It is not the length but the girth in torpedoes
 

The Germans, Americans, British, and Japanese submarines all used torpedoes that were the same size in diameter.

533 mm or 21 Inches.

This is a strange number. Not 525 mm or 550 mm but 533 mm. In imperial measurements it is still strange. Not 20 inches or 24 inches but 21 inches.

The Germans had the G7 Series
The British has the MK VIII and MK X
The Americans had the MK X, MK XIV, and MK XVIII
The Japanese had the Type 92 and the Type 95

Now all the counties’ torpedoes were different lengths but all has the same odd diameter.

Any idea why four different countries (there were actually more that used the 533 mm torpedo) who were developing individual submarine models that really did not have much in common, would all use the same odd diameter torpedo?

I don’t think there were any common components shared by these countries so that eliminates that as a reason.

Where there any shared industrial gigs or dies used by all four countries that would account for all the common submarine torpedoes to be not only the same diameter but to have the diameter to be a “strange” number 533 mm/21 Inch?

Are torpedoes 533 mm in diameter because that was the limitation of the capability to build a torpedo tube?

Or are torpedoes tubes 533 mm in diameter because that was the most efficient size for a torpedo?

Is there an optimum diameter for torpedoes?

Inquiring minds want to know

Well, we know...
 

that there's not an optimum diameter for torpedoes because air dropped and ship launched American torpedoes had different diameters. That still leaves a mystery. Did the Germans plan on capturing superior American submarines and using them against the coutry of their origin?:-?

Were the British going to ally with the Germans and have compatible torpedoes? Were they all taught to make torpedoes by the same advanced extraterrestrial life form? And what about Mary Lou? :confused:

Edit: hey man, those space aliens do get around. I found a list of the world's torpedoes and although there are many torpedoes that are not 21" or 533mm, the US, UK, Holland, USSR, China, Germany, Japan, and Sweden all use or have used that diameter torpedo! I am sure there are probably others and we could plot the course of the flying saucer around the world. This is truly bizarre!

I'm no expert on this by any means, but is it not likely that the marine physics people of the belligirents did a water resistance vs speed vs payload calculation and came up with roughly the same answer?

Really interesting observation. And mysterious. On a sillier note, i was always wondering why they didn't build a _really big_ torpedo - like a BB buster - one big bastard - a tactical nuke:)

Good question.

Is a 533 mm torpedo efficient with respect to water resistance? Is water resistance solely defined by diameter? I think parasitic drag is also effected by length.

Does anyone have any references that cite any such marine physics testing?

Considering all the bonehead mistakes all four countries made (although each country eventually changed their torpedo designs with the Americans bringing up the rear), I kinda doubt that this much thought went in to the design of the torpedoes with respect to the diameter.

Was this a treaty issue? Washington Naval Treaty does not make torpedo size restrictions but was there another treaty that did designate a diameter restriction?

This is starting to drive me nuts :damn:

:)

Because you need the tube to fire it, and this tube would be unable to fire anything else ^^

But don't worry, after the war, as soon as they found a way to miniaturize nuclear warheads, they did put them into torpedoes (and everything else, including artillery shells, depth charges and air to air missiles...). The Soviets were especially fond of that kind of torpedoes - remember that the original Shkval, to compensate for its inaccuracy, was supposed to be nuke-fitted, so that the attacker firing the first torpedo wouldn't have a chance to avoid the backfiring blast...

I think Slateford has a darn good theory here. It is odd that all countries have the same diameter. The fleet boats was probably standardized for all tubes in the boats and probably the other countries as well. But, for all to the same diameter?:hmm:

Here is something that will make your head spin:

http://www.sciencedirect.com/science...fa5688d888fe71

I think if we dig into it it will turn out to be that 21" and 18"
(which just to confuse things more was 17.7") were probably
started as British torpedo's that enjoyed some distribution
and as torpedo manufacture came along to be marketable
then the new torp would be more cost effective if it fit
into an existing tube.

(This was only speculation)
M

The original design for the Russian November-class SSN would have carried a single giant nuclear torpedo, 1550 mm in diameter and 77 feet long.

http://www.subsim.com/books/images/November.jpg

:D - now that's what i'm talking about! But perhaps squeeze in a tube or two for regular service torpedoes. I just wish sometimes in SH3, that I could lauch a sure-fire BB buster - one that _will_ crack her armour...

Here's another monkey wrench in the works, World War I torpedoes came in three sizes:

British: 18", 21", and 24" (which was the size Nelson and Rodney carried)

German: 45cm (17.7"), 50cm (19.7"), and 60cm (23.6")

Go figure.

I believe the reason for the difference in torpedoe sizes came down ti the fact that aircraft couldn't carry the larger torpedo due to weight restritions, still hapens today in that the ASW torpedo is smaller than the Mk 48 or similar.

