Naval Torpedos with Internal Combustion Engines

I recently learned that the Japanese Long Lance Torpedo used an eight cylinder two stroke radial engine. They are always described as oxygen propelled but it was actually some type of oxygen rich fuel being fed into the two stroke engine. I've been looking around the web for a couple of hours but can't find hardly anything on torpedo power plants from any country.

I found this document on US torpedo which shows a radial engine, I think, but doesn't say anything about it at all:

Torpedoes Mark 14 and 23 Types


As the torpedo is fired, the starting lever is thrown aft by the tripping latch in the tube, and this action lifts the starting piston off its seat. As the starting piston is lifted, the high-pressure air banked up over the starting valve is released, thereby allowing the starting valve to lift. As the starting valve lifts, the air passes to all the operating mechanisms of the torpedo.

I did learn that it is OK to have an even number of cylinders in a radial engine bank if it a two stroke.

Anyone have any pictures or other info on these engines?

Thanks

EDIT:

I just tried "Torpedo Radial Engine" in Google and got a good hit on HMVF

8 Cylinder Torpedo Engine - Restoration

 

How do torpedo engines work under water?
Batteries and an electric motor -- This is the same technique that any non-nuclear submarine must use when running underwater.
Engines that use special fuel -- Most engines that we are familiar with, like car engines and jet engines, draw their oxygen from the air around the engine and use it to burn a fuel. A torpedo cannot do that, so it uses a fuel that either does not need an oxidizer, or it carries the oxidizer inside the torpedo. OTTO fuel (see the links below) has its own oxidizer mixed with the fuel. Hydrogen Peroxide (as discussed on this page) does not need an oxidizer.


https://www.epa.gov/sites/production/files/2014-11/documents/tsd11.pdf
Propylene Glycol Dinitrate1,2. Acute Exposure Guideline Levels. SUMMARY. Otto Fuel II, a liquid propellant used exclusively by the U.S. Navy in torpedoes and ...

Haven't fully read this one yet - its getting late here and my eyes are tired -
https://www.quora.com/What-type-of-engines-were-used-to-propel-the-torpedoes-in-WW2

TD



G7a torpedo - Wikipedia
The Type 93 torpedo had a main chamber filled with pure compressed oxygen, a joint regulator valve preventing reverse flow, and a small (approximately 13-liter) high-pressure air tank. First, compressed air was mixed with fuel, and the mixture was supplied to a heat starter. Ignition started gently, with the mixture burning steadily in the engine (if oxygen was used at this stage, explosions were common). As the compressed air was consumed and lost pressure, high-pressure oxygen was supplied from the main chamber through the joint valve into the compressed air tank. Soon the air tank was filled with pure oxygen, and combustion continued in the engine.

 

The main torpedo used (although there were others) by the RN in WW2 was the 21" MkVIII powered by a Brotherhood burner-cycle engine.
From Torpedoes of the United Kingdom/Britain - NavWeaps
Britain held a technological lead in torpedo development for much of the period between the World Wars, but they were overtaken by the Japanese with their use of pure oxygen. However, the British remained ahead of all other nations. This success was mainly due to the adoption of the Brotherhood burner-cycle engine. The burner-cycle engine was in effect a semi-diesel. Typically, air pressurized to about 840 lbs./in2 (59 kg/cm2) was heated to about 1,800ºF (1,000ºC) by burning a small amount of atomized kerosene-type fuel. This hot air/gas mixture was then fed into the engine via poppet valves and more fuel was injected into each cylinder a little before TDC (Top Dead Center). The spontaneous ignition of this mixture powered the engine.

Tim

 

Thanks Tim

Found this page with a Brotherhood engine on it. Looks like it might be a three cylinder radial. I wonder what the displacement is.

HERBIE!: More on that engine and life aboard another kind of boat

 

Apparently, when tested, the 4 cylinder radial Brotherhood burner cycle engine routinely produced 550 hp.

