Torpedo Design Thread

I split this thread off from

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because we really had two topics going on at the same time.


THIS THREAD is dedicated to the technical design of the torpedo, safety, & its feasibility.

THE OTHER THREAD is dedicated to the theory, game balance & rules implications.


Anyone posting in this thread MUST PAY ATTENTION to the discussions happening in the other thread, as otherwise design will run a muck.

 

Has the possibility of allowing larger than scale torpedoes been discussed? Given my robotics background I tend to view the world through microprocessor-tinted glasses. Using a micro would allow for easier manipulation of motor speeds, warhead triggering and even heading control using a gyro or accelerometer IC. I've ordered some gyros and accelerometers for another project I'm working on and using a torpedo as a test bed for the control systems would simple enough. Would that be something you all would like to see?

iamscottym

Slightly off topic, the first version of my automated airsoft gun will be done this weekend. I'll post a video.

 

Anybody thought of resin casting as a way to keep costs down?

I don't know if it would be sturdy enough, but it might be a way to create at least the portion of the torp.

How about the prop? The easiest way to make a small prop would probably be to take a small disc of brass and cut an bend it into blades. To counteract the torque of the prop, the fins of the torp could be bent in the opposite direction of the props rotation.

It might be possible to cast the tapered rear section of torpedo, with the fins in place, out of resin. Perhaps even cast the pager motor in place, and then attach the prop with glue.

A rear, cast portion could then be attached to a piece of brass tubing containing the battery and some wood or foam for floatation. Then a 3rd piece, the "warhead" attaches to the center section.

How should we launch torps? I like the idea of a non-conducting strip or pin hold the battery away from the motors' contacts. Pull the pin and the prop starts spinning. A strong spring could be used to launch surface torps, and a burst of compressed air for submerged. The "impulse" air doesn't have to come from a regular CO2 system, it could be from a small reserve tank that is pumped up on shore, especially if you only have a couple of torps to launch.

 

If building a miniature clockwork-style mechanism (although very costly) is not out of the question, there's no reason that a locomotive torpedo couldn't be developed to use a spring-powered system to drive a prop. That would help to alleviate environmental concerns with lost torpedoes. For small vessels, launch impulse could be provided by non-reloading torpedo cannons (accumulator, not tank-based), modified to integrate the torpedo triggering mechanism into the barrel. This would limit the need for as much of a division of resources to develop an effective design. It would also make it possible to switch a ship's configuration between existing torpedo cannon fucntion and locomotive torpedo launching, depending upon local rule restrictions, ammunition availability, or even just tactical needs (long-range, maneuver-denial action versus short-range, harder-hitting engagements).

 

IIRC,

The thickest Big Gun hull is 1/8", but one thing to consider, the purpose of torpedo is to strike below the armor where the hull is weaker.

We may have to accept that damage to thick armor will be considerable reduced.

I would think some kind of "drop test" would be a place to start. Since you can't drop a BB or ball bearing from a few feet and have it penetrate a hull, if we can do it with a torp, I think we are on the right track.

I'm currently trying to put my shredder warhead idea to paper so I can start work on a crude test torp ( since I don't have a lathe or mill yet ). I plan to test it with a drop test.

 

Hey folks, I had an idea for making gas-propelled torpedoes safe. The big concern about gas-powered torpedoes is that if they have enough power to penetrate balsa after several feet of moving, what happens if one breaches the surface? It becomes a rocket, and poses a significant danger to people on shore. But what if it had a way to vent the remaining gas and "safe" itself the moment it surfaces?

My idea is to put several flaps on the outside of the torpedo, covering vent holes. The hinge on each flap faces the front of the torpedo, so that when the torpedo is moving forward through water the flaps are held shut. However, if the torpedo leaves the water, the forces holding the flaps closed disappear, the flaps open up, and all the remaining gas in the torpedo drains out.

 

Anybody found a good source of tiny batteries?

I found this: http://www.evergreencpusa.com/battery/silverwatch.htm

They have two batteries under 5.8mm (which is about .22 inches) but they seem to way too much run time.

I would say we need something that is only good for a minute or so of power.

