Technical lost opportunities: Japan

trurle

Banned
Japanese were buying a lot of military hardware from UK, Germany and France before ww2. It might be plausible for them to take a look at the Somua tank, then on the Pz-III, then on the Stug-III, and decide to combine the best features in a tank and in a self propelled SP gun for direct fire.
They can take a look at Birch gun, and un the French 194 mm SP artillery, and go with a SP artillery piece of their own.
A SP AAA, mounting 2 x 20 mm might come in handy, both for AA duties and for direct fire against infantry and light obstacles, much like the Soviets used the Shilka in Afghanistan.

Japanese had the designs you mentioned.
Type III Ho-Ni was an analog of Stug III was a high-performance 75mm universal SP gun. Also, the Type 98 20 mm AAG Tank (To Be exact, Ho-Ki variant) was the 2x20mm armoured vehicle. Unfortunately, with US phasing out bombs in favour of HVAR rockets, none of these designs (or any plausible alternative to them) was survivable. 20mm AA guns were simply out-ranged by HVAR, and tanks top armour was easily pierced by earliest semi-HEAT HVAR warheads.
 
The Japanese should have developed and used their own in-line designs instead of licensing the DB 601. In 1940 the Japanese were developing and experimenting with two engines in particular that caught my eye:

The Mitsubishi Ha21 was a liquid cooled V-12 of 1470ci 900hp at 2900rpm at 4000m, 1067 pounds and a BMEP of 167.21.

And the Nakajima "NLF", a liquid cooled inverted V-12 of 1689ci; 940 hp at 2700 rpm at 3650m, 1089 pounds and a BMEP of 163.25.

Both very close in relative power to the Kawasaki built HA-40, a licensed Damiler Benz DB-601 of 2070 ci and a 1100hp at 2400 rpm and 4200 m and a BMEP of 175.36. Of course this is the version installed in the production Ki-61 beginning in August of 1942. No telling where the two domestic in-lines would have been had they not had the rug pulled out from under them.

http://www.warbirds.jp/kakuki/sanko/en_japan.htm

https://ww2aircraft.net/forum/threads/data-base-japanese-aircraft-engines.19466/



The Japanese fighters with V-12 enngines make plenty of sense. They can indeed start with H-S 12X and/or RR Kestrel, later transition to H-S 12Y or DB 601. The lower drag of that kind of powerplant, coupled with easy usage of exhaust thrust will mean either greater speed and range on same HP, or same speed and greater range on, say, 10% less power. The Ki 61 was exceptional here - better range, speed, protection and eventually firepower than the Zero, on comparable HP.
 
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I'm not sure what those engines buy for the two Japanese air forces. The HS12Y offers already in 1934 the power of 860 CV (metric HP) at 4000 m, weighting ~1020 lbs. Stick that on a monoplane with retractable U/C and there is a 500 km/h cannon-armed fighter? Later with refinements in aerodynamics and engine installations - 550 km/h? This is also the point when the DB 601 should take over, offering 20% more power.

The BMEP and engine's power-to-ratio values look nice on sales prospects, but they don't propel the aircraft. Light engines don't stand up to big manfold pressure, nor to increase in the RPM, hence the power will remain low. Let's recall that Soviet M-105 gained 100+ kg over M-100 (= license-built HS 12Y), the VK-105PF gained another 150 in order to use more boost, and Soviet fuel was better than Japanese. With DB 601, they already have that level of power 2-3 years earlier.
Japanese aircraft need (as other people's) performance, firepower, protection, range, maneuverability. 900 HP might buy that in late 1930s, but not in 1942 and later - see Zero and Oscar.
 
Japanese had the designs you mentioned.
Type III Ho-Ni was an analog of Stug III was a high-performance 75mm universal SP gun. Also, the Type 98 20 mm AAG Tank (To Be exact, Ho-Ki variant) was the 2x20mm armoured vehicle. Unfortunately, with US phasing out bombs in favour of HVAR rockets, none of these designs (or any plausible alternative to them) was survivable. 20mm AA guns were simply out-ranged by HVAR, and tanks top armour was easily pierced by earliest semi-HEAT HVAR warheads.

US was not phasing out bombs, they actually make sure that even their fighters can carry bombs as the war progressed. The medium bombers were seldom equipped with rockets.
The Type 98 seem to be the example of 'too little, too late'? Rocket-armed aircraft were lousy in hitting AFVs/tanks anyway, though the nearby explosions will trouble the non-armored stuff, and upper half of the Type 98 was not armored.
Type III Ho-Ni looks like the eqivalent of Marder series (but with roof)? StuG-III was far better armoured, the Ho-Ni will be killed by 37-40 mm gun.
 