 

Over on the other side (HMVF) there is a thread about the investigation into how an 8 cylinder torpedo motor worked.
it is ongoing not complete yet.
8 Cylinder Torpedo Engine - Restoration

 

Extracted from: 21-inch Torpedo Mk.VIII (Demonstrator) This link also contains more info and pictures.
Mark 8 Torpedo Mod 4
This version was wired and connected to the submarine by an umbilical cable which allowed electrical pre-set of depth and direction before launch.
Propulsion System
The torpedo is powered by a 4 cylinder radial engine. Compressed air from the main tank at 2500 psi is fed via a reducer (down to 550 psi) into the engine. Fuel is also added. The fuel was original Broxburn shale oil (home produced) but went on to be paraffin or kerosene.
Starting
The start lever knocked back on launch. This allowed compressed air into the system to start pressurising. Water or compressed air is used to force the torpedo from its tube. The torpedo does not start running until its outside it tube. The propeller would be windmilling to assist t engine start up. Heater starts up to heat pocket in front of motor casing. This heats air before going into reducer to prevent freezing and also heats fuel. Increases engine efficiency. There is no speed control. Engine will run at full power for 4 – 5 mins to give the torpedo a speed of 41 knots and a range of 7000 yds. The engine exhausts via the hollow prop shaft and out through the centre of the propellers. Engine compartment floods to keep engine cool. A flap valve at the side of the engine operates on launch. This starts the heater, allows fuel into the engine and can determine the length of run. If the torpedo did not hit its target it would then sink. German torpedo’s didn’t do this. They floated and became mines.

Tim

 

Hi Tim. I saw a couple of WW2 torpedoes down at Portsmouth but I don't remember seeing any sort of a lever for starting the engine, just a smooth unbroken metal surface. Would it be on the underside of it I wonder? Also had the same query with a V1 down at the De Havilland museum I.e. could not see how the starter was connected to start the spark plug but I didn't consider it until later so never asked at the time?

 

Is this the one? I use Google "ww2talk bla bla bla" for searches now.

Wire-guided Victorian Torpedoes.

 

Now forty-five years ago whilst at university, one with a plethora of military-scientific links and funding, a postgraduate friend was working on a "sealed" steam engine - he was convinced it would work. His puzzle was why it had to fit a tube 21" diameter. When told he was not concerned it would be a military development, nor was it openly MoD funded.

 

Short answer is I don't know. I would however think that any external lever would be subject to damage when loading a torpedo firstly into the submarine and then into the tube. It may be there is an internal lever which is thrown back by the inertia of launching.

Tim

 

This is an RAF instructional film from early in WW2 about the operation of the airborne Mk.XII torpedo used by the RN & RAF.

 

Ok Tim. It could work by inertia. The thing that suprises me is the amount of detail that goes into explaining how a torpedo works and no-one seeming to know what started the engine. What I used to think was that when the torpedo left its tube the pressure of the water started the propellers revolving which, as it were, kick started the engine, but it would be good to know for sure.

 

Can only talk about air dropped British.

The primary engine starting control was the air lever, the upper part of this projected above the top surface of the shell, attached to a quick release clip,
A cable pulled the lever aft, over a pawl, as the torpedo fell from the aircraft. It was initially held into safe position by the action of a small spring loaded plunger.

This admitted air from the bottles into the engine where the RNTF or B cycle heater/generator/igniter in conjunction with the fuel was used to complete the pre combustion process.

Gyro was cocked by being wound up against a spring. Action on dropping moving the air lever also moved a pushrod which tripped the trigger tappet allowing the wound spring to spin up the gyro.

So as soon as it left the aircraft crutch the props would turn by internal bottle air pressure, gyro spin up and almost immediately the combustion engine would ignite and self sustain

At 13.19 time mark on the above video, in the cut away engine room, you can see the crescent shaped air lever protruding with the associated spring for the plunger.

28.30 is an above view with the range dial

Ross

 

Ok Ross, many thanks for that. I was wondering about the ones that dropped in the sea from a MTB, I can only take it that a torpedo dropped by a Motor Torpedo Boat without a tube would work the same way. I.E. with a cable?