Japanese Design Philosophy

Howard Gibson said:

The small American radials coped with the enemy. Everybody had the same sized engine up into 1943. By 1943, the 2000HP American aircraft were faster, they had armour protection, and they could carry significant bomb loads. Getting late war Zeroes up to 350mph was a remarkable accomplishment for the Japanese, but the enemy was doing 390mph+.

The small British radials were in biplanes, right? Gloster Gladiators did well against FIAT Cr42 biplanes. The Fw190 had a 42liter engine.

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Just a note, the 1,200 HP R-1830 engine in the Wildcat and 1820 in the Buffalo were technically inferior in most ways to the Zero and Oscar's Sakae 11/12 and 21, which made around 975 and 1,115 horsies respectively, with smaller displacement, weight, and frontal area. On paper, the Wasp and Double Wasp appeared to be roughly in the same category as the Sakae, given that they had similar horsepower. But the math shows that the Sakae was marginally better, as it should have been, being a newer engine.

FD=1/2 x p x v(squared) x CD x A

Where:

• FD is the drag force,
• p is the air density,
• v is the velocity of the aircraft,
• CD is the drag coefficient
• A is the frontal area.

My math skills are total garbage but frontal area plays a major role in how fast an aircraft can go (particularly as velocity increases). A reduction in frontal area has a somewhat similar impact as an increase in horsepower. So to a certain extent, going smaller makes sense. Not only could a smaller engine perform as well as a slightly larger and more powerful engine, it was also oftentimes cheaper to make with expensive imported metals. This is a theme we see repeated again and again with many nations. The US for example initially planned on using a smaller engine in the Hellcat, before switching to the R-2800.

The Japanese military leadership were somewhat aware that they would lose a war of attrition. Although in Myths of Empire, it's shown that many leaders in Japan had bought into their own propaganda, believing that the US would immediately sue for peace after the first year of war. As with many illiberal democracies, the truth had been largely covered up by a cadre of sycophants. For example, before the war, a Japanese Major conducted a strategic analysis of the US's war making capabilities and found that war was not winnable. His superiors destroyed the report and drummed the Major out of the service. Similar stories abound in Nazi Germany, with Hitler and his minions frequently ignoring intelligence reports because of their gut "feelings".

Shortround6 said:

F4U showed up in Jan 1943, by early July there were 8 Marine squadrons operating in the Solomon's.
There were no carrier to carrier battles in all of 1943.
The Zero was in no way, shape or form capable of fighting the F4U on a squadron to squadron (team to team) basis. Zero's shot down F4Us but much more often than not they came out on the loosing end or were not able to keep the F4Us and other US fighters from shooting down numbers of bombers.

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This is because the Japanese leadership had tricked themselves into believing that the US would have negotiated for peace within the first year of the war. Their belief was based on a common myth oddly held by both the Germans and the Japanese that the US was "soft" and "decadent". As such, they didn't accelerate the development of a next generation fighter or fighter engine until it was too late. That's why you have the Kawanishi N1K1-J appearing before any other next generation Japanese fighter was available, because it was an unsolicited, private venture, which plugged a hole in the IJ Navy's development schedule.

AerialTorpedoDude69 said:

Just a note, the 1,200 HP R-1830 engine in the Wildcat and 1820 in the Buffalo were technically inferior in most ways to the Zero and Oscar's Sakae 11/12 and 21, which made around 975 and 1,115 horsies respectively, with smaller displacement, weight, and frontal area. On paper, the Wasp and Double Wasp appeared to be roughly in the same category as the Sakae, given that they had similar horsepower. But the math shows that the Sakae was marginally better, as it should have been, being a newer engine.

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R-1830 was the Twin Wasp. The Wasp was not a military engine for the 1st line aircraft, while the R-2800 was the Double Wasp.
Sakae indeed was a decent engine, but being better than the 4th and 5th best US engines is not something to be proud of, IMO.

IMO, Grumman with Wildcat didn't take the advantage of the 48 in diameter of the R-1830, leaving the aircraft draggier than necessary.

AerialTorpedoDude69 said:

My math skills are total garbage but frontal area plays a major role in how fast an aircraft can go (particularly as velocity increases). A reduction in frontal area has a somewhat similar impact as an increase in horsepower. So to a certain extent, going smaller makes sense. Not only could a smaller engine perform as well as a slightly larger and more powerful engine, it was also oftentimes cheaper to make with expensive imported metals. This is a theme we see repeated again and again with many nations. The US for example initially planned on using a smaller engine in the Hellcat, before switching to the R-2800.

