Hi Modelbuilder

First I must say that I have not read all the comments so far,
Have you had a look on the Association of Model Submariners site (http://www.theassociationofmodelsubmariners.com) you just may fine the answers to some of your questions there.

Fred

Thanks Doug.

Martin.

Hi Peter,
Before I explain the system that I have made I looked at where I was thinking of using the submarine.
As most ponds/rivers/lakes that we use the water is not clear unlike a swimming pool.
As I have no access to a swimming pool that ment I would only be able to use it in water that when the submarine is submerged you would lose sight of it very quickly.
So I decided that I would make the ballast as a separate tank.
I first made the tank without a balloon in it but then found out that when the water was pumped out there was still a small amount of water left in it.
Fitting the balloon solved that problem.
The system that I use is I think the simplest and easiest.
I pump the water in the air is then forced up through a small tube to the periscope and out.
Now as I do not have a solenoid valve fitted the water inside the ballast balloon wants to slowly force it way back through the pump and as the submarine has slight positive buoyancy it will rise to the surface on it own after about three or four minutes.
So that I don't lose sight of the submarine the deepest I would run at will be periscope depth, so to surface I would just pump the water out and the air will be sucked back in through the periscope and in to the tank.
In the photos you can see the grey balloon inflated when submerged.
I forgot to mention that if you plan on going deeper then you must get to periscope depth before pumping out the ballast.
I hope that this makes some sort of sense.

Martin.

"I do like your idea Martin but I am trying to save weight in any way that I can ..."
Hi Pete,
You don't need a large 'standard' servo to operate a couple of micro switches.
Use a micro servo (4gm) and the smallest micro switches and the whole shebang shouldn't be much more that about 6gm and would be much smaller.
I guess Martin used 'standard' sized components cos they were in his bits box.😉
Cheers, Doug 😎
BTW; torps with compressed air or a micro e-motor?
Somewhere I've seen a vid clip from a guy who did this with an MTB model!
I've been pondering a similar, perhaps baking powder driven, system for my destroyer.
Launched by a spring loaded ratchet arrangement triggered by a servo.

"I have just had another thought."
Oh! 😮
Heads down and hang on to yer hats lads, Martin has had another thought!
Where are we off to this time 😁😁
Just pulling your chain a little Martin.😉
You are a refreshing source of tangential inspiration👍 Keep it up.
Cheers, Doug 😎

Hi All potential submariners!
Please consider this before you happily launch your latest creation!
You're down at the lake on a nice warm sunny day for a bit of 'messing about in boats'.
So far so good.
BUT ... before you launch your sub into the deep consider that the water temperature will be considerably less than the air temperature.
So what? you might say.
This what!
To help keep the wet stuff out of the sub and away from your sensitive electronics you need a little over-pressure within the pressure hull (WTC), to keep it WT!
Outside in the warm air this will occur naturally. BUT .. as soon as you dunk your sub in the cool wet the air in the hull will also start to cool and reduce the pressure within the hull.
This is often enough to create an 'under-pressure' within the hull which can cause ingress of water by literally sucking it in through the drive shaft and control rod glands.
Glug glug glug glug😭😭 Time to wish you'd worn your swimming trunks and brought some goggles with you!
Solution?
1 Acclimatise your boat on the surface before you sail away and start diving; i.e. let the water cool the hull and contained air before final sealing of the pressure hull and sailing off.
2 Fit a cycle tyre valve and take a cycle pump with you so you can pressurise the hull slightly before sailing. Don't overdo it, one or two pumps should do, or you might blow the sealing glands from the inside 😮😭
3 A rubber (or similar material) membrane fixed into the pressure hull is a useful indicator of over or under pressure within the hull (WTC).
4 Fit a Pressure switch and a Fail-safe device which will automatically surface the boat on loss of radio signal (some RXs can be programmed to do this; i.e. all servos and ESCs go to programmed settings) or on exceeding a preset depth; e.g. 1 metre.
Happy sailing / diving / surfacing🤞. Cheers, Doug 😎

Hi Pete,
"My problem is simple. Where does the air come from to take the place of the water."
I assume you meant 'dive' system and not 'drive' system, a subtle difference😉
Let's go back one step!
Where do you suppose the air in the tank goes when you pump the water in?
Right ... It gets compressed.😮 Air compresses easily, water is practically impossible to compress.
When you 'blow' the tank the compressed air expands again and helps the pump to eject the water. The small amount of air you have compressed will not alone be enough to 'blow' the tank without the pump. That's why real subs have compressed air tanks and separate compressor systems.
It's preferable in models to separate the air / water components. (Just like 'in real'!)
That's why Martin is using a balloon, aka bladder.
(Oh😮 that reminds me ... I need a P! Back in a mo!! ...... Aah! Dat's bedda😊
As the bladder fills with water and expands on diving (😭) the air in the tank section is compressed.

