What's new
British Ordnance Collectors Network

This is a sample guest message. Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!

Japanese Mortar Round Fuze

Hi guys,

Hold on to your seats, down below follows Takehito Jimbo's reply. As I already assumed (or better put: correctly deduced from other Kanji markings and their references), my interpretation of 'Howitzer Mortar' only being able to be interpreted as 'Howitzer AND Mortar' and not just 'Howitzer' is correct!
These fuzes must then definitely have been suitable for SOME mortar; even if they're not suitable for the smooth bore kinds.
I'm suspecting that either:
1) This fuze had no rotational arming mechanism, or:
2) The fuze was intended for the Type 11-year RIFLED mortar.

Possibility 1 can be easily enough verified, by having someone section such a fuze. Does anyone have a spare that can be 'sacrificed' for this?

Alright, down below follows Takehito Jimbo's unedited reply to my e-mail, regarding this marking:

"On the instantaneous T-88 fuse, I had always pondered the same questions that you had in mind. There simply are too many examples of the 81mm round fitted with the T-88 fuse and have been a real enigma. Your read on the fuse markings are correct in the 野山加 does not mean a "field mountain gun" as a single type of weapon, that does not exist, but denotes the use for rounds with field guns, mountain guns and cannons as per Japanese military nomenclature. Similarly the 榴臼 does mean howitzer (example : The Type 4, Type 91, Type 96 howitzers) AND mortar (example : 9cm, 15cm Mortars), although the two, in all practicality, have become almost the same weapon as the design progressed, but was differentiated for the military nomenclature system sake (most "臼砲 or Mortar" nomenclature were placed earlier in Meiji era weapons). However, having said all this the Japanese 81mm launcher in question is called the 九七式曲射歩兵砲 under military nomenclature, which translates directly to Type 97 High Angle Infantry Launcher and does NOT use either the word 榴砲 nor 臼砲, so we have a bit of a self defeating problem here with the theory.
Have you ever had a chance to disassemble the T-88 榴臼 fuse and check if
the centrifugal locks are eliminated on these ? I'll also check some of my
original military references in Japanese for answers to this."

Cheers,
Olafo
 
All very intersting. Now lets get down to the fine details of the Type 88 Artillery Fuzes. Without me having to go into long lengths here, the most in depth detail in all aspects of the fuzes can be found in:

"Chief Inspector of Ammunition Kirkee - Technical Report No. 34 - Nose Percussion Fuzes Type 88 for Gun Ammunition with 24mm Fuze Hole"

This was made available for downloading by Bonnex some time ago. If any of you downloaded it then have a good read of it. Very interesting. Remember when the British do something they do it well and this report is no exception.

Basicly in a nut shell both forms of the fuze need centrifugal force as each and every one of them have 4 brass centrifugal segments.

I'm not discounting that the low velocity version could've been use with rifled mortars at some stage after it's development. They definately were not intended for or used in smooth bore mortars except maybe out of desperation.

I keep on seeing mention of the number of mortars in collections which sport a Type 88 Fuze. Lets get things straight as it looks like what has been said before hasn't sunk home. An army never transports ordnance in a fuzed state. The Japanese were no different. Ordnance was only fuzed just before use. A vast majority of Japanese Mortars in collections would've been recovered with transit plugs in place. The Type 88 Fuzes would've been erroneously added at a latter stage because it looked better than not being fuzed.

The Type 88 fuzes of course being very plentifull due to the large number of ammunition calibres that used them, gave them a higher proportional chance of being added to a mortar to make it "look good" rather that the correct Type 93 or Type 100 fuzes which were not as numerous as the Type 88s.

Cheers,
BOUGAINVILLE
 
Hi Robert,

Thanks for having thoroughly checked the British documents; this was next on my 'to do' list (as soon as I would have gotten some time for it again).

As you confirm that the 'Howitzer Mortar' marked ones also have these wedges, it virtually certainly means that these fuzes were indeed NOT usable on the smooth bore mortars. Surely the British took them apart themselves too, and did not rely on (copied across) findings of US studies.

This is an important finding, as that makes clear that indeed the 81mm, 90mm, 120mm and 150mm mortars would have ONLY used the Type 93 and/or Type 100 fuzes; a thing consistent with their type numbers too. Making that part of the documentation pretty much beyond a doubt sound and correct.

In due time (i.e. once everything has crystalised out some more), I will amend my page to properly reflect all these findings, but not quite yet until some other things have been determined.

What I'd like to see better explained still before doing so, is the lack of an explanation (in the documents) for the 'Howitzer Mortar' kind fuzes clearly being marked for 'Howitzers' AND 'Mortars'.

