A MK48 heavyweight 21" torpedo costs around $3,800,000 (£2,396,917) and is nowhere near so much fun to fire and steer onto a target at a community pond, as a model torpedo costing about £250. Also, nobody gets hurt @ 1/20th scale. Imagine naval war-gaming setting a Scorpion HK against a battleship. What a shame that at this scale, SAMS may not be guided. There is though hope the bigger cruise missiles. How about a prize for hitting an enemy target. You'd then have a bunch of students developing guidance systems to be able to compete with one another.

THE 1/20th SCALE NAVAL MODEL - TORPEDOES

Firstly, and please note that BMS have no aspirations to be and MOD supplier or subcontractor. This exercise is simply some harmless wargaming fun. Please bear that in mind when reading how we went about producing a warship of the future. We'll let the Navy catch up in about 30 years.

A military version (Scorpion HK) of the Bluefish zero carbon cruiser (ZCC) is to have the equivalent of up to four MK 48 type torpedoes installed. Two of these torpedoes will fire facing forward and two will fire backwards on the 1/20th scale model to prove the concept. These steel fish are to be carried in the active hull in tubes so that buoyancy adjustment for loss of mass on firing is automatically compensated by the vessel's true running system. Using the existing feature of our ZCC design saves complications. At this time, no other vessel has such a feature.

Scorpion's torpedoes will be launched using compressed gas, then the outer doors closed to enable whatever water has got in, to be pumped out. The run distance of each model torpedo will be around 1 mile @ 5 knots, using lithium cells, and they can be guided onto a target - provided you have a wicked set of binoculars. That sits well with John Drain's findings. His torps run for about 15 mins at (we guess) 2.25mph = .56 mile range. You can increase the range and speed, by simply adding more cells and using higher gearing (or steeper pitch props). We'd also suggest using some efficient brushless motors, to really blaze a trail.

A Scorpion HK - fitted with 4 x SAM turrets (one per corner), for 360 degree independent cover. Each SAM turret carries 8 missiles (Rapier example), giving a battery of 32 rockets to fend off enemy aircraft. The micro battleship is also shown here with 4 Tomahawk cruise missiles in protected bays, fore and aft, and 4 x 21" MK48  torpedoes in the outriggers - all drawn to scale - as a prelude to proof of concept. The torpedoes and cruise missiles would not be visible, but we've shown them as though the drawing were an x-ray. The OAL of this genius design is 52.7m or 171 feet. She can cruise all day and night at 7-10 knots and sprint up to 25knots, depending on specification.

This original concept vessel is design copyright © BMS Ltd 2014. The technology is also patent applied for. Being an unmanned drone, there is no need for crew quarters, provisions or other life support. What is essential is a robust onboard navigation system that is artificially intelligent. Another essential, is encrypted satellite communications, such that firing of missiles is sanctioned by a human operator. If fired upon, the robot ship will return fire in self-defence mode. RoboShip is about to come of age. 

The battleship also carries a ROV that may be deployed from the mothership remotely, with other sensors to locate and clear mines. In tandem with military surveillance duties, the ship can sample and map the oceans all at the same time. That could save any navy a pretty penny - not to mention - that this vehicle is powered by energy from nature. So, no nuclear waste and no diesel smog.

The length of a MK 48 is 19 ft (5790 mm) and the diameter is 21 inches (533 mm). The 1/20th model torpedo will thus be 290mm (11 7/16th") x 27mm (1 1/16th"), or as near as we can manage to that using cheaply available off the shelf parts. That is a pity, because there are some talented model makers out there and we were hoping to be able to simply purchase ready made torps, where all the graft may have already been done. (Some fine examples of other modeler's methods are given below)

The same Scorpion HK model will carry 1/20th scale SAM and cruise missiles. The cruise missile will be mounted under the solar decks and launched horizontally using rockets, much as they launch Tomahawks from the decks of ships at the moment. The SAM missiles will be mounted on twin fore and aft turrets to enable rapid, truly independent, multiple target acquisition. You can read more on these other features using the links below:

1. SAM MISSILES

2. CRUISE MISSILES

3. TORPEDOES

4. ROV MINE COUNTERMEASURES

WHAT'S SO SPECIAL ABOUT THE SCORPION & DRAGONFLY HKs?

