Japanese Design Philosophy

[Shortround6]

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?

Yes, no, maybe. The overlap was short.
There were two R-2600 engines at this time, the A (1600hp) and the BA (1700hp) and there were two R-2800 engines, the A (1850hp) and the B (2000hp)

Year.....................................................1941..................................1942
Wright R-2600 A (P)......................7168................................6393
Wright R-2600 A (C)......................----................................----
Wright R-2600 BA (P)...................--**..................................147*
Wright R-2600 BA (C)..................----..................................5981
P&W R-2800 A (H).......................1461................................49
P&W R-2800 A (F)........................262..................................692
P&W R-2800 B (H)............................2..................................4300
P&W R-2800 B (F).............................2..................................5711
P&W R-2800 B 2 stage (H)............6..................................1079

Records for the R-2600 at Patterson are incomplete. Main use in 1941 was for B-25s.
Wright (P) = Paterson NJ
Wright (C) = Cincinnati Oh
P&W (H) = East Hartford CT
P&W (F) =Ford
The R-2800 A engine was pretty much used in B-26s and prototypes. There was a fair amount of interchange between the two R-2800 engine types.
The Wright R-2600 engines were two different engines that used the same bore and stroke.
The Wright R-2600 engine continued in production for most of the war, ending at the end of 1944.
Except for a very few months the R-2800 was making 250hp or more over the R-2600 engine. Once you get to the "B"s there is a 300hp difference.
This is take-off power, power at altitude could be different.

Merlin supercharger - which resulted in other engine manufacturer analyzing their force induction systems with similar results.

Not sure if you mean the 2 stage supercharger or the Merlin XX/45 supercharger of 1940. Most countries supercharges were pretty terrible in 1938-1940

Solving the R-2800 crankshaft issue (holes in crankcase bulkhead between front and rear cylinder rows allowing 100+lbs of oil to be drained off rotating mass resulting in immediate 100 hp gain while allowing for future improvements.)

That was the major change between the "A" and "B" engines. The "B"s were limited by cooling problems and were never rated at over 2000hp unless there was water injection available.

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.)

I think the difference is the production rate. How many engines per day by how many workers? Hand assembly can go both ways, really good to really terrible.

 

[don4331]

Yes, no, maybe. The overlap was short.
There were two R-2600 engines at this time, the A (1600hp) and the BA (1700hp) and there were two R-2800 engines, the A (1850hp) and the B (2000hp)

Year.....................................................1941..................................1942
Wright R-2600 A (P)......................7168................................6393
Wright R-2600 A (C)......................----................................----
Wright R-2600 BA (P)...................--**..................................147*
Wright R-2600 BA (C)..................----..................................5981
P&W R-2800 A (H).......................1461................................49
P&W R-2800 A (F)........................262..................................692
P&W R-2800 B (H)............................2..................................4300
P&W R-2800 B (F).............................2..................................5711
P&W R-2800 B 2 stage (H)............6..................................1079

Records for the R-2600 at Patterson are incomplete. Main use in 1941 was for B-25s.
Wright (P) = Paterson NJ
Wright (C) = Cincinnati Oh
P&W (H) = East Hartford CT
P&W (F) =Ford
The R-2800 A engine was pretty much used in B-26s and prototypes. There was a fair amount of interchange between the two R-2800 engine types.
The Wright R-2600 engines were two different engines that used the same bore and stroke.
The Wright R-2600 engine continued in production for most of the war, ending at the end of 1944.
Except for a very few months the R-2800 was making 250hp or more over the R-2600 engine. Once you get to the "B"s there is a 300hp difference.
This is take-off power, power at altitude could be different.




Not sure if you mean the 2 stage supercharger or the Merlin XX/45 supercharger of 1940. Most countries supercharges were pretty terrible in 1938-1940

That was the major change between the "A" and "B" engines. The "B"s were limited by cooling problems and were never rated at over 2000hp unless there was water injection available.

I think the difference is the production rate. How many engines per day by how many workers? Hand assembly can go both ways, really good to really terrible.

I was actually thinking even earlier - during the time that Grumman would have been designing the Hellcat, the R-2600 was a running engine, while R-2800 was still experimental. Best way to sabotage an experimental airplane is to use an experimental engine. And the spec was for 1,650hp@2,500 rpm per Graham White's tome (R-2600A made 1700hp@2,400 rpm). Replacing the Wright with a P&W, that was more than delivering on promise for the second prototype was right thing to do.

AerialTorpedoDude69 Why does acknowledging R-2800 had issues during development mean I'm trash talking it. Merlin had development issues - especially with ramp head. There probably isn't an engine that hasn't had some development challenges.