You mentioned before in a PM venting the air to the other compartments in the boat and then relying on the air so partially compressed to drive the water out again.
Sorry but it ain't quite that simple.
Firstly: that would be fraught with danger as you then need breakthroughs into the other compartments from the dive tank chamber. These have to be not only securely sealed but also capable of being opened to accept and then vent back the air evacuated from the dive chamber. (If you did this in a real sub you'd probably pop the eardrums of the crew🙊😭)
So you would need either some very well engineered and precisely machined mechanical valves to control the air flow and prevent leaks and/or a complicated control system, solenoid valves perhaps? Very dodgy! (With apologies to Mr Geezer😁) The chances of flooding the whole boat are much higher than with a contained system.
Secondly; the pressure of the air expelled from your dive tank would be reduced by dissipation within the compartments outside the dive tank.
Martin's system is contained within one compartment using the bladder (that word again🤔 er, Could you excuse me a moment please Cpt Mainwaring!)
The system for my Akula 2 (Typhoon) is also contained, but will use a piston tank. To dive the piston is driven to the far end of the cylindrical tank, compressing the air behind it as it draws in water in front of it. Exactly the reverse procedure to surface.
Only disadvantage of this system is that you have to arrange space down the centre of the WTC to accommodate the drive spindle for the piston when submerged.
Big advantage is that you have full control of the piston and thus dive depth.
Given a suitable programmable TX Periscope depth and max depth could be preset.
A max depth Fail-safe controller is also highly recommendable!
Have a look on this site, the German model dive system specialist > 30000 systems sold.
This is where I got my Akula 2 kit.
https://engel-modellbau.eu/shop/en/home/
Also Hall Effect sensors for the dive tank ! Such as you mentioned Pete.
They determine the position of the piston in the dive tank and feed it back to the dive / fail-safe controller.
https://engel-modellbau.eu/shop/en/Submarine-Kits/AKULA-II/Hall-Sensor-for-Compact-Tank-Switch-CTS2-2-upgrade-set.html
Cheers, Doug 😎
BTW: If you want to understand more about the principles of how submarines work, whether 1:1 or scale models, I can heartily recommend this book-
Submarines Models and Their Originals, by Carsten Heintze.
Originally published by
Verlag Für Technik und Handwerk (VTH)
English edition 2005 by
Traplet Publications Ltd.
ISBN 1 900371 86 3
Or specifically for model submarines-
Model Submarine Technology by Norbert Brüggen (the German model sub guru!)
ISBN 1 900371 32 4
Also by VTH in original German and Traplet in English.
Should be able to find both on Amazon/Ebay.
I've just realised that somehow I have acquired two copies of the latter🤔, English edition!
If you want one PM me.
BTW 2: you can use the electronics of a servo as a mini ESC or even to drive an electronic switch, BUT you will need to beef up the output transistors to handle the current your pump motor will draw, or add a change over relay to the output! If you want to go that way I can help as I did something similar years ago to use as a winch driver.
Standard and mini / micro servo drivers are rarely designed to handle more than about half an Amp, esp the mini / micro versions.

Hi Martin.
The drive system is my biggest mystery so far. I am slowly looking into it by looking at as many different forums that I can. My initial thoughts are to fill the central tank with water to submerge and just pump it out to surface. My problem is simple. Where does the air come from to take the place of the water. I suppose this could come from three possible places. 1) From a breather pipe at the top of the tower. This would restrict the dive depth. 2) Some form of air cylinder releasing whilst the pump is draining. Seems complicated. 3) Drawing the air from the two electrical compartments, Possible but would the negative pressure be too much for the tube. Also, how would you replace it when surfaced.
How have you done it Martin. I was always going to ask at some time but I was trying to navigate the problem myself first so that I could get as much knowledge as possible. I have found that even with all of the surfing I have done on this, the secrets are well kept.😐

Peter I am interested to know why you feel that you will need sensors.
Assuming that you want to forward and reverse the ballast pump it would be possible to fit limit switches to the ballast tank.
What voltage are you supplying your ballast pump with as this will also affect what sort of forward/reverse switch.
I am not sure how you are making your dive system but I am interested to know.

Martin.


Martin.

Thanks Graham. I have an old Futaba servo I can try first but I think your alternative will be good too.
After looking into this a little more and as the pump is going to be part of a submarine ballast system, I am wondering if a control with sensors might be needed. Sounds a bit expensive so I hope not.

There is a commercial unit on the Technobots site that does the job ( at a price). It will drive a bigger motor if the stripped down servo solution can’t provide enough drive current.

Hi Peter,
I have just had another thought.
The PCB from a stripped down servo can be used to control LED's and as a speed controller for a small motor, it has the capability of forward and reverse.
I don't know if it will do what you need it to do.
I have not done many experiments with it to see what it is capable of.
Just an idea!

Martin.