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  #1  
Old 8th February 2018, 02:57
bearoutwest bearoutwest is offline
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Kawasaki Ki-61 - Ha40 vs DB601

It has been noted (possibly anecdotally) in a number of publications, that the Kawasaki Ha40 engine was not manufactured as well as the Daimler-Benz 601 upon which it was based. Japanese air and ground crews have been noted to be impressed with the clean state of Allied in-line engine aircraft and the lack of oil stains. This perhaps reflecting the Japanese experience with oil leaks from the Ha40.

So my question is this: would a Kawasaki Ki-61 have performed more to its fuller potential if powered by imported DB601s rather than the locally-produced Ha40s?

...geoff
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Old 8th February 2018, 09:06
Laurent Rizzotti Laurent Rizzotti is offline
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Re: Kawasaki Ki-61 - Ha40 vs DB601

Probably, but the fact is that it was not possible for Japan to import from Germany the thousands of engines needed for the Ki-61 it built.
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Old 8th February 2018, 09:24
bearoutwest bearoutwest is offline
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Re: Kawasaki Ki-61 - Ha40 vs DB601

Hi Laurent,
Not intending to re-write history as to why the DB601 wasn't used. I'm happy to accept history as it was.

The intent of my question is more to explore the differences between the Ha40 and the DB601, as manufactured; and to understand how much of a difference this might/would have made to the performance of the Ki-61 Hein.

Thanks for starting the ball rolling.

...geoff
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Old 8th February 2018, 11:04
Graham Boak Graham Boak is offline
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Re: Kawasaki Ki-61 - Ha40 vs DB601

I think this is a general reaction to the way sealing technologies in Japan were behind those in the west, rather than being particularly directed at the Ha 40. It should be added that the Merlin was notorious for leaking.
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Old 8th February 2018, 16:36
Revi16 Revi16 is offline
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Re: Kawasaki Ki-61 - Ha40 vs DB601

Performance and reliability are two different things. The aircraft would have performed the same with either the Ha40 or DB 601, 1150hp is 1150hp no matter which engine supplies it. Same power to weight ratio, etc..

Perhaps the aircraft could have been more reliable with the DB 601, but we'll never know.
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Old 8th February 2018, 17:33
Laurent Rizzotti Laurent Rizzotti is offline
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Re: Kawasaki Ki-61 - Ha40 vs DB601

Maybe the difficulty for Japanese was that it was their first in-line engine.

From my recents reads about Guadalcanal, it seems that in 1942 far more US aircraft were lost to engine failure than Japanese ones, despite the Japanese ones flying far longuer missions. So at least in the first part of the war, engine quality seem not to be an issue for Japan.
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Old 8th February 2018, 21:19
John Beaman John Beaman is offline
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Re: Kawasaki Ki-61 - Ha40 vs DB601

Quote:
Originally Posted by Graham Boak View Post
I think this is a general reaction to the way sealing technologies in Japan were behind those in the west, rather than being particularly directed at the Ha 40. It should be added that the Merlin was notorious for leaking.
Wasn't Napier-Sabre also renowned as a leaker?
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Old 8th February 2018, 22:21
bearoutwest bearoutwest is offline
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Re: Kawasaki Ki-61 - Ha40 vs DB601

Quote:
Originally Posted by Revi16 View Post
Performance and reliability are two different things. The aircraft would have performed the same with either the Ha40 or DB 601, 1150hp is 1150hp no matter which engine supplies it. Same power to weight ratio, etc..
Not necessarily. The design output for two originally similar engines may have been the same (e.g. 1150hp), but the quality of the build, the quality of materials, the design modifications to facilitate large-scale manufacture, the closeness to design specifications and tolerances, etc, even the quality of secondary items such as sealants mentioned by Graham; would have a great bearing on how much of that design power output could actually be achieved.

As Laurent said, perhaps the lack of experience with producing high-power in-line engines was a factor. Or there may have been other, more significant influences: perhaps the Ki-61 was just a "draggy" design compared to the Bf109F or the Macchi C.202?

Or perhaps the anecdotal bad reputation of the Ha40 was mistaken?

...geoff
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Old 9th February 2018, 04:03
bearoutwest bearoutwest is offline
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Re: Kawasaki Ki-61 - Ha40 vs DB601

I discovered this the other day. Some kind soul has made available the Japanese assembly and service manuals for the Kawasaki Ha40 in-line engine, on this linked page:
http://www.aero.or.jp/isan/archive/h...0_and_ha60.htm

I downloaded the files (6 in total) without difficulty but as expected, it's in period Japanese script (very similar to classical Chinese script). Unfortunately, I am fluent in neither. So short of picking up 1 word in 20, it sheds no further light to my query. (Though I am in awe of the laborious, hand written nature of the technical translation.)

Perhaps someone with a working knowledge of the DB601 might be able to spot any obvious differences between the two engines from the drawings or technical charts?

...geoff

**Forgot to note reference page from J-aircraft website which sent me to the page with the Ha40 manuals.
http://www.j-aircraft.org/smf/index.php?topic=17127.0
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Last edited by bearoutwest; 9th February 2018 at 04:11. Reason: Reference source update
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Old 9th February 2018, 13:39
Graham Boak Graham Boak is offline
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Re: Kawasaki Ki-61 - Ha40 vs DB601

My comment on sealants was thinking particularly of oil seals in the lubrication system and the engine, and directed at the "leakiness" of the engine rather than its performance. Most if not all of the criticism I've seen about the Ha 40 has been about its reliability, not any lack of power when it was working. So whereas the performance of any one Hien was unlikely to benefit from an original DB601, the performance of the Hien force as a whole could be another matter.

As for the design of the Hien compared to the Bf10F or the MC 202, it appears to have a large wing and so a larger surface area, giving an increase in skin friction drag (probably further increased by lower build standards) and therefore lower top speed. This would be balanced by lower lift-induced drag (at the same weight) with better performance at altitude, better turning at low speeds. It might be more or less agile, depending largely upon the quality of the aileron design, not something I've seen discussed. The aircraft are not optimised for the same conditions: which would be described as the better performer would depend upon where they were fighting and against whom.
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