Diesel-Electric Submarines: World’s Biggest Hybrids

The Chevy Volt has gotten a lot of attention for its ability to run its electric propulsion motor from its internal combustion engine/generator, batteries, or both. Submarines having been doing that since the 1920s or so. I managed to spend some time on subs, and was always interested in what made them go. Apparently that interest is shared by a lot of folks.  Even during the cold war we had something called Visiting Ship Day.  Civilians were allowed to tour a designated boat.  The depth gauges were covered and some areas were off limits but they did tour.  There were three questions we could always count on:

1. Where is the picture window? (thanks to tv)

2. How many engines turn the propellers and how big are they?

3. How long until you start to run out of air to breathe?

Answers to them, and much more follow:

Graveside. Museum at Patriots Point, Charleston SC.

Let’s get those out of the way first:

1. There is no picture window regardless of what you saw on television.

2. There are no engines (directly) turning the screws.

3. It took about 10-12 hours until the guys couldn’t keep their cigarettes lit. Then we had to start managing the air.

Here’s the “more”. Now I’m a fan, not a gearhead, and I have no intention of passing myself off as an engineer.  Certainly you won’t learn enough from this to qualify either.  I was the ship’s corpsman but found all of this interesting.

L to R, propeller, shaft, reduction gear, main motor,cubicle, battery, generator, engine

What turns the propellers is an electric motor (seen here with reduction gear)  One major attraction of an electric motor is the immediate torque.  A series wound electric motor has 100% of its torque at zero rpm.  The type motor used in diesel electric subs is a series/shunt combination.

The diesel (far right) turns a generator (connected).  The electricity from the generator is sent to the propulsion motor, to the batteries to charge them (black box), or to both.  It is routed through the green box which actually may look like this.

It is here that the electricians mate distributes that electricity according to orders received from the control room.

The diesel electric system has a few drawbacks. Yet in some respects it is considered by many to be superior to a Nuclear Submarine. One of the advantages was that diesel-electric subs could run quieter under water, because nuclear subs had to keep their reactor circulation pumps running. That eventually was solved. And of course, nuclear-powered subs have an almost unlimited underwater range. Nevertheless, diesel-electrics were built for a long time yet.

Starboard (right) engine GM16278AS.

This is the room where it all starts.  With no engine there is no electricity being produced and no battery being charged.  Most of the engine is below the deck plates.  For a better scale of size, see picture below. And for a more detailed look at the inner workings, here’s a good link.

Others diesel engines have been tried, but two types of engines (with almost identical horsepower characteristics) were used on almost all the operational diesel electric submarines during and since WW2. Winton Motor Company developed a 2 stroke diesel engine that was a reliable powerhouse. They were later bought out by GM, and later versions built at GM’s Cleveland Diesel Engine Division.  The model numbers were 248 and 278, which referred to the cubic inch displacement of each cylinder, similar to GM’s Detroit Diesel engines. Each cylinder had an individual head for convenience of maintenance.  Many times an engine would have a head change (normally underwater where they were shut off anyway) and be back on duty in few hours.

This engine was so big that they did not use a starter motor.  Bore and stroke on the 278 was 8.75 by 10.5 inches.  They were rolled over and started with a massive bank of compressed air.  The fuel racks were shut down to turn off the engine.  They were an unfailing source of fresh air when the air got stagnant.  Just a few minutes sucking atmospheric air changed the whole atmosphere.  The wheels on top of the engine in the picture above determined the source of the engine air.   In the top/center of this engine you can see the large induction manifold.  I hope this picture can convey just how huge these engines really were.

GM16248 loaded on a truck bound for repair shop

I believe those engines would have burned rags if we could have gotten them through the injectors.  Lubricating oil came through a separate external tank and pump. Frequently the engine would be burning lube oil or anything with a viscosity lighter than water as the fuel tanks were pressurized (from the bottom) by the trim and drain system.  Simply put, anything in the bilges made it to the trim and drain system and, if lighter than water, floated with the fuel and above the water in the fuel tank.  It was probably consumed.

They wouldn’t burn water, despite what any fuel saver advertisements in the magazines might say.  Pistons compress more than the water does and rods break.  How do we know this? Because someone forgot to drain down the condensate on one of my boats and ruined an engine.

