Shortround6
Major General
Put the sleeve valve Kool-Aid back on the table.
Back away from the table.
Turn towards the light.
RUN towards the light.
Fall to your knees and bask in the light of the poppet valve.
Improve That Design: How Aircraft Could Have Been Made Better
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Put the sleeve valve Kool-Aid back on the table.
Back away from the table.
Turn towards the light.
RUN towards the light.
Fall to your knees and bask in the light of the poppet valve.
MiTasol
1st Lieutenant
The MII Spitfire had no protection when designed and when it left the factory. Not even the flotation kit that the A6M had.
And it had one
EDIT note to self - do not post when still half asleep. Drink coffee and turn on brain first. Convert miles to Km and vice versa
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Shortround6
Major General
The A6M could fly 4000 miles!!!!!
Holy Crap!!!!!!!!
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
I knew someone would do a "range check" on that post.
The question asked was what would the Japanese have built if they followed European design philosophy, well my guess would be the same planes the Europeans designed. Are you sure the MkII Spit didn't have protection installed from the factory?.
Shortround6
Major General
Something like this??
Got two out of 3?
Only so much you were going to do with 1250hp engine.
Admiral Beez
Captain
There was nothing inheritently wrong with their Mercury, Neptune and Pegasus engines to suggest to Bristol that the poppet valve should be abandoned. Poppet valves were a stupid distraction at both Bristol and Napier, wasting time, treasure and talent that could have seen superlative, R-2800-like poppet valve engines in early RAF service.Fall to your knees and bask in the light of the poppet valve.
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GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
They would have probably ended up with a Nakajima KI-84, Kawasaki N1K1-J or Mitsubishi J2M.
...several years earlier than they historically did. How about going up against them in P39s and P40s?
Shortround6
Major General
They could prioritize whatever they wanted.
Without the needed engines they were stuck.
The Ki-44 started with a 1260hp engine at 12,149ft with a single speed supercharger, repeat, single speed.
The two speed engine using the same cylinders didn't show up until the summer of 1942 in prototypes. In the fall of 1942 in pre production and in Nov 1942 in actual production.
The two speed engine 1440hp at 7,000ft and 1320hp at 17,220ft.
But until you have the improved engine with the 2 speed supercharger you are stuck.
The Navy had planned to improve the engine in the Zero, but Nakajima could never get the water injection to actually give them any real increase in power. Without the increase in power they could either "improve" protection and loose performance, or leave protection less than wanted and keep performance, also less than wanted.
Shortround6
Major General
It is hard to say, it is probably a combination of a number of things.
The US was fortunate in having a large number of engineers. Many of whom worked in manufacturing and processes.
It doesn't matter how good your design is if you can't produce it, and not only produce it but produce it in quantity.
At different points US companies figured out different ways of doing things. See some of the photos here.
Photos...The Secrets of Casting Those Elegant Pratt and Whitney Radial Heads...
...Pratt and Whitney R1830 Twin Wasp engines for the B-24 Liberator...being Manufactured at Buick's plants... ...and some shots of crankshaft manufacturing for the same engines... ...lots more photos on the source pages... ...source page one...CLICK HERE...
www.practicalmachinist.com
You build forged heads if you can't cast good heads.
Or you design ganged slitting saws controlled by cams that cut all the grooves in pass with each wheel controlled in depth independent of the wheel next to it.
I think it was Ford that figured out how make parts on a rotary casting table? The molds were spun on the table to get the air pockets out of them as the metal flowed into the mold, but their were eight (?) stations on the table. The system allowed for both high quality and high production.
The US made a number of mistakes in production and production planning in WWII, they just didn't make quite as many as some other countries,
But the US was always trying to eliminate as much hand fitting/finishing as it could even if it meant machinery that costs hundreds of thousands of dollars.
The Japanese didn't have that luxury.
In some cases the Americans weren't using exotic alloys. They were using manufacturing technology to make thinner and closer spaced fins to allow for better cooling of the air cooled cylinders even if the alloy/s were the same. And build thousands of engines in one month in one factory.
drgondog
Major
Hmm, depends on the atitude you are playing with? The P-51B-5 w/1650-3 at 67" @29K delivered 1275Hp and 440+mph clean.. This is unfair comment to you when the discussion relates to early war designs - which were around 1000-1100 hp at Low FTH -
Shortround6
Major General
Got me
We do tend to look at engines as gross power and not net power. That 1275Hp 1650-3 at 29K may have been making around 1800-1900hp(?) in the cylinders. Overcoming friction, pumps and the hundreds of HP to drive the superchargers. In low gear the engine made the same power in the cylinders but got around 1600hp to to the prop.
The KI-44's engine was improved over the first one. The supercharger was taking around 120hp more to drive at the higher altitude on the later engine.
If you want higher power with poor fuel you either need a really big engine and/or you need high rpm. And either way is going to increase weight unless you have alloys the guys with the better fuel don't.
MiTasol
1st Lieutenant
They certainly did not suffer from a shortage of engineering talent as the below A6M items will show.