Kotori87,

Thats a good idea but would water pressure be enough to hold the flaps shut? Would they seal so you wouldn't have gas loss? If your using propel liquid gas I think the rocket fears are overstated, I simply don't think that stuff evaporates fast enough to cause that much thrust. Thats the reason people use it, its a slow, steady release of pressure... The pressure is low enough that the RC Subs guys just plug the nozzle of the torp with a pin, pulling the pin out releases the torp.

But I have never used the stuff personally, so I don't know. More testing needed...

 

Here is another link for tiny batteries:

http://www.sonet.org.uk/Products/MicroBattery/sr/spec.html

Some as small as 4.8mm in diameter.

Does anybody know how environmentally safe these mercury free silver oxide batteries are?

 

Silver Oxide are classified as hazardous. Found a good link to double check against:
http://www.ehso.com/ehshome/batteries.php#Summary

There are some good research links at the bottom of the page.

 

Here are geared pager motors:
http://www.robotshop.ca/home/suppliers/solarbotics-en/solarbotics-gm15-gear-motor.html

I would say a supercap of some sort would be the way to go if it really needs to be scale size. For my design I'm scaling it up to use standard 16800 series (~5/8" OD) (typical laptop battery size) li-ions since I have them handy.

For my control surface layout I'll use a rear rudder and forward dive planes like on this fish robot:
http://io9.com/5017410/schools-of-robot-fish-will-soon-infest-the-seas
They will be controlled by planetary geared motors with right angle bevel gearing at the output. I will use a pot for position control of each motor (basically a servo).

For my prototype I may just use these servos for control since I already have some: http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=3715&Product_Name=Arrow__3.6g_/_.5kg_/_.12sec_Micro_Servo

An analog devices gyro ADXRS150 gyro mounted to control roll about the longitudinal axis and an ADIS16209 inclinometer/accelerometer (or similar analog chip) will control pitch.

I haven't decided on a micro but since I'll need to do numeric integration I'll want a 32bit micro like an ARM7 or 32bit PIC.

To trigger the torpedo to launch I could take advantage of having an accelerometer on-board by perhaps storing the torpedoes upside down and then righting them to fire or I could use a discrete hall effect sensor onboard and applying an external B-field would fire it. To detect impact I'll watch for a spike in the accelerometer data and trigger the warhead with another servo or some such. Since these will make for fairly expensive torpedoes I'll use an IR-emitter to act as a beacon and look for them using a webcam with the IR filter removed.

Total cost: sensors + micro(sampled) $0, batteries (owned) $0, servos (owned) $0, assorted tubing and sheet metal (owned) $0.

One last thought, since these torpedoes can steer can I implement homing or a zig-zag path like the German torpedoes?

iamscottym

 

Check out this link,

http://www.ehso.com/ehso2.php?URL=http%3A%2F%2Fdata.energizer.com/PDFs/silveroxide_disp.pdf

If I am reading it correctly, the small ones that would be useful to use are not considered hazardous waste, only the larger ones that test positive for mercury.

The batteries are completely solid, with no liquid component to leak out.

 

"For my design I'm scaling it up to use standard 16800 series... "

Keep in mind that LiION doesn't like water, unlike it's LiPoly cousin which is fine with it. (the Lithium in LiPoly is bound to the polymer making it a lot safer)

 

Iamscottym,

That pager motor is awfully expensive compared to some others. Any advantage to a geared one?

Did you see these?

http://pagermotors.com/Products.php?f_category=Pager

Simply doing a google search for pager motors brings up a lot of choices in the $1.50 to $2 range.

 

You shouldn't need an actual ship hull, just a frame to support whatever size sheet you plan to use. Prepare some doped & silkspanned sheets in advance, clamp them in the frame, & test away!

JM

 

Yeah, it actually has enough torque to turn a prop! Even geared it only has .28 oz-in or torque. I don't have any benchmarks to go by but I'd guess that may not even be enough to turn a prop, much less overcome friction from an oring seal on the shaft. This is another benefit to scaling up a little- geared motors are less expensive.

I think a brushless motor from a cpu fan would work pretty well. RC plane guys used to take the ones out of cd-rom drives and rewind the stators with heavier gauge magnet wire for more power back before commercial motors were available.

If you all a really intent in sticking with scale size you ought to find a watchmaker and pick his brain about gearing and such. My dad used to have a watchmaker friend and I remember seeing some of his work. It looked difficult to do to say the least.

iamscottym