Zeroes to Skylines, a link to the past

I thought it might be interesting to break from regular content to discuss an interesting connection to Nissan and the Skyline.

One of my majors in university was modern East Asian history, coupled with me being quite the WW2 nerd it didn’t take long for me to stumble upon the distant relatives to the powerplants of the Skyline.

Tracing back the origins of the Skyline most of you will already know about the Company called Prince Motor Company which gave brith to the Skyline. As you also know they later merged with Nissan bringing their expertise in building racing engines such as the GR6 in the R380 racing car and the S20 engine of the first GTR. Not to forget the Skylines before the GTR who were tearing up Japan’s race tracks. This much most of us hardcore Skyline nerds will know.

Going back further Prince Motor Company (previously named Fuji Precision Machine Co.) and Fuji Heavy Industries (Subaru) were formed from the dissolved Nakajima Aircraft Company following the end of the war. Each company respectively was started by former engineers of Nakajima Aircraft Company.

Nakagawa Ryoichi, a brilliant aerospace engineer. He lead a team at Nakajima Aircraft which was responsible for several key fighter aircraft engines during his time at Nakajima Aircraft was apointed head of engineering at Prince Motor Company and oversaw the design and development of the majority of Prince’s models including the Skyline.

In this post I thought I would bring to light one of the engines Nakagawa’s team, when they were at Nakajima Aircraft worked with. The spiritual decendant of the first Skyline engines, the Sakae 21.

The Zero

The Sakae 21 was indeed the engine mated to the infamous Mitsubishi Zero Fighter. But you must be wondering where is the “Mitsubishi” in the plane if the engine was made by Nakajima Aircraft.

In the late 1930s when the Imperial Japanese Navy (henceforth will be refered to as IJN) was looking for a replacement for the A5M fighter both Mitsubishi and Nakajima were competeing for the tender which Mitsubishi’s design ultimately won out. So the airframe of the Zero is indeed as the aircraft’s name suggests was made and designed in house by Mitsubishi.

Mitsubishi also had their own engine designed for this airframe, the Kinsei engine. However during trials the Navy top brass decided to go with the more powerful solution provided by Nakajima Aircraft, the Sakae 12. These aircraft, designated Model 21. You can think of as the “Zenki” or series 1 of the Zeros (A6M2). They were produced until 1942 meaning they were the model which conducted the Pearl Harbour mission. I could not find any information on whether Nakagawa or his team designed or worked on this engine.

The zero saw a period of low performance with the subsequent models following the 21. Even with the introduction of the Sakae 21 equipped model entered service in 1942 with brought little advantage over the initial Model 21 with the Sakae 12.

I believe Nakagawa’s team only were involved in the later iterations of this engine. The model 52 Zero (A6M5), which is often agreed as being the best generation of Zero with a revised Sakae 21.

The above photo and the following were taken by yours truly. There is a A6M5 (Model 52) on display at the Military Museum in Tokyo.

The above document details the difference between the Model 21 and 52. Chief among the changes was a redesign of the exhaust outlets to face rearwards to forming a ring just infront of the leading edge of the wings. This slight rearward thrust generated by the exhaust along with the increase in horsepower from the revised engine increased the maximum speed to 565kph.

The silver sticking out bits are the new design exhaust system. Not the one near the landing gear housing is shortened to prevent the tyres from being heated by the exhaust.

Mitsubishi were not entirely responsible for the manufacturing of the airframe of the Zero by this stage and production was divided between them and Nakajima.

This was actually my first time seeing a WW2 aircraft in the metal and I was surprised at how large it was.
Main armament was Type 99 22mm cannons mounted one on each wing. This example is from a Model 22 Zero.
600 meters per second muzzle velocity and 100 round capacity drum.

It is amazing how expertise can transfer from one industry to the other. Aerospace -> Automotive or Maritime -> heavy industry. In that sense the Sakae 21 engine of the Zero can be thought of as the grand father of the first Skyline and R380 engines. Work on this engine was not Nakagawa’s final work in the aerospace industry, there was one more engine/aircraft which he played a bigger part in which was an unsung masterpiece of a fighter aircraft at the time but that is a a story for another time…

References

I have not done full academia style referencing but here a few papers I used for reference.

https://www.japantimes.co.jp/news/2004/01/14/national/zero-inspired-todays-innovations/#.XhFthib7TIU

https://www.jstage.jst.go.jp/article/jsmemag/85/759/85_KJ00003082325/_article/-char/ja/