Water-Pump Ballast Systems

[junglelord]

How come the Static RC Subs are broken down into the two camps of mainly RCASB and LPB. At least thats what I seem to find.

Why is a simple Waterpump Ballast System not more common>

http://www.youtube.com/watch?v=nPIluczFoac&feature=related

I showed this system on this thread.

http://forum.sub-driver.com/showthread.php?t=4

I realize that the Snort also utilizes a water ballast, but it is either full or empty from what I understand. With a two way waterpump, two fish aquarimum valves, one or two urine bladder bag, one could have a very simple, cost effective, static system of control.
:p

How come this is not more common?

[Slats]

If only it was that simple.

I have used many types of water ballast (pump systems) over the years.
I'd say that they are still very much in use and yes they do work.

The system you describe must be fiitted within a dry space - hence the bag filling and emptying ballast within the space acting as a ballast tank controls the dived / surfaced states. The bag my friend in filling creates internal pressure within the dry space, so much so that I have seen end caps blow off WTCs and seals within dry hulled subs can fail using this method too. I have seen first hand big failures where by the pump switch fails to cut off and the hoses to the bag come away from the pump conduits causing massive flooding. All of this can be overcome but its not as simple as you put it. 15 years on in this hobby, I am still learning, and lesson number one about ballast systems is nothing is perfectly simple and without issues. I think people who are using the latest evolution of the D&E Gas system (the Subdriver), are finding it to be quite a simple way to proceed and the addition of the low pressure blower adds to this evolution too.


The current and emerging new ways of doing things over say the last 5 years or so has been RCABS and more recently the snort (Low pressure blower coupled with gas). Its not that water pump systems don't work, its just at the moment the current and emerging methods are being explored and people are finding them very effective. Hence there is lots of discussion about them, and perhaps less on more old school methods.


J

[junglelord]

Agreed and I appreciate the experience.

The one I linked too, was specifically for my Robbe Seawolf conversion.
The person that made that, has never had a leak, or blown the end caps in that particular WTC with the ratio of water which is 200-250cc. Granted that internal system is not good for MANY reason, but of course, external tanks that have water filled by the pump seems good.

I do not want to link to other competitor sites, but one gentlemen is using external ballast water filled and emptied that is basicly the idea with cylinders.

I was thinking the bag outside the WTC ala RCABS, but water instead.
I know the bag must allow proper pitch as well as static dive.
Maybe the one competitor is the only one I have found with neither Snort or RCABS. I found one that also sells water pumps. Again I do not want to post competitor web sites.

I am a newbie. My Robbe is dynamic and only tube tested as of yet. I look forward to my LPB Seaview that is ovbiously state of the art.
I'll drink to THAT!

[Slats]

Agreed and I appreciate the experience.

The one I linked too, was specifically for my Robbe Seawolf conversion.
The person that made that, has never had a leak, or blown the end caps in that particular WTC with the ratio of water which is 200-250cc. Granted that internal system is not good for MANY reason, but of course, external tanks that have water filled by the pump seems good.

I do not want to link to other competitor sites, but one gentlemen is using external ballast water filled and emptied that is basicly the idea with cylinders.

I was thinking the bag outside the WTC ala RCABS, but water instead.
I know the bag must allow proper pitch as well as static dive.
Maybe the one competitor is the only one I have found with neither Snort or RCABS. I found one that also sells water pumps. Again I do not want to post competitor web sites.

I am a newbie. My Robbe is dynamic and only tube tested as of yet. I look forward to my LPB Seaview that is ovbiously state of the art.
I'll drink to THAT!

How would a bag filled with water OUTSIDE the dry section / WTC or dry hull dive the sub?
Think here mate - Being outside - the bag is in the water - so you are just relocating the water from the wet hulled area to a bag within the wet area. Doing so there is no change in displacement. Bag used as WATER filled ballast tanks are always within the dry hulled / WTC space where being filled the Dry area weighs more and you dive.

RCABS works by AIR in the bag acting upon the wet area (i.e. causing positive displacement against the wet area). The air space outside the WTC (within the inflated bag) replaces what was water and you surface. When deflated, the air space that was occupied by the inflated bag is then re-occupied by water and you dive.

J

[He Who Shall Not Be Named]

Good discussion, guys.

I don't have a problem if you link us over to a site that gives us a well presented look at their specific system. Knowledge is a good thing.

David,

[junglelord]

I found this kilo on another forum.
I am sure that you know the person Mr Merriman
Here is a quote

The WTC system is designed especially for the Kilo. It features twin floating piston ballast tanks driven by 2 pumps. Water is pumped into and out of the tanks as required to maintain perfect neutral stability, and allows the submarine to dive and surface.

Extreme precise adjustments and simplicity are the key. The system is fast acting also. You can hover this boat underwater, rock it back and fourth, and return to a perfect hover, all without expensive and complex electronics and systems.

The Kilo also has a inherent stability in pitch when submerged, it wants to stay level all by itself. This is from the special "stability tanks" located inside the hull, on each side of the WTC. These are maintenance free and work amazingly well. On the other hand, they also make it much more stable in roll when surfaced, as compared to a sub without them.


http://www.rpmtech1.com/

[Slats]

It looks interesting enough - too me two tanks in such a small sized model is overkill.
Its a piston tank which is a proven method of ballast control - but again its not a simple or perfect system - no system is perfect.

A shame he does not just state in his ads that its 1/68 (weird scale I know) but as 1/72 scale nut, the difference is 3 inches. Not much but its not 1/72.