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R-2800 was a smaller engine than the R-2600 if we talk only about the frontal area

Change in the Japanese-design-philosophy.

From May 1939 to Sept 1939 the Japanese were involved with the Soviets in the Nomonhan incident. The combat results made the JAAF question their emphasis on maneuverability as the paramount quality for fighter performance. Rather than renounce their previous stance they decided to obtain at least some aircraft for special purposes and/or evaluation.

Kawasaki had given up on the old BMW derived V-12 and had entered into negotiations with Daimler Benz in 1937 which lead to a license agreement in March of 1938, but with little or no interest by either the Army or Navy Kawasaki didn't do anything until Army started asking for Proposals that lead to the Ki-44 and the Ki-60/61 in Feb 1940. Ki-44 may have started a bit earlier. Kawasaki sends a tech team to D-B in April of 1940 and the team returns in early summer with blue prints/drawing and sample engines.

Things do not go well. The Nakajima Ki-44 was planned as a 4850lb plane with a 161 sq ft wing with the Ha-41 engine (1250hp single speed engine) . Estimated speed was 600kph (370mph) with two 12.7mm guns in the wings and pair of 7.7mm guns in the fuselage. First prototype flew in Aug 1940, it was 16% over weight and due to higher than expected drag topped out at 342mph. By July of 1941 they had only managed to coax 354mph out of it (not that bad for summer of 1941 but not great either).

Meanwhile Kawasaki was screwing together their Ki-60 prototypes and things were not going well for them either. They were hoping for 6371lb airplane with a 171.2 sq ft wing holding about 410 liters of fuel and using two 12.7mm guns in the fuselage and two German MG 151 guns in the wings (when these showed up?) but drag calculations were off and the speed wound up at 340mph when it flew in March 1941. There were also stability and control problems. The 2nd and 3rd prototypes got another few sq ft of wing area, the wing guns were changed to 12.7mm guns to reduce weight. A few minor tweaks and better sealing got them up to 348mph but most of the stability, control, high landing speed and poor maneuverability remained.
The effort changed to the Ki-61(detail design had started in Dec 1940) but this larger (but not lighter) airplane didn't fly until Dec 1941.In addition to the larger wing of 215sq ft (and the perhaps the highest aspect ratio of any mass produced single engine fighter) they used the two 12.7mm gun and two 7.7mm gun armament and crammed 140 liters more fuel into the plane. Weight was 6540lbs (?) They got 367mph in trials which was very close to the hoped for 600kph (370mph).

returning to the Ki-44, changes to the engine cowl, supercharger intake and improved sealing had progressively raised the max speed to 367mph and finally 389mph. In usual Japanese fashion there had been a small series of prototypes/trial aircraft completed and 9 of theses were refurbed to greater or lesser extent than it was these aircraft that took part in the fighting Malaya. Opinions were divided and claims that the plane needed a 1000 meter runway counted against it. Nakajima tooled up and made another 40 aircraft with the Ha-41 engine while work on the Ki-44 II with the two speed engine proceeded. The First of the 2 speed aircraft didn't show up in service until the end of 1942.

The advent of these "high" wing load aircraft seems to have meet with high resistance from the service pilots with claims that pilots needed 1000 hours to be able to handle them and other negative comments.

And that ends the 1940-42 segment of the Japanese design philosophy with the high speed fighters sneaking their noses under the tent and the most of pilots fighting for the status quo. P-38s (in small numbers) and P-39s and P-40s were increasingly getting harder for the Japanese to deal with in the areas were they could fly.

tomo pauk said:

R-1830 was the Twin Wasp. The Wasp was not a military engine for the 1st line aircraft, while the R-2800 was the Double Wasp.
Sakae indeed was a decent engine, but being better than the 4th and 5th best US engines is not something to be proud of, IMO.



R-2800 was a smaller engine than the R-2600 if we talk only about the frontal area

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Good comment. But I'm not sure about some of your points. If you mean to say that the R-2800 was a small engine, that isn't true as it was larger and heavier than the r-2600 IIRC. Although the smaller frontal area on a 9x2 engine compared to a 7x2 engine is impressive engineering, but my point was that the Navy tried to cheap out at first before realizing the R-2600 was probably not going to do it against upgraded versions of the Zero or a next-generation Zero.

