Japanese Aircraft Engine Piston

Oppama thank you for all you help.

Kanji remains difficult for me to understand and I rely upon Google translate, Kanji drawing programmes and Chinese/Japanese colleagues for assistance.

So to conclude this is a Nakajima Sakae piston with a bore of 130mm – liberated from a crashed aircraft.

The bore and design suggest it is from a Sakae 12 as used in a variety of IJN and IJA aircraft ?

Lovely piston and great homework Oppama.

Thanks, Oppama, for the “homework”. It is interesting and it does, in essence, bear out what I said in very broad terms in my earlier post about foreign (UK & US) engines being studied for their technical advances.

I think it contradicts your offhanded-looking “copied the best of it” remark and the negative connotations that go with it. If representatives of the companies concerned were actively seeking out licensees and travelling to Japan to sign up/advise and collect the payments, I think that’s quite a different situation than “copying”. Presumably most people don’t think of such things when they drink Indian-grown tea from English blue & white porcelain? We might like to bear in mind that where ‘copying’ was concerned, ‘we’ copied first…

As for the term “Japs”, I think it best left to the Japanese nation to tell us if they find it disrespectful or not regardless of where they see or hear it. Personally I don’t find it much of a hardship to type out an extra four letters to avoid the question coming up and the abbreviation seems quite forced, to my eye at least. I don’t want to get into an argument about it but I think it better to make the effort in order to avoid any misunderstanding.

Thanks, Oppama, for the “homework”. It is interesting and it does, in essence, bear out what I said in very broad terms in my earlier post about foreign (UK & US) engines being studied for their technical advances.

The Japanese also took the licence for Hamilton-Standard propellers; many of their aircraft types utilising various models of the Mitsubishi-Hamilton airscrew.

And Japs – yes. It’s an abbreviated title and does not indicate, at least from my viewpoint, any lack of respect for that race. I also use the term Jerries in a similar way. In any formal writing I would use their full title but this forum is not of that ilk.

Anon.

You understand that Sakaes varied in capacity, right?

Actually no, I didn’t know that…..hence my confusion! 🙂

The Japanese were aware of the excellent engines/aero technology emanating from the US before the war and, no-doubt, as good as copied the best of it.

Some homework for you:

http://www.ne.jp/asahi/airplane/museum/nakajima/nakajima2-e.html

The Japanese were aware of the excellent engines/aero technology emanating from the US before the war and, no-doubt, as good as copied the best of it. It was usual for details of the technical advances to be published internationally (Jane’s, etc). It will be certain that US engines were obtained pre-war to enable Japanese designers and engineers to study those advancements. The Japs had a great vested interest in producing powerful aero engines earlier than the US did as they were involved in military conflicts far earlier, not least with their advances into China.

“Obtained”? Most of the Japanese manufacturers – in common with the rest of the world – licensed designs and patents from abroad (including the UK and USA, and especially Germany) as well as coming up with their own designs, innovations and improvements. To write them off as not much more than idiot savant copyists is to make the same mistake that the Allied powers made in the 1930s.

And “Japs“, really…?

So the larger piston is only 130mm in diameter?

The blog says it is 150mm, so where are you getting 130mm from?

You understand that Sakaes varied in capacity, right?

It was common for parts/relics (especially enemy ones) to be liberated by personnel abroad, with access to the enemy’s equipment remains. The “liberator” could have been an aircraft engineer/mechanic with an interest in such things or also, quite plausibly, an officer who has been presented with a relic – perhaps one in which said officer played a part in its destruction.

There is a reason that the piston is in the state it is in and I’d put money on it that they damage is tied up with that reason. As I remarked earlier, unfortunately we’ll probably never know what the circumstances and background are.

The Japanese were aware of the excellent engines/aero technology emanating from the US before the war and, no-doubt, as good as copied the best of it. It was usual for details of the technical advances to be published internationally (Jane’s, etc). It will be certain that US engines were obtained pre-war to enable Japanese designers and engineers to study those advancements. The Japs had a great vested interest in producing powerful aero engines earlier than the US did as they were involved in military conflicts far earlier, not least with their advances into China.

Great find, Brian.

Anon.