Apart from the fact that once launched there are no fuel costs for these naval drones, the unique hull design provides a degree of flexibility that is unparallel in naval military history for such a compact craft.

To now, it has not been possible to use one basic design platform to undertake so many different military functions. On this page we take a look at the method of housing and firing standard 21" and 12.75" torpedoes. The 1/20th scale is just big enough to be able to use components and materials that are commonly available in most well stocked hobby and hardware stores.

J. COSTING ESTIMATES FOR R/C MODEL TORPEDOES x 4 @ 1/20TH SCALE

OTHER MODEL MAKERS METHODS

When deciding on making model torpedoes, it pays to look at how other model makers have tackled the subject. There are several different methods that seem to work well, each with advantages and disadvantages. Two of these are investigated below. Remember though that our objective is just to show that a Scorpion HK is capable of housing torpedoes and other armaments - by way of a very basic feasibility study.

This is Mike Dory's rather neat solution to recharge a compressed gas powered torpedo. The range is not that great, but the torp steers straight.

MIKE DORY'S COMPRESSED GAS TORPEDO - “Does it shoot torpedoes?”

One of the biggest crowd-pleasers for a model submarine is working torpedoes. These torpedoes are relatively inexpensive to build, very durable, easy to maintain and ALWAYS please the crowd! This is how Mike Dory builds torpedoes for his RC model submarines. 

This isn't the only way and may not be best way to do it, but it's what works for Mike. He stresses by way of disclaimer, that if you decide to make this design of torpedoes, you are on your own! BMS say that that goes for any torpedo on this page or in the internet ether.

THE MATERIALS MIKE USES FOR HIS TORPS:

1. Aluminum tubing 5/8” X 6 1/4” with .02” wall thickness for the torpedo body
2. Hardwood dowel rod from any good hardware store or lumberyard, 

3. Cylindrical aluminum block as a base for the tire valve 

4. Schrader tire valve to fill propellant into torpedo body

5. Hot Stuff brand CA adhesive

6. an old .035” drill bit for the firing pin 

7. Nyrod with threaded brass end-piece to pull the pin 

8. Nylon rod for nozzle 

9. Sheet styrene plastic for fins

Mike's torpedo is 8.75” X 5/8” diameter and is divided into three parts. This is considerably smaller than those we will be constructing for the Scorpion HK. More in tune with the other standard 12.75" diameter torpedoes, though his is longer than many torps this size.

The nosepiece is a bullet-shaped piece of hardwood dowel rod glued into a 2.25” section of 5/8” aluminum tubing. The next 4.75” is aluminum tubing and the aluminum tail section is 1.25 with .25 of that fitted into the end of the tube. A Schrader tire valve (available at any auto parts store) is mounted in a hole in a cylindrical aluminum block that is glued and press-fitted into the aluminum torpedo body using a CA adhesive product called “Hot Stuff”. I remove the rubber part of the valve that goes into the tire rim with a lathe.

A bit of the threaded end of the valve is trimmed off to increase the torpedo's buoyancy. The valve is for filling the torpedo with compressed liquid propellant like Propel or Super Duster. Mike switched to Super Duster in his sub's ballast systems a number of years ago since it seemed to be less corrosive to the ballast valves. 

Mike uses “Hot Stuff” to bond the aluminum block onto the torpedo body because it is the only CA glue product that is marketed as being truly waterproof. You don't want your Schrader valve caroming out the end of your torpedo due to a water-failed glue joint and winding up in the eye of the curious six-year-old son of a lawyer standing nearby! The last 1.25” of the torpedo is tapered down to a diameter of 3/16” at the exterior if the stern. He drills the inside of the torpedo at the rearmost part of the end in a taper matching the exterior with the final .75” left solid in which to fit the shaft seals/bearings.

This is the engineering magic that reverses the direction of rotation of one shaft that is located within another. The essential element of this design is the crosshead and bevel pinions.

The above drawing shows how complex is the workings of a torpedo. This one is compressed air powered, the gas escaping through the hollow propeller shafts. They stopped using compressed air during WWII because it was too easy for men on watch to spot the bubbles on the surface. The move to electric motors cured that.