The model is very well made and looks quite like a simple assembly. I have e-mailed him to enquire if he sells the hull kits only (without the WTC).

J

[Albion]

As an engineer with 30 years experience of LARGE pumps, i will share a few of the potential problems of a pumped system. I have never tried a pumped system in a model this is theory.

Firstly RCABS and a pumped system share the same basic philosophy, in changing the displacement of the craft, however water is not compressible at these pressures and so is less forgiving.

In a pumped system the action of pumping in water will create pressure which must be held in either the ballast tank or the complete WTC.

There are two basic types of pumps Centrifugal and positive displacement.
A positive displacement pump will always pump the same amount of water per revolution. This is good because it means you can easily calculate your flow /time. However they will keep doing this even when the tank is full, this means something will give, either the tank or the pump. Therefore you will need a pressure switch or level switch to turn off the pump. At these low pressures a pressure switch is not going to perform well. Also with a long tank with sloshing water a level switch may give false readings. baffles may help overcome this - EDIT PD pumps work in both directions by reversing the polarity of the motor

Centrifugal pumps have varying flow with pressure, as the pressure increases the flow drops. so intheory this would be great it will pump until there is no flow:), but a centrifugal pump running at no flow generates energy and eventually burns out. (slats has previously advised of some cent pump failures which would seem to bear out this issue, especially when the pump would initially run at high flow (Zero pressure) where the power is highest, so the pump is cycling from its two worst conditions). Pressure / level switches would help but as before may not give the best feed back for controlling the pump.

Going back to the pressure issue. If using the ballast tank alone to hold the pressure then the volume of tnak must be large to absorb the compressed air. If using then WTC, then care must be taken to ensure no spliggage of water out of the tank in case of steep dive/ rise. Also the presurised air will be damp leading to potential electrical problems.

If i were to try something like this i would use a PD Pump, into baffled tank, which vents into the main WTC through a sub chamber which has a restriction between it and the main tank. the sub chamber would have a float switch, and vent system with traps to avoid water carry over. The restriction should help remove any sloshing or diving action affecting the float switch, EDIT - with a relief valve on the tank to avoid overpressure if switch fails, all theory of course, and with several more common solutions available seems a complex route to take.


My 2cts, BTW there is always Piston tanks :)

[Subculture]

This is the most popular system in the UK. It's largely overtaken the use of a variation of RCAB's which itself was a modification of John Darnells old USE steam pump ballast system.

Piston tanks aren't terribly popular (they do have a small following though) owing to the fact that a lot of model submariners don't have access to workshop machinery, like a lathe, and you really need one of these to make a decent piston tank, unless it's a very small tank- then you can press a syringe into service.

There are commercial alternatives from Germany, but they are quite expensive, so folk tend to look to alternative systems. The water pump system can be built with basic hand tools, with inexpensive items available off the shelf. It's also easily adapted to large or small(ish) boats.

There are at least two commercial systems operating out there that use centrifugal pumps into a sealed tank, and their owners seem happy. The systems tend to pump to one atmosphere- perhaps this is low enough pressure to avoid damage to the pump?

These systems tend to find favour with boats that require a large tank; the centrifugal pumps shift a lot of water. As this system utilises an esposed water surface, it's essential to fit baffles in the tank to prevent sloshing.

Some people use a vented tank with a snorkel, these systems need to be trimmed for slight positive buoyancy.

Other systems I've seen use a geared pump (PD) pumping into a small bag. These require a check valve of some description to prevent the water pushing back out the pump- they do leak a bit. Another variation is to use a peristaltic pump, these are self sealing, so no check valve required, but tend to be rather slow.

The Thundertiger Neptune and Norberts little Delta submersible both use the latter system. The low freeboard of these boats only require a small bag/tank, so the slow pumping action of the peristaltic pump isn't such an issue.

[Slats]

.........
Going back to the pressure issue. If using the ballast tank alone to hold the pressure then the volume of tnak must be large to absorb the compressed air. If using then WTC, then care must be taken to ensure no spliggage of water out of the tank in case of steep dive/ rise. Also the presurised air will be damp leading to potential electrical problems..........

Yes -Been there done that - humid electrics galore and big issues with longevity of a range of electrical devices in the WTC - servos, ESCs, you name it!

A humid boat IMO is a wet boat - sure the concentration of H20 is less than drenched or flooded conditions but H20 is H20 - it is not a friend to circuit boards and electrical devices and has no place in a designated "DRY" space

J

[Subculture]

Here's a new take on a vented tank system that's been developed by a club member for another members 1/96th Ohio. Two centrifugal pumps mounted inside the tank to pump the water out. A servo actuated valve at the bottom which lets water in to dive. Simple, cheap. This is a bit like the snort system in reverse.





If you wanted to get really fancy, you could mount a small trim tank inside the centre of the main tank, and have it fed by a peristaltic pump.

[toppack]

It appears that Vent and Blow would be fairly Slow with that system, since it's a large cylinder, but I guess it would be close to scale speed?
I'm wondering what type of level activated Valve that is, that's used for Vent? I've not seen one like that before? Did he make the valve?

[Subculture]

The valve is scratchbuilt. Alf is a very good builder of model submarines.

The speed of the system is reported as fast.

[Albion]

If the pumps, pump the water out, where does the air come from to replace the lost volume?

[Slats]

If the pumps, pump the water out, where does the air come from to replace the lost volume?

Yes Andy....I was thinking the same. Else aren't you pumping against a vacuum?

J