Torpedo settings...Real life?

[cj95]

Hi all.

Enjoying my return to the game after a long absence.

Got a History question: How exactly did crews plug the various fire control solutions/torpedo settings into the torpedoes?

Is there some sort of knob, or dial on the outside that the torpedo room fiddled with?

What about fish already loaded in the tubes? Did the tube have to be open to make settings?

Was there some sort of dial in the room itself that somehow interacted with the sealed up fish?

Just wondering?:salute:



On another note, what did torpedo men do all day when not in combat? A daily hernia -inducing exercise of running fish in and out of the tubes over and over? Take the whole thing apart, and then put everything back together hoping you didn't forget a screw?
What if you spotted a ship and your deck is covered in torpedo parts from the one you just took apart?

[RConch]

Research the TDC and get back to us.

Crews would never take apart a torpedo on the surface on the deck.

All work on them was in the cramped forward or rear torpedo rooms.

Constant maintenance kept them busy.

[cj95]

>>>Research the TDC and get back to us.


I Know what a TDC is....I meant how was the data from the Computer transferred to the Torpedo itself? Was there a physical linkage? Manual input from torpedo room crews? Something else?


>>>Crews would never take apart a torpedo on the surface on the deck.

Ummm...yeah...I never mentioned bringing a torpedo topside.
I presume the floor of the torpedo room is still called a deck?

The question remains.:03:

[RConch]

Yes, you know what the TDC is-you saw it in the game. If you research it instead of someone else doing it, at least it works for me, you can learn better.

It is all explained.

[Sniper297]

Problem with doing in depth research when you just want a simple answer to a simple question is you need a key word to start, and if you don't know the basics you wouldn't know what the key word is. "SPINDLE". The torpedoes had a gyro compass and depth control gadget inside which were set by a mechanical spindle inside the torpedo tube, linked to the TDC so the settings were automatically updated. The firing mechanism automatically withdrew the spindle from the torpedo at the moment of firing.

https://maritime.org/doc/fleetsub/tubes/chap7.htm

As for passing time, I was on aircraft carriers rather than submarines, but I imagine it was the same - playing cards or other games, reading, cleaning, swapping lies, or just sitting around being bored between flight ops. Anyone who's ever been in any branch of the military can tell you there's either too much time and not enough to do, or too much to do and not enough time, nothing in between. Standing watches and staying alert with hour after hour of nothing happening was the most tedious part, even though it was the most important.

[Rhodes]

Doing Josephine Baker impersonations!:D
https://www.youtube.com/watch?v=kkCdgmx6bLY



Torpedo fire control system on German U-Boats

http://tvre.org/en/torpedo-fire-control-system-on-german-u-boats

[BigWalleye]

And there was nothing called a "TDC " on a German submarine. There was a Torpedo Vorhaltrechner, a TVR, which performed similar fire control calculations. But the TVR was not just a TDC in German.The TVR lacked the US TDC's Position Keeper capability, but did have a lead angle calculator - a useful capability which the TDC lacked. There were other design differences as well. Both TDC and TVR had the capability to set torpedo run parameters while the torpedo was in the tube, although the mechanics were somewhat different. For more information search for TVR, not TDC.

[Sniper297]

I don't know how you figure the TDC didn't have lead angle capability, target speed, relative bearing, and AOB equals lead angle - which was automatically updated in the torpedo gyrocompass. Put the crosshairs on the target, hit the button to send the latest bearing to the TDC, which sets the gyro angle for the correct lead angle, and shoot. Don't even need to know the lead angle, TDC sets that automatically.

[CaptBones]

The link from Rhodes and the link and comments from Sniper297 are very good and quite thorough answers to most of the original question.

If you want to see some additional technical details about the adjustment mechanisms on and inside the torpedo itself, have a look at the G7a drawings at uboatarchive.net. Take note of the "lugs" on the top of the "engine compartment" body and the upper tail fin; they are there to ensure the torpedo is lined up in the tube to mate with the adjustment spindles.

As for maintenance; like all other complex modern weapons, torpedoes were (and still are) designed and built to be "easily" maintained. The crew did not have to take them apart and put 'em back together again in order to do the routine maintenance. Yes, you did have to pull them from the tubes, but the handling gear in the torpedo room was designed specifically to be able to pull the fish from the tube, do the maintenance and put it back in the tube without serious disassembly.