The Mark 14 torpedo was the US Navy's standard submarine launched anti-ship torpedo of World War II. This weapon was plagued with problems which crippled its performance early in the war, and was supplemented by the Mark 18 electric torpedo in the last two years of the war. Nonetheless, the Mark 14 played a major role in the devastating blow US Navy submarines dealt to the Japanese naval and merchant marine fleets during the Pacific War. By the end of World War II, the Mark 14 torpedo was a reliable weapon which remained in service for almost 40 years and even longer with other navies.

The Mark 14 was central to the torpedo scandal of the U.S. Pacific Fleet Submarine Force during World War II. Due to inadequate Depression-era peacetime testing of both the torpedo and its exploder, defects tended to mask each other. Much of the blame commonly attached to the Mark 14 correctly belongs to the Mark VI exploder. These defects, in the course of fully twenty months of war, were exposed, as torpedo after torpedo either missed by running directly under the target, prematurely exploded, or struck targets with textbook right angle hits (sometimes with an audible clang) and failed to explode. Responsibility lies with the BuOrd, which specified an unrealistically rigid magnetic exploder sensitivity setting and oversaw the feeble testing program. Its pitiful budget did not permit live fire tests against real targets, instead, any torpedo that ran under the target was presumed to be a hit due to the magnetic influence exploder, which was never actually tested.

JOHN DRAIN'S SUPERB MKXIII 1/20th SCALE MODEL TORPEDO DEVELOPMENT

John's objective was/is to produce an operational 1/20th scale WW2 US Navy MkXIII torpedo, complete with dual counter-rotational propellers. John had completed a relatively easy to make single prop model that performed well except that the body of the "fish" rotated in the opposite direction to the propeller caused by the bearing friction (a problem common to helicopters, and that just was not good enough, where such a design will give you a torpedo that wanders off course - hence, misses its target. His first torpedo was made of balsa wood, that is cheap, so he could afford to lose a couple in testing. John's balsa model torpedoes in 1/20th scale are 26mm dia and 206mm long. The resin cast project is 28.5mm diameter and 204.5mm long.

BALSA BEAUTIES - SINGLE MABUCHI MOTOR/PROP

The main body of the balsa wood based torpedo is made from 25 mm telecom conduit, which fits tight to a Mabuchi 260 motor. The outside diameter is just over 26mm - perfect! Both the front and rear ends are shaped from wood. The domed end and the tapered tail are turned in a stand drill to fit within the tubing, then drilled to allow the prop shaft to pass through. Final shaping is with with sandpaper. We prefer production paper.

John's lovely brass master tail fin

RESIN BABES - DUAL MABUCHI MOTORS & CONTRA-ROTATING PROPS

In real life, torps are fairly complex and that means costly. Regardless of the technical challenge, John decided to make a 1/20th model with contra-rotating propellers. Wow! Not only that, but he developed two different systems, one with a single electric motor and a bevel geared arrangement to drive two shafts, one inside the other. And then a two motor  system, where one motor is ahead of the other, driving a shaft that passes through the rear motor. This meant replacing the solid drive shaft of the rear motor, with a hollow shaft - as both motors were in-line. Brilliant. John describes knocking out the steel motor spindle (2mm) and replacing that with hollow brass tube (2mm OD 1.5+mm ID), as being "tricky but not difficult!"

Not only that, but John designed a printed circuit board for the project. Possibly a bit over the top, but then casting your own propellers in silver is also going that extra mile.

ABOVE: The superb PCB sporting dual Mabuchi motors - BELOW: complete torpedo resin casing assembled and ready to paint. The same 'through-motor' system could be used by aircraft modelers to recreate contra-rotating propellers on WWII aircraft. Why is no motor manufacturer making such a setup now that the space-saving innovation has been revealed?

To house all this wizardry John elected to make resin cast casings. He began by making a master tail for his moulds out of brass - and a fine piece of work that is. From this threaded master, and after several failed attempts at making a mould himself (it is tricky), a local jeweler made up a rubber (probably silicone) mould. This was used in conjunction with a brass inner, or plug, such that the resin casting came out hollow. Obviously, this process is fiddly, but imagine using a shaped charge to form a rocket cone, as NASA do sometimes. Or, making a swaged tube, which requires a tungsten two-piece dies (the metal equivalent of a mold) and plenty of lard for lubrication - as a spinning tube is pushed into the dies. By this means metal pen caps are made from brass or gold tubing, and soft drink cans are deep drawn from aluminium sheets. You need to make a very accurate nose cone, or dome, or any skew will act to steer the torpedo in different directions as the body rotates, especially with a single prop - making things very unpredictable. A bit like firing a fuse cannon in a swell. Who knows on which roll of the ship it will fire.

