German G7e torpedo with FAT (Federapparat), 1943
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- เผยแพร่เมื่อ 1 พ.ค. 2022
- The Federapparat (FAT) or ‘spring device’ was developed to increase the probability of hitting a ship or escort in a convoy. The idea was to make the torpedo zig-zag across the convoy if it missed the initial target. The FAT run structure had 2 parts - an initial straight run to close the intended target, and to ensure the torpedo was clear of the firing submarine before it reversed course, and a series of course reversals where the torpedo turned through 180 degrees after running a defined leg of 1,200 m or 1,900m.
The FAT was introduced in 1943, initially for the wet heater air-driven G7a torpedo, but restricted to nighttime attacks in case the allies observed the looping paths of the air trails. Use in the Mediterranean and North sea were also forbidden due to the clearer water.
The electric G7e torpedo was a candidate of the FAT, but was restricted initially by its limited range - 5,000m. With the increasing convoy escort convoy capability, it was becoming dangerous to approach too close to a convoy. However, the German engineers managed to upgrade the batteries by developing a 17-plate cell (previous their lead-acid cells had 13 plates) which delivered a 50% range increase for the torpedo at 30 knots. This torpedo was designated the TIIIa, and is the subject of this animation.
The TIIIa used compressed air to drive its control surfaces: the Gyro, Gyro servo to operate the rudders and depth servo to maintain the desired depth. The FAT was also powered by comprised air. Because of the increased range capability (and run time), two additional compressed air flasks were fitted at the front of the battery compartment. The control air did not leave a significant trail, however, so the torpedo could be used in all theatres and time of day.
The FAT had 4 control disks, one for each of the run paths - long loop, initial turn to the right, long loop turn to the left, short loop right and short loop left. The run path and initial straight run distance were set using a single input shaft. 4 turns of the shaft would firstly select the initial run distance, and then physically raise the control disk set to the next run path type. Thus 16 turns of the shaft would cycle through all 4 run types and return to the default setting - 15,000m initial run for Long loop path, turn first to the right.
When the setting cam set was being raised (or lowered) the indicator shows the marking ‘flasch’ (wrong), since if the torpedo was fired with ‘falsch’ showing, the initial run would be zero, and the tun to left or right ambiguous, thus endangering the firing submarine. The torpedo tube-mounted setting device physically prevents a setting when ‘falsch’ is showing.
The control disks have a set of ridges, valleys and mid-levels. A control piston rides on these cams. In the mid-level, the gyro controls the rudder servo in the normal manner. However, when a ridge or valley is encountered, the air driven FAT piston forces the rudder servo to the left or right, and so turns the torpedo through 180 degrees. The Gyro outer gimble now has two control cams, one to steer the selected fire control gyro angle, and the other (lower) to steer the reciprocal course.
The FAT was relatively short lived. With a FAT, the convoy would pass over the looped run path. However, the next variant, LUT, was arranged to advance the loop pattern along a convoy’s course and speed. This is too complex for me, and I shall not attempt to animate it.
See also my TH-cam animation of the G7e torpedo:
• German G7e Torpedo 1941
The animation was made using Cinema 4D and Quicktime Player v7
Music tracks are:
Revelation and October Sky, Copyright AKM Music, www.akmmusic.co.uk
References:
‘Die Torpedos der deutschen U-Boote’ Eberhard Rösseler, 2005, ISBN 3-8132-08427
RM6-3149 Federapparat für den Torpedo G7e, 1942
Amazing how they did this with purely mechanical means 80 years ago. Nowadays, a 10 cent IC would do all this, but having watched this that feels like cheating 😉
I just realized that an additional benefit of the FAT Torpedo is that the explosion can occur on the opposite side of a ship than the sub is on! This means the Destroyers and Destroyer Escort would like go off in the wrong direction looking for a U-Boat that wasn't there!!!
Had to be terrifying the first time the sailors witnessed that torpedo turning around.
These mechanical simulations of the torpedo mechanism and the maritime simulations of them being fired into a convoy are amazing, especially how you did all the torpedo internals! You must have put a lot of time and effort into finding out how they worked and producing the simulations, I doubt it could have been easy finding that information? Your video's deserve to be on something like Discovery Channel or National Geographic!
they just wrote aq phy script for boomboom delivery
We Germans are mind-bogglingly clever.
Jesus christ
At first this seemed like a training video for subs on why you should always get your math correct or you will always miss by a meter.
Today's tech probably uses a μprocessor.
Masterpiece of German engineering. Pure art
The alternative meaning of FAT was the "Flächen-Absuch-Torpedo", translated to something like "Area-Search-Torpedo".
Impressive engineering, the FAT is basically a mechanical programmable computer, impressive to see such a system fitted inside a torpedo.
The effort put into making this video must have been huge. Great job
Great to see that you are still working on stuff like this 🙂
Fascinating! I had no idea that such a system existed! Thank you!
Very nice and detailed animation of the Fat I function. However, here are some notes to consider:
Glad to see your still posting these feats of engineering, via that smooth animation. You deserve a gig doing this for the history/military channel. Best of luck and thank you brother.
I don't know what's more impressive, the German's amazing engineering, or your incredible video. So well explained. I'm deeply impressed with your work Rob. Thanks for sharing this with us!
Absolutely incredible animation and attention to detail. This is so much work. Truly impressive!!!
Amazing, finally a new video, i like how your videos goe very deep into how everything works