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3 small spars might be both stronger and lighter than 2 big spars. Remember that the skin handles some of the load/spreads it out.How could such a slender, delicate wing be so rugged? The weights of the Ki-61/100 in comparison with similar fighters do not indicate heavier structure.
How were three spars possible without being heavier?
I thought the Me 109 had a main spar with two auxiliary spars as well.
The forward wing spar must have been almost identical with the wing leading edge.The details about the Ki-61-I/Ki-61-II/Ki-100 structure:
In the spring of 1942, the Ha-140 was developed, a 1,500 horsepower liquid-cooled inverted V12 engine while retaining the basic structure of the Ha-40. This new engine increases the intake pressure to increase the engine speed from 2,500 rpm to 2,750 rpm, and increases the take-off power from 1,175 horsepower to 1,500 horsepower[16], to cool the larger supercharger. Water-methanol injection device was introduced[16]. However, the production of this engine was very difficult. The first model equipped with this engine, Ki 61-II, was discontinued after 8 prototypes from September 1943 to January 1944[17][16], and from the ninth aircraft Ki 61-II was revised. , Type 3 fighter Type 2 was produced, but by August 1944, even after 30 additional prototypes[17], Production of the Ha 140 engine, which is still not stable, has not been stabilized. Captain Tomoo Natori of the Examination Department, who went to the Akashi factory to investigate the trouble, also thought that the Ha 140 had no prospects, and as a mechanic, he could not say that he would fly on it[18].
I recently came across a reference in Japanese Wikipedia that the Ki-61-II's Ha-140 engine used water methanol injection. Does anyone know if this is true?
Here's the Bing English translation of the Japanese Wikipedia article on the Ki-100:
I am surprised that they achieve a higher HP rating not by drilling it out the Ha-140 but by increasing RPMs, boost presssure, and adding WM injection. Germany had struggled with adding WM injection to the DB 603 because of cylinder cracking. I guess injecting water into the supercharger was more reliable?
The Japanese entry on the Ha-40 also claims that the Ha-140 had the same cylinder sizes and just added WM50 injection, higher RPMs, higher boost pressures, and (also) a higher compression ratio, which suggests it required a higher octane fuel.
I always assumed that the DB 603 issues with WM injection had to do with the Bosch patent on injection directly into the combustion chamber. IIRC, the Bosch process provided more of an increase in performance but it caused more damage to the engine. Supercharger injection seems far less risky due to there being less of a change in temperature and less microfracturing.The DB 603 had the water-alcohol injection in the eye of the S/C, too (when installed).
Spinning the DB 601 faster, along with many other changes, was also done by DB, when 601A became 1st 601N, and then 601E.
That was a direct fuel injection thing, not the injection of the MW 50 mixture.I always assumed that the DB 603 issues with WM injection had to do with the Bosch patent on injection directly into the combustion chamber. IIRC, the Bosch process provided more of an increase in performance but it caused more damage to the engine.
But all the sources that I've checked do state that the Ha-140 was not a licensed copy of the DB 605 but rather a modification of the 601 series.
But then that doesn't make sense because the Ki-61-II had an enlarged wing to compensate for the increase in engine size. But that little factoid makes even less sense because Kawasaki reverted back to the original wing in the final production version of the Mk II model and apparently everything was gravy. That just doesn't happen if the center of gravity has shifted. So it seems a lot of the available data isn't really all that reliable.
Thank you that makes a lot of sense. I must have misread the entry on the 603's development.That was a direct fuel injection thing, not the injection of the MW 50 mixture.
An increase in performance was achieved via the greater valve overlap, that allowed for better cylinder scavenging. About 10% more power was the gain.
Carburated engines didn't work well (or at all) with the big valve overlap since that would've meant that the un-burned fuel is also dumped through the exhausts.
From what I've read about the Ha 140 (and that is not much), it was the improvement of the Ha 40.
OTOH, just how many Ha 140s were tested by the Allies - who knows?
Can you double-check the wing sizes?