Getting back to the assertion that the 1820/1830 managed to blunt the Japanese offense, code breakers, submarines, and the New Guinea and Solomon Islands campaigns accounted for 90% of the blunting. But also, the US could pump out enough small engines to simply overwhelm the Japanese.

Going off the limited reading that I've done of reported aircraft losses, even the Thatch Weave was not giving the US a favorable victory-to-loss ratio. I can see why the US continued to make small engines from an economic and strategic perspective, but those small engines weren't suitable for front-line aircraft even in 1942.

AerialTorpedoDude69 said:

Good comment. But I'm not sure about some of your points. If you mean to say that the R-2800 was a small engine, that isn't true as it was larger and heavier than the r-2600 IIRC. Although the smaller frontal area on a 9x2 engine compared to a 7x2 engine is impressive engineering, but my point was that the Navy tried to cheap out at first before realizing the R-2600 was probably not going to do it against upgraded versions of the Zero or a next-generation Zero.

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R-2600 diameter was 55in, that of the R-2800 was 52.8 in.
Navy and/or Grumman was perhaps of the opinion that P&W has it's plate full wrt. next-gen engines for the fighters, so the 2-stage supercharged R-2600 was a way to cover their bets?

AerialTorpedoDude69 said:

Getting back to the assertion that the 1820/1830 managed to blunt the Japanese offense, code breakers, submarines, and the New Guinea and Solomon Islands campaigns accounted for 90% of the blunting. But also, the US could pump out enough small engines to simply overwhelm the Japanese.

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There is no doubt that the blunting was a team effort.
My whole tirade about the small radials being worth it was in response to the other fellow member claiming that "successful WWII radial engines were big" - a notion that I disagree with.

AerialTorpedoDude69 said:

Going off the limited reading that I've done of reported aircraft losses, even the Thatch Weave was not giving the US a favorable victory-to-loss ratio. I can see why the US continued to make small engines from an economic and strategic perspective, but those small engines weren't suitable for front-line aircraft even in 1942.

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I was trying to count in the R-1820s that powered the SBDs that sunk most (all?) of the Japanese fleet carriers in 1942. F4Fs were trying their best and were killing a lot of IJN's carrier borne attackers, as well as Zeroes when the opportunity presented itself.
Small radials also powered the PBYs and B-17s, these were instrumental in keeping tabs on Japanese ships before and during the battle of Midway.

Granted, going against Luftwaffe with small radials during the daylight was a recipe for disaster. Even the success of the B-17s came after some other Allied tech and whatnot was applied to help out.

AerialTorpedoDude69 said:

Although the smaller frontal area on a 9x2 engine compared to a 7x2 engine is impressive engineering, but my point was that the Navy tried to cheap out at first before realizing the R-2600 was probably not going to do it against upgraded versions of the Zero or a next-generation Zero.

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It is not impressive engineering. Part of it is that the 14 cylinder engine used larger cylinders 155 X 160 mm vs 146 X 152. Part may be the rod length that each company favored.
And you need enough cooling fins on the heads to keep the head cool. And you need to keep the valve gear (rocker arms, valve size/length and springs) of suitable size.
The R-3350 was, for all practical purposes, the same diameter as the R-2600. They used the same size cylinders.
Wright was having trouble with their big cylinders. They redesigned the engines/cylinders several times but they were running on the ragged edge of cooling.
P&W had run into trouble with the Hornet B (R-1860 9 Cylinder 575hp) in the late 20s/early 30s and never used a cylinder over 155.8 cu in again. They phased out the R-1690 Hornet A with the R-1830.
Wright stayed with the big cylinders. Wright attempts to get power at altitude ran into trouble once you get passed the R-1820 in the B-17s.
I Think Grumman and the Navy realized the R-2600 in the Hellcat was a bad idea. They had ordered the R-2800 powered prototype well before the R-2600 version flew.

This discussion started with Japanese fighter design philosophy.
For the Japanese this pretty much meant radial engines. The Kawasaki Ha-9 derived from the BMW VI had run it's course and the Japanese high command (both of them) hadn't pick-up the DB-601 quick enough. Maybe it was always doomed. Maybe a 12 month head start would have helped straighten out, I don't know.
But for the most part it was radials or nothing for the Japanese and unfortunately for them, the US didn't play by the "radial" rules and used liquid cooled engines in their army fighters.
Which meant around a 30mph speed advantage (see P-36 vs P-40) The greater weight affected turn and climb.

