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Do these unit numbers seem a bit low to anyone else, given Japan's wealth and industry?

I understand there's an agreement for the United States to assist in Japan's defense, but such agreements haven't worked very well for some other countries lately.

 

Not really considering the JGSDF's sole mission is based on defence of the home islands. Japanese doctrine depends on the armoured being easily transportable (The dimensions of Type 61, 74, and I think 10s are constrained by rail tunnels) to where they are needed for rapid deployment to maximize numbers. Considering the fact that if the enemy lands on Japan in large numbers, the battle is pretty desperate as the navy and air force have failed in their mission, you'd have to admit that armour is lower on the totem pole than for most countries.

 

Apart from the Kanto plain (Tokyo area) and Hokkaido (Where the bulk of the Typeu 90s are based), very little of Japan is tank country, so the need for large amounts of armour is moot.

A conversation I had with someone who was in the JGSDF in the 70's was they were afraid of (in order of importance) was:

1. Getting nuked

2. Spetnaz

3. Airborne forces

4. Naval Infantry

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Remember that the US occupation divisions in Japan in the late '40s replaced their M4E8 mediums with M24 lights because of bridge and highway limitations. That is why the first US divisions to reach Korea had M24 in their div tk bns and their regt tk cos.

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Apart from the Kanto plain (Tokyo area) and Hokkaido (Where the bulk of the Type 90s are based), very little of Japan is tank country, so the need for large amounts of armour is moot.

I've seen quite a lot of the Kanto plain, & I think it's lousy tank country. Most of it is taken up by Greater Tokyo, & there's not much open land left.

 

 

I was just thinking plain old (*ahem*) topography. ;)

 

Ken,

 

What could the Soviets bring across considering commitments in, say, late 1960-75ish? Would it be essentially just T-55s and later T-62s? I did read that by the time the Type 74 came out if the Russians brought T-72s to the party it might be a trickier proposition for the them.

 

It would be interesting to get hands on design documents that led to the decision for the 90mm. For all I know, they were never even offered the 105mm in designing the Type 61 and it was the only gun they had access to. *shrugs*

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90mm AP was hopeless vs T-54/55 frontally. HVAP only slightly less so. From a flanks both would work fine.

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90mm AP was hopeless vs T-54/55 frontally. HVAP only slightly less so. From a flanks both would work fine.

 

Except in the middle east where IDF M48s reported no problems with Arab T55's?

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What could have been landed in Japan anyway? Some jeeps, maybe light tanks and some APC the rest light infantry mostly. Landed by air or sea. Against such a 90 mm is fine.

That may be the case in many areas but the 800+ Type 74s were meant for soviet tank hordes. And the Type 90s were meant for T-72s. If the US could land M4 Shermans, surely a serious SU could land many T-54s/T-55s on some areas and establish a foot hold with the tanks.

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Did they have any of those left in 1973?

 

Remember that the US occupation divisions in Japan in the late '40s replaced their M4E8 mediums with M24 lights because of bridge and highway limitations. That is why the first US divisions to reach Korea had M24 in their div tk bns and their regt tk cos.

Yebbut that was over 60 years ago. Japan's built a lot of roads & bridges since then, & those I've seen don't look fragile. It was relevant to the design of the Type 61, but no longer.

Edited by swerve
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No, the Israelis used regular APC, but also had HEAT as I recall. APDS was only fielded by the Bundeswehr, I think, and that was pretty late. We have threads on this stuff somewhere.

 

I did some new work last November at the US National Archives and pretty well have the 90mm and 120mm issues resolved. I will do a thread on these in the techie forum one of these days.

 

Here are the basics on K.E. for 90mm:

 

 

Now, to this I can finally add good detail material on KE including vs greater slopes, plus the last word on US 90mm HEAT.

 

This is a table presented in OrdTechCmteMemo 34243 dtd 20Mar52, "Comparative Effectiveness of AP, APC, and HVAP Shot"

 

 

 

 

I'll rescan the new pdfs I have into .jpg a little later but for now, the US T300 HEAT was initiated in 1953 and did not go limited standard until late 1958* as the T300E54, and Standard A in 1961 as T300E59! I am not making this up. They struggled through 59 E-series versions to make it finally the M431 HEAT-T. They never were able to meet the required dispersion requirement [.15mil @ 1000 yds], however DeptArmy allowed Ordnance in 1957 to accept initial dispersion in performance up to .17 mil at 1000 yards and .23 mil at 2000 yards because of the "urgent need for these rounds." With the final Reduced Diameter Fin design ["the limit reached with available technology"] the dispersion was .13-.17 mils. The performance was: "successfully defeated 6" of homogeneous armor at 60 degree obliquity and 12" at 0 degrees obliquity at all conditions of range and temperatures. The shell functioning reliability is satisfactory since 10 duds were obtained out of 225 rounds fired."

