Technical Question - Engines
 

1) a)Why are diesel engines used by Submarines on the surface? Why not Electric?
b)Again, why electric underwater...why not diesel?

2) Can ships use Electric engines? (WW2 era)

Diesels require air as well as people in the submarine therefore under water you have just so much air to breath and run diesels. Not until the schnokel was developed that diesels could be run underwater as they had an air source above the water. When this schnokel would submerge for a split second, the pressure from the diesels sucking air from inside the boat would make ears pop and hurt the lungs of the crew.

Electric engines were used on the surface. Usually leaving port. Other than that, the batteries were saved for submerged action or escape.

As far as ships using electric engines. Does not make much sense for electric on ships unless your trolling for trout.

This game does not allow you to run electrics on the surface.

Was it not true that if for whatever reasons the diesels running at standard had only the air inside the submarine to feed them that they would evacuate the entire subs air supply in like 3 seconds and turn the tube into a vacuum?

Think I read that in Iron Coffins, then the men working in an almost "outer space" type environment would have to clear whatever was keeping the schnorkel from supplying air. Or die.

Chuck

Yes, what would happen if the schnokel submerged for a brief second, this was enough time for the diesels to suck the air up inside the boat. Ears popped, eyes bulged, lungs hurt and headaches occurred. For a guy like me who has had three collapsed lungs, I would not want to try this out for fun:nope:

I do believe that it took longer then 3 seconds however. Not sure of the exact time.

You have to remember to that with snorkel raised the uboat could only do around 6 kts or it would snap off
And I think its safe to say that in rough weather it wouldnt be used

I bet it didn't. These diesels were very large and I suspect each piston in high rpm sucked quite a few cubic feet of air rather quickly. There is a way to find out. We need to know the litre of each piston, the cubic feet air within the boat. How many revolutions (intake stroke) each piston is making. I do not have access to this information.

We also have to consider that the air taken is not replaced as the boat is submerged. I bet it gets real ugly real fast.....

To the first question: electric motors can be used on the surface, but the electricity has to come from somewhere. It can be (and is) stored in batteries, but the electricity gets used up (which is why they are actually known as storage batteries) and they have to be recharged. This can only be done by applying an outside source, such as a generator which has to be run by something like a diesel engine.

Does anyone know the names of the engines used by german u-boats? IE: MAN or anything like that...Like the ViiC, for instance.. How many HP, how many pistons and so on... Technical data, all in all...:hmm:

The following only applies to the type VII subs as my knowledge on other types is limited.

There were two makes of diesel engine used they were the Germaniawerft & the MAN,

They were fundamentally the same in appearance & HP, both were six cylinder direct reversing engines.

The main difference was that That the GW was supercharged (shaft driven) & the MAN had a turboblower. (turbocharger)


The horsepower ranged from 2310 to 3200 depending on year & variant, at a maximum of 485 RPM.

The bore And stroke was 40 cm x 46cm.

When snorkels were fitted the reversing cams were removed & replaced with snorkeling cams to overcome the increased exhaust back pressure, so reversing had to be done using electric engines as the diesels could no no longer run in reverse.

When the snorkel dipped under water it took about sixty seconds for the engines to consume the air in the boat but the effects were felt much sooner due to the sudden pressure drop inside the boat.

I hope this is of interest & helps answer a few questions.

Thanks for the replies guys, that was a valuable insight into the world of Pistons and grease.

You could make a hell of a vacuum cleaner with a pair of those motors.

Q1a: Because diesel engines (in WWII era) is capable to generate a large power for a huge U-boat

Q1b: Diesel engines burns diesels to generate power. Oxygen is used as a result

If it operates underwater, it draws oxygen from the boat and give out carbon dioxide (and even poisonous carbon monoxide due to insufficient air supply)
As a result, the crews will ... die

Q2: Yes, but practically impossible since no electric engine has been made to let a heavy merchant ship to cross Atlantic (due to lack in power and endurance)

Also, I believe the US boats in WWII technically ran off electrics all the time, that is, the electric motors would always drive the screw shafts, and the diesels would be used simply to generate power for them.

http://www.fleetsubmarine.com/propulsion.html