ELECTRIC MOTORS

The later, twin-motor, resin torpedo really moves. John says he's clocked them at the equivalent to a full size 72 Km per hour (45mph), this was using two modified 130 Mabuchi motors and two 750mAH AAA NiMH batteries. With this setup the torp goes for more than 15 minutes on a full charge. Now that is some chase. John was enjoying the runs so much he bought a new battery charger, reducing the NiMH charge time to a couple of hours. His old charger was taking days. John likes his Sony charger that takes two AA or AAA batteries for about USD$30.

A far simpler modeling solution - still with the crosshead and bevel pinions

CONTRA ROTATING PROPELLERS

Once again John leaves behind him a wide development trail. His contra-rotating gearbox is built using two each of the "Scalextrix" type slot car (Crown (big) and Pinion (little)) gears. These are a bit bigger than the tiny AFX gears. This means that the inner shaft can be 2mm diameter, the same as the diameter of the motor shaft and shaft on a single prop torpedo. 

The assembly will fit in the new resin body to hold the cross beam with the pinion gears. The crown gears are modified by cutting off the "hat" section with a sharp scalpel and the holes need to be drilled out slightly to fit.

John's splendid silver props. Contra-rotation not only balances out bearing friction spin, but also increase the conversion efficiency of the propellers, in creating thrust from what is in effect a rotary wing.

SILVER PROPELLERS

John had his props cast in solid silver, saying that it was cheaper to use silver than cast in brass, but we think he used precious metal because his torpedo is a gem. Incidentally, once you have the props made in any material, you could then investment cast them in virtually any material, including titanium. This is a jewelers method, but they also use investment casting to make stainless steel hip replacements.

The silver hubs are tapered to match the shape of the torpedo body, so the front prop has a larger hub than the rear and different size holes: 2mm for the first (closest to the torp body) and 1mm for the shaft within the shaft (the end prop). The blades were made the same size for both props to move the same amount of water for a balanced thrust - to help prevent torpedo body rotation. This means that the rear (end) propeller is smaller in overall diameter by the difference in hub size.

John's drawing of the US Navy torpedo, scaled as the 1/20th model

TWIN MOTOR CIRCUIT BOARD

A nice touch (of class) was using a printed circuit board with:

* Three "Ultra Low On Resistance" MosFet transistors per motor

* A reed switch

* Two surface mount resistors (smr)

* Three surface mount capacitors (smc)

* Seven surface mount transistors (smt), and

* Four battery clips. 

Lastly, in go the two modified motors, one of which has a hollow shaft. Hence, the torpedo is a: "hollow shaft torpedo." John prefers "hollow motor torpedo." Whatever name you give it, it's hats off to John for thinking of it. Didn't Ken Norris do something like this with Donald Campbell's jet engined Bluebird CN7, where drive shafts came out of the back and front of the engine, to give four wheel drive? Not quite, but the logical thought (drive) train is similar.

Simple but effective. The above magnetic reed switch keeps the motor power circuit open, until launched into the water, where there us no magnet - so the circuit completes and off she goes.

MAGNETIC REED SWITCH

The magnet fore this switch is mounted on the Roll Off Rack of the PT-Boat, the reed is mounted inside the torpedo. The purpose of the reed switch is to make the motor spin as soon as the torpedo rolls off the side of the PT-Boat.

The magnet must be mounted the right way around or it won't work. These switches are magnet biased to stay ON when away from the main magnet.  Be careful here, you need a reed that is OPEN when near the magnet - rather than closed. The heavy mountings can be cut off to reduce the overall weight.

You try and buy a true 8 channel digital proportional RC set for under £100. Not only that, but this combination rig allows some neat tricks without getting all hot under the collar. It's ideal for aiming SAMS, firing cruise missiles and guiding torpedoes - all in one command unit.