 

 

 

*"The critical need for better armor-defeating ammunition for the M48 tanks necessitates production of the round prior to standardization" (OrdTechCmteMemo 36889 dtd 22Sep58, "Cartridge, 90mm: HEAT-T, T300E53 - Classification as Limited Production Type")

Edited by Ken Estes
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...

 

Except in the middle east where IDF M48s reported no problems with Arab T55's?

 

They used HEAT which worked OK up the 60 deg but after that experienced problems with fusing. Read about it:

http://www.tank-net.com/forums/index.php?showtopic=18562&hl=%2Bguns+%2Barmor

Edited by bojan
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...

I'll rescan the new pdfs I have into .jpg a little later but for now, the US T300 HEAT was initiated in 1953 and did not go limited standard until late 1958* as the T300E54, and Standard A in 1961 as T300E59! I am not making this up...

 

Interesting, a quantity of T300 HEAT rounds (IIRC 3000 or 4000, I don't remember exactly and am away from sources)) were shipped to Yugoslavia sometime in '57 as an emergency after Soviet invasion of Hungary. Those arrived by aircraft from US. Other tank ammo was also sent, including 90mm and 76mm AP and HVAP, but those were shipped by train from stocks in Europe. So those would be still experimental back then or could it be early production of limited standard T300E54?

Whatever those were those rounds were used in tests vs T-54. Later more T300/M431 was acquired (IIIRC 15000, about two full combat loads for all M47s available), sometime in 1962/63 (as a results of tests that noted that HEAT was only effective 90mm round vs T-54s)...

 

 

They never were able to meet the required dispersion requirement [.15mil @ 1000 yds], however DeptArmy allowed Ordnance in 1957 to accept initial dispersion in performance up to .17 mil at 1000 yards and .23 mil at 2000 yards because of the "urgent need for these rounds." With the final Reduced Diameter Fin design ["the limit reached with available technology"] the dispersion was .13-.17 mils.

 

 

I have dispersion as 0.18@1000m and 0.24@2000m for initial batch of T300, so that is about it - round in question would be most probably be T300E54...

 

 

 

...The performance was: "successfully defeated 6" of homogeneous armor at 60 degree obliquity and 12" at 0 degrees obliquity at all conditions of range and temperatures. The shell functioning reliability is satisfactory since 10 duds were obtained out of 225 rounds fired."

 

Which explain why they did not have failures to fuse, those occurred at angles over 60deg. - T-54 glacis (60deg) from side angle of 20deg* (compound angle ~65deg,).

Soviet BK-5 was somewhat better, it started to have troubles fusing at angles over 65deg but it was also unsatisfactory hence was modified when accepted for domestic production.

12"/6"@60deg fits welll with local data for initial batch of T300 of 300@0deg / 150mm@60deg.

 

*So called "safe side angle zone", 20deg for hull, 30deg for turret.

Edited by bojan
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Looks like we are on the same wavelength, Bojan. The same doc of 22Sep58 reports three previous fiscal years [July-June back then] of R&D production as follows:

FY59 200

FY58 1400

FY57 1050

 

HEAT was clearly the US hoped-for 'silver bullet' but had a long way to go in development and quality control

 

Interesting we in the M48 crews were never told what the performance of our rounds were, just to use HEAT against frontal aspect targets, but that it became more unstable beyond 2100m or so [meaning dispersion I now suspect]. The only thing I ever read that was suspicious was the number of suspensions for certain manufacturing lots for duds, in bore separations or - worse - in bore detonations.

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Did they have any of those left in 1973?

 

A couple of books I've read have mentioned their use in the Golan by reservists.

 

Don't have any ORBATs on hand though.

 

I certainly wouldn't want to be facing down T62s and T55s in one, thats for sure!

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...Interesting we in the M48 crews were never told what the performance of our rounds were, just to use HEAT against frontal aspect targets...

 

 

Same here, after tests "HEAT is to be used in frontal engagements, from ambush position shooting on flanks AP and subcaliber are also effective"

 

, but that it became more unstable beyond 2100m or so [meaning dispersion I now suspect]. The only thing I ever read that was suspicious was the number of suspensions for certain manufacturing lots for duds, in bore separations or - worse - in bore detonations.

 

It was probably not a problem locally, from all possible battlefields only less then 1% had possibility of fire at more then 2000m.

Edited by bojan
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Abraham Rabinovich's The Yom Kippur War talks a fair bit about a unit of them from memory.

The book is totally Israeli-centric and you get the feeling they probably could've beaten the Arabs with soggy cabbages if they weren't so outnumbered in the initial advances, but overall seemed like a reasonable account.

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Abraham Rabinovich's The Yom Kippur War talks a fair bit about a unit of them from memory.

