Submarine Torpedo Launcher for Battlestations!

So i'm pausing my project on the Sevestapol for a bit until it gets warmer or I can refuel the tank for the propane heater. Since there's not much I can do right now, my mind has wondered onto the subject of building a German XI U-Boat for Battlestations. Since I started my research for the Sevestapol from the stern on up, i decided to take this from the bow back. Once I got the plans, I started working on the weapons, which I decided to use torpedos. to save space, I decided to make each of the four tubes as a complete set up, fired by a servo. What I thought of was having a piece of 1/4" tube threaded on one end to thread an endcap on. Then you drill a smallhole through the side, straight through the pipe. A spring is then attatched to the endcap and the endcap is then threaded onto the pipe. A 1/4" circle is then fitted in the barrel, which then gets pushed down by a small rod, compacting the spring. Once the circle passes the holes drilled in the barrel. you fit a small pin through the holes. It's now able to fire. Then you place your ammo down the barrel, which in my case is going to be a sabot version of a flechette. then you hook a string to the pin, around a pully, and connected to a servo.
When you fire it, the servo spins, pulling the string which pulls the pin out. The spring then launches forward, pushing the circle and launching the torpedo. The pully is used to make the string perpendicular with the pin, so it pulls it straight out. I'll post pics tomorrow to help explain it some more. In theory, it sounds like it may work, but I'm new, and it may have been tried before. If anyone has any sujestions, please post them, like I said, I'm new and i'd like all the help and criticism I can get.

 

RE: Spring Torpedo Launcher for Battlestations!
A couple of things to consider:
- The torpedo tubes will be under water. If you simply drill a hole through the side of the tube. how will you prevent water from entering your boat?
- Will a spring system be strong enough to drive the torpedo through the water and still do damage? I am most curious about this issue, maybe some initial experiments before you build the whole system would give you confidence that it is possible.
- Even in 96 scale you will be very limited in space, so keep that in mind when you are designing. A guy in our club is working on a 96 scale Surcouf and it is scary small!
I'm not sure what you have in mind for your torpedoes, but check the Battlestations rules because it describes what can be used.

 

RE: Spring Torpedo Launcher for Battlestations!
I have thought about the water issue, and I have a few ideas, but I shall have to test them first to see if they work well enough. The spring should fire it at a high enough velocity as long as it's a strong one. I am going to do some tests, but I wanted to post this to make sure I didn't forget it, andto get some feedback on the design, thatc's the reason I haven't posted any dimentions, I have to figure it out through trial and error. It will be limited on space, about a meter long, which is one reason I thought about this, since it wouldn't need any CO2 tanks. The ammo I'm tempted to use are basically a shaped rod with fins on the end. It's 1/4" im diameter at the fins, and its the scale length of atleast one type of torpedo, though I can't remember which type right now.

 

RE: Spring Torpedo Launcher for Battlestations! Perhaps if the tube were open at the front and the torpedo always in the water. The spring could push against a washer that could keep the tube sealed even after firing. I am probably explaining this badly. You would need to keep the tube well greased so the washer would not cause friction but that no water would get past the grease.

 

RE: Spring Torpedo Launcher for Battlestations! Tug: I'd probably hold on to the gun itself when I reloaded, so I don't have to worry about breaking the mounts.

Anachronus: That's actually a good idea, in my original plans, I had a wooden disk, however this would expand and block a lot of the water, however using a metal disk with an O-ring seal would be much more reliable, and the grease would stop water getting through any gaps. I think you just solved my leaking issue. I'll post a simple drawing when I get home.I'm going to run some numbers and see what I need to get this thing working, and if it all goes well, I may have a couple of prototypes for testing this weekend.

 

RE: Spring Torpedo Launcher for Battlestations! A metal oringed disk (aka piston) can even be taken a step further to help in recocking the cannons. Mount the piston on a rod that sticks out the back of the breech, stick a knob on the end sticking out, and we would have a simple way to cock the cannon by simply pulling the knob/rod/piston back to compress the spring inside the cannon.

 

RE: Spring Torpedo Launcher for Battlestations! Yes...PISTON that was the word that was eluding me.

 

RE: Spring Torpedo Launcher for Battlestations! So here's the basic idea drawn out , not to scale, but you get the idea.

From Recently Updated​

That's the original one this next one is the updated one per current ideas.

From Recently Updated​

The wooden piece surrounding the torpedo is what's going to guide it down the tube, it's split into four pieces so it will fall away once it's outside the tube. The piston will probably have an O-ring put on it to help it seal. I'm trying to figure out how strong the spring needs to be.

