Diesel-Electric Submarines: World’s Biggest Hybrids

-NOTE: Today’s post is another one by my friend Lee Wilcox. If you’ve been getting tired of all my ’70s-era luxocruisers, here’s something completely different. And very interesting. -TK

The Chevy Volt has gotten a lot of attention from 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


18 Replies to “Diesel-Electric Submarines: World’s Biggest Hybrids”

  1. -Nate

    Thank you ! .

    This is fascinating .

    Uncle Bill was in Diesel boats early in WWII before some accident that caused his loss of smell .


  2. Newbie Jeff

    Great piece, thanks for sharing…

    …something that always comes to mind when I read about the mechanical intricacies of military equipment, whether it’s a P-51 Mustang, a Sherman tank, a U-boat, or an aircraft carrier: it’s one matter to just turn the thing on and keep it running, it’s quite another matter to deploy it against enemies and fight with it. And in WW2 especially, you were likely fighting against enemies (regardless of which side you were on) with military equipment that was equal, or even superior, to your own. Words really can’t express the respect I have for WW2 combat veterans…

  3. JustPassinThru

    When I went in the Nav…I had decided, two things I wasn’t going to do, were, jump out of a perfectly-good airplane, or get on a boat that sinks itself. We had a fair amount of the sub-surface fleet rotate through my carrier, partly because it was home-ported Stateside. Sometimes an enlisted has to take a less-desirable assignment to have a more-desirable location.

    Of the non-nuke submarine fleet, I knew little…the guys with experience there had all gone. But, from the Navy, I went railroading – that massive Cleveland Diesel (former Winton Engine) engine, is, in general size and shape, quite similar to the modern EMD two-stroke locomotive diesel engine.

    Of which, the photo you used, is one I’m familiar with. CSXT 786 had come through my assigned territory a number of times. I’d run it. Long ago, locomotives were assigned to terminals to aid in maintenance schedules, but those days went away at least 20 years ago. CSX runs their power all over the country – even on run-through trains, they’ll often leave power on for Western railroads to take through to West Coast ports or terminals. So, power that had been around Buffalo or Cleveland, could easily pop up in Atlanta or Jacksonville, or even take an extended tour of the West.

  4. Tyler

    I have heard it said that you will know we are really scared when we start building diesel electric subs again to patrol our own littoral waters.

    On the other hand I’d love to see them take one out of dry dock and give it to Michigan DNR to scare the pants off some drunken pleasure boaters.

    great stuff.

  5. hank chinaski

    Nice piece. I was lucky enough to score a tour on an Ohio class some time ago. One quote that still comes to mind: when passing through the compartment housing rows of targeting computers (which today would probably be nearly Raspberry Pi sized), and I paraphrase: “all of the equipment in this room is designed to survive a blast up to [very large number] of G’s, except the people”.

    The series/shunt design always struck me as a more logical approach to automotive efficiency, given current infrastructure and battery tech constraints, but lacks the virtue signalling of a full plug-in. One design I recall, and it may have been floated only on paper in a dentist office’s Popular Mechanics, was powered by a sub-13B sized all-fuel turbine engine. IIRC, Mazda did toy with a single rotor, horizontally placed Wankel series/shunt in a ‘2’ prototype.
    The Volt should have done better than it did.

  6. Compaq Deskpro

    It wasn’t just asbestos. Daily contact with battery acid, lead paint, and lit cigarettes, all crammed into a tube. What exactly went into managing the air?

    • Buck Turgidson

      ‘managing the air’????…. ‘managing the air’??? Sonny, them Rooskies are gonna blow us and everyone you love clean off this rock, and you’re worried about ‘managing the air’? Damn son… take one for the team: stand your watch, fix those batteries and never mind about the air! You can breathe after you’re back in civvies!

  7. Jax

    Arguments against hybrid systems are produced by auto makers..that rather should be producing hybrids..
    The battery tech just does not exist ( but it will) to be fully electric in a commercial truck..
    Unless of course a hyway run that Walmart or Fedex uses..
    My turbo diesel Benz 700 mile range is old and heavy..if its AWD had an integrated hybrid system my MPG would be 50 mpg rather than 28 mpg..

