Torpedo Firing Solution (how germans did it during wwII)
 

Torpedo Firing Solution
Gyro Angled Shots
(how germans did it during wwII)

These pages will show you how the germans solved the Torpedo Firing problem for gyro-angled shots during wwII.

This pages sequence is devoted to Maciek Florek (aka ''Snakedoc'',subsim nickname ''snakedocpl'') who has left us so early. Maciek had analysed ,at his site, the way Torpedo Vorhalt-Rechner's components (TVR) worked and this helped me very much to understand the solution to firing problem as germans did it at wwII.
(Today , is more easy to solve the Torpedo Firing Problem with geometry-trigonometry on modern computers which 'locking' when a boolean is satisfied. During wwII, were availiable only some mechanicals computers for solving basic equations and therefore they developed the TVR which main purpose was to calculate the gyro angle for the shot).
I want to thank our member ''La vache'' for a document he sent me which ,also, was very helpful.

So, here is how they did it back then (some maths are necessary to understand it):

The most important part to understand is the position of Equivalent Point of Fire (EPF). EPF is the imaginary point that the torpedo tube should have been in order to perform a straight shot to the target at the moment of firing (This point is point N at the drawings). Its position is altered by the demand that its distance from impact point must be equal with the torpedo's travel distance to impact point.The positions of the EPF for every gyro angle could be calculated as explained at the pages and its position for rounded gyro angle values from 0° to 90° can be seen at appendix 1 (page 4).
Next important part to understand is the point N'. N' is the position ,at a specific gyro angle p, that this N should have been in order the 'velocity' triangle to be the correct one.This means that,based on torpedo's and target's speeds, N' is the position that the N should have been,at this specific gyro angle p, in order target and torpedo 'meet' at the impact point.

So , for each gyro angle , two points were altered ,the N (from the 'distance' triangle) and the N' (from the 'velocity' triangle). The 'key' for the Torpedo Firing Solution was to be found that gyro angle which made both N and N' get identical (N≡N').

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Nice information.

I wish there was a mod for SH3 which could simulate fully functional TVR. Is this even possible?
- to make TVR account for changing u-boat's course (unless the scope is "locked" on a target nothing changes during course change now, and even if it is - it's wrong)
- to make that changes in firing solution set on TVR is relayed to torpedoes with a delay caused by servomotors trying to adapt
- to make TVR has all knobs and dials as close as possible - even if they could only act as passive displays (eye-candy), not used to enter data

Anyone?

http://www.subsim.com/radioroom/imag...n_Salute-1.gif

hello B_K,

for the first , afaik, TVR was not equipped with position keeper

for the second, that can be possible only by digging in executable files

for the third, also requires digging in executable files even if you want the dials showing valid results at passive mode. For example , the parallax angle dial that is described above can be viewed at a passive mode (if we overcome the fact of the existance of the knob for manually operating it.we can pretend that the electro-mechanism for that dial is doing its job) but ,firstly,there is the need to insert into game's code the (above) equations which altering the needles for δ and δ'.This code doesn't exist know in game's engine so ,without the code ,the dial can't be viewed even at passive mode.

Hi :-)
Position keeper was implemented in US subs, and calculated terget position in real time. I am talking rather about simple angle keeper fed by gyrocompass data. I read in a few articles that TVR kept all angles independent from u-boat turns, when set to auto update. It seems real, because since you have your solution set, any change is within the same geometry, the same target triangle. It should be doable to implement this.
Since locking on a target by "L" causes TVR neddles to move, so should u-boat manouver do.

hello B_K,
i didn't know that TVR had such abillity.Maciek is not mentioning anything like that but ,if it true, would be a nice feature for TVR to had

I am thinking that without the position keeper , is not possible to update the solution becuase ''Range to Target'' (at the moment of firing) is also a critical value for the calculation of gyroangle

Hi! From tvre.org, especially http://tvre.org/en/torpedo-calculator-t-vh-re-s3 : "It should be noted that the component for calculating current angle on the bow also compensated for changes to the target bearing resulting from the changes of own course (...)"
(near the bottom of the page)

So it was possible.

Keeping bearing and aob angles updated would be just enough. We know that range wasn't updated by tvr anyway.

Hello B_K,

yes, you are right ! i haven't noticed that part and it is ,indeed, saying what you stated.This is a wonderful feature of TVR and it is really sad that the sh3's devs didn't model it at all.