Use of engines by bombers, recon planes, flying boats is getting a bit far afield except to figure out where the fighter designers could have borrowed engines from.

A lot of designers (both engine and aircraft) in the 1930s placed way too much emphasis on the frontal area of engines/streamlining. Not enough emphasis on the streamlining of the actual installation and the airframe. The use of engine cowls meant that the frontal area of the radial was not the same as the drag. It also doesn't take into account drag of the rest of the airframe. Again see the Curtiss Hawk series.

First Hawk 75 prototype with experimental Wright R-1640 14 cylinder radial engine of 45in diameter.
Rather spoiled by the upright seating of the pilot and the fact that a lot of the fuel was under pilot. Engine was dog and soon replaced by other engines, including a P&W R-1535 14 cylinder radial (briefly) and then the famous R-1820 9 cylinder of 54l25in diameter.
Once you start sticking guns in the cowl to fire over the top of the engine and sticking fuel low in the fuselage or in the wing the smaller size radials loose some of their attraction.
For our Hawk 75, no matter what we stick in the nose we have the same wing, the same tail (pretty much) and the same fuselage size/surface area.
We now have to deal with the engine installation, and on this particular airplane, it sucked. It had the famous NACA cowl, what it did not have was an adjustable air outlet (cowl flaps), interior baffling was probably dubious. Cab inlet? Exhaust pipes that stuck straight down. Note the grove in the top of the engine cowl to clear the machine gun in the fuselage.

The Japanese (and everybody else) did a much better job in the late 30s and 1940-4, This Photo is from 1935. After several engine changes this airframe became the XP-37 with a turbo Allison. As to what progress was in 1935 the Hughes record setting airplane was also not using an adjustable cowling (fixed air exit). Air cooled engines create a lot drag with the air flowing through the cowl and over/around the engine. Very few museum engines have the baffles installed as looing at bent sheet metal is not very interesting.
The Japanese used narrower cowl openings that some other people. Getting the right airflow for high speed and high power/low speed climb could be tricky. Some the liquid engine planes didn't get it right either.

AerialTorpedoDude69 said:

Getting back to the assertion that the 1820/1830 managed to blunt the Japanese offense, code breakers, submarines, and the New Guinea and Solomon Islands campaigns accounted for 90% of the blunting.

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The code breakers told those R-1820/R-1830s where to go.

The US got away with small radials on 4 engine bombers for as long as they did for two reasons.

1. Turbos
2. Long runways.

The turbos, at cost of weight and volume (and frontal area/drag) offered the same power at 20-25,000ft that larger engines without turbos did.
But that means that the sea level power was several hundred less per engine for take-off.

Shortround6 said:

The US got away with small radials on 4 engine bombers for as long as they did for two reasons.

1. Turbos
2. Long runways.

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3. Long range escort fighters

Shortround6 said:

The turbos, at cost of weight and volume (and frontal area/drag) offered the same power at 20-25,000ft that larger engines without turbos did.
But that means that the sea level power was several hundred less per engine for take-off.

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The turbo-chargers allowed the American bombers to fly at the P-47 Thunderbolt's favorite altitudes -- 25,000ft+

Howard Gibson said:

3. Long range escort fighters

The turbo-chargers allowed the American bombers to fly at the P-47 Thunderbolt's favorite altitudes -- 25,000ft+

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We are also getting the time line out of order.
They were ordering the mass production of the B-17 and B-24 well before the P-47 ever flew, however the they were also ordering the P-47 off the drawing board (733 ordered in Sept 1940) and the XP-47 flew Early May of 1941.

This is an example of philosophy vs actual results.
The 8th Air Force and the US Army heavy bomber "philosophy" actually dates to around 1939-40 as far as real hardware goes. The "philosophy" goes back even longer than that.
The B-24 design started in 1939 when Consolidated wanted to build their own plane rather than license the B-17 (which would have been the shark fin version?) .

