TDC

[CapnScurvy]

Originally Posted by TorpX

This begs the question: since the Germans linked the p/s to the TVR, and we had a link from the TBT, why didn't they link the p/s to the TDC?

Regarding my statement of the TBT having a "direct link".......I miss spoke. The TBT signaled in which direction it was focused, however the input was only to a device that the TDC operator could read as Relative Bearing. The direct input to the TDC was made manually by the operator.

[BigWalleye]

Originally Posted by TorpX

This matches my understanding of the USN's fire control and procedures.

This begs the question: since the Germans linked the p/s to the TVR, and we had a link from the TBT, why didn't they link the p/s to the TDC?

From BigWalleye:

I don't see what you mean here.

How are you defining deflection and lead angles?

If you input the correct Target bearing, range, Aob (i.e. target course), and speed, it calculates the required gyro angle to hit the target, and this is updated in real-time. What else is do you need?

Maybe I've been missing something here. I always understood that you had to establish your own lead, as Robbins describes above. I thought the fish would go where you pointed the 'scope, not ahead of the aim point. Maybe I always misused the TDC. Honestly, I haven't played SH4 in a couple of years. While my love for the Silent Service goes back to RAdm Dykers (and despite my distaste for Nazism!), I pretty much focus on SH3. In SH4, I always used a normal approach and Kentucky windage, often successfully, but I can't claim to have mastered the TDC.

[snakedocpl]

Originally Posted by TorpX

This begs the question: since the Germans linked the p/s to the TVR, and we had a link from the TBT, why didn't they link the p/s to the TDC?

I think, that is by design. The Angle Solver of the US TDC is driven by Position Keeper. I mean, that Angle Solver calculates final solution based on the target parameters calculated by Position Keeper (which is modelling the relative position between the target and own ship). After inputting some initial values into Position Keeper, it constantly updates the position of the target relative to the own boat. There are some outputs (for instance GENERATED BEARING), which are used to verify, if assumed initial values were correct. So they read GENERATED BEARING, set the TBT or periscope at this bearing and then - if the target was there - that meant, that model is correct. If not - the initial target parameters were wrong.
Look here: http://archive.hnsa.org/doc/attack/index.htm
Paragraphs from 520.
It seems, that - based on the visual (and radar) observation, operators input the target speed and range. Then the Position Keeper calculates the target position relative to the target, and then GENERATED BEARING is compared with the real, observed bearing. And then corrections to the speed and/or range were applied.
And so on.

The German TVRe was only Angle Solver. So it calculated gyro angle, based on the actual target bearing, angle on the bow and parallax correction. It did not contain mathematical model of the target movement relative to the own ship (as in US TDC). So direct link from UZO/Periscope was necessary to have up to date gyro angle (which is the function of the target bearing).

So there are to different approaches.

--
Regards
Maciek

[snakedocpl]

Originally Posted by BigWalleye

Erm, beggin' yer pardon, but yer a bit late to the party. You really should read all the posts on this thread. Then go check out tvre.org/en/ for an eyeopener as to what the Siemens T. Vh. Re. S3 actually was, and still is, capable of doing. That would include getting continuous input from the sub's gyrocompass and the periscope/UZO target bearing transmitter, continuously calculating a firing solution, and automatically (No human intervention!) setting the torpedo gyro angle while the eel is in the tube. The TVR S3 was in service in the KM from mid-1941 on.

Please note that tvre.org represents the results of reverse-engineering the existing Siemens S3 which was installed in U-995 when it was launched in 1943 and can still be seen on board that vessel at the Laboe museum today. Check it out. Better than a movie!

And to be precise - on the photo Aktungbby has attached, the crew does not "programmes" the torpedo, but is checking the depth-steering engine of the G7a or G7e torpedo.

