I found some information about it in the “Navy Department Chief of Naval Opertions Washington. Final Report - G/Serial 29. Report on the Interrogation of Survivors from U-172 Sunk 13 December 1943” Page 23. http://www.uboatarchive.net/U-172INT.htm
Ok - I know this info. As it has a lot of errors and irregularities, I just haven't paid much attention to it though: It's from 1943, when the acoustic torpedoes were new and the germans were of course very keen on keeping the info secret. As it also appears from the interviews, the (low rank) mechanics aboard only got as much info they needed. You should also consider that the POW might have tried to give false or misleading information in the interviews.
The first drawing I did of the cover was metal and fastened with pop rivets. Then I noticed in some of the photo’s I have of the TV at Chicago the cover is very dark, so I presume the Germans wrapped the copper wire around the outside and then used the asphalt to smooth it off. Like the cross-section below.
Well, compared with war-time photos there might be lacking an external cover on the torpedo in the U-505 exibition (see attachement)? I see from a close up, that the Chicago-torpedo for sure has a "soft" cover showing the wireturns underneath, but as the torpedo has been completely dismantled and refurbished, this might very well be the solution they chose at the museum (and we see from the colours they chose that they didn't get it all correct - I remember some guy from the museum was researching several issues regarding the restoration on some internetforums a few years back, and they didn't get any answers there).
Also from the photo’s I have it clearly show where no screws or pop rivets to fix the metal section of the cover. So I presume the Germans either spot wielded or wielded it straight on to the body, so I remove the pop rivets from my drawing.
Possible. I don't know. I see remains from the "salamander" on the TXI torpedo in a photo from the recovery-operation. It is almost completely corroded, so that might be the explanation for the missing part on the U-534 torpedo in UK.
It also talks about bigger rudders in the report above on page 23/24.
The rudder of T-5 is one and a half times the size of the rudder of an ordinary electric torpedo. Estimated dimensions: 19 cm. long, 3 cm. wide, 4 mm. thick. The rudder is painted red.
Yes, I noticed that. I don't see any difference in the sice of rudders compared to TII / TIII though, so my guess this is just a reference to the "ausschiebbaren vertikalflossen"?
I will remove this marking.
Again: I'm not sure about this - maybe the guys in Chicago has some info we don't have (I would think that the ONI / US Navy made thoroughly documentation (including photographs - although probably only b/w) when investigating the captured torpedoes).