Both the B-17 and the B-24 were contracted out in late 1940 and early 41. The B-17 consortium was known as "B.V.D." in a word play on a popular brand of men's underwear.
Boeing with the Seattle plant being joined by a new plant in Wichita Kansas was joined by Vega (division of Lockheed) and Douglas with plants in Santa Monica and a new plant in Long Beach. Several of these plants were brand new plants on bare plots of ground. To provide engines for these aircraft Studebaker was brought in to build R-1820 and the deal was signed before the end of 1940. It takes time to build new factories and Studebaker delivered the first engines (6) in Feb 1942 and they finished just over 6,000 by the end of 1942. They built just over 23,000 in 1943.
Buick and Chevrolet were building R-1830s for the B-24 program (which had 5 different airframe plants) by March and April 1942 respectively. They boult about 12,400 of them in 1942 and roughly tripled production in 1943. The US was sort of locked into the small radials from a production stand point unless they failed on a large scale.

The "radiator" matrix right above the 4 step stair is the intercooler for the turbocharger and entire outer "scoop" on the cowl feeds cooling air to the intercooler, the inner scoop is divided between the oil cooler and the carb intake. This gives an good look at the "cost" of the turbo installation on even a small radial in terms of drag and volume required to make the small engine act like a big one.

These massive industrial complexes were being built well before anybody had any idea of using the P-47 as an escort fighter.
The US Army had a design "philosophy" for 20-25,000ft fighters and bombers that goes back to the mid 30s if not before.

They built 50 of these in 1936 with the turbos. Basically it proved that the turbo technology was not quite ready for service use in the 30s but the "philosophy" was there.

Changing course in midstream was very hard which may be one reason that the Americans waited for the B-29 instead of trying to introduce "intermediate" heavy bombers with R-2600 or R-2800 engines. Improvement in performance was not worth the disruption in production.

No long range escort fighters used the R-1820 (B-17) or R-1830 (B-24).

The F4F-3 used the R-1830 and the FM-2 used the R-1820, but that's it.

GrauGeist said:

The code breakers told those R-1820/R-1830s where to go.

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You're right because there was no production R-2800 in 1941 and Allison engines weren't being used by the Navy. and US strategic planners made the best of a bad situation. The 1830 was the best engine available for carrier aircraft at that time and the Sakae 21 was a marginally superior engine.

That's technological progress. As you know, with radials, engines got larger and more powerful up until jet engines dominated front-line aircraft. Japan's strategic thinkers were initially right. They could build better aircraft by going for efficiency and minimizing weight. For the first year of the war.

Getting back to the primary topic: "what was Japanese design philosophy?"

Based on what I've read, it was based on frugality up until 1943, Japan being an island nation. Virtually all Japanese aircraft designers wanted to increase horsepower and engine weight in order to meet performance requirements and include armor and self-sealing fuel tanks. In most cases, up until 1943, the Japanese military denied requests to include armor and self-sealing fuel tanks. If there is a design philosophy, it was the conserving on resources.

AerialTorpedoDude69 said:

The 1830 was the best engine available for carrier aircraft at that time and the Sakae 21 was a marginally superior engine.

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If it was it was 1 to 1 1/2 years late in terms of design. They were building (putting them in service aircraft) the R-1830-76 with two stage supercharger in mid 1940. They changed to the -86 engines some time in late 41 (?). The Japanese were testing the A6M3/Sakae 21 in the summer of 1941, The A6M3 sees service units in late spring of 1941.
The 1830-86 was unchanged for the duration of the F4F-4 production. Yes it was heavy, it was about 3in larger in diameter which meant nothing on the fat American fuselages.
It had also hit a design limit. It (and most of the 1939-40 R-1830s) had been designed for either 91 octane or 100/100 fuel. 100/130 did nothing for them and it fact the 100/100 didn't do much for them. Some of the Navy manuals show 2700rpm available in neutral supercharger (engine supercharger only) 2700rpm in low gear aux supercharger and only 2550rpm in high gear. Some sort of heat problem may be going on. Either the intercooler cannot remove enough heat or the cylinder fins cannot dissipate the heat in the cylinders in the thinner air. None of the R-1830s were rated at over 1200hp at any altitude with any supercharger until they got new cylinders (and heads?) well into 1944.
The Japanese had done a very good job with the Sakae 21 supercharger.
What we do not know it how the two engines stacked up in regards to reliability and durability.

AerialTorpedoDude69 said:

Virtually all Japanese aircraft designers wanted to increase horsepower and engine weight in order to meet performance requirements and include armor and self-sealing fuel tanks. In most cases, up until 1943, the Japanese military denied requests to include armor and self-sealing fuel tanks. If there is a design philosophy, it was the conserving on resources.

