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"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
(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
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.
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.
1 month ago by RNinMunich
Re: Joining the fuselage.
My U25 at 107cm is about 8/10 the size of your Gato, but probably heavier as it's hull is made of four planks of carved wood!😮
Anyway she goes just fine using two 385 motors on 6 or 12V driving 3 blade 30mm props.
On 12V way too fast of course but it's fun to show up the speed merchants once in a while😁
Re dive plane retraction-
Here's two possibilities!
This one from the German model Sub tech expert Engel where I got my
It comes with a controller.
This one from your rc sub guys
Neither particularly cheap 🤔 but maybe the pics on these sites can provide some inspiration.
Good luck and welcome to the 'Pig Boat' club!
Cheers, Doug 😎
BTW, having put the 'fuselage' together when are you going to stick the wings on!?😮😉