Engine Hydrolocking, Airspace

Onkel Neal · 02-15-23, 10:56 AM

and that's why the air intake on a U-boat has an air gap between the intake manifold and the air induction.

Now, let's see a video of what happens when the exhaust line is flooded with 20meters pressure water!

.

Onkel Neal · 02-15-23, 11:02 AM

Also, great analysis of the whole water/diesel thing.

BrendaEM · 02-16-23, 01:40 AM

(Thank you @Onkel Neal)

I did a little looking, and I found a video showing an original U-Boat U-505 piston, with text stating that, yes they did carry spares, and they could be swapped at sea.

I haven't got a good look at a U-Boat engine, on it's own, but I've noticed that some diesels have a squarish access panel just above oil sump, which would be my guess as to how they got the piston and connecting rod out, as pulling a oil pan on any engine quite a feat.

You can stop the video here and there to read the text. I am not sure of the size, but if I knew the piston diameter, the rest would be easy. Well, it could be resized later, as long as it's in scale. In the video the some rings appear missing.

BrendaEM · 02-16-23, 01:42 AM

Wow, that's big! And a mere 1,100 lbs!
"From top of the piston to the bottom of the connection rod that is one and one half [1 1/2] meters. "
It looks like the piston on the photo above is about 10" in diameter.

https://www.pinterest.com/pin/a-big-...9628502868161/

And there it is, though missing the (piston) rings:

Notice that the big-end bolts are on the top. That is how they could take it apart without dropping the pan.

BrendaEM · 02-16-23, 02:08 AM

There's a piston @5:33, but it's different. I wrote the museum, the get the piston size.

LOL! Post from the thread: "...I also notice they are turning the engine over by hand; the Layman's term for that is "Barring" the Engine over, its done to make sure no Lube Oil, Fuel, or Coolant has gotten into the combustion chambers which would cause a "Hydrolock" condition, rendering the engine completely inoperable."

BrendaEM · 02-16-23, 03:17 AM

Well, here is the translated bore and stroke for various engines. It didn't do well with Roman numerals.

https://www-u--historia-com.translat..._x_tr_pto=wapp

Interesting:

"...A pair of Motoren-Werke Mannheim (MWM) RS34S (six-cylinder) engines were to be used as generators in the type IXd2 Uboats. These engines developed a power of 575cv at 750rpm. and had a bore by stroke of 260x340mm.
An engine almost identical to the RS34S, the RS134S would be fitted to the Type XXIII Uboats that began entering service in 1944. This engine gave the same power as the previous one but at 860rpm.

In both engines the crankcase and cylinder block were made of one piece. Each cylinder had two intake and two exhaust valves, a starting air valve and a pre-combustion chamber. This pre-combustion chamber could be electrically preheated to aid in cold starting. The engine had a valve to purge seawater that could accidentally enter when the uboat was submerged. ...."

260mm is a pretty big piston, my 10" guess was pretty close, 10.236220 Inches : )

BrendaEM · 02-18-23, 01:45 AM

(Updated)

For Haha's, I made a piston model (1st photo) in Rhino 3D. It's based on the U-Boat U-505 sub museum (3rd photo).
The German engine museum from the video above, wrote me back : ) They stated that the piston was a whopping 260mm in diameter, which makes the piston roughly a meter in length.

* Piston top is unclear in the drawings, done was added to top of piston.
* The flange/washer thing that holds the wrist-pin (gudgeon-pin) in is polygon-hungry, because the flatter of the areas is actually bend to match the piston radius. The original part appears stamped steel.
* Unlike a real-piston there is no gap on top/bottom of the rings in the model. This could save mesh complexity.

A U-Boat engine blueprint, with my piston drawing over it (rings would be compressed in cylinder):

A rendering 3D modeled piston. Boards are about 4" wide, like you would have on a deck. Piston is huge!:

The piston is pretty strange, in that the wrist-pin has a bolt and nuts holding it together--instead of C-Clips. I am unsure if they had distorted thread locknuts back then, such as Stover Nuts. It would be bad if the thing loosened up in the cylinder.
The piston is still huge. They must have had a special place for a spare.

I did a test in CAD. If the piston could have been removed from the bottom, then perhaps the notches on the piston crown would help the piston clear the lower part of the cylinder liner. The access panels on the side of the motor are pretty big. I had read that they could do a piston replacement at sea, but I have not yet read whether or not the head would have to have been removed or not. If they head had to be removed, that would be a major undertaking. But if the piston could be unbolted with a spanner, and sneaked out through the access port, then it wouldn't be so bad. Most pistons have their bolts on the bottom of the connecting rod, and perhaps the spanner nut would have allowed the connecting rod to be removed from the panel. The blueprint does not give a good indication of the stroke, which would let the position of the crank big-end be known. So it looks like the piston could be removed--if the connecting-rod would clear the crank.