The most frequent maintenance action was just removing, regreasing and reinstalling; every time you open the outer doors and flood the tube, you're introducing the steel "hull" of the torpedo (and all of those fittings on it) to one of its biggest enemies...saltwater. The next biggest maintenance problem was based on the type of propulsion. For the G7a you had to check the levels in the fuel tank and lube oil tank and the pressure in the air flasks. For the G7e, the primary check was the battery charge and water level in the cells. There were fittings to add fluids/air if necessary and there were also numerous grease fittings, including the steering rudder and depth rudder linkages.

All-in-all, plenty to do to keep the torpedomen occupied.:yep:

[Tupolev]

http://www.tvre.org/en/torpedo-fire-control-system-on-german-u-boats

Some good info on how fire control data (gyro angle) was input.

There's an amazing amount of info on that whole site. Well worth reading.

T

[cj95]

Yes, you know what the TDC is-you saw it in the game. If you research it instead of someone else doing it, at least it works for me, you can learn better.

It is all explained.


Wow. You sir are a mean person.

If you don't want to answer....fine...don't answer.

But to actually go out of your way...not once...but twice....in order to highlight the fact that not only are you not going to answer a simple question ,but enforce the opinion that nobody else should do so either because I should "find out on my own."

That sir is the very definition of a mean person who is ugly and small on the inside.






For the others: I thank you greatly. I was not aware of the tvre website or the maritime article. Very informative and insightful. I now have a better picture in my head of what my pixel sailors are doing when not dancing in drag.

CaptBones: I had not considered the effect of saltwater every time I open the tube doors. Excellent point.

[BigWalleye]

I don't know how you figure the TDC didn't have lead angle capability, target speed, relative bearing, and AOB equals lead angle - which was automatically updated in the torpedo gyrocompass. Put the crosshairs on the target, hit the button to send the latest bearing to the TDC, which sets the gyro angle for the correct lead angle, and shoot. Don't even need to know the lead angle, TDC sets that automatically.

We are talking about 2 different uses of the term "lead angle". I used it in the sense of shooting at a moving target,where the shooter "leads the target" to compensate for target motion. The TVR provides this lead angle, deflection angle, aim point offset, call it what you will, for the Approach Officer (or German equivalent). The TDC does not.

As you correctly described it, the TDC continuously updates the torpedo gyro angle setting, based on the target estimated position from the Position Keeper. It is fully automatic. Once the target position, course, and speed have been entered, the Approach Officer can point the periscope at a seagull. If the correct target position, course, and speed have been entered in the TDC, and IF the target course and speed do not change, then the torpedo will intercept the target. At firing time, the Approach Officer is out of the fire control loop.

For a variety of reasons, some more valid than others, there were US skippers who prefered a less automatic fire control procedure. The "Dick O'Kane" Constant Bearing Technique is an example. Once the fire control party has determined gyro angle for the desired torpedo impact geometry, the Approach Officer observes through the periscope until the target crosses an offset aim point (based on estimated speed) and gives the command to fire. ("Fire on the wire.") The TDC Angle Solver is used to calculate the gyro setting - and set the gyro - but it does not provide any assistance in determining the aim point offset. There were tables and rules of thumb for this.

The TVR, on the other hand does not have a fully automatic mode, because it does not have a Position Keeper. Once target position, course, and speed are entered and the TVR is activated, the TVR calculates an impact point based on the current periscope bearing and sets the gyro angle accordingly. The TVR does automatically introduce an aim point offset, based on target position, course, and speed. The Approach Officer needs to put the periscope wire on the intended impact point on the target. If target position, course, and speed were entered correctly, the torpedo will impact the target at the aim point. This allows for a spread to be fired simply by moving the periscope. It also allows for rapid shifting of targets in a convoy, where all ships have the same course and speed, and approximately the same range - TVR data do not have to be changed.

The TDC and TVR reflect two distinctly different design philosophies - computer automated fire control versus computer assisted fire control. Which is better? Coke or Pepsi?

[Sniper297]

Um,

"We are talking about 2 different uses of the term "lead angle". I used it in the sense of shooting at a moving target,where the shooter "leads the target" to compensate for target motion."

Lead angle is firing at where the target will be when the projectile (in this case a torpedo) crosses the target track. Unless you're shooting at a moving target you don't need a lead angle.

The TDC had the same capability of shooting multiple targets and/or spreading by shifting crosshairs, there was a button on both periscopes and the TBT to send a new bearing to the TDC - if the speed and course of the target(s) didn't change all you needed was a new bearing. And the TDC had enough sense to fire at where the target would be rather than where it is at the moment the button was clicked, that's lead angle. I agree that the actual lead angle is nice to know if for no other reason than a double check on the accuracy of the TDC solution, but I'm sure there was someone on the plotting team responsible for checking that. Many skippers had someone on the attack team standing by with a "banjo" and Is/Was just in case, especially early in the war when the TDC reliability was still unknown.

