force. If you approach it from that view, I think you’ll see that the penis is not pressing against water, which is less compressible, it’s being extruded by the water.

I believe we have hit upon the correct explanation.

When you pump water out of the tube, you are reducing the pressure within the water and the relatively higher internal pressure of the penis causes the penis to expand to equalize the pressure between the water and the penis. Or, in other words, the penis expands to take up the space previously occupied by the expelled water. The same thing happens in an air filled tube only a greater volume of air is required to be removed to accommodate the same volume of penile expansion.

Under the laws of physics, both liquids and gases operate in basically the same fashion when an equal force is applied to the fluid in a sealed container. http://www2.ignatius.edu/faculty/de…%20PRESSURE.htm Remember D= M/V and the formula should not change much when comparing air to water.

The difference between air and water is that water is significantly denser (more mols per same area) than water. Because there is a difference in density between air and water, to increase the vacuum in a tube filled with water by 1/2 hg, for example, you would have to remove a significantly smaller volume of water as compared to air. Though Lampwick claims I am faulty in my thinking, I still feel the difference in volume is on the order of 775 : 1, though I concede the actual ratio is probably less

I agree that water is relatively incompressible, in fact, water is not absolutely incompressible. This is why water becomes slightly less incompressible when it is pumped out of the tube (density being reduced), but in comparison to air it would appear to be incompressible.

.

I’m now thinking 5hg is 5hg regardless, either way you have a negative pressure situation which has reached equilibrium so technically both mediums could be argued to be pressing on the penis in the same way that at normal atmospheric pressure you have 14psi pressing on you, you just cant feel it because inside your body is in balance.

I think there are two differences with a tube full of water
1, you can actually feel it on your skin which may make it more comfortable and or beneficial to pumping, and
2, pressure within water, either an increase or decrease is distributed evenly thoughout so pressure within the penis will be distributed evenly,
in an air pump its possible to have areas of high and low pressure i believe ? so all areas of the penis may not experiance the same internal pressure .

Either of these reasons may be why people have better perceived ? or better actual result.

What say you ?

To the point of the thread, I personally feel I get a slightly spongier erection when I water pump at the same relative vacuum as air pumping.

Originally Posted by capernicus1
I’m now thinking 5hg is 5hg regardless, either way you have a negative pressure situation which has reached equilibrium so technically both mediums could be argued to be pressing on the penis in the same way that at normal atmospheric pressure you have 14psi pressing on you, you just cant feel it because inside your body is in balance.
…..

My first thought when I read the original post was this. But, even if the absolute force is the same, we are intrested in how much expansion will it cause.

Originally Posted by capernicus1

I think there are two differences with a tube full of water
1, you can actually feel it on your skin which may make it more comfortable and or beneficial to pumping, and
2, pressure within water, either an increase or decrease is distributed evenly thoughout so pressure within the penis will be distributed evenly,
in an air pump its possible to have areas of high and low pressure i believe ? so all areas of the penis may not experiance the same internal pressure .

Either of these reasons may be why people have better perceived ? or better actual result.

What say you ?

1 is rigth; among other factors earlier cited, there is the fact that penis is very deeply and easy warmed with a water pump.

2 is wrong I think, differences in pressure at different points of the tube will be negligible, differences in water could be significative.

Originally Posted by marinera
My first thought when I read the original post was this. But, even if the absolute force is the same, we are intrested in how much expansion will it cause.
….

I see this is not explicative, so let me emend : what I thought (and still think) is that pressure is nothing else than force per area (F/A). So, if you read 5hg on the gauge, than this is the force that is expanding every squared cm of both the medium and your penis.

As for the absolute expansion, the medium makes no differences as long the pressure is the same, so we agree on this; what I think is the difference could make a difference in the ‘shape’ this expansion is obtained, due to the weigth and density of the medium : water will cause slightly more length-wise expansion and slightly less girth expansion (all other things being equal).

As already said, I think the medium is also relevant if you are looking at the absolute levels of pressure. I think water can create a better vacuum, AKA a greater level of pressure.

