What was the most efficiently-built aircraft engine in World War II?

[Conslaw]

We've had a lot of discussion on what is the best engine of World War II. My question is what was the best engine from an economic standpoint. I have seen film of the giant custom-made milling machine drilling the cooling fins in the R-2800 blocks, And that looks really efficient to me - but on the other hand, it is a big engine. Do other engines have a claim to the most-efficiently manufactured title, if so, why?

 

[Shortround6]

Measured how?????
Least material used per hp?
Least man hours per hp?
Least investment in tooling per engine?

And I have no idea where to look for the statics except the price per engine divided by power, and that will always favor the big engines.

 

[MiTasol]

And in what time frame?

• During ww2?
• During total life of production?

The R-2800 and R-1820 were in production for many years after the war so their tooling costs were relatively low per engine even though they may have been high initially.
A short production run engine - say something like the V-770 or Scarab may have had a very low production cost excluding tooling but if you divide that tooling cost per engine the total cost will be relatively high.

Something like the Pratt R-1340 on the other hand had a proverbial squillion engines built so the tooling cost when spread both during the war and over the total production run is much lower. Especially seeing some R-1340 parts were used on other Pratt engines.

The Allison should have had a far lower production cost than the Merlin because the engine was modular and very many parts were common to many submodels. The number of parts that differ between the left and right hand rotation engines is very low - from memory one idler gear and the starter dog. The wiring harness is different but the parts that make up the harness are almost exactly the same though a few cables may be different lengths. On most, if not all, Merlins the differences are massive between left and right hand versions of the same engine so the tooling costs will be far higher.

 

[ThomasP]

Armstrong-Siddeley Cheetah

 

[WARSPITER]

Armstrong-Siddeley Cheetah

Nicely done.

 

[Conslaw]

Measured how?????
Least material used per hp?
Least man hours per hp?
Least investment in tooling per engine?

And I have no idea where to look for the statics except the price per engine divided by power, and that will always favor the big engines.

 

[Conslaw]

I think debating what metric is most useful should be in play.

 

[pbehn]

Over the course of its life the Merlin would be near the top and near the bottom in the efficiency stakes. The early ones were made in the same place other engines were made with expected production of a few thousand units. The Packard factory was set up for high production using the infrastructure the USA had while the Glasgow Merlin factory was almost completely self contained with parts made in house. An additional quirk for the Merlin was that parts not suitable for aircraft use and engines from crashed planes were used in the Meteor tank engine.

 

[blueskies]

Find out the manhours per each engine. Then find out lbs of different metals were used in each engine. Keep in mind that some metals were in very short supply for certain countries, so you might want to have a correction factor for that. Once you've done all this research, come up with some sort of performance metric for engines and weight the manpower and material cost against that.

I strongly suspect that the 003 and 004 would beat all others.

 

[pbehn]

Find out the manhours per each engine. Then find out lbs of different metals were used in each engine. Keep in mind that some metals were in very short supply for certain countries, so you might want to have a correction factor for that. Once you've done all this research, come up with some sort of performance metric for engines and weight the manpower and material cost against that.

I strongly suspect that the 003 and 004 would beat all others.

So if you use a criteria that favours the 003 and 004, by a miracle the 003 and 004 beats all the others.

 

[blueskies]

So if you use a criteria that favours the 003 and 004, by a miracle the 003 and 004 beats all the others.

Those engines required significantly fewer manhours to build. Off the top of my head, the 004 was under 600 hours when introduced, under 400 hours near the end of the war and Junkers claimed they could get it under 300. By comparison the Jumo 213 was >2000 manhours. Its pretty hard to beat that sort of a discrepancy.

Added to this is that most of the work done for those jets was sheet metal operations that low skilled labor could perform. Piston engines required a lot of skilled labor.

 

[WARSPITER]

Perhaps the number of hours to build correlates with the number of hours before failure.

 

[blueskies]

Perhaps the number of hours to build correlates with the number of hours before failure.

Not really. The issues with the 004 and 003 engine life were related to alloys. When the Soviets made copies with better alloys the life went way up.

German piston engines had similar life issues caused due to lack of metals, ie the valves corroding quickly due to chromium shortages.

 

[pbehn]

Those engines required significantly fewer manhours to build. Off the top of my head, the 004 was under 600 hours when introduced, under 400 hours near the end of the war and Junkers claimed they could get it under 300. By comparison the Jumo 213 was >2000 manhours. Its pretty hard to beat that sort of a discrepancy.

Added to this is that most of the work done for those jets was sheet metal operations that low skilled labor could perform. Piston engines required a lot of skilled labor.