Japanese aircraft need (as other people's) performance, firepower, protection, range, maneuverability. 900 HP might buy that in late 1930s, but not in 1942 and later - see Zero and Oscar.

I was envisioning this 860HP HS-12Y powered Ki-12Kai as a high performance interceptor (for the late 1930s period) bridging the gap between the traditional japanese light fighters like Ki-27 (complementing, not replacing it) to the Ki-44 and Ki-61 that would enter production and combat in 1942-43. Considering that it will still be a lightly built aircraft in the japanese tradition, i would guess that this Ki-12Kai whould have speed actually slightly superior to the latter Ki-43 (say 520 Kph), due to the lower drag of the inline engine. It won't have the range or maneuverability though, although it will still be quite maneuverable, which is how the Ki-44 (cannon armed too in my ATL) and Ki-61 (maybe with a 20mm engine cannon and two 12,7mm in my ATL) turned out to be. So it could be built between 1938 and 1942, in OTL they built about 2000 Ki-27, i'm thinking of having 1200 Ki-27 and 800 Ki-12Kai in the same timeframe.
 
We know that Japanese pilots were excellent prior late 1942, however the IJA was rather late to introduce cannon armed 1-engine fighters - talk late 1943? Zero's cannons were nothing stellar, but a seasoned pilot will plant it's shells in the enmy A/C, and Zero got better cannons by late 1942.
Going with Hispano, and later with DB engine, allows for a cheap way to install just about any 20 mm cannon that is around, mount is rigid and does not need separate heating. The cannon will ruin anybody's day once shells hit home. Later, the 30 mm chould be tailored for the V-12 engine installation.
Sure enough, the 3 cannon Ki-61 does not require crystal ball.
 

trurle

Banned
We know that Japanese pilots were excellent prior late 1942, however the IJA was rather late to introduce cannon armed 1-engine fighters - talk late 1943? Zero's cannons were nothing stellar, but a seasoned pilot will plant it's shells in the enmy A/C, and Zero got better cannons by late 1942.
Going with Hispano, and later with DB engine, allows for a cheap way to install just about any 20 mm cannon that is around, mount is rigid and does not need separate heating. The cannon will ruin anybody's day once shells hit home. Later, the 30 mm chould be tailored for the V-12 engine installation.
Sure enough, the 3 cannon Ki-61 does not require crystal ball.
Every weapon developer or engineer in Japan knew the advantages of 20mm aircraft cannons. The problem was not technical, but rather stiff resistance of pilots and supply men to adopt them. Problem was what 20mm canon run out of available ammunition in mere seconds, making pilots extremely nervous. Ammo drain (weight per second) was ~15 times of 7.7mm machine gun. So people were afraid what they will be either not supplied with 20mm ammo or the supply will run out during combat (and this was essentially true). Only after some Allied aircraft was found to be nearly immune to 7.7mm or 12.7mm machine guns, the resistance of the Japanese pilots to 20mm gun introduction broke.
 
The IJN did not shared those fears, they introduced cannon-armed Zero rather early - in late 1940. The Type 99-1 was not ideal waepon, but worked, as did the similar MG FF.
An engine-mounted cannon can allow for 100-rd container, that should give 15 seconds of firing time. Earlier introduction of Oerlikon FFL (= Type 99-2 in Japan) means flatter trajectory than what FF (= Type 99-1 in Japan) offered. The Type 99-1 recceived 100-rd container, too late to matter (late 1942). There was a version of He-112 that mounted the powerful MG 30/C, with 100-rd container, used in Spanish civil war.
100 rds at 500 rpm will allow 12 seconds of firing time, and having 20 mm cannon does not exclude LMGs as back-up, as seen on Bf 109, He 112 or French and Soviet fighters (this is all/just for late 1930s).
That is all before belt-fed cannon is introduced, OTL in 1943 (again, IJN; IJA is late and uses German MG 151/20 to help out), ITTL already in 1941? Not sure when the Japanese were aware of the ShVAK.
 

Saphroneth

Banned
A story I've heard to indicate the skill of the IJN Zero pilots was that they used their twin MG as tracers to aim their 20mm cannon... despite the different ballistic characteristics of the two guns.
 
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