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Aircraft designers are often stuck between the rock and the hard place. It is their job to make the best plane they can to the customers specifications. However they also need to anticipate that what the customer wants now may not be what they need or want 6-12 months in the future so a bit of growth potential is a good thing. But trying to sell protective equipment on a plane that won't meet desired performance is a very hard sell. Very few designers got to tell the customers what they needed for Equipment. Yakovlev was one but since he was both designer and vice-minister of aircraft production at the same time he was in a rather unique position.

All during the 1930s (if not from WW I) the was an ongoing argument between the the maneuver school and the speed school in many air forces. The Italians and Soviets funding both types if fighters at the same time and thought they could coordinate both types (biplanes and monoplanes) in battle at the same time (real optimism, especially since Yakovlev and others didn't radios were useful enough to put in fighters). The Japanese were not isolated in their thinking, at least until the summer of 1939. Even the Spanish civil war had not actually settled the question although it may have leaned on it. Japanese experience in China was not showing any advantage on the speed side, but the Chinese air force/s were not the best quality. The Nomonhan Incident was the wake-up call for the JAAF.
The Japanese really screwed up here as both air forces decided they needed both maneuver aircraft and speed aircraft and even for land based interceptors they could not use a common aircraft for either role. Japan did not have the industrial base to deal with different types of fighters at the same time and especially not multiple types in each of the 4 categories.
Sometimes conserving resources (frugality) if carried to extremes is counter productive. Needing more aircraft (or artillery shells) to do the same job is sometimes more expensive that using more expensive equipment to begin with.

Shortround6 said:

We are also getting the time line out of order.
They were ordering the mass production of the B-17 and B-24 well before the P-47 ever flew, however the they were also ordering the P-47 off the drawing board (733 ordered in Sept 1940) and the XP-47 flew Early May of 1941.

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I assume the American bombers had turbochargers to let them fly at high altitude where they would be harder to intercept and to hit with flak. In the real war, the bombers were not fast enough to avoid German fighters. Also in the real war, the Germans failed to develop two-stage superchargers. At high altitude, they were at a disadvantage against two-stage supercharged Thunderbolts and Mustangs.

It was not planned that way, but the bomber turbochargers created an opportunity for the allies.

Howard Gibson said:

I assume the American bombers had turbochargers to let them fly at high altitude where they would be harder to intercept and to hit with flak. In the real war, the bombers were not fast enough to avoid German fighters. Also in the real war, the Germans failed to develop two-stage superchargers. At high altitude, they were at a disadvantage against two-stage supercharged Thunderbolts and Mustangs.

It was not planned that way, but the bomber turbochargers created an opportunity for the allies.

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It worked out that way but it was not planned that way, reality vs philosophy (planning).
The American bombers were harder to hit with flak, which meant the Germans needed more guns and larger guns.
Germans used the 109 which was small and light with a powerful engine (for the size of the plane) to fight in the 25,000ft range. Which also meant short range and less than desired firepower. Make-do rather than desired.
The US was making-do as well as the need to use large formations and larger than planned bomb loads affecting the both the speed and altitude of the formations and the lack of research on the health effects of flying at high altitudes for hours at a time also cut into the effective operating ceilings of the planes compared to the philosophy/doctrine/wishful thinking.

Now back to the Americans, they got away with using the small radials with the added weight/bulk of the turbo systems instead of larger non-turbo engines (R-1830s from F4Fs would not have worked even with the existing two stage mechanical superchargers) and the US got away with it because they were the only country in world that could build good turbos in the required quantities. Good means in regards to the ability to last for hundreds of hours and to do the job required. GE superchargers were not particular good from the efficiency standpoint. But the turbos masked that with lots of power to drive the compressor. The US had the industrial base to build well over 100,000 turbo chargers (B-17s and B-24s needed over 120,000 not counting replacements, P-38s, P-47s, and B-29s) with the high temperature alloys needed in the turbine blades.

Also please note the disconnect between philosophy (planning) and reality. 10 factories being built or modified to make 4 engine bombers with turbos and little or no work being done to expand production of the only US fighter even in small scale production (1940-41) able to fly at those altitudes (P-38), yes they were working on the P-47 and working on several factories but in 1941/42 the P-47 was an unknown item.