Early German jet engines had a life of 25 hrs, so to compare to an engine that goes 300 hrs before it needs a major service you need 12 engines or 3,600 man hours.

Gas_turbine.pdf

View Gas_turbine.pdf from SCIENCE 227 at University of Notre Dame. Gas turbineA gas turbine, also called a combustion turbine,is a type of continuous flow internal combustionengine. The main parts com

www.cliffsnotes.com

Mechanically, gas turbines can be considerably less complex than internal combustion piston engines. Simple turbines might have one main moving part, the compressor/shaft/turbine rotor assembly, with other moving parts in the fuel system. This, in turn, can translate into price. For instance, costing 10,000ℛℳformaterials, the Jumo 004 proved cheaper than theJunkers 213 piston engine, which was 35,000ℛℳ,[26]and needed only 375 hours of lower-skill labor to complete (including manufacture, assembly, and shipping), compared to 1,400 for theBMW 801.[27]This, however, also translated into poor efficiency and reliability. More advanced gas turbines (such as those found in modern jet engines or combined cycle powerplants) may have 2 or 3 shafts (spools), hundreds of compressor and turbine blades, movable stator blades, and extensive external tubing for fuel, oil and air systems; they use temperature resistant alloys, and are made with tight specifications requiring precision manufacture. All this often makes the construction of asimple gas turbine more complicated than a piston engine.

 

[Shortround6]

All this often makes the construction of asimple gas turbine more complicated than a piston engine.

As could be seen when the small gas turbines replaced the 300hp and up piston engines in helicopters, AG planes and light transports. Purchase price went up but longer times between overhauls made them more economical in the long run. The 300-400hp range was the cross over.

 

[ThomasP]

Armstrong-Siddeley Cheetah X TBO was 1200 hrs at the end of 1941? TBO of 1400 hrs by 1943?

[edited the date, added the engine Mark and the CDN TBO of 1400 hrs]

 

[blueskies]

Early German jet engines had a life of 25 hrs, so to compare to an engine that goes 300 hrs before it needs a major service you need 12 engines or 3,600 man hours.

Gas_turbine.pdf

View Gas_turbine.pdf from SCIENCE 227 at University of Notre Dame. Gas turbineA gas turbine, also called a combustion turbine,is a type of continuous flow internal combustionengine. The main parts com

www.cliffsnotes.com

Mechanically, gas turbines can be considerably less complex than internal combustion piston engines. Simple turbines might have one main moving part, the compressor/shaft/turbine rotor assembly, with other moving parts in the fuel system. This, in turn, can translate into price. For instance, costing 10,000ℛℳformaterials, the Jumo 004 proved cheaper than theJunkers 213 piston engine, which was 35,000ℛℳ,[26]and needed only 375 hours of lower-skill labor to complete (including manufacture, assembly, and shipping), compared to 1,400 for theBMW 801.[27]This, however, also translated into poor efficiency and reliability. More advanced gas turbines (such as those found in modern jet engines or combined cycle powerplants) may have 2 or 3 shafts (spools), hundreds of compressor and turbine blades, movable stator blades, and extensive external tubing for fuel, oil and air systems; they use temperature resistant alloys, and are made with tight specifications requiring precision manufacture. All this often makes the construction of asimple gas turbine more complicated than a piston engine.

Again alloys matter a lot. German piston engines of the time had lifespans significantly shorter than 300hrs, I think well under 100hrs was probably typical in the late war period. That is more like 4 engines for equivalent life.

The Soviets, building essentially the exact same engine with better alloys, managed to double engine life pretty much immediately and got it up to 75hrs with a few tweaks.

Additionally if you want to make a comparison of jet v turbine engine cost you must also factor in the propeller for the piston engine.

 

[Shortround6]

Anybody know the overhaul life of a P & W R-985? Fixed wing version, not helicopter.

 

[ThomasP]

I have the R-985 numbers from the 1975 overhaul manual, but not from WWII.

In 1975, R-985 TBO for helicopter engines was 500-800, agricultural aircraft engines was 600-1000 hrs, and 'long range' aircraft engines where cruise settings were the norm was 1000-1600 hrs.

 

[Shortround6]

Forget the Germans. The British and Americans were lucky they could get 25-50 hours out of their early jets and there wasn't much of a shortage of alloys for them.

Designed for/expected life and real life were two very different things with jet engines in 1946-47.
Martin XB-48

First flight 22 June 1947
In it's first 44 flights it went through 14 engines. GE/Allison J-35s.
By about 1950-51 they were getting over 1000 hours out of later model J-35s.