If you go to utube and type in(rc submarine piston ballast) you will find lots of videos.
Maybe you might find something that will be of interest to you.

Martin.

Thanks Martin. That video is exactly what I was looking for. Now, your next project is to find the same for a piston tank solution😀😀😀😀😁😁😁😁😁⚡🤓

Yes, that is what I almost got around to telling Doug but sleep interfered.😊

Hi Peter,
This might help.

I have noticed that a lot of model submariners use compressed air from airbrush containers.

Martin.

Shucks!
Nothing happening😐
"No shipwrecks and nobody drowndin ...
In fact nuthin to laff at at orl!" 😁

So I'm off to me bunk 💤💤💤
Up the wooden stairs to Bedfordshire. (Or in my case down!)
C U on the morrow, i.e. later!
Sweet dreams people. 😴
😎

Ho Peter,
What gas do they use then?
I was actually thinking more of Sparklets syphon soda blubs, er 'hic' 😮
If you want to go the gas route I suggest you look for some US model sub sites.
They seem to favour gas tanks whereas in Europe the piston tank is more popular.
I've been wondering for a few days why our antipodean colleagues haven't chipped in to this discussion! Reilly 4 for instance. He has at least one great sub model and has posted super videos of his underwater travels.

BTW Pete,
It doesn't end with just the ballast / dive tank system!
If you want to keep an 'even keel' while travelling underwater the following are highly recommended.
- Attitude controller (Pitch Controller), which constantly adjust dive planes to stop the boat pitching up and down, or even porpoising along the surface 😮
- Reverse detector. This actuates as soon as the motor reverses. It commands the pitch controller to reverse the action of the dive planes if you also want to be able to reverse while underwater. Otherwise the planes would have the opposite effect to that which is required and make the pitching worse instead of smoothing it out.

Of course you can still sail and dive without these but depth control will be very difficult.
You'll be constantly correcting and correcting the corrections 🤔 Just like with a dynamic diver.
The Yo Yo effect!
Cheers, Doug 😎

Thanks Martin. What I could really do with is a few plans of the different systems. I have a lot of pictures now so I will study them and work out a plan. As Doug and DG said, the piston route seems to be the easiest once the thread and nut system is sorted. If I did choose the gas system, by the way Doug, they do not use CO2 for this mainly due to the excessive pressure and the environment, I would like a drawing of the pressure vessel so that I could make one. The drawback here is the electronics to operate it. The more I write the more likely it is that I will go for the piston route.

Hi Peter,
This explains some of the different systems.
https://www.gettingstartedinrc.com/rc-submarine-ballast-systems/

Martin.

Hi Doug,
Er .. No! Due to the cooling effect of the water it will actually contract, thus reducing the internal pressure. Venting air from the dive tank to the internal tube counteracts this effect.

Thank you Doug I stand corrected.

Martin.

Hi Peter,
"I am slowly being swayed towards a gas system where the water is pumped in and whilst being pumped out, the gas bottle replaces the air. This will enable a deeper dive than periscope depth. You just have to avoid running out of air."

Hmm! Must admit I also once considered experimenting with something like Sparklets bulbs.
But they are very difficult to control. How often have you sent the soda down one side of the glass only to see the whisky shoot out of the other side?😭
Also they run out! Not to mention all that CO2 release to the atmosphere - Bad Footprint😮
I concluded it was best to leave that to less critical things like experiments with torpedoes.
A 'gas tank' per se would be very heavy.
One of several reasons that I opted for the Akula with a piston / tank solution.
Cheers, Doug 😎

"why would you risk losing sight of it."
That's the whole thrill of it Martin.
"Obviously the deeper you go the higher the pressure, the air inside the compartment will expand."
Er .. No! Due to the cooling effect of the water it will actually contract, thus reducing the internal pressure. Venting air from the dive tank to the internal tube counteracts this effect.
Trick is not to overdo it and blow the seals.
Some systems use two smaller tanks and vent to forward and aft sections separately. Too complex for me😮
I'm off to the cellar to dig out my Akula kit and read up on how that should work.
Cheers, Doug 😎

I have an open mind at the moment. I suppose with this method an automatic trim device would be essential.