Rubbra has improved RR superchargers from 36% to 60% before Hooker got involved. So, the Merlin supercharger was decent even in '38-40. And of course, great later.
Wright improved from the GE designed supercharger with mid 30s efficiency to one of their own similar to RR - mid 70s after analysis of what could be done.

Interestingly, I don't have any references to similar improvements at Allison/Bristol/Napier/P&W but I would have to assume they did so.​

P&W had individuals hand polishing R-2800 master rods - not sure what else. They obvious found enough workers for the number of engines being built. Agreed that hand assembly can go either way.

 

[GrauGeist]

ALL engines have to be hand-assembled.

 

[Shortround6]

I was actually thinking even earlier - during the time that Grumman would have been designing the Hellcat, the R-2600 was a running engine, while R-2800 was still experimental.

Grumman was working on paper with a couple of designs that used R-2600 engines in modified F4F airframes but they quickly concluded that they would need a new airframe. This was in 1938 and with the work needed on the F4F to get into production all work on the R-2600 powered machine was stopped and not restarted until Sept of 1940. Problem here is that Vought had flown the prototype F4U in May of 1940. Both engine and airframe needed work.
The R-2800 had passed it's military type test (single stage) on July 1st 1939, first flown July 12 1939, Feb 12th 1940 5000 hours of run time (most on the bench) Still needed more work but a lot of other engines (Sabres and Vultures) needed work.

Best way to sabotage an experimental airplane is to use an experimental engine.

Quite true but what is an experimental engine and what is a modification of an existing engine? And some modifications do not work out. More later

And the spec was for 1,650hp@2,500 rpm per Graham White's tome (R-2600A made 1700hp@2,400 rpm).

And that spec is for April 21, 1937. In 1937 the handful of R-2600s delivered were giving 1500hp for take-off as were most of the engines delivered in 1938.
The R-2600A made 1600hp at 2400rpm, the early 1500hp versions ran at 2300rpm.
The R-2600B made 1700hp at 2500rpm (mostly, some were supposed to give 1700hp at 2600rpm?)
There were a couple of R-2600BB engines that were supposed to give 1800hp at 2800rpm but they don't show up until 1942-43.
The R-2600s in the F6F prototype was a B series engine that was supposed to give 1700hp engine at 2600 & 2800rpm (?), there were 2 engines built with the 2 stage supercharger and they went 2127lbs.
The B-engines changed from aluminum crankcases to steel crankcases among other changes. One does wonder where the cross over from experimental engine occurs.
For some reason Wright never got a two stage R-2600 of any if the 3 different versions into production, either mechanically supercharged or turbo charged. They planned to, but they were always cancelled. Lack of orders or problems in development or both?

 

[Shortround6]

We (myself included) confuse hand fitting and hand assembled and hand finished at times or we use the term/s as short hand.
What truly matters is the tolerances and the production rate (engines or at least parts per day)
It is quite possible to make and fit parts to tight tolerances using somewhat primitive tools.
Trouble is the man hours needed are going to be very high. Lots of man hours for low number of engines.
Just adding workers sometimes doesn't work well, especially in societies with a low level of industrialization/technical knowledge.

You have a group of highly skilled engine fitters/assemblers but taking each one of them and giving them 3 helpers, one a 19 year old college student, one a mid 30s woman who has worked as a sewing machine operator her adult life and 60 year old farmer who thought an iron tipped plow was a revelation, none who have owned or even driven a car is not going to quadruple engine output. The woman may be the best bet. She knows the machine needs a certain amount of lubrication and forcing it may make it bind/jam/malfunction.
The US used a lot of semi-skilled (or unskilled) workers in WW II. The US also had better training programs and had lots of machines that didn't require as much attention. Some machines were set up to make hundreds of the same part day after day, the operator just the part in, clamped it down and turned it on. Machine stopped on it's own (or went to a ready position) and the worker didn't even actually measure the part. They used a go/no go gauge. They also looked to see it the cutting tool was broken or worn. If the part was not right or tool edge broken or deformed then the "operator" called a higher level worker to look at things or replace/reset the cutting tool/s.
They could use complicated machines to make up for lower skilled workers. But you need a machine tool industry that can supply the complicated machine tools.

Materials can also make a huge difference. Not just the steel alloys to make certain parts out of, but the "high speed steel" to cut the alloy steels with, often replaced by tungsten carbide tipped tools which allowed for higher cutting speed and deeper cuts and often better finish. Germans stopped using tungsten carbide anti tank ammo to save the tungsten carbide and plain tungsten for machine tools. There are a number of different families of high speed steel and some were developed in WW II to get around material shortages.
What did the Japanese have? And in what quantities? Sometimes you can substitute a lower grade cutting tool steel for a higher grade but you may have to slow down the speed( speed of the cutter against the surface of the part), or take shallower cuts and/or replace/sharpen the tool bit more often.