Water-Pump Ballast Systems

[He Who Shall Not Be Named]

John Darnell and Steve Warner really should be mentioned here. John Darnell produced the first truly affordable kits for those wishing to enter into model submarines here in the UK. His hulls are still produced, now by Models by design.

Steve Warner is really the main modelmaking arm of OTW. He stays out of the limelight, but he is the man responsible for the hull masters.

Very good.

Andy, and the rest of you, keep this going.

Marshall Clark and Jim Cristley also come to mind.

David,

[Subculture]

John Darnell and Steve Warner really should be mentioned here. John Darnell produced the first truly affordable kits for those wishing to enter into model submarines here in the UK. His hulls are still produced, now by Models by design.

Steve Warner is really the main modelmaking arm of OTW. He stays out of the limelight, but he is the man responsible for the hull masters.

[He Who Shall Not Be Named]

Andy mentioned Nick Burge.

Now, there was an r/c submarine inventor and builder of the First order. He was truly one of the innovators and talents in the field!

On that thread (and you'll have to excuse me if I get some of the spelling wrong here) I present a few more notables in the field:

Brother Otto, Dave Weeks, Dave Manley, Mike Dorey, Ray Mason, Bob Dimmick, Dave Welch, Skip Assay, Norbert Bruggen, Ron Pierrot, myself, Art Meyer, Matt Thor, and others.

Significant people who invented or have refined the devices, produced the hull kits. People who have advancement the game of r/c model submarining.

My success in the field is due, in no small part, because of the things I learned from others; I stand on the shoulders of those who came before me and to those today who are my peers.
No genius works in a vacuum.

David,

[Subculture]

You'd have to rely on positive buoyancy or if that was lacking, due to a leak or caught in weeds etc. a back-up system to bring you to the surface.

I don't know if the latter is being fitted.. The system is being built for another member, who purchased an old Eden models Ohio (now Sheerline). These early Eden Ohios used a Craycraft dive module, which was based on a design by Nick Burge.

The dive modules were among the most expensive and elaborate I've seen produced for the hobby market. They had a small twin cylinder compressor on board which sucked air out of the central ballast tank and stored it under pressure in the forward compartment of the dive module. Probes mounted in the tank detected when the water level reached about 80% of the volume and cut the current to the compressor to prevent it sucking in water and flooding the boat.

The system worked well enough but had a few caveats- the air bubble in the tank is compressible, as the tank is vented at the bottom. This results in a boat that gets heavier as you dive deeper.

Also the air sucked out of the ballast tank is very humid. This air is stored in the same area as the compressor servo controlled valve, electronics for controlling the pump etc. Electronics and water isn't a very good mix.

In practice there are a lot of these systems doing good service out there. Most submariners rarely dive beyond a couple of feet, and the electronics seem to hold out well against the humid atmosphere.

However better systems exist, and as the module in the Ohio was in need of a minor refit, it was decided to try a different system.

[Slats]

Tank will be vented to the surface via a mast I reckon.

But how then do you empty the tank at depth? Looks like you can't.

[Subculture]

Tank will be vented to the surface via a mast I reckon.

[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

[Albion]

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

[Subculture]

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

The speed of the system is reported as fast.

[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]

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.

[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]

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.

[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 :)

[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