If you are tried of building things that fly, why not try a submarine like [DIYPerks] did? As you can see in the video below, the key is to control buoyancy, and the mechanism used is impressive. The sub has two giant syringes fore and aft to compress or decompress water. The plungers are now 3D-printed actuators that travel on a lead screw. Two high-torque motors and some batteries sandwiched in acrylic disks make up the rest. This is a big vessel — you won’t be trying this in your bathtub and maybe not even your pool unless it is a big one.
Of course, everything needs to be watertight. Instead of trying to waterproof a power switch, this sub uses a reed switch so that a nearby magnet can turn it on. Not an original idea, but we always think it is more elegant than seals and potting compounds.
The best part, though, was the modification of a servo control board to close the loop with a linear slide resistor instead of a rotary pot. A clever hack and seems to work well for this application. The downside is the RF control. As real submarines know, 2.4 GHz signals don’t go very far underwater. Like a real submarine, this one floats an antenna array on the surface so it can receive control signals from the shore. It also sends video up in real time.
A bunch of water pumps work as thrusters. The submarine’s hull is a tube that is the same diameter used for irrigation pipes so the sub can use off-the-shelf parts meant for that purpose.
The sea trials were done on a lake with a friend’s much smaller submarine. There were the usual issues to work out, but in the end, the addition of some ballast and preventatively adding some seals got everything in working order.
We’ve seen several subs lately. Some of this one reminded us of Subnautica.
I think there were two submarines in Popular Science or Mechanics in the sixties, one on the cover. Build it yourself. Though more like a sled, it wasn’t waterproof, you wore a diving suit and sat on it.
I remember that article !
water doesn’t compress appreciably. It can be pumped in and out but that’s about it…. That’s what those syringes do, move water in and out of the buoyancy/trim tanks
…which, presumably, has the effect of compressing and decompressing the air in the sub.
You just need to displace the water in the tank. What remains is empty of water. The pressure of whar fills it doesnt matter – it could be a vacuum and it would still work.
>appreciably.
Thank you.
“to compress or decompress water” !!! I was not alone being highly surprised by such a sentence..
I decompressed some water when I made the tea this morning.
So build a nuclear power plant, and heat up water to propel this.
Tom Swift jr did it.
I still don’t understand why The Repelatron Ray could not be used to provide motion in any case. Imagine two Repelatron Rays cross synched and aimed at each other diametrically to provide molecular displacement to rapidly heat the coffee . . Wait, my Microwave Oven just beeped.
Tom Swift jr. made stuff beeep, didn’t he ??
This is really a cool project. It could float like a real one if the weight is more and head was little pointy.
It needs to be yellow!
B^)
There are other license-free low power radio bands available that may penetrate water better than 2.4 GHz. (Around 170 kHz, and in the AM broadcast band.)
But incredible power is used to send signals to submerged subs, and then it’s incredibky slow.
I recall the license free band at 170KHz alows 1W input to the final stage, and that’s into a very short antenna
75 Mhz works….
https://www.rcgroups.com/forums/showthread.php?1190035-2-4-underwater&highlight=2%204
Buoyancy control is mainly necessary in a manned submarine because of the displacement of the sail, that part that pokes up out of the water and would displace water when submerged. Once submerged, the sub should have neutral buoyancy and they typically use the front vanes to steer higher and lower with changes in buoyancy only required when there is a change in water density due to temperature or salinity. In the case of this model there may be some problems due to squeezing of the hull, though I expect deformation to be minimal. It should be able to be trimmed slightly positive in buoyancy and use forward motion to dive and maintain depth.
There are several issues to deal with. They are center of gravity, center of buonyancy, and variable displacement due to hull compression. These are all factors on real submarines as well. The use of variable displacement tanks (syringes) with no air in them, takes away the center of buoyancy problem
That doesn’t sound right. If ballast adjustment for buoyancy control were needed solely for the surface/subsurface interface, SCUBA divers wouldn’t need to vent their BCDs when descending from ten to thirty meters and the Trieste wouldn’t have needed to use its gasoline and metal pellet ballast system which only impacted its buoyancy changes needed for much deeper depths.
Yes, that is not true at all. You constantly have to use either trim tabs, propulsion, or buoyancy control to maintain depth on a submarine. One big difference with a SCUBA BCD though is that it is flexible. Displacement is increased by adding air pressure inside of it. It is decreased by venting and allowing surrounding pressure to collapse the BCD. You generally are not filling the BCD with water, it is the presence of air that makes it work. In a submarine tank, there is a volume that is either air or water. The BCD has a very complex set of dynamics due to its flexibility, as external pressure increases displacement goes down but internal pressure increases due to the compression. Think of the BCD more as rate control. It is a big no-no in SCUBA to use a BCD as an elevator button, you are generally supposed to propel your self up and down and use the BCD for trimming.
Non-intuitively for non-divers, you also have to continuously VENT the BCD when ascending to keep your ascent rate under control (remember BCD volume is increasing with decreased external pressure). Remember you are SWIMMING up not riding the BCD like an elevator.
It’s also used frequently on AUV Gliders. Giant wings with variable ballast. They can go insanely long distances with minimal power.
Neutrally buoyant is a surprisingly variable target, especially for saltwater subs. They have to deal with temperature fluctuations, pressure waves, salinity and general water currents.
I am tried of life.