The reson for the early varation in sizes is due to limitations in propulion and space reqirements in early subs (smaller torpedo means smaller tube and less space to carry them in) As they became more advanced they grew (as did the submarine) and gained a bigger warhead to cope with bigger , more heavly armored targets.

The Russians do have a 650mm tube in their newer subs

http://en.wikipedia.org/wiki/Type_65_torpedo

Might have an answer
 

I think I may have found half the answer.

My original question was actually two separate but related questions

1. Why did Japan, Britain, Germany and United States all use torpedoes with the same diameter (533mm/21”)?

2. Why was 533mm/21” chosen?

The answer for the first question is that Japan, Britain, United States, Germany and Italy were all in cahoots with Robert Whitehead’s through his and other related companies.

Stabilimento Tecnico di Fiume (and its many incarnations)
Schwartzkopff (later known as Berliner. Maschineubau A.G.)

both were developers of Whitehood’s designs. They all had dealings with Japan, Britain, Germany and Italy. Representatives from all countries interacted with each other.

In 1908 as Whitehead moved toward 533mm/21” torpedoes, it is understandable that the other distributors would follow suite.

The Whitehead Mk VIII was the first UK developed 533mm/21” submarine torpedo. Its design dates back to 1925.

Germany’s G7a was their first 533mm/21” submarine torpedo designed in 1930. The G7a is an oddity as it was a follow on to the ship launched G7. The G7 was 500mm/19.7” in diameter. Why the G7a needed the extra 1.3” is still a puzzler.

Italy developed the W270/533.4x7.2 Velosa in 1935. Japan was especially interested in the design of the Italian W270/533.4x7.2 Velosa torpedo and copied some of the components.

Japan was using Whitehead designs for their 21” Type 43 ship launched torpedo in 1910. In October 1917, the Japanese Navy decided to move toward the 533mm/21” design for their submarines. The 533mm Type 92 was designed in 1934 and used designed from the G7a.

The United States is an oddity. The relationship between Whitehead and the United States Navy was stormy at best.

Even though the Whitehead torpedoes were successful and widely sold, from 1870-1900, the United States Navy concentrated on other non-whitehead designs.

Lay, Barber, Ericsson, Lay-Haight, Sims-Edison, Cunningham, Howell were all designs evaluated and used by the United States Navy with the Howell design having the most usage.

In 1891, the United States Navy contracted with the Bliss corporation to build the Whitehead Mk 1 ship launched torpedo. This started the short relationship between the United States Navy and Whitehead. This also started a longer relationship between Bliss and Whitehead in the joint development/improvement of torpedo designs.
By 1901, the last Whitehead torpedo, the Mk 5 was contracted for use in the United States Navy. It was an 18” ship launched torpedo.

In 1904, the United States contracted with the Bliss-Leavitt corporation to build their Mk 1 21” ship launched torpedo. This started a long history of USN - Bliss-Leavitt contracts.

Starting with the Mk-X 21” torpedo in 1917, the design and production of future was under the auspices of the United States Naval Torpedo Station in Newport with few exceptions.

The United States Navy decided on 21” as a standard diameter for ship launched and submarine launched torpedoes in 1917 with the commissioning of the USS Caldwell (DD-69) that was designed to fire the new Bliss-Leavitt Mk-8 21” torpedo. One of the few exceptions to this was the Mk-27 19” torpedo developed in 1943.

So we have somewhat of and explanation as to why the United States used 21” torpedoes. Command decision in 1917.

We also have an explanation as to why Britain, Japan, Italy, and Germany used torpedoes of the same diameter -- they shared designs and variations in designs with the Whitehead designs.

What is still unanswered is why did Whitehead, Bliss-Leavitt, and Schwartzkopff all decide around 1920 to change to the 533mm/21” design in the first place?

There had to be a reason.

I suspect that come from signed treaties , like Washington or London and same is aplicable for calibers amd tonnage allowed for the different typers of crafts.
Of course there are variations but in caliber for example, was allowed:

152nm- Light cruisers
203mm -Heavy cruisers
381mm-Battleships
406mm-Batleships
120mm-Destroyers

There are variations with 133mm, 150mm, 280mm,320mm,330mm,356mm, 460mm,etc.

In tonnage , 10.000 t was for example the standard for a Heavy Cruiser with 203mm guns.

a lot of the minor naval powers following suit is easily explained if you consider the logistics

dutch yards built subs for the royal dutch navy and it was quite handy to be able to just buy the torpedoes elsewhere, anywhere, wouldnt it? so i can imagine they designed em with a universal torpedo to fit

but that's just theory, i have no idea whether the dutch built their own torps or not