electric torpedoes in rear tubes

[Aktungbby]

Originally Posted by the beast

What game are you playing?
If this is SH4 or earlier, I believe, you cannot preheat torpedoes. I've never been able to do that in SH4 or SH3.

Originally Posted by the beast

Oh I'm not sure about the realism part. In the game UBOAT, though, you can preheat torpedoes in a type VII sub in the fore or aft tubes. I think from watching it they would take it out of the tube.

I don't think I'm of much help here. Sorry.

EDIT

Yes I think they did actually. The U-47 was outfitted with all G7e TII torps for the raid on Scapa Flow.

Originally Posted by Aktungbby

Well I'm goin' nuts: what was actually used in the torpedo room to heat the batts to 30 degrees celsius? How long did the process add to the reload procedure? And, is there a photo of one? It's worth noting that as the beast points out, all of Prien's eels were G7e's but I cannot determine if they were preheated for the first salvo: at 1200 meters, only 3 eels departed their tubes!...causing Prien to maneuver to fire the stern eel, also a G7e, which also failed to hit. I cannot imagine in the frantic haste to reload the next salvo in the heart of Scapa, precious time would have been expended preheating the second batch... I do always preheat in SH-V.

Originally Posted by LGN1

Hi,


I was looking for information about the preheating for many years until someone (I don't remember who it was) pointed me to this web page:


http://www.ubootwaffe.pl/en/u-boats/...german-u-boats


At the bottom you can find lots of information about it. It answers quite a few questions from this thread.


Best, LGN1

^Question answered THANKYUO!: outta the tube to do it and it must have taken time so the Prien second bow salvo reheated at only 1200 meters to target probably didn't occur! THen again:

1. After the current was automatically cut off, torpedoes in the tubes are connected in pairs to two control boxes. Two times less current maintains the battery's temperature at 30 °C. The other two boxes are connected to the four reserve torpedeos stowed in torpedo room ("Schaltbild 2" on Drawing 13). The time to heat reserve torpedo's batteries up to 30 °C is about 20-25 hours.

And a photo of the heater is from Chicago U.S.A. on U-505 !

8. Torpedo tubes and electric torpedoes G7e

To ensure maximum performance of the battery cells powering the electric motor driving the G7e torpedo (that is achiving speed of 30 knots at distance 5000 m for T-II and T-III torpedo and running distance of 7500 m for T-IIIa torpedo), shortly before the launch the cells were heated up to a temperature 30 °C. (At least I k new the correct temp. ie: 86° F.)Electric heaters controlled by a thermostat were embedded in the cells for this purpose. The powering socket was located at the top part of the torpedo hull, in the aft part of the battery compartment. There was a dedicated hole in the top part of the tube, in the area between the gyro angle setting gear and the pressure hull to enable connecting the cable with the powering plug to the torpedo loaded into the tube. This hole was closed with a water-tight plug when not in use. The tubes were not provided with an interlock that would prevent launching torpedo with the connected powering cable.
The G7e torpedo battery consists of two battery trays. Each tray has its own heating device that consists of resistance grids, vulcanized into special heating plates, which lie between the pairs of cells and which heat their transverse sides. The resistance grids of all the heating plates of a battery are connected in series. Their rating is measured in such a way that they pass a heating current of 7 to 8 A across a voltage of 110 to 130 V. The battery heating circuits of the two trays are connected in parallel resulting in a current flow of 14 to 16 A. The two poles of the battery heaters are wired to two pins of a 4-pin socket, located in the top, aft part of battery compartment. Each battery tray contains an opening for the thermostat. The thermostat has a form of contact thermometer - a long glass tube inserted through the tray's top cover into the electrolyte. Inside this glass tube are two wires and a mercury reservoir. When the temperature of the battery reaches the desired limit (30 °C) the mercury column has risen sufficiently to short circuit the two wires. The contact thermometers of two trays are also connected in parallel and two poles are wired to another two pins of 4-pin socket.

The torpedo battery heating devices are connected to the heating control box (ETO Heizkasten) by means of 4-wire cable plugged into the powering socket in the torpedo and in the heating control box. There are four heating control boxes in the forward torpedo room (boats of type VII and IX) and one in the aft torpedo room of type VII boat and two in type IX. The heating control box dimensions are 24,1 cm x 21,6 cm x 11,4 cm.

Its inner circuit consists of the following: a two pole isolating switch, a moving coil ammeter reading up to 20 A and enclosed in a bakelite case, a bi-metal relay switch and heater sealed into a glass tube, a small 1 nF mica capacitor and a 600 Ohm resister. The circuit is powered from the regulated part (110 V) of the boat's electric network.


On closing the main two-pole switch, the power supply is connected across the bi-metal relay switch heater. The heater in turns closes the bi-metal switch thus switching on the battery heating pads which are placed between the pairs of cells in the battery tray. When the temperature of the battery rises to 30 °C the contact thermometer closes and shorts out the bi-metal relay switch heater, which in turn causes the bi-metal switch to open and cut out the battery heaters. On the battery temperature falling to 29 °C the contact thermometer opens, due to a fall in mercury level, and the operation of the circuit is repeated. The 1 nF capacitor is connected across the bi-metal switch in order to protect the contacts by reducing sparing, on breaking the circuit, to a minimum.

As mentioned above, there were four control boxes in the forward torpedo room and one or two in the aft torpedo room (in type VII and IX U-Boats respectively). Each control box was provided with the splitter, which enabled connecting two torpedoes to one control box, in such a way, that the heaters of each torpedo were connected in series and contact thermometers - parallel. There were two basic heating procedures: single heating ("Einzelschaltung") and series heating ("Reihenschaltung"). In the first case, only one torpedo was connected to each control box - the second socket in the splitter was plugged with the stub, which shorted the heater's poles and left the thermometer's poles opened. The current drawn by the heater of a single torpedo was 13-16 A. In the second case, two torpedoes were connected to each control box. Their heaters were connected in series and thermometers - parallel. The current drawn by the heaters of the two torpedoes was 7-8 A.

The standard procedure for heating was as follows:

1. four electric torpedoes loaded into torpedo tubes are connected with four control boxes ("Schaltbild 1" on Drawing 13) for single heating. The temperature of the battery reaches 30 °C (from starting 15 - 18 °C) after 3.5 - 4 h (the total weight of the electrolyte in the battery is almost 100 kg).
2. After the current was automatically cut off, torpedoes in the tubes are connected in pairs to two control boxes. Two times less current maintains the battery's temperature at 30 °C. The other two boxes are connected to the four reserve torpedeos stowed in torpedo room ("Schaltbild 2" on Drawing 13). The time to heat reserve torpedo's batteries up to 30 °C is about 20-25 hours.

The torpedo tubes were not equipped with any installation that allowed charging the battery of the torpedo while it is in the tube. This was probably not done because there would also have to be provisions for ventilating the battery compartment (because of hydrogen gas generated during the charging process) and that would just further complicate the torpedo tube. The G7e torpedo had to be withdrawn from the tube to recharge its batteries.