As far as cultural obstacles go my belief is that, like the USA, they had military "experts" who would not permit the engineering talent to shine. The things holding back the Japanese aircraft industry in many ways mirror the reasons the Allison never had a two speed or integral second stage blower. A beauracracy that will not bend to the changes in what is happening in the real world. As another US example the P-51 is aircraft that would never have seen the light of day if not for the British purchasing commission.
Shortround responded At different points US companies figured out different ways of doing things.
The Japanese were masters at that. Compare the tailgear of any Brit or US aircraft with the tailgear on the A6M. For example compare the P-40 tailgear (or Spitfire, or Grumman, or F4U or P-47) with the A6M. On the P-40 the fore and aft arm and hockey stick weigh about the same as the complete A6M tail gear. Add to the diagram below two gear doors and the operating linkages which is more weight and complexity and more maintenance and more items to get damaged. All the US and UK aircraft had similar contraptions. Some, like the F4U were absolutely massive, far far more complex and weighed a proverbial ton.
Below is the A6M tail gear. The magnesium casting, the magnesium hockey stick and the wheel become the gear door when retracted.
The oleo and shock strut are a single unit so not only far lighter but also far stronger and there is no need for any linkages etc to adjust and jam and fail. I am sure Shimpachi can provide some diagrams of the gear assembled and in both the extended and retracted positions
Then compare the arrestor hook on the A6M. Unlike most or all of the pre 1943 US and UK aircraft the A6M arrestor hook swivels from side to side which means it will swing to hook the deck cable rather than slipping off if the aircraft is not in line with the deck. Once the aircraft came to a stop the A6M hook could be released from the cockpit. As far as I know no US or UK aircraft could do that.
Also the A6M spar caps are made from essentially what is now called 7075 alloy. The Japanese had this material long before the US.
Photos taken today
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yulzari
Staff Sergeant
At the time Bristol decided to go to sleeve valves in lieu of poppet valves it made complete sense. Poppet valves were being limited by low knock levels and valve seat erosion. However, very shortly thereafter developments in fuels and materials allowed poppet valves to deal with higher compression ratios and boost which took away the undoubted previous advantage of the sleeve valve. What Bristol did not do was drop the sleeve valve and revert to poppet valves. Whether this was personal or company face savings or the inertia of having got so far with sleeve valves already I cannot comment buy the original decision to go sleeve valve was justified when it was made. The classic AH Bristol engine is the frequently touted double Pegasus.
Shortround6
Major General
That is a general progression and it takes number of paragraphs (if not pages) to even do a decent over view.
It took Almost 15 years to get the Sleeve valve up to the standards of 1939.
There were a few zigs and zags.
Yes the Sleeve valve was supposed to solve a lot of problems as you said.
And yes, some of the problems went away in the late 20s or early 30s.
The Sodium cooled exhaust valve was a big equalizer.
SO were better valve springs, valve spring failure/breakage was a very real problem in the 1920s but by the early 30s engines were running hundreds of hours without such a failure.
Better fuel helped a bit but was actually not that big a deal until the late 30s. 87 octane fuel was only going to work with 3-5lbs of boost in air-cooled engines.
And with 3-5lbs of boost and higher RPM than the older engines cooling was becoming a real problem with both types of valves. It was a constant battle to get enough cylinder fin area to keep the engine cool enough.
Admiral Beez
Captain
At which point, Bristol should have seized on the sodium valve stems and better springs and canceled their sleeve valve projects. Maybe the Perseus gets to run in 1932, as a proof of concept. But by then the engineering and materials improvements available should have canceled any need to proceed to the Aquila, Taurus, Hercules and Centaurus.
However we get there, this, the early abandonment of sleeve valves was one of Britain's best opportunities for better results.
They did, just not at the same time as the Allies. As I mentioned, the generation of fighters that entered service, or were to enter service after Pearl did so and steered away from older, more traditional means of flighting. Japan wasn't alone in this, Italy was the same, as was the RAF. Th crucible of actual combat changes things in unexpected ways. Before the Spitfire and Hurricane entered service, the Gloster Gauntlet was the RAF's principal fighter. The Spitfire and Hurricane were plenty manoeuvrable and in a slow speed dogfight both could easily defeat a Bf 109 - this was amply demonstrated during the BoB.
Japan didn't have that widespread combat experience at that time to work from - in fact, neither did the USA, so that concept really only came about from the Battle of Britain that such things were vital - no internet for armchair historians to tell the Japanese what they think. We like to think we were superior than Japan because of this, but the lessons were learned, just later simply because the air forces they initially experienced in their Pacific expansion were far less capable or sizable than their own. When you're winning at the time, you don't think about what to do to prevent losing as much as you do to continuing winning. Japan did learn that lesson. It just took time. Yes, though, engine development was less extensive as Allied/German work so did hamper them, but it suited their philosophy.
Thumpalumpacus
Major
I think the Japanese had some experience in slow-speed dogfights over China well before they entered WWII. The Chinese weren't flying any hustlers, mostly I-15s, some I-16s, the occasional Hawk. The IJN naval air corps built a good body of experience there, so far as my reading has shown. I don't know much about their army air ops, but one reason why everyone regards their naval aviators in 1941 as being premier was from this experience dating from 1937-38 and onward. They knew how to dogfight slow, and had the equipment that could do that very well indeed.
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