But again, we are interested in levels of expansion at the same levels of pressure, not the higher level pressure achievable, since we all agree that even pumping with air can create levels of pressure that are too high as far as safety goes.

Fucking cofusing, isn’t it?

Last edited by marinera : 08-24-2011 at .

I’ve been trying to figure out how to explain this, let me give it a shot.

I don’t think the penis will ever “push” on the vacuum medium (air or water) once it is expanded past its max size due to internal pressure.

Think about it, if you put your penis in a cylinder of either air or water, without any vacuum applied, it will be in a state of equilibrium. That means, if you put it in a closed system, and allow free flow of water or air in or out, none will move in or out once it is fully in.

Now, if you get an erection, it will push out the water or air (again assuming the valve allows it to flow freely.) Once you reach your theoretically max erection, it again is at equilbrium and no more water or air will more in or out of the cylinder (unless you lose your erection).

So, if you are at the max erection your system (blood pressure, valves, b.c. etc) can produce, then any expansion you induce with a partial vacuum, will want to either immediately decrease when vacuum is released or at best, stay at that level. But NEVER be able to further push against it.

That last paragraph is my key assumption for this concept. Said another way, it at best will hold the increased volume temporarily or at worst, reduce volume slightly immediately when vacuum is removed.

There is nothing (in my understanding) that will cause it to want to expand FURTHER other than the amount due to vacuum force applied. It will NEVER exceed the force due to vacuum force applied, because it is already in either a pressure state that is already slightly less than its max or at the most, in EQUILIBRIUM. If it is in a slightly negative state (from its max as in max erection) or equilibrium, then it CANNOT press against the vacuum medium.

If thats true, then water CANNOT prevent expansion any more than air would, because past its max normal expanded state, the penis will not expand past the amount caused by the vacuum itself.

The big difference between water and air then is that for the penis to not fill ENTIRELY the volume displaced by the movement of water out of the cylinder, it would have to resist an almost perfect vacuum. At least a massive vacuum force, because it would be almost airless or complete vacuum.

If you have water in a closed system and were able to draw out all the air, the water would boil and the water vapor would fill the vacuum. However, in our case, the penis will expand to fill the displaced volume, because I assume the penis is unable to withstand the high pressure differential that type of vacuum would be. Air doesn’t create this near perfect vacuum.

Anyway, just my thoughts on this subject.

Someone should start a thread, “If you have technical knowledge of Fluid Mechanics…HELP”. And just link them to this thread. :)

Happiness begins where selfishness ends!

I’m reading this a bit on a hurry, I’ll re-read after for full understanding.

This sentence : “There is nothing (in my understanding) that will cause it to want to expand FURTHER other than the amount due to vacuum force applied. It will NEVER exceed the force due to vacuum force applied..” should imply that the expansion is the same in water and in air (at equal pressuress)? Water is not compressible, air is. But, whe we read 5hg on the gauge, the system is not in equilibrium : inside the tube, matter is striving (so to speak) to fill all the space.

Expandibilty of air or incompressibility of water doesn’t means anything after you create the same level of pressure; it is only relevant before creating the vacuum, because using water requires less work to reach the desired level of vacuum.

I suppose water is limiting expansion - but this is not true, otherwise you wouldn’t read X pressure on the gauge; you suppose air is dropping expansion, but this also is wrong if you read X pressure on the gauge.

I’m start to think my first, knee-reflex thought on the subject was the right one and the discussion about mediums lead out of the right path.

Well I’ll chew on this later. I posted the question on a physics forum, we’ll see if any physics nerds can shed light on the subject.

Originally Posted by marinera

Well I’ll chew on this later. I posted the question on a physics forum, we’ll see if any physics nerds can shed light on the subject.

Good deal.

Happiness begins where selfishness ends!

Originally Posted by marinera
I posted the question on a physics forum, we’ll see if any physics nerds can shed light on the subject.

Did yiu use another hypothetical situation or did you use the penis example?

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