 

RE: Spring Torpedo Launcher for Battlestations! I would make the piston more of a cylinder than a disk, have a machined grove near the front for the o-ring, and have the pin hole as a large slot so it would be easier to insert the pin. The piston would act as a seal to keep water on the outside.
More thoughts:
Tap the "rear" of the cylinder for 4-40 or 6-32 and thread-lock it to your pull rod. Put a knurled nut on the other end of the rod.
Don't use wood. It swells when wet. Nylon bushings (impregnated, maybe?) would be a good place to start.
The concept seems sound, but prototyping will be the key...

 

RE: Spring Torpedo Launcher for Battlestations!
A crude drawing:

 

RE: Spring Torpedo Launcher for Battlestations! Thanks Dustin, that's what i had in mind, the drawing wasn't too exact, but i'll make a more detailed one once i get the dimensions worked out, and don't worry, the only wood on here is the part that surrounds the torpedo, and It shouldnt expand enough to impede firing, but your right, finishing a prototype would help me know what do and doesn't work. I may finish one up tomorrow if I can get the materials, and test it friday. I may also drop by the swap meet in ohio to see what they think of it.

 

RE: Spring Torpedo Launcher for Battlestations! Suggestion: dont use the spring to propel the torp directly, use it like an old fashioned potato gun.
The spring moves a piston in a cylinder which feeds the air compressed by it to the breech

 

RE: Spring Torpedo Launcher for Battlestations!
Check out the mechanism of an airsoft gun for an example of using piston compressed air to fire something.

 

RE: Spring Torpedo Launcher for Battlestations! So here's the redesign based on the piston.

From Recently Updated​

I'll make the chamber bigger to allow for more power and a bigger spring.

And I'll see if I can't cannibalize the parts from one of my old spring guns, it's clear, so I can see how the mechanism works before I take it apart.

 

RE: Spring Torpedo Launcher for Battlestations!
ok...delete the pin.
Make the shaft on the piston thicker, at least 1/8". Possibly thicker...even 1/4".
Cut a notch in it 1/8" behind the piston to engage on the edge of the hole in the endcap.
Use a servo with a cam on it to disengage it....bang.

 

RE: Spring Torpedo Launcher for Battlestations! For the first prototype, I'm going to do the original design using Darren's firing method. It doesn't take long to build and it's cheap enough to make several modifications to. If that works, I may not add the chamber to the final design, to save some space. I do believe that I found a spring small enough and strong enough to launch it, along with the piston to use in it. I got some of the stuff yesterday, and I should get the rest today. If I get home in time, I'll set up a test and see how it does.

 

RE: Spring Torpedo Launcher for Battlestations!
So I ended up being able to test it, with mixed results. Since it was a rough prototype, it was missing some of the stuff that will be in the final product. I used a piece of 1/4" copper pipe about 6 1/2" long. the spring I ended up using was 2 1/4" long and 3/16" in diameter. The piston was a nail put through the spring with the head on the inside of the pipe. I launched a nail about 3 3/8" long and 3/16" wide. I wanted to test and see if it would work without using the piston to compress gas. When I put it all together, It ended up looking like this:

From Tests​

From Tests​

Since it was a rough model,I ended up not making a firing mechanism, instead, I used a vice to hold the nail until ready for firing:blush:

From Tests​

It turned out reasonably well all things considering, the first test I did was to launch it at a 1/2" of foam

From Tests​

From Tests​

It went about halfway through the foam, then lodged it'self inside the foam. I then tested to se if it could penetrate 3 pieces of 1/32" balsa put onto a styrofoam frame. The first test, I cut out to large of a hole in the foam behind the balsa, so it did more damage than it normally would.

From Tests​

From Tests​

I fixed it by making a smaller hole about 1 1/2" square and shot it again. I didn't get a picture of this one, but it only went through the first two sheets and started on the third.

What I could to to make it better:
Use a bigger" spring: I went to the local gunsmith and he let me get part of a spring, next time i'll get the full thing in a bigger diameter.
Use a longer nail: I had a hard time making the nail protrude enough outside the spring to be able to set it into place, so a longer and thicker nail would definitely help with setting it.
Use a better projectile: this one worked, well sort of, but it has no aerodynamics, i tried a distance test, the nail hit the Styrofoam sideways! That is not what I'd want to happen in the water.
Make a firing mechanism: It ended up taking a long time relaoding and firing it, so a firing mechanism would definitely help.

Conclusion: I believe this design will definitely work, It's just a matter of setting it up right. I'll be at Lowes selling popcorn tomorrow, so I should be able to slip away during lunch and get the new supplies. If it works, they should only cost me about $8 each along with the time it takes to make each, which is about ten minutes, although it doesn't really matter because I'm a student and can't get a job till the summer.

 

RE: Spring Torpedo Launcher for Battlestations! Looks like you need a hollow projectile, so it'll allow water to enter the hull, but even then, you'll have the problem of it tearing a bigger hole if it's left protruding and gets sideswiped....
Perhaps the standard 1/4 ball is the way to go...
or a tapered tip which will tend to fall out after penetrating?
Maybe even tether it, like a harpoon?