    • -Nate

      I guess you just ignore the inner city Coca Cola all electric big rigs that are every where now….

      I too wonder how they manage this but don’t say it isn’t possible when it’s being done right now .


  8. Mrfixit1599

    When I was on boomers, you would think the nuclear reactor and all the warheads would be the most frightening thing to malfunction in some way. Not even close. The laundry, where there would be a small fire at least once a patrol, and the oxygen generator were the scariest.

    The oxygen generator would take water and split into oxygen and hydrogen, so basically a very large bomb should anything malfunction on it.

  9. Ronnie Schreiber

    My brother-in-law was in the sub service and did a couple of tours assigned to a nuclear sub (later served on sub tenders, then got a desk job doing IT). When you have enough surplus electricity that you can turn salt water into fresh water and then turn fresh water into hydrogen and oxygen, things get interesting.

    “How long can you stay underwater?”

    “Until we run out of food.”

    The thing about the cigarettes is true. They’d know it was time to make oxygen when it got difficult to light their cigarettes.

    • MrFixit1599

      That was true. Keeping a cigarette lit at times was a challenge, especially on weekends after a particularly long week.. They would let the oxygen level run down. Supposedly with the lower oxygen level, you had less energy, so it was easier to sleep longer, and get more rest before the next week started. No idea if that is true, but that was the theory I was given.

    • MrFixit1599

      That was true. Lighting a cigarette and keeping it lit at times was a challenge. Most of us had Zippo’s, but we all had Bic backups when the oxygen level got low.

      It was especially true on weekends after a particularly long week. They would let the oxygen level run down. Supposedly with the lower oxygen level, you had less energy, so it was easier to sleep longer, and get more rest before the next week started. No idea if that is true, but that was the theory I was given.

  10. bullnuke

    I operated and maintained Fairbanks Morse D38-8 1/8 engines as a nuke during my career in the Navy. They were the later 10 cyl/20 piston opposed engines used in later class submarines of WWII as well as main propulsion for LST’s. For our purposes they developed 1600hp with 1 mW 450VAC generators used for emergency power generation. They were indeed monstrous and fairly relentless when operating – saw a young guy drop down into the diesel room with an open box of poly trash bags, bags that were quickly sucked out of the box into the air intake silencer. The silencer (about 2 feet in diameter by 3 or 4 feet long with an 18″ or 24″ opening) sucked those bags out of that box like toilet paper off a roll. The engine was loaded, running at 720 rpm, but didn’t skip a beat – that now-plugged silencer collapsed like a beer can, ripped the horizontal welds out of it, and created its own air path to the engine. Tremendous engines that are still in routine use today.

  11. stingray65

    Great story, but the worst part about US submarines during WWII is that they (and torpedo bombers) carried defective torpedoes until rather late in the war so that even a direct hit wouldn’t set off the explosive charge. Imagine putting yourself in grave danger to get within torpedo range only to shoot off a bunch of duds against targets that would then have the opportunity to shoot back with working shells and torpedoes

    • bullnuke

      Stingray65 – Thank heavens we’re beyond that today. Look at those fantastic weapons elevators on the USS Gerald Ford that didn’t need to be tested prior to installation for use… whoops, maybe a bad comparison. Okay, then, how about those several dozen LCS 40+ knot wonderships that spend most of their time tied to a pier due to propulsion failures and cracked aluminum…. again, whoops, another bad comparison. Geeze, guess we haven’t learned much since the Mk XIV torpedo debacle (bad magnetic exploder, bad depth sensor, bad contact exploder) but luckily haven’t put many folks in immediate harm’s way utilizing these Puzzle Palace ™ transformational systems.

      • MrFixit1599

        I know when I was in, the Mk 48 torpedo we used was garbage, and that was the 90’s. Granted the few test shots we did were with test Mk 48’s but from my best memory, there was at least a 25% failure rate on the test shots.

  12. Dirt Roads

    I love this break from Tom’s fare of 70s land yachts. While I am a Boomer and gew up with those cars, for many years I looked at them with disdain while I drove my Fiat Spiders and little 128 econoboxes as hard as I could.

    Now let’s see some aviation-related posts to help round things out 🙂


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