This scan is from the Book "Allied Coastal Forces of World War II" by John Lambert and Al Ross, page 210.
There is a very similar drawing on page 86 of the book " British Naval Weapons of World War II - The John Lambert Collection - Volume III - Coastal Forces Weapons" by Norman Friedman.
If you click here or on the picture above you will get a larger version.
The bottom detail in this image (just above the page number) shows a slightly different setup with the explosion vessel (16) and shows a shrouded control panel (18), it also shows a ring of bolt heads where the explosion vessel joins the tube wall.
Above is a photo of my 18" torpedo body and the Vosper 18" torpedo tube, the tube has a threaded inlet to suit a compressed air fitting and the torpedo body is a snug fit within the tube.
I guess I will need to work on a new version printed circuit board, to fit this torpedo, as my existing versions are for the 21 or 22.5" torpedoes. I have been working on a remote control steerable torpedo with 3D printed propellers and gearbox and of course servo controlled rudders, revision one has some issues but I do need to make them come back!
This photo shows a comparison of the 3D torpedo tube vs the laser cut torpedo tube base that I have added as part of the superstructure kit. I have shown a short piece of 25mm carbon fibre tube representing the main tube, if you'd rather craft your own. The main issue with 3D printing these things is the cost and of course some people want to craft their own!