Hi Doug.
The part of the Danube my house is on has very little flow. There is no danger of it being carried away unless the local Swan takes a liking to it. It is also only 4 1/2 feet deep as well. The river at my house is like a little bay. Perfect for the submarine. I will put a net across the area maybe. This is dependent on me actually finishing this project. My history so far does not look too good regarding project completions.😀
The blow valve is a small version of the gas tank ballast system. It is quite small and just blows compressed gas into the ballast tank to empty.

"Have you looked at the piston and cylinder approaches? These seem to offer the best control... "
I'm inclined to agree Dodgy👍

Hi Pete,
"which would react if signal was lost or can be triggered manually. "
Hmm!? How would you know WHEN to trigger it manually?
May already be too late!

"safety blow valve" what does it 'blow' and where from?
If you use the piston tank method and Fail Safe module it should automatically vent the tank on signal loss or excessive depth. S'pose the same could be applied to a bladder and pump system. Read the book carefully, I'm sure you'll find the inspiration you need in there👍

BTW: have you ever watched a submarine race!?
'bout as exciting as watching grass grow 😁😂

Funny coincidence!
There is a documentary on the haunted fishtank (GEO channel) at the moment about the Apollo programme. 50th anniversary of the first landing coming up at the weekend!
And right now they are showing the background of the 'cardboard, sticky tape and old sock' incident!! They just showed the 'prototype' and one that the crew made😀
Cheers, Doug 😎
PS "I will be running the sub in a bit of a murky river ..."
Recommend then that you fit a brushless motor with some Ooomph in case you get caught by a current! I'd be scared stiff to dive a sub in a river 😮

Peter,
This might help with your decision.



Martin.

Hi DG.
I must admit I have been looking at all of the different options. The piston method looks as though it should not be too difficult to construct. I am still open minded as to which approach I will take but I am sure that I do not want a breather tube restricting the dive depth. I will be running the sub in a bit of a murky river which, I hear you say, should not be allowed to go below periscope depth. My plan was to fit a safety blow valve which would react if signal was lost or can be triggered manually.

Hi Peter,
If you look at the sites that I have mentioned in my text below you will be able to see the systems and get a good idea of how you could make one.

Martin.

Have you looked at the piston and cylinder approaches? These seem to offer the best control...

Good idea Martin. This could stimulate some very interesting conversation.
As for my dive system, I am slowly being swayed towards a gas system where the water is pumped in and whilst being pumped out, the gas bottle replaces the air. This will enable a deeper dive than periscope depth. You just have to avoid running out of air. I am looking for either a plan of the pressure unit so that I can make one or a ready to fit unit. Cannot be too difficult to make. Cheaper too.
Peter.

Hi Guys,
In the thread (motor reversing) we drifted on to the subject of Submarine Watertight Compartments.

Well I am by no means an expert on this subject but I have been following with interest.

Please correct me if I am wrong.

At the depth that most model submariners use there subs is normally at periscope depth or just under especially when the water is not clear.
In a swimming pool then the submarine will be used at much deeper depths.
There are a lot if different WTC's on the market today each having different ways of securing end caps and different ways of ballasting.
Each design has it good and bad points, therefore when considering what system to purchase or make you should consider how you will be using your submarine.

All model submarines will reach the bottom if you don't stop them, and as model submarines are not cheap then why would you risk losing sight of it.

Now this bit is the tricky bit.
The pressures that most model submarines would normally come across are not that great but are greater if using it in a swimming pool.
From what I can see the conversation on wall thickness,depth,and pressure seems to be more on the side of belt and braces.
Obviously the deeper you go the higher the pressure, the air inside the compartment will expand.
Depending on the system that you choose the air pressure inside the tube could increase as the ballast tank is filled forcing the air in to the electrical sections.
Other systems vent the air from the ballast tank and do not increase the pressure inside the tube.

As I have said I am not an expert so please feel free to call me an idiot or something.

As I am sure that we try to over engineer things just to be on the safe side.

Martin.