Real Submarine Technology & History Q&A

[RodBorza]

Originally Posted by Deamon

Are you sure it is only small ? in my understanding it should actually become even higher than what is drawn from the batteries cause this is the only way how you can send current from the motor to the batteries. You have to reverse the potential, means produce a higher voltage with the motor than what the battery currently have.

No that is not what i wanted to know. I am talking about how does the current batteries voltage gets topped by the motor, i mean how does the current gets reversed and flow from the motor to the batteries ?

Again, in my current understanding to achieve this you need to generate more voltage with the motor than what is in the batteries(overpowering). But you said the motors generate only little voltage so how do you top the battery voltage ?

Ok, there's a miscommunication here. So, what you want to know is even simpler: the current flow occurs naturally from the point with the higher voltage (source) to the point with the lower voltage (load).

Now I understand what you meant.

Let's say you have 90% battery charge and put the generator to recharge. So, in this case you need to put the gen at flank speed because it will generate more voltage (100% V) than what the batteries have, so current will flow from the gen to the batteries. It goes until the batteries are at 100% V, then the current flow would get to zero and there's nothing else you should do.

In other scenario, if you have the batteries at 10% V and the generator set at ahead standard (let's say 50% V power being generated) you would recharge the batteries up to 50% V. In order to recharge the other 50%, you would need to set the generator at a higher speed (more V).

That's is the reason why they put the generator at Flank speed. It will generate at the highest voltage available and send it to the batteries. Depending on the state of the batteries, if the charge is very low, more current will flow from the generator to the batteries and it will get lower as the battery voltage increases.

Then it is a matter of opening a switch, enganging the clutch again and that's it. Batteries charged, propulsion normal.


When feeding the motors with the batteries, things are even simpler.
Once you submerge, the engine is disengaged from the motor by the clutch, then you close the switch and the current will naturally flow from the batteries to the motor, since the batteries will be at higher voltage than the motors. In this case, for the source (batteries) the load (motor) will always be at a lower voltage. No need for a special operation of any kind, since it occurs naturally.

[Deamon]

Originally Posted by RodBorza

Ok, there's a miscommunication here. So, what you want to know is even simpler: the current flow occurs naturally from the point with the higher voltage (source) to the point with the lower voltage (load).

Now I understand what you meant.

Let's say you have 90% battery charge and put the generator to recharge. So, in this case you need to put the gen at flank speed because it will generate more voltage (100% V) than what the batteries have, so current will flow from the gen to the batteries. It goes until the batteries are at 100% V, then the current flow would get to zero and there's nothing else you should do.

In other scenario, if you have the batteries at 10% V and the generator set at ahead standard (let's say 50% V power being generated) you would recharge the batteries up to 50% V. In order to recharge the other 50%, you would need to set the generator at a higher speed (more V).

That's is the reason why they put the generator at Flank speed. It will generate at the highest voltage available and send it to the batteries. Depending on the state of the batteries, if the charge is very low, more current will flow from the generator to the batteries and it will get lower as the battery voltage increases.

Then it is a matter of opening a switch, enganging the clutch again and that's it. Batteries charged, propulsion normal.


When feeding the motors with the batteries, things are even simpler.
Once you submerge, the engine is disengaged from the motor by the clutch, then you close the switch and the current will naturally flow from the batteries to the motor, since the batteries will be at higher voltage than the motors. In this case, for the source (batteries) the load (motor) will always be at a lower voltage. No need for a special operation of any kind, since it occurs naturally.

RodBorza, thanks. However this much i already figured out. What i wasn't sure about though was how much voltage does a particular motor generates at a given RPM ?

I wasn't sure what a realistic approximation would be, cause it seems to me that the motor, even at top speed, would run on a fairly low voltage, compared to what the battery provides. Would you agree on this ?

Another thing i need to figure out is what is the maxim current that we can take out of a battery ? Or in other terms what is the internal resistance of a typical u-boat battery cell ? and what can the typical resistance of the power lines from the batteries to the motors be ? Lets say we have a battery of a nominal voltage of 130.

What i also need to know how much amps do we loose through the resistance ? Particularly when we run the current through serie resistors for regulation purposes.

Also can i load the batteries with any power level or is there a limit how much the batteries can take ?

[RodBorza]

Daemon,

Try these links:

http://www.uboat.net/articles/id/54

http://www.uboat.net/technical/batteries.htm

http://sourceforge.net/apps/trac/derleitendeing/wiki/VIIbatteries

http://sourceforge.net/apps/trac/derleitendeing/wiki/MainPropulsionEngines

These gives you a very good information source to start. But I believe that for the kind of info that you are looking for, the best course of action is to try to contact the original manufacturers. They are still around (although with different names). Since you are in Germany, I believe it would be easier for you to ask them what you need.

[kraznyi_oktjabr]

Hello gentlemen!

I just started playing in Balao boat in 1944 and I got question about radar use.

How US boats used their radar? Did they keep it on all times or did they do just occasional sweeps?


At my understanding todays radars' problem is that they often tell more about yourself (radar type, bearing etc.) to enemy than you find out yourself. Is that correct and if so what was situation during WWII? Did fleet boats have any radar warning equipment? Capability to identify radar types?

Thanks!

Tim

[DaveyJ576]

Originally Posted by kraznyi_oktjabr

How US boats used their radar? Did they keep it on all times or did they do just occasional sweeps?

At my understanding todays radars' problem is that they often tell more about yourself (radar type, bearing etc.) to enemy than you find out yourself. Is that correct and if so what was situation during WWII? Did fleet boats have any radar warning equipment? Capability to identify radar types?