[BigWalleye]

Sniper, I understood perfectly well what you meant by "lead angle" which was precisely why I clarified my use of the term and subsequently refered to "aim point offset" to avoid further confusion. If you can post the source for information that the USN's Torpedo Data Computer Mark 3 provided an aim point offset, I would certainly like the chance to read it. I don't see anything in OP 1056.

[Sniper297]

Well, a quick google search turns up this;

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

Relevant part is "In addition to the standard angle solver" - the function of calculating the lead angle was such a basic part of the system it was only mentioned in passing. If it wasn't programmed to calculate the lead angle it wouldn't have been very useful, unless the ordinance that you're shooting has a velocity of 186,000 miles per second it's rather pointless to shoot at a moving target where it is now rather than where it will be.

Fire control computer on a modern tank is a good example - there's a wind speed and direction system on the turret, if the gunsight automatically compensates for crosswinds why would you need a readout to tell you what the crosswind factor is? My thinking is if the German TVR had a separate readout for lead angle more power to them, if the TDC didn't have a dial for that it was probably because it would have been redundant.

I've used both systems, I currently have a German ATO career and a US Pacific career active in SH4, and even though I don't use the PK much I still find the TDC easier to use simply because the "own ship" and "target" dials one above the other makes it easier to visualize the situational awareness "picture" for the approach. I have used the "angle off" method where you estimate the intercept angle, set the fish for a zero gyro angle, then offset the scope 10 to 15 degrees and fire when the target hits the crosshairs, but that's usually reserved for the S-class which wasn't supposed to have a TDC in real life.

[BigWalleye]

Sniper, please read my last post. I am not, and have never been, talking about the variable which you call "lead angle." I concede that the variable which you call you call "lead angle" is calculated by the TDC. Please either do me the courtesy of addressing my question regarding the aim point offset, or at least stop arguing against claims which I did not make. At the very least, please read my posts comprehensively before replying. Thank you.

[snakedocpl]

Hi Gentlemen,

I've used both systems, I currently have a German ATO career and a US Pacific career active in SH4, and even though I don't use the PK much I still find the TDC easier to use simply because the "own ship" and "target" dials one above the other makes it easier to visualize the situational awareness "picture" for the approach. I have used the "angle off" method where you estimate the intercept angle, set the fish for a zero gyro angle, then offset the scope 10 to 15 degrees and fire when the target hits the crosshairs, but that's usually reserved for the S-class which wasn't supposed to have a TDC in real life.

If you are sharing with us your experience based only on feeling from SH (and not on a base of real documentation), your opinion is quite irrelevant. Until now, there is no submarine sim with correctly implemented torpedo fire control computer (neither TDC nor TVRe).

The TDC had the same capability of shooting multiple targets and/or spreading by shifting crosshairs, there was a button on both periscopes and the TBT to send a new bearing to the TDC - if the speed and course of the target(s) didn't change all you needed was a new bearing.

No, TDC had no capability of shooting multiple targets and/or spreading by shifting crosshairs (if we are talking about real TDC Mark 3). The reason: there was no connection between target bearing transmitters (at periscopes or TBT) and TDC (or more strictly with Position Keeper).

Source document: https://maritime.org/doc/fleetsub/elect/chap14.htm#14C

At TDC were only target bearing receivers, which were observed by TDC operator and their value was compared with the target bearing value generated by Position Keeper. If these values matched, the target data (course, range and speed) entered to the Position Keeper were correct, if not - the target data has to be adjusted.

Here you have the functional diagrams of Position Keeper and Angle Solver and there are not electrical inputs for target bearings.
https://maritime.org/doc/tdc/pg068a.htm
https://maritime.org/doc/tdc/pg086a.htm

BTW, the only values electrically inputted to TDC were own speed and own course.

So you could train the scope and TBT and it does not influence the solution at all.

Similarly, the TDC did not calculated the spread angle. The spread angle had to be calculated by human and entered manually to the Angle Solver as so called Offset Angle. The Offset Angle modified the gyro angle entered to the torpedoes, so the Offset Angle handle had to be trained after launching each torpedo in salvo.

And the TDC had enough sense to fire at where the target would be rather than where it is at the moment the button was clicked, that's lead angle. I agree that the actual lead angle is nice to know if for no other reason than a double check on the accuracy of the TDC solution, but I'm sure there was someone on the plotting team responsible for checking that. Many skippers had someone on the attack team standing by with a "banjo" and Is/Was just in case, especially early in the war when the TDC reliability was still unknown.