The book is totally Israeli-centric and you get the feeling they probably could've beaten the Arabs with soggy cabbages if they weren't so outnumbered in the initial advances, but overall seemed like a reasonable account.

 

There were no 76mm armed Shermans in 1973, there were some 75mm (AMX gun) armed, that was probably a confusion.

OTOH, in Bosnia Hellcat managed to get one T-55 (short, range, fog, side hull hit), so it is possible, just very unlikely.

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Abraham Rabinovich's The Yom Kippur War talks a fair bit about a unit of them from memory.

The book is totally Israeli-centric and you get the feeling they probably could've beaten the Arabs with soggy cabbages if they weren't so outnumbered in the initial advances, but overall seemed like a reasonable account.

The only Arab "voice" is Shazly's, but the book is apge turner.It needs to be complemented as it's a partial history at best.

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Does anyone have any specific info regarding the performance/capabilities of the Type 61's stereoscopic rangefinder?

 

Check back to the other thread :)

 

http://www.tank-net.com/forums/index.php?showtopic=38154&page=64&do=findComment&comment=1139490

 

"According to Ground Power, the Type 61 optical rangefinder in the Type 61 tank is a 倒像合到式. I can't find a direct translation for it but the characters roughly mean "Inverted image aligning type". It has one eye piece in, or close to, the center of the meter long base line. I am no expert on these things but if all stereoscopes have two eye pieces, then the Type 61 rangefinder is definitely not stereoscopic. Furthermore, stereoscope in Japanese is either 立体鏡 or 自体鏡. Maybe the Type 61 rangefinder is, in English, a coincidence rangefinder? It has a view range of 200m to 10,000m and a magnification power of 12. Now, directly above the Type 61 rangefinder eye piece is an M15 binocular which outside of the tank the view port is directly beneath the copula MG. It has a magnification power of 7. The English wiki jumbled up the info."

Thanks for that info...what I'm looking for is both a confirmation if the Type 61s rangefinder was stereoscopic or something else, and how well it worked (having only a one meter baseline, etc.)

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Does anyone have any specific info regarding the performance/capabilities of the Type 61's stereoscopic rangefinder?

 

Check back to the other thread :)

 

http://www.tank-net.com/forums/index.php?showtopic=38154&page=64&do=findComment&comment=1139490

 

"According to Ground Power, the Type 61 optical rangefinder in the Type 61 tank is a 倒像合到式. I can't find a direct translation for it but the characters roughly mean "Inverted image aligning type". It has one eye piece in, or close to, the center of the meter long base line. I am no expert on these things but if all stereoscopes have two eye pieces, then the Type 61 rangefinder is definitely not stereoscopic. Furthermore, stereoscope in Japanese is either 立体鏡 or 自体鏡. Maybe the Type 61 rangefinder is, in English, a coincidence rangefinder? It has a view range of 200m to 10,000m and a magnification power of 12. Now, directly above the Type 61 rangefinder eye piece is an M15 binocular which outside of the tank the view port is directly beneath the copula MG. It has a magnification power of 7. The English wiki jumbled up the info."

Thanks for that info...what I'm looking for is both a confirmation if the Type 61s rangefinder was stereoscopic or something else, and how well it worked (having only a one meter baseline, etc.)

 

 

Yea no problem. I have more but it will take some time for me to familiarize myself with the Japanese rangefinder specifics written in what I have before conveying it in English here. In the meantime, anyone else, feel free to jump in.

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The description points towards a coincidence range finder. That needs only one ocular to work. And well, if it is not stereoscopic, coincidence is the other way of building an optical range finder. Advantage is that all people can use these, whereas steroscopic range finders cannot be used by some people as their spatial sight does not play well with stereoscopy. Just like some people gain nothing from a movie in 3D or cannot see those magic pictures that produce a 3D object after looking at for an amount of time. Disadvantage is that coincidence range finders are more tiring to the eye than stereoscopic because those can be used with both eyes open.

 

There is a sub type of coincidence range finders that uses an inverted image that is being aligned with the target. I think the IJN used this type on their ships. I guess this is the type used.

 

 

What boggles my mind is, that afaik the JGSDF did not replace the range finder with a laser sometime in the 1970ies or 80ies. It is Japan after all, the land of good cheap electronics and a laser range finder is much easier to use and faster than a optical device. And less influenced by climate as thermal expansion/compression of the tube changes the base length, many small mechanical pieces that can break etc.

 

 

edited to add: The wikipedia entry has an interesting quote from a report on a comparative trial made in WW2 concluding that there is not much practical difference between the two types and that base width is not the single biggest factor influencing precision of measurements.

http://en.wikipedia.org/wiki/Coincidence_rangefinder#Coincidence_vs_stereoscopic_rangefinders

Edited by Panzermann
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