02-15-23, 10:56 AM	#1
Onkel Neal Born to Run Silent Join Date: Jan 1997 Location: Cougar Trap, Texas Posts: 21,385 Downloads: 541 Uploads: 224	and that's why the air intake on a U-boat has an air gap between the intake manifold and the air induction. Now, let's see a video of what happens when the exhaust line is flooded with 20meters pressure water! . __________________ SUBSIM - 26 Years on the Web

02-15-23, 11:02 AM	#2
Onkel Neal Born to Run Silent Join Date: Jan 1997 Location: Cougar Trap, Texas Posts: 21,385 Downloads: 541 Uploads: 224	Also, great analysis of the whole water/diesel thing. __________________ SUBSIM - 26 Years on the Web

02-16-23, 01:42 AM	#4
BrendaEM Bosun Join Date: Aug 2022 Posts: 62 Downloads: 0 Uploads: 0	Wow, that's big! And a mere 1,100 lbs! "From top of the piston to the bottom of the connection rod that is one and one half [1 1/2] meters. " It looks like the piston on the photo above is about 10" in diameter. https://www.pinterest.com/pin/a-big-...9628502868161/ And there it is, though missing the (piston) rings: Notice that the big-end bolts are on the top. That is how they could take it apart without dropping the pan. Last edited by BrendaEM; 02-16-23 at 03:02 AM.

02-16-23, 02:08 AM	#5
BrendaEM Bosun Join Date: Aug 2022 Posts: 62 Downloads: 0 Uploads: 0	There's a piston @5:33, but it's different. I wrote the museum, the get the piston size. LOL! Post from the thread: "...I also notice they are turning the engine over by hand; the Layman's term for that is "Barring" the Engine over, its done to make sure no Lube Oil, Fuel, or Coolant has gotten into the combustion chambers which would cause a "Hydrolock" condition, rendering the engine completely inoperable." Last edited by BrendaEM; 02-16-23 at 03:00 AM.

02-18-23, 01:45 AM	#7
BrendaEM Bosun Join Date: Aug 2022 Posts: 62 Downloads: 0 Uploads: 0	(Updated) For Haha's, I made a piston model (1st photo) in Rhino 3D. It's based on the U-Boat U-505 sub museum (3rd photo). The German engine museum from the video above, wrote me back : ) They stated that the piston was a whopping 260mm in diameter, which makes the piston roughly a meter in length. * Piston top is unclear in the drawings, done was added to top of piston. * The flange/washer thing that holds the wrist-pin (gudgeon-pin) in is polygon-hungry, because the flatter of the areas is actually bend to match the piston radius. The original part appears stamped steel. * Unlike a real-piston there is no gap on top/bottom of the rings in the model. This could save mesh complexity. A U-Boat engine blueprint, with my piston drawing over it (rings would be compressed in cylinder): A rendering 3D modeled piston. Boards are about 4" wide, like you would have on a deck. Piston is huge!: The piston is pretty strange, in that the wrist-pin has a bolt and nuts holding it together--instead of C-Clips. I am unsure if they had distorted thread locknuts back then, such as Stover Nuts. It would be bad if the thing loosened up in the cylinder. The piston is still huge. They must have had a special place for a spare. I did a test in CAD. If the piston could have been removed from the bottom, then perhaps the notches on the piston crown would help the piston clear the lower part of the cylinder liner. The access panels on the side of the motor are pretty big. I had read that they could do a piston replacement at sea, but I have not yet read whether or not the head would have to have been removed or not. If they head had to be removed, that would be a major undertaking. But if the piston could be unbolted with a spanner, and sneaked out through the access port, then it wouldn't be so bad. Most pistons have their bolts on the bottom of the connecting rod, and perhaps the spanner nut would have allowed the connecting rod to be removed from the panel. The blueprint does not give a good indication of the stroke, which would let the position of the crank big-end be known. So it looks like the piston could be removed--if the connecting-rod would clear the crank. Last edited by BrendaEM; 02-19-23 at 01:38 AM.

02-16-23, 01:40 AM	#3
BrendaEM Bosun Join Date: Aug 2022 Posts: 62 Downloads: 0 Uploads: 0	(Thank you @Onkel Neal) I did a little looking, and I found a video showing an original U-Boat U-505 piston, with text stating that, yes they did carry spares, and they could be swapped at sea. I haven't got a good look at a U-Boat engine, on it's own, but I've noticed that some diesels have a squarish access panel just above oil sump, which would be my guess as to how they got the piston and connecting rod out, as pulling a oil pan on any engine quite a feat. You can stop the video here and there to read the text. I am not sure of the size, but if I knew the piston diameter, the rest would be easy. Well, it could be resized later, as long as it's in scale. In the video the some rings appear missing.

02-16-23, 03:17 AM	#6
BrendaEM Bosun Join Date: Aug 2022 Posts: 62 Downloads: 0 Uploads: 0	Well, here is the translated bore and stroke for various engines. It didn't do well with Roman numerals. https://www-u--historia-com.translat..._x_tr_pto=wapp Interesting: "...A pair of Motoren-Werke Mannheim (MWM) RS34S (six-cylinder) engines were to be used as generators in the type IXd2 Uboats. These engines developed a power of 575cv at 750rpm. and had a bore by stroke of 260x340mm. An engine almost identical to the RS34S, the RS134S would be fitted to the Type XXIII Uboats that began entering service in 1944. This engine gave the same power as the previous one but at 860rpm. In both engines the crankcase and cylinder block were made of one piece. Each cylinder had two intake and two exhaust valves, a starting air valve and a pre-combustion chamber. This pre-combustion chamber could be electrically preheated to aid in cold starting. The engine had a valve to purge seawater that could accidentally enter when the uboat was submerged. ...." 260mm is a pretty big piston, my 10" guess was pretty close, 10.236220 Inches : )