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Torpedoes and Missiles

R/C Submarine modelers

Torpedoes and Missiles

Postby Ramius-II » Sat Dec 06, 2008 8:24 pm

Hi All! :D
I'm still plugging away. A couple of questions about missiles and torpedoes.

I have read the write-ups on missiles and was wondering why use PVC pipe? I took a 5" lenght of 1/2" schedule 40 PVC and measured it's weight at 1.1 ounces. I took the same lenght of 1/2" brass tubing and it was .55 ounces! It seems the brass weights about half of PVC and since this is the case, why PVC?

Question about the exhaust tube of a gas torpedo. It seems the final air outlet tube size from what I have read is .006" Damn, that's small! Is it really that size for a 1/96 scale torpedo? The other part is if you are using 1/16" x 2" aluminum tube as the start size, what lenght is good or correct for the reducing tube down to the .006"?

Question about the firing of a gas torpedo. When you go to launch your torpedo, how much air (gas) do you use? Do you only use an impulse of air (momentary on/off) or do you allow the whole storage cylinder to be come depleted?

Thanks for reading this and your answers, Ed
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Postby Wheelerdealer » Sun Dec 07, 2008 2:49 pm

I guess as long as the completed torpedo is bouyant thats all that really matters, if you can get the brass on to float then thats all that matters.

I fined insulin syringe needle work well for small torpedoes, you can fix them inside a larger tube. I cant work as small as 1/96 for torpedoes, but missiles for the Typhoon, thats much easier :)

I have never tried gas to launch a a torpdedo, always mechanical means. I guess you only need an impulse.


Ramesh
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Hey Ramesh!

Postby Ramius-II » Sun Dec 07, 2008 3:23 pm

Long time no talk to! I decided to go to something more like what I would do and that is to take a photocell sensor at the end of the tube and once the fish has almost completely left the tube, turn off both the charge supply and launch supply. This also gives one more ability and to be able to indicate (green and red) launch tube status ("Charged and ready" and "Nothing to fire!).

On another note since I am writing you, I am still waiting for one optical engineer to say what the final lens should be for the periscope. It needs one more lens for correct focus. Video wise and transmitter wise I borrowed some test equipment from work (Fox Television) so I am good for sending absolutely correct video from a little more that 1.5 meter underwater at a 100 meter distance. It could be futher and I ran out of extenstion cords even from my neighbors!

Best, Ed :D
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Postby Sub culture » Mon Dec 08, 2008 6:24 am

Do be careful using brass under pressure, it has been known to suddenly split and fracture. This is why people tend to use copper- much more ductile, and thus less likely for this to happen.

Thin gauge stainless steel would be very strong and lighter than PVC or brass.

Andy
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Thanks!

Postby Ramius-II » Mon Dec 08, 2008 9:18 am

Thanks Andy!
As far as I know though you can not solder or epoxy to stainless?

Ed
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Postby Sub culture » Mon Dec 08, 2008 10:23 am

You can braze it (hard soldering). Never had cause to epoxy it, but I don't see why it wouldn't work, so long as the surface was well abraded.
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Stainless steel soldering

Postby Theo » Mon Dec 08, 2008 12:18 pm

It has been my experience that you can braze as well as solder Stainless. If you want to solder Stainless, use a liquid acid flux and then try and rinse it well in warm/hot water following soldering. Only use Rosin flux after you have successfully used an acid flux. A Rosin flux alone won't work on Stainless steel.
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Postby Ramius-II » Mon Dec 08, 2008 10:01 pm

Thanks Theo!
I am trying to figure out a material to use for 1/96 scale missiles. Stainless would be great from a weight standpoint and the problem becomes one of how do you seal the ends of the tube and attach fins? Epoxy will stick to brass and I would imagine the fins could also be brass. The alternative with stainless is to drill "attachment holes"?

Anyone know the pressure rating of thin wall brass?

Best, Ed
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Sealing missle!!

Postby Theo » Mon Dec 08, 2008 10:56 pm

Hi Ed,

As for building missiles, I have some experience and some might say enough to be dangerous!! Anyway, first, I would consider using thin wall Aluminum tubing as it is light, can withstand the pressure you will encounter and is easy to work with. What ever you want to use to put at each end, use small Silicon O-ring seals, glue the end pieces in with Fast Glue and round off the edges of the ends of the Aluminum tubing so that the missile won't blow apart. I'm not sure what you plan to use for the propellant so you might comment as if you plan on using a COLD gas then the end pieces (nose) can be made of plastic/metal if you have a quality lath. The tail piece can also be molded from plastic with a stainless steel tube for the exhaust gas (depending on how many missiles you plan to make) by making a model end pieces from a piece plastic/Aluminum and cutting some sheet plastic like an old credit card for the fins and gluing them using the fast glue. The key is what type of propellant you want to use. As an idea if you want/plan to use a HOT gas, you may consider Stainless steel rod that will fit in the end of the Aluminum/Stainless steel tubing and making some Magnesium powder (by sanding down a piece of Mag) with a small (very small) model rocket propellant in the end of the missile and packed with the Magnesium. You will have a great launch. you might want to write me for more INFO on safety measures and other considerations. Having said what my thoughts are, you will also have to tax your brain a little!! :)

Jack
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Postby Ramius-II » Tue Dec 09, 2008 9:47 am

Hi Jack!
Thanks for the info! I figured I would stick with cold gas (compressed air) at about 65-85 PSI. I read the article “Launch This” and figured to follow what was already done with a few small changes to the firing mechanism. Mine is a 1/96 Typhoon so it will only accommodate a total of two missiles. I very much liked what Nuke Power came up with as a design for releasing the missile, that is basically a cup with a large o-ring for the missile to sit in and then using air to force the missile off the center sealing pin. The biggest problem I have ever found in where to get such items as thin wall aluminum tubing! My guess is that the diameter is about 5/8”? Stuff like T-88 epoxy seems to work well as an end sealant for the tube and CA glue seems to stick well for attaching the guidance fins. Stainless is a great material and you have to grind off the coating which weakens the tube at the places you have ground it. Then, it seems painting stainless can be another challenge.

Best, Ed
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