That’s the Sakae piston. It is being compared to the smaller ‘mystery’ blank forging for reference…

So the larger piston is only 130mm in diameter?

No need to apologise- thank you for all the images.

Sorry to bombard you with links, but there are rich seams to be mined on Japanese blog sites, such as:

http://home.f04.itscom.net/nyankiti/ki43-sub3-engine1.htm

…from the very excellent ‘The Japanese Army Type 1 Fighter Hayabusa (Ki-43 Oscar) Research Laboratory’ blog:

http://home.f04.itscom.net/nyankiti/ki43-top1-page1.htm

A nice Sakae piston reference on one of (arch enthusiast) Taizo Nakamura’s blog pages:

http://a6m232.server-shared.com/CCP1.html

Well I will be blowed – the picture of the used piston with R2 and Kanji markings etc is virtually identical to the one I have here. Thank you very much Oppama.

Pictures ( hurrah) of them side by side.

A nice Sakae piston reference on one of (arch enthusiast) Taizo Nakamura’s blog pages:

http://a6m232.server-shared.com/CCP1.html

What is the other (150mm) piston?

That’s the Sakae piston. It is being compared to the smaller ‘mystery’ blank forging for reference.

Some nice marks on that particular Sakae piston, including the Mitsubishi logo and the Sakae star.

Good blog with Sakae piston markings here:

http://blog.goo.ne.jp/kourasankyusyakai/e/34249a02e75db76e65a2ef2b479d5220

Astonishing photographs; I’ve never seen a forged ‘blank’ for an aero-engine piston of any nation, let alone anything a rare as a Sakae piston. A truly remarkable relic!

What is the other (150mm) piston?

Sakae piston relic…

Are both Sakae piston relics; complete on the right, smashed fragments with gudgeon-pin on the left?

If the complete one is a Sakae piston then the grooves machined into the inside of the thrust-face are remarkable; this is such an American feature for any piston to have.

‘…press forging was indicated by the internal smoothness of the piston. Even deep in the waffle pattern, no machining marks were evident…’

First time I’ve heard that distinctive forging design called ‘waffle pattern’ in an official document (not that I’ve read many official documents, of course)!

Thank to all who have replied.

P&P just been cleaning out the waffles with a dremel brass brush.

There is the slightest hint of a pin head in 5 of the waffles. A number 1 in the centre waffle.

Marking around the edge –

Front edge R 2 and Kanji for front. Below 40-1328.

Other edge
1.17OKG

markings below – obliterated except for an S at the end.

Weight ( without) rings -1170-80 g

Definitely from a damaged machine – gudgeon retaining pin still in one groove. Bottom scraper ring edge broken.

But also lots of chisel marks suggesting enthusiastic liberation.

P.S. the RAF cap badge was on a home made wooden circle and painted with Humbrol red- so nothing authentic – apart from the badge.

BIOS Reports 1466/1467 “Metallurgical Examination of a Sakae 12/21 Aircraft engine” show photos of a piston crown in the 21 similar to yours, with the stolen P&W ‘nicks’ for the valve heads. Then within the text for the 12, ” press forging was indicated by the internal smoothness of the piston. Even deep in the waffle pattern, no machining marks were evident.”

Sakae 12 “piston assembly” (including rings?) is given as 1660 grams.
Sakae 21 “piston” is given as 1210 grams. There are images of kanji & markings given for both pistons, so use your bead blaster…
If it looks like a duck, quacks like a duck…

I didn’t know that Japanese dialects persisted to 1945 and that written characters were also affected by regional influences. That is, somebody in Tokio in 1945 might not be able to automatically read characters from another region. On top of this is the obtuse technical language relating to concepts such as ‘hydraulic reservoir strainer security fastener’ that your average kimono clad tea hostess would be reduced to shamed giggles in trying to grasp. Then the fact that most folks in Japan want to forget that they had ‘hydraulic reservoir strainer security fasteners’ connected to aircraft dropping HE on a number of places, means that there aren’t a lot of people to connect with in deciphering this stuff. I would be interested to converse with anybody grappling with WW2 Japanese technical translations.

The J Forum you can’t seem to get on, mods are probably under some table as the earth shakes, or drinking whiskey in a karaoke bar. As Winston would say, key mods are the worst in the world, except for all the other ones!