TORPEDO GUIDANCE SYSTEM

Neither of Mike or John's masterpieces are steer-able, but it is a relatively simple matter to include a rudder and magnetic coil system, to be able to guide the torpedo to her target using a standard R/C set. We will be doing this with our version of the MK48s. We've worked out how to obtain running stability for the steering to work, with just one fin-rudder. As time allows we will post for other submarine modelers to enjoy.

We'll leave it to John to give the weapon bite with an explosive head. Wargaming clubs used blanks as the charge, routinely leaving 2" holes in the side of ships targeted - at which point they were written out of the rules. Why? We'd not be content with a crack from a firing pin. Most torpedoes though, use proximity fuses - so even easier. The problem then is disposability and cost per shot. That is of course the cost of real warfare, where torpedoes cost an arm and a leg.

THE SUB COMMITTEE

The SubCommittee is a not-for-profit organization of members from around the globe who share an interest in building model submarines. As a group they are dedicated to the advancement of the submarine modeling hobby. The SubCommittee was created in 1990 as a network of like minded submarine enthusiasts to pool their resources. The founding members were Ken Hart, Marshall Clark.

In pursuance of the shared interest in submarines SubCommittee compile specific information on the latest techniques for building model submarines, both for static display and radio-control, reviews of model kits, and sources of modeling supplies. Sc's interest also extends to the history and design of submarines of all nations and eras, research and reference material about submarines, the collecting of submarine memorabilia and anything else submarine related.

SubCommittee members are some of the most knowledgeable submarine historians around. They have served as consultants for museums, authors, and film-makers. SC's ranks contain former submariners from several navies. This includes the late submarine legend Edward L. "Ned" Beach a former member.

Direct contact between members by phone, email, letter, and our message boards is promoted. The SubCommittee is at its core an information network of friends helping friends. 

The SubCommittee brought together outstanding modelers from around the world and pooled their resources in the SubCommittee Report, or SCR, the world's first magazine dedicated to submarine modelling.

SUBREGATTA

With membership growth SC held their first international meeting called: SubRegatta. SubRegatta was so successful that it became an annual event, initially hosted by the U.S. Submarine Base in Groton, CT. The event moved to Johnston, RI following the commencement of the War on Terror in 2001. SubRegatta subsequently moved to Carmel, IN in 2005 and has been held there to this day.

SUBMARINE INDEX

Alvin DSV - Woods Hole Oceanographic Institution

Deepsea Challenger - Mariana Trench, James Cameron 2012

HMS Astute 1st of Class

HMS Vanguard- Trident

INS Sindhurakshak - explosion & sinking

Littoral combat vessels

Lusitania - Torpedo attack

Nuclear submarines lost at sea

Predator - Covert submarine hunter/killer

Seawolf - Autonomous wolf pack deployment of Predator mini-subs

Torpedoes - UUV anti submarine weapons

Trieste - World record depth - Mariana Trench 1960

U20 - Kapitan Leutnant Walther Schwieger

USS Alabama - 

USS Bluefish WWI submarine

USS Bluefish - Nuclear submarine

USS Flying Fish

USS Jimmy Carter - Seawolf class fast attack nuclear submarine

USS Nautilus - 1st nuclear submarine & subsea north pole passage

USS North Dakota - 11th Virginia class submarine 

USS Scorpion - Lost at sea with all hands

LINKS & REFERENCE

http://www.rc-submarines.net/torpedoes.html

PT boat contra rotating electric torpedo

Sub Committee

Radio Controlled submarines how do you keep the water out

Wikipedia Mark_14_torpedo

http://en.wikipedia.org/wiki/Mark_14_torpedo

https://www.schraderinternational.com/

http://www.rc-submarines.net/how-do-you-keep-the-water-out.html

http://www.subcommittee.com/

http://www.rc-submarines.net/torpedoes.html

http://www.pt-boat.com/torpedo/torpedo.html

This website is Copyright © 2014 Bluebird Marine Systems Ltd.   The names Bluebird™, Bluefish™, SeaNet™, SeaWolf™ and the blue bird and fish in flight logos are  trademarks.  CONTACTS   The color blue is a protected feature of the trademarks.