The $64,000 question is: which mortars exactly?

In my opinion, out of the documentation the only one I have come across that seems to be a viable option is the old Type 11-year 70mm RIFLED mortar.

Still there is a very worrying 6 year gap between the dates of official adoption of the Type 11-year (i.e. adopted in 1922) mortar and the Type 88 (i.e. adopted in 1928) fuze. This is odd, as one would not expect this 6 year period to have been completely deprived of fuzes for the 70mm mortar! Surely SOME form of fuze must have been available in the meantime.

Two possible explanations:

1) Possibly the Type 88 fuze had a predecessor, intended for the 70mm mortar rounds. Who knows... maybe even the alleged one that's only marked with the word 'Mortar' as Jeff mentioned having been reported to him.

2) Perhaps just a sign of the times. In the specific 6-years interval, a regime change took place, as well as a modernisation program of arms and ammunition. Possibly Type 88 fuzes were already in earlier experimental use/development, without having yet been officially adopted.

I think it's safe to stop looking in the direction of the smooth bore mortars for usage with the Type 88 fuzes (though, as per Jeff's suggestion, it would be great to see a sectioned/disassembled one, to beyond a doubt establish the presence of the wedges in a real-life specimen), and to start looking at other mortars.

I'm putting my money on this fuze having been intended for the 70mm mortar rounds, and I think it's great to see further corroboration of the almost certainly correct statement that combinations of smooth bore mortar rounds with Type 88 fuzes are NOT correct.

Isn't it nice what new lines of thought and findings can evolve when people are shell-shocked somewhat by a bold (in this case incorrect) theory being proposed....? ;)

At the very least one omission in the documentation has almost certainly been identified here: lack of mention of which mortars the Type 88 'Howitzer Mortar' fuzes were intended for. I have only seen mention of the howitzers they were used in. Yet, as opposed to what others may think, I put NO doubt at Takehito's translation backing up my interpretation of the fuze markings being the only correct reading, and I'm 100% behind the fuze itself saying that it was manufactured for usage with howitzer and at least one type of mortar rounds.

The quest is on for finding references to establish precisely WHICH mortar rounds...

Cheers,
Olafo
 
Hi Olafo,
Yes the British always did things very thoroughly in a rather Tutonic fashion and all of their work that I've ever seen has been original and not copied from Uncle Sam. They disassembled everything and went to great lengths to record every minute detail as one will soon see when reading the above mention intelligence publication.

It also happens that I have a heap of Type 88 fuzes in verying degrees of condition and have so far partly dismantled some of them but not to the stage of making up a photo collage. Both the high and low velocity forms have the same internals. Except for the lighter setback ferrule and stirrup spring in the low velocity fuze everything else is exactly the same internally.

Cheers,
Robert
 
Last edited:
Any news about this subject?- the mortar fuzes didnt use any collar or segments,bur simply a sheer wire.
The normal T88 could be converted by removing the segments and add an shear wire. Simply needs the dismantling of some "Mortar" marked fuzes.
They could be unscrewed easily.

To blow the whistle :)

If I had a smoothbore mortar and mortar rounds. And if I only had T88 fuzes. I would remove the segments and fire it with safety fork in place
:).
 
Hi,

Bougainville took one of the 'Howitzer Mortar' marked fuzes apart: it has all the safety mechanisms (i.e. a collar and the wedges) as the 'Field Mountain Cannon' marked ones has, but with the difference that the latch springs are weaker and hence require less set-back.

Now, you're last remark is an interesting thought: I wished someone had such a mortar and sufficient rounds and fuzes at hand to actually fire the bl**dy thing equipped with a Type 88 'Howitzer Mortar' fuze and see what would happen. :)
Really, it SHOULD result in a dud, yet it would be an interesting test nonetheless (even if only for seeing such a mortar getting fired once). :)

Anyway, make sure to read my revised theory on this fuze perhaps having been destined for the 70mm RIFLED mortar. That would certainly be more likely to give a working combination.

Also: Jim has some very, very interesting news (he'll elaborate later), as he has one of the improvised 58mm mortar rounds, and has two modified Type 88 fuzes for it. From what he describes it definitely sounds like field modifications.

Jim: feel free to chip in anytime you can. :)

Cheers,
Olafo
 
Last edited:
I must correct myself. The safety fork in place with removed segments would be very dangerous.
The safety fork simply fix the setback collar - removing the segments
results in a floating striker. No bore safe then.

As a last result we could note that the T-88 always need rotation to work,
so they are always wrong on mortar bombs.
 
You must log in or register to reply here.
Top