Both the General Motors and Fairbanks Morse engines developed 1600 bhp.  The GM units developed it at 750 rpm and the FM at 720 rpm. I know a lot less about the Fairbanks Morse engine.  The typical FM engine was a 7 cylinder engine but it had 14 pistons.  It was an opposed piston engine based on the Junkers Jumo design, and spending time looking at it seems to be fascinating to most gearheads.

Fairbanks Morse Opposed Piston 2 cycle Diesel Engine

The enginemen who maintained these engines seemed to prefer the FM, although both brands had their fans.  Not having cylinder heads, I am told they required less maintenance.  When they did break, however, the consensus is that they could be much more difficult to repair.

Sub Fairbanks Morse engine with cat engine alongside

This picture is of a seven-cylinder Fairbanks Morse.  For comparison you can see the block of a Caterpillar six cylinder engine as might be typically used in a semi truck.  These engines turned this generator below.

Main Generator Not much different than the generator on an old car except for the size and output.; 300 KW at 1200 rpm. Every engine had one of these. Without electricians mates throwing the sticks below, the power had nowhere to go.

In World War Two, each submarine had four engines and two batteries. What you must understand is that these are huge battery banks.  Frank Sinatra used car batteries in his film “Assault on a Queen”.  They could have hardly kept the lights on.  Each battery had 126 cells.  Each of these cells was about 54 inches high, 15 inches deep by 21 inches wide.  Each cell weighed about 1650 pounds. That’s about 104 tons per battery.

Battery Well

These were lead plate batteries containing electrolyte.  As if being a heavy space hog weren’t enough, each one produced hydrogen gas when charging or discharging and the electrolyte made dangerous chlorine gas when mixed with salt water.  This is what those large cells really look like.  Just a clutter of wires and battery tops.  We lost the Cochino to a hydrogen battery well explosion with chlorine gas release in 1949.  These batteries contain a lot of energy.  Sometimes that energy is released in a violent manner.

These cells had to be serviced every day.  That was normally done by the youngsters in the electrical gang.  You could always spot them by the condition of their clothes which were eaten up by battery acid.

These batteries were normally placed in parallel for routine underwater propulsion.  When placed in series they could be run down in 30 minutes. Shutting down from series battery and having a power surge is alleged to have been the cause of a deep dive misadventure of another submarine.  I was on SS343 and the two boats I just mentioned were also SS34_.  Gives one reason to pause.  Obviously, series battery operation would have been used for escape or other emergencies.  Whether being charged or being discharged these batteries produced hydrogen.  A battery might have to be secured if a single ventilation fan in the battery well shut down.

Direct drive main propulsion motor

During the period after the war the Navy felt the need to increase the underwater power and increased the number and power of the batteries. Two batteries became four batteries at the expense of space.

Motors:  There were either two main motors or four main motors.  Therefore each shaft might have one or two motors attached.  The ones in the schematic are running through a reduction gear and would have been rated at 1370 horsepower running at 1300 rpm. These direct drive motors in the picture would have been lower speed.  They would have pulled about 2600 amps at 415 volts.  Obviously if the shaft has two motors, double that. If you have ever bump moved a car with a starter, for comparison that is 12 volts at less than 50 amps.

I suppose all this talk could get confusing.  It isn’t complex, there is just a lot of it.  Hopefully, this drawing will put the parts in perspective.

Thinking of this as unique would be correct because of the scale.  The Navy was probably at the forefront in developing the hybrid vehicle.

There is of course a land based vehicle that uses diesel engines and electric motors in much the same way. But there is an important distinction: locomotives aren’t hybrids, because their power source always comes only from the the diesel- driven generator. The exception being some very recent yard-switching locomotives that do have batteries.

The Fairbanks Morse submarine powerplant was essentially the same as the company used in their locomotives produced after the war. For years the railroads were an excellent source of employment for ex-sub engine men. Here’s a more detailed explanation of how these F-M opposed-cylinder engines worked.

Needless to say, nuclear-powered subs eventually replaced the diesel-electric sub. Since we haven’t yet seen nuclear-powered locomotives, maybe Ford’s Nucleon concept mock-up of 1958 will not be a harbinger of things to come. Of course, Nissan Nuke does have a nice ring to it.

Mama and I when we were younger