So they're saying that the II-Kai used the original wing and the Ha-140 engine.Compared to the Ki-61-I, the Ki-61-II had 10% greater wing area, used more armour and was powered by the Kawasaki Ha-140 engine generating 1,120 kW (1,500 hp). After overcoming initial fuselage and wing stability problems, the new interceptor reverted to the original wing and was put into service as the Ki-61-II-KAI. However, the Ha-140 engine had severe reliability problems that were never fully resolved, and around half of the first batch of engines delivered were returned to the factory to be re-built. A US bombing raid on 19 January 1945 destroyed the engine factory in Akashi, Hyōgo, and 275 Ki-61-II-KAI airframes without engines were converted to use the Mitsubishi Ha-112-II radial engine, resulting in the Ki-100. While the Ha-112 solved the problems encountered with the Ha-140, the new engine still had a major weakness: a lack of power at altitude, which diminished its ability to intercept high-flying B-29 Superfortresses relative to the Ki-61-II.[12][16]
yes, there was a 95L methanol tank behind the cockpitI recently came across a reference in Japanese Wikipedia that the Ki-61-II's Ha-140 engine used water methanol injection. Does anyone know if this is true?
Here's the Bing English translation of the Japanese Wikipedia article on the Ki-100:
I am surprised that they achieve a higher HP rating not by drilling it out the Ha-140 but by increasing RPMs, boost presssure, and adding WM injection. Germany had struggled with adding WM injection to the DB 603 because of cylinder cracking. I guess injecting water into the supercharger was more reliable?
The Japanese entry on the Ha-40 also claims that the Ha-140 had the same cylinder sizes and just added WM50 injection, higher RPMs, higher boost pressures, and (also) a higher compression ratio, which suggests it required a higher octane fuel.
Aichi was supplying the Navy, while Kawasaki was supplying Army - that would've stood against the Ki-61 usage of the Atstutas even if there was enough to spare?If you're wondering why the Ki-61 didn't use an Atsuta 32, the reason is simple: Aichi's alloying process was time intensive. They had to remove nickel from the process and they used some kind of quenching process to make their drive shafts more resilient. They knew that naval orders were constrained by IJN's dwindling number of carriers but the army's demands far exceeded their capacity for building engines.
This is interesting because the Atsuta 32 has the same stroke and bore as the DB600Ga. That means in order to get more horsies, Aichi engineers needed to pump up compression ratio, RPMs, and boost pressure on a carbureted engine. The 600G was basically a 600A without fuel injection.
Would you be so kind to provide a source for that?yes, there was a 95L methanol tank behind the cockpit
Fair enough. The way the data is given, seems to imply that there may be an additional 95L tank. But yeah, I don't know where it would be. The same source also gives 95L for the methanol tank on the Ki-100. Maybe we need to look at that airplane instead.Because if it were, the total fuel load would show 500 Liters instead of 595 Liters.
With a Take-Off boost pressure of +480 mm, it makes sense that Ha-140 SHOULD have ADI, but as your figures note, the fuel capacity numbers are in agreement with the Ki 61-1d, so if there is a 95 Liter Water / Methanol tank, One has to wonder where it might be. Perhaps the fuel was relocated somewhere else? I haven't been able to find a drawing or description of changes to the fuel system or mention of a ADI tank, but I don't read Japanese at all.
Perhaps it was a system like C3 Einspritzung which used direct fuel injection into the supercharger for charge cooling and and anti detonant? That would explain the lack of an extra tank.
- Ivan.
Because if it were, the total fuel load would show 500 Liters instead of 595 Liters.
With a Take-Off boost pressure of +480 mm, it makes sense that Ha-140 SHOULD have ADI, but as your figures note, the fuel capacity numbers are in agreement with the Ki 61-1d, so if there is a 95 Liter Water / Methanol tank, One has to wonder where it might be. Perhaps the fuel was relocated somewhere else? I haven't been able to find a drawing or description of changes to the fuel system or mention of a ADI tank, but I don't read Japanese at all.
Perhaps it was a system like C3 Einspritzung which used direct fuel injection into the supercharger for charge cooling and and anti detonant? That would explain the lack of an extra tank.
- Ivan.
Thanks again.The 601 were also with the variable speed drive for the S/C, while I believe that even the last 600 versions were with the 1-speed S/C drive. TAIC manual notes the variable speed drive on Atstuta 22 and 32, as well as the fuel injection.
Japanese Wikipedia says this:Thanks again.
If TAIC has the Atsuta 32 as having direct injection, then either Aichi retrofitted a 600G with direct injection (Daimler supposedly designed the DB600 series to be upgradeable to DI) or the Atsuta 32 was based on the 601A and Japanese wikipedia is in error.
EDIT: Or the more likely scenario that TAIC got bad information somehow.
View attachment 806301
There's something in this drawing that is bigger than the oil tank, outlined in blue. It may be the best clue. Perhaps it is beside/under the oil tank on the starboard side? Or maybe, that's just an access panel. We may never know!