TLDR: Only certain classes of IJN cruisers and destroyers carried this.
Sendai-class**, Furutaka-class, Aoba-class, Myoko-class, Takao-class, Mogami-class*, Tone-class*, Ibuki-class*, Agano-class
Hatsuharu-class, Shiratsuyu-class, Asashio-class, Kagero-class, Yugumo-class, Akizuki-class
* I'm not entirely sure if Mogami-class and Tone-class had them, but there does appear to be room for it. Ibuki was also a copy pasta job of Suzuya, which was a modified Mogami.
** Of the three in class, only Jintsu and Naka got the upgrade in a very late remodel.
Stop worrying/asking if Shimakaze or Kitakami will get this, they never had it historically and never will in game.
No other nation will get this either, as it is purely an IJN invention and nobody else sought to copy the idea.
The long version
Technically, it is called the 「次発装填装置」, or, roughly translated, "Next loading device" and it was an IJN invention.
The idea behind this device was in how the flow of battle was envisioned and physical limitations of the ships that needed it, thus creating a "problem" for the IJN battle doctrine. The "flow of battle" was seen as a two part battle, where the Destroyers would launch one set of loaded torpedoes at enemy Destroyers, breaking enemy defensive lines, and then another set of torpedoes for the meaty bits, capital ships. The key word in there was "loaded torpedoes", as only loaded torpedoes can be fired correctly. The problem with this, was that Destroyers would typically have to launch their full set of loaded torpedoes at the enemy destroyers, leaving no more torpedoes for a second battle.
At the time, reloading torpedoes was not practical to do at sea and usually took a full day at port. The most obvious way to solve this problem is increasing the number of torpedo tubes, however, at the time, this had its own set of problems. Increasing torpedo launcher tubes could be done in two ways. One is increasing the number of torpedo launcher mounts and the other was increasing the number of launchers per mount.
The first method of increasing torpedo launcher mounts requires more deck space. More deck space means the ship itself must be larger, which, in turn, increases displacement. At the time this device was implemented, the IJN was treaty restricted from building any more Fubuki-class special type destroyers with large displacement and were, in turn, forced to build Hatsuharu-class destroyers with a smaller displacement. The IJN did initially manage to retain 3x triple torp launchers on Hatsuharu, but this turned out to be too ambitious.
The second method of increasing torpedo mounts per launcher requires stronger motors from the increased weight. This was also a problem that IJN had, where they lacked decent motors. There was also a unique IJN design compounding this issue, where the IJN used larger and heavier 61cm torpedoes compared to other nations, as well as splinter guards on their mounts. Eventually, the IJN did overcome their motor problems. They did progress from triple launchers to quadruple and quintuple as development progressed. They even had a design for a Septuple torpedo launcher mount, but his idea was discarded because it would have been too heavy to turn by hand, should the motors get knocked out.
The IJN Solution was to use a reloading device. The reloading device could turn a full day job into a one hour job and effectively doubled the number of torpedoes that could be fired in a single sortie. While the extra torpedoes did increase weight of the ship, it did not drastically increase the size of the ship, nor did it increase the weight of the torpedo launcher mount.
The first ship to feature this device was Hatsuharu. Hatsuharu, as initially built, was quite insane. Following in the footsteps of Fubuki, she featured Three Triple launchers, each with a quick reload, on top of her 5 guns. A total of 18 torpedoes that could be fired in a single sortie. This proved to be too top heavy and she had her armament reduced to two triple launchers with quick reloaders and 5 guns in a remodel. This was still 12 Torpedoes total, so Hatsuharu still had more Torpedoes than Fubuki, but the IJN considered Hatsuharu a failure in design, and thus moved on to Shiratsuyu. Shiratsuyu had the triple launchers improved to quad launchers with quick reloaders, giving a total of 16 Torpedoes, and this design stuck around for a while, until the advent of Shimakaze.
Shimakaze was closer to a complete design change and did not feature the quick reload device. Using three quiintuple launchers, Shimakaze was able to launch 15 torpedoes. The IJN must have considered this to be plenty, even if it was one less torpedo than their previous designs, and did not equip Shimakaze with a torpedo reload device.
Cruisers were not left out and many of them had this device fitted as well. As cruisers had more room on them, they were easier to fit. Most of them feature this device under deck and may not be visible. A vast majority of older model IJN light cruisers, which is Tenryu through Yubari, did not feature this device and only Jintsuu and Naka, of the Sendai-class, seem to have gotten this device fitted when they were remodeled, even though they were not the only older IJN 5500t light cruisers to get a remodel.
In conclusion, this torpedo quick reloading device was a uniquely IJN solution to a uniquely IJN problem that no one else seemed to have. Even the IJN themselves did not fit this device onto ships which they deemed had enough torpedo firepower for their intended role.
Edited by MrDeaf, 27 February 2017 - 11:56 PM.