American one engine to rule them all?

[tomo pauk]

Yes, tough luck to convince the P&W to make what Wright designs, and vice-versa, but lets give it a shot.
How should look an engine that, in different version of a basic design, is slated to power majority of US 1-st line combat aircraft for the upcoming ww2? The design job will start some time in 1935, so the 1st engines can be flying in 1939, and start powering the aircraft by late 1940. The design should be nothing complicated, but a type of engine the even non-specialized factories can make en masse. It is not about the most powerful engine either, not about the cheapest one, but the engine that is the best blend between power, size, weight and reliability. The plausible/feasible growth in power is also a factor.
Certainly, the USN will ask for a 2-stage