Despite the fact that the USN only employed it's first primitive radar set in 1939, American scientists (using in part technology borrowed from the British) made rapid advances in radar development during the war. By the end of the war, radar technology had advanced to the point that nearly every USN platform, including some aircraft and even PT boats carried relatively powerful and capable radar sets. When combined with the Plan Position Indicator (PPI) scope, which gave an overhead "birdseye" view of the battlespace, radar proved to be an absolutely key factor in the defeat of the Japanese. The importance of this technology to the U.S. war effort can not be overstated.

Japanese developments in this regard were far behind the U.S. Japanese warships did not begin to see radar sets until almost halfway through the war. Even then they were primitive when compared to the USN sets, were unreliable, and were very scarce. It was very hit or miss when it came to which ships received the few sets available.

Accordingly, radar detection and classification technology was non-existent on the IJN side and only in it's most primitive state in the USN. There was no ability classify and/or jam radars as there is today. Therefore, USN submarines could use their radars with virtual impunity. It would be a stretch to say that they left it on all the time, but nearly so.

However, as the USN operators got more and more experience with their new gear they found that it had an unintended capability. In February, 1945 the USS Batfish (SS-310) detected strange intermittent interference patterns on their SJ radar set. When an IJN submarine showed up a short time later, the crew of the Batfish concluded that it was radar sweeps from the submarine. They promptly dispatched the RO boat, and two others that were detected in the same fashion over the next three days.

[DaveyJ576]

As some of you have already noticed, the awesome website Navsource Naval History (www.navsource.org) has published a series of articles called "A Visual Guide to U.S. Submarines". The index page with the articles can be accessed through this link:

http://www.navsource.org/archives/08/10idx.htm

(Insert shameless self-promotional plug here! )

I have been busy over the last several weeks. I have been working on the articles for the last several years, with early versions of the S-boat articles originally published on the site that my website partner and I founded a few years ago: www.pigboats.com. I have spent the last several weeks reformatting the articles and converting them to .pdf format. Deciding to try to expand the exposure of the articles, Michael Mohl, the webmaster of the Navsource submarine pages, graciously agreed to post them on his pages. I have also been working with Neal Stevens and eventually they may be posted here as well.

The intent of the articles was to provide the casual reader a better understanding of how to visually identify the various classes of USN submarines of the WWII era. You would really be amazed at how many photos I have found over the years, some in respected publications, that are misidentified. The fleet boats are all similar enough in appearance that it is easy to make a mistake. But when the photos are carefully studied, definite patterns emerge. The articles were a result of what I found from looking at literally hundreds and hundreds of photographs.

The photographic record is maddingly incomplete and as I come across new ones I try to refine the articles. If new info turns up I will update the articles accordingly. I am working on follow on articles for the Salmon/Sargo class and eventually the Porpoise/Shark/Permit, Balao, and Tench classes.

This is a rather arcane subject so if after reading the articles any questions come up, post them here and I will do my best to explain. Enjoy!

Dave

[virtualpender]

Dave - I never made the connection that you were the author of the Visual Reference Guides. Thank you so much for publishing these! The Gato guide in particular is exceptionally useful. You work is very much appreciated!

[Ducimus]

Originally Posted by DaveyJ576

As some of you have already noticed, the awesome website Navsource Naval History (www.navsource.org) has published a series of articles called "A Visual Guide to U.S. Submarines". The index page with the articles can be accessed through this link:

http://www.navsource.org/archives/08/10idx.htm

(Insert shameless self-promotional plug here! )

That is VERY interesting. I had no idea that Tambor/Gars orginally had a control room mounted periscope, nor that they sported 5/51 deck guns at one point in time.

[LukeFF]

Originally Posted by DaveyJ576

Accordingly, radar detection and classification technology was non-existent on the IJN side and only in it's most primitive state in the USN. There was no ability classify and/or jam radars as there is today. Therefore, USN submarines could use their radars with virtual impunity. It would be a stretch to say that they left it on all the time, but nearly so.

The one exception to this was SD radar. Commanders started noticing a disturbing tendency for Japanese planes to start showing up when the SD radar set was turned on, so it became standard procedure to use it only intermittently:

In operating radars due consideration must be given to the possibilities of the SD radar signal being picked up by the enemy. Intermittent use of the SD for 5 seconds at irregular intervals of not more than one minute is considered to be fairly safe procedure.

When using the SD radar in enemy waters, turn on and off at irregular intervals, leaving it on 5 seconds and off 40 to 70 seconds.

http://ibiblio.org/hyperwar/USN/ref/....html#section4

http://ibiblio.org/hyperwar/USN/ref/....html#section5

[LukeFF]

And yes, let me add that those Visual Reference Guide articles are a great resource. I look forward to seeing your articles on the other classes.

[LukeFF]

Dave, with regards to the Gato, Balao, and Tambor/Gar classes, when was the transition made to the late war haze gray paint scheme?

[Sailor Steve]

Those are outstanding!

[virtualpender]

Luke, not to answer for Dave but Alden's "Fleet Submarines In The U.S. Navy" states that Measure 32 was required to be applied to all subs that did not already have it during their next refit beginning April 1944 (pg. 88).

Hope that helps.

[Jan Kyster]

Found this source collection yesterday: http://www.researcheratlarge.com/Ships/S19-7/index.html

Very interesting compilation of instructions, memos, counter-instructions, lost instructions

[DaveyJ576]

Originally Posted by LukeFF

Dave, with regards to the Gato, Balao, and Tambor/Gar classes, when was the transition made to the late war haze gray paint scheme?

I actually did not write the section on camoflage. The webmaster, Michael Mohl, inserted that part in there as it fit well with the theme of the other articles. I actually have not done a lot of research on the various camoflage schemes, but from what I have read the info contained in that section is quite good. For further info, refer to the references that I listed in the article.