As I explained above, there was no button. TDC philosophy was to have ability to fire without periscope. I mean, if you entered the correct values to the Position Keeper, it continually calculated the correct relative position of the sub and target. Based on the output from Position Keeper, Angle Solver calculated continually the correct gyro angle, so you can shoot any time, without seeing the target.
The periscope target observation were done to check the accuracy of the Position Keeper solution. The TBT/Periscope operator shout "Bearing Mark!" or pushed the button, and the TDC operator compared observed target bearing with target bearing generated by Position Keeper. If target was at position calculated by Position Keeper, everything was ok, if not, target data has to be adjusted. It was iterative process.

I don't know how you figure the TDC didn't have lead angle capability, target speed, relative bearing, and AOB equals lead angle - which was automatically updated in the torpedo gyrocompass. Put the crosshairs on the target, hit the button to send the latest bearing to the TDC, which sets the gyro angle for the correct lead angle, and shoot. Don't even need to know the lead angle, TDC sets that automatically.

Most of misleading information were corrected above. One more: torpedoes were not fitted with gyrocompass (which is devices based on fast-spinning disc and the rotation of the Earth, using the effect of gyroscopic precession, used for finding true north), but with gyroscope (device based on fast-spinning disc, used for determining fixed direction in space).

--
Regards
Maciek

[CaptBones]

Although this thread is way off track from the questions in the original post, there is a lot of good information in it, as well as some not particularly good, or useful, information also. The discussion has not only been “spirited”, but respectful as well, which is something that isn’t typical of most forums on the internet; that is a feature of the Subsim community and its members that I really find to be refreshing and somewhat “comforting” as well. Nice to deal with people who can be civilized and respectful, despite their different opinions and points of view. A large part of this discussion is simply semantics, which everyone seems to be dealing with without a lot of fuss. But, on to a couple of my own comments; regarding the USN TDC only.

snakedocpl has identified a couple of things that are quite correct in the differences between the real world TDC and the “object” we use in the game. I would add my own semantic problem first, that there is no such thing as a ”lead angle” used in USN submarine torpedo fire control solutions. In the real world, target speed, relative bearing and AOB do not equal a “lead angle”. The geometry of the solution is more complex and consists of own course, target course, target relative bearing, angle on the bow, range to target, distance to target track, gyro angle and track angle…which doesn’t produce a simple “lead angle.”

Why? Well, as was mentioned, a “lead angle” is what a shooter uses when firing at a moving target. The statement was then made that unless you’re shooting at a moving target you don’t need a lead angle. That may be true if you’re a hunter or marksmanship shooter or on a fixed gun battery. But in submarine warfare, whether the target is moving or not, the shooter is moving and generally so is the target; plus, they are usually both moving on different paths at different speeds. Determining the correct “lead angle” is a much more complex problem. Then on top of it all, we have the torpedo itself and its gyroscope.

The torpedo cannot instantly turn to the proper intercept course when it is fired. First of all, dealing with WWII torpedoes, the gyro isn’t powered up until the fish is fired and it takes a few seconds before it is stabilized and functioning. The torpedo thus runs blindly straight ahead (we hope) before taking the gyro angle input set by the fire control system and turning onto the intercept course. Then, you have to recognize that the fish can’t turn on a dime either…its course change involves the same kind of advance and transfer geometry that the firing sub and its target both also have. It would be nice if the angle between the line of sight and the torpedo track was a simple angle, with the opposite side equal to the target run during the time the torpedo takes to reach the target track.

But it ain’t so. The geometry of the torpedo track seriously screws up the simple solution. The good thing is that the real world TDC ”knows” what the geometry of the torpedo’s turn to the intercept course will be…or should be. In the game that turn is instantaneous and our TDC does calculate an actual “lead angle”. Back in the real world, you’ve also got to deal with things like changes in the target’s course and/or speed as well as necessary changes in the sub’s course and/or speed. That’s where the manual plot takes over and compares the DRT trace of the actual tracks of the sub and the target with the TDC solution. The plotting team was the key to accurate firing, especially at a zig-zagging target, single ship or convoy.

One final note…snakedocpl mentioned a key factor regarding the TDC; provide fire control solutions without visual observations. It was developed prior to the war, when USN doctrine was for firing at 100’ depth on hydrophone bearings only. The resulting “automatic fire control procedure” was almost completely useless. The submarine COs didn’t simply prefer something else, they had to come up with better methods in order to have any chance of success at all. Dick O’Kane himself once commented that he (along with Dudley Morton and many others) thought that about the only real useful features of the original TDC were the Position Keeper and that it accounted for the geometry of the torpedo’s turn to the intercept course and then calculated the gyro angle correctly.