Shortround6 said:

Why were the Japanese radials operating 2-300 slower than the British/American radials at certain times? Japanese are not stupid. Perhaps they don't have the steel alloy for the crankshaft/connecting rods? or bearings? or perhaps they cannot make the cylinder fins of the size needed to cool the engine at the higher power?
Wright changed the cylinder fins on the R-1820 at least 5 times during 1930s to improve cooling. many times had to change the tooling to do it.

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Yes, very pertinent given what I wrote, but when did they become aware of the differences between what they were doing compared to what others were and was it a hindrance before this time? This is important given their industry developed in semi-isolation. Once the fighting starts is really when Japan finds out it does things differently, but in 1940-through to 1942, was that difference qualitative? Not really. Their aircraft and tactics probably masked the differences (as opposed to deficiencies) compared to the Western designs and engineering, yes, but therein lies the issue, was it critical at that time? It obviously became so, but this is where we see the industrial mess Japan was in working against it. The components within the military industrial complex made things difficult for the engineers. Once they began to realise the qualitative differences as the war wore on, they had little control over expediency and capability at an organic level. Like I said, their deficiency would only be apparent if it were demonstrated to them, and before 1943/1944 and the advent of superior aircraft being fielded would the differences begin to matter.

As for fixed gear, the fighters like the Ki-27 and A5M produced excellent performance given their local opposition. When they entered service, Japan was not planning on meeting Spitfires, Bf 109s, Curtiss P-36s etc in combat. This is the downside to isolationism, but regionally, Japan was able to dominate, regardless of the engineering trends overseas. By 1941, when their decision to drag the West into their war plans happened, any measured differences in technological ideology was masked, or did not matter. It only became apparent later because strategically, unbeknownst to most of them, Japan bit off more than it could chew. As I mentioned, the technological differences would have become apparent once their opposition became better than they were used to, but before then, were they a hindrance? The issue is complex and individual examples of differences or deficiencies are met with other areas of clever thinking and engineering.

Fixed gear aside, the Japanese had fairly good success with floatplane fighters like the A6M3-N and N1K1.

They were not world beaters, of course, but still impressive.

tomo pauk said:

R-2600 diameter was 55in, that of the R-2800 was 52.8 in.
Navy and/or Grumman was perhaps of the opinion that P&W has it's plate full wrt. next-gen engines for the fighters, so the 2-stage supercharged R-2600 was a way to cover their bets?

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Wasn't the R-2800 eating cranks like they were kid's candy at the time and barely making more power than the R-2600?

There is a lot of just in time delivery on the Allied side:

While there might not have been direct competition between RR, Bristol, Napier, Allison, P&W and Wright, studied each others work as much as the competition, and used a lot of the same sub contractors. The information sharing between 6 firms probably beats just 2 if only to be moving things along a year or 2 faster.

On the other hand, if you spend millions on a custom machine which completely machines a R-4360 head in one stop in couple minutes, it becomes very difficult to change to new design of the head - the disadvantage of mass production.

Aside: When I hand assemble (blueprint) engines, they make more power/burn less oil, so I'm surprised by the comment that hand assembly of the Japanese aircraft engines resulted in more oil being burned (IMOH, there is something else involved.)

don4331 said:

Wasn't the R-2800 eating cranks like they were kid's candy at the time and barely making more power than the R-2600?


Aside: When I hand assemble (blueprint) engines, they make more power/burn less oil, so I'm surprised by the comment that hand assembly of the Japanese aircraft engines resulted in more oil being burned (IMOH, there is something else involved.)

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Why do so many people trash talk the R-2800. Once the bugs were ironed out, it looks like it became one of the best piston engines ever made. Was there a much better radial that I've never heard of or something? I tried looking for four-valve engines of the 40s but never found one.

Regarding your knowledge of building blueprint engines, that's fascinating. I'm going to hazard a guess and say that for small batches, you are likely taking more time than with mass produced engines that are being cranked out as fast as possible. If not that, then my best guess would be that they used a lighter grade of oil. A Nakajima engineer said that they had problems finding a suitable lubricant for the Homare engine during its development period.

It's mentioned in numerous historical texts that all Japanese aviation engines had looser tolerances and had higher oil consumption compared to US engines. The most interesting anecdote to me is found in "The Miraculous Torpedo Squadron" by Juzo Mori. If I remember correctly, in late thirties Mori compared the Sakae engine in his Kate torpedo bomber to a captured US aircraft in China. He said that Japanese engines leaked constantly.