--
Regards
Maciek

[BigWalleye]

Originally Posted by snakedocpl

I think, that is by design. The Angle Solver of the US TDC is driven by Position Keeper. I mean, that Angle Solver calculates final solution based on the target parameters calculated by Position Keeper (which is modelling the relative position between the target and own ship). After inputting some initial values into Position Keeper, it constantly updates the position of the target relative to the own boat. There are some outputs (for instance GENERATED BEARING), which are used to verify, if assumed initial values were correct. So they read GENERATED BEARING, set the TBT or periscope at this bearing and then - if the target was there - that meant, that model is correct. If not - the initial target parameters were wrong.
Look here: http://archive.hnsa.org/doc/attack/index.htm
Paragraphs from 520.
It seems, that - based on the visual (and radar) observation, operators input the target speed and range. Then the Position Keeper calculates the target position relative to the target, and then GENERATED BEARING is compared with the real, observed bearing. And then corrections to the speed and/or range were applied.
And so on.
J
The German TVRe was only Angle Solver. So it calculated gyro angle, based on the actual target bearing, angle on the bow and parallax correction. It did not contain mathematical model of the target movement relative to the own ship (as in US TDC). So direct link from UZO/Periscope was necessary to have up to date gyro angle (which is the function of the target bearing).I

So there are to different approaches.

--
Regards
Maciek

Best simple concise explanation I have ever read! Excellent. Thank you.

Now I really understand how I always misused the TDC. I was using less than half its capability, in a way that was never intended. Still, I sank ships! Don't let BuPers find out, or I'll wind up shuffling papers at Mare Island!

[Aktungbby]

Originally Posted by Aktungbby

Precisely!"The crew programmes the torpedo."

Originally Posted by BigWalleye

Erm, beggin' yer pardon, but yer a bit late to the party. You really should read all the posts on this thread. Then go check out tvre.org/en/ for an eyeopener as to what the Siemens T. Vh. Re. S3 actually was, and still is, capable of doing. That would include getting continuous input from the sub's gyrocompass and the periscope/UZO target bearing transmitter, continuously calculating a firing solution, and automatically (No human intervention!) setting the torpedo gyro angle while the eel is in the tube. The TVR S3 was in service in the KM from mid-1941 on.

Please note that tvre.org represents the results of reverse-engineering the existing Siemens S3 which was installed in U-995 when it was launched in 1943 and can still be seen on board that vessel at the Laboe museum today. Check it out. Better than a movie!

Apologies! I did include a "" after 'precisely' I couldn't believe the photo's verbatim caption myself. Another caption for the same photo reads "World War 2 torpedoes were quite fickle. They had to be pulled from their tubes and serviced every two or three days." As per snakedocpl: I assmed it would have to do with the 'eel's' notorious depth problems prior to Lt Ites pressure discvery/solution abord U-94. Yer Siemans-ship don't mean a thing if the eel won't run at depth!

On January 30,('42)!! the crew of U-94 made a little extra effort and conducted an on-board examination of their torpedoes amidst the Atlantic. They thus discovered an excess pressure in the torpedoes' balance chambers, where the hydrostatic valve controlling the depth at which the 'fish' ran was located. When they radioed back their findings, the Inspector of the Torpedo Department ordered a check on board all submarines in port. Half of the torpedoes were found to have the same problem, and the mystery of the torpedoes' deeper-than-set-depth run was finally fathomed. The results of this and later investigations were summed up into a Memorandum by Grand Admiral Raeder on Feb 9, 1942.

Proof: Heads rolled at German torpedo technology development (arrests and jail) and Ites, a POW until 1946, retired in 1977 as Konteradmiral!

America and Germany learned the hard way that torpedoes are finicky weapons that cannot tolerate shortcuts. The most complex naval weapons of World War II, they demanded meticulous design, rigorous testing and intensive maintenance—not to mention exacting targeting and launch procedures. Lack of rigor at any stage from initial design to the torpedo's use in combat could result in failure, and the many opportunities for mistakes made it hard to tell where the fault lay, even after the weapon's poor performance became obvious.

Seen in this light, German and American torpedo failures are quite understandable. Only in hindsight is it apparent that the more complicated torpedoes developed for World War II demanded an unprecedented level of technical and operational evaluation. And even Germany's veteran submarine leaders never thought to second-guess their Torpedo Directorate until the problems became obvious.

Germany fixed most of her torpedo problems in less than half the time it took the United States because her submarine leadership was more experienced and because submarines were the mainstay of her navy. Doenitz and his staff knew from the start how to establish a trusting relationship with U-boat skippers and how to evaluate their reports. Senior American submariners had to learn those skills on the job. U-boats took the lead in Germany's naval war, while American submarines played second fiddle to battleships before Pearl Harbor and to aircraft carriers afterwards. If U.S. carriers had lost the Battle of Midway because their bombs failed to explode, it's safe to say the problem would have gotten a lot more attention than torpedo failures did.

I've been following this thread with great interest, look'd up all the links and had actually written two previous posts but deigned to submit due to the superiority of the ongoing discussion upon which I could hardly improve.
It's the best discussion of the two systems I've seen in the forum in over two years. Anything though to get a rise out of a 'ol Wisconsinite A Hamm's all 'round!

[Hitman]

With the TBT, there was no Stadimeter to help in range finding attached to it. Neither were there Telemeter Divisions for judging range.

IIRC the reason was that, by the time the TBTs started being installed, all subs had radar -which was used on a quick impulse to get range on the already trained bearing and then switched off again for stealth.

[BigWalleye]

Originally Posted by Aktungbby

A Hamm's all 'round!

And one for the bear!

[Sailor Steve]

Originally Posted by BigWalleye

While my love for the Silent Service goes back to RAdm Dykers...

I just finished watching the entire series just a couple of months ago.

[Rockin Robbins]

Originally Posted by Hitman

IIRC the reason was that, by the time the TBTs started being installed, all subs had radar -which was used on a quick impulse to get range on the already trained bearing and then switched off again for stealth.

Fluckey tells about hooking radar to a telegraph key. Train the bearing, hit the key, get the range and no chance of any meaningful info getting out. They were too paranoid about such things. But when your life's on the line I suppose you take no chances. If it accomplished nothing else, and there's no evidence that it did, it let his crew know that their lives wouldn't be needlessly risked.

[BigWalleye]

Originally Posted by Sailor Steve

I just finished watching the entire series just a couple of months ago.

Way cool! Where? Cable TV, on the Web, or DVD? I'd love to see the old shows again. Prolly get me back playing SH4!

Originally Posted by Rockin Robbins

If it accomplished nothing else, and there's no evidence that it did, it let his crew know that their lives wouldn't be needlessly risked.

And that, so I have read, mattered a lot to Fluckey. And his crew would have volunteered for a cruise to Hell as long as he was skipper.

[ColonelSandersLite]

Since we as captains aren't actually operating the TDC directly, I honestly don't see the practical difference between the tbt sending bearing information directly to the tdc and the tbt sending bearing information to the tdc operator who then enters it into the tdc.


That being said, there is something very important in the link provided by snakedocpl. It says directly on the very same page:

14C6. New installations. The latest design installations have, in addition to the units described above, additional transmitters operated by the sound gear and the periscopes for the transmission of both bearing and range to the stations equipped with indicators. In addition, an improved model of the target bearing transmitter is provided with an own course dial energized from the gyro repeater panel so that the true as well as the relative bearing may be read at the instrument. The ship's plans should be consulted for details.

The question is what is meant by new installations? 43? 44? Just after the war? That manual was published less than a year after japan surrendered. I wonder if anybody has more specific information?

[ColonelSandersLite]

So I found a periscope manual from 1940 and I'm pretty sure there was no bearing transmission then. I did find somthing really cool that I wish was in the game though.

http://www.maritime.org/doc/pdf/peri...type2-1940.pdf

Read page 9 of 15 (of the pdf, the actual pages are not numbered), right hand page under the headings "description of stabilized azimuth line" and "operation of stabilized azimuth line". That is one cool tool. Also, pretty sure it's impossible to get it in the game.

[BigWalleye]

Originally Posted by ColonelSandersLite

So I found a periscope manual from 1940 and I'm pretty sure there was no bearing transmission then. I did find somthing really cool that I wish was in the game though.

http://www.maritime.org/doc/pdf/peri...type2-1940.pdf

Read page 9 of 15 (of the pdf, the actual pages are not numbered), right hand page under the headings "description of stabilized azimuth line" and "operation of stabilized azimuth line". That is one cool tool. Also, pretty sure it's impossible to get it in the game.

Cap'n Scurvy has a periscope photo of the stabilized azimuth line and a description of how it was used in Post #26 of this thread.

[BigWalleye]

Originally Posted by ColonelSandersLite

Since we as captains aren't actually operating the TDC directly, I honestly don't see the practical difference between the tbt sending bearing information directly to the tdc and the tbt sending bearing information to the tdc operator who then enters it into the tdc.

You're right. There is no practical difference. Actually, as Approach Officers, we do send target bearing data directly to the TDC, when we click on the "Send" button. R/L Approach Officers didn't. They just said: "Bearing mark." and other members of the approach party did the rest. If you want to follow the R/L prototype, you have the install SH4Speech. Then you can order: "Bearing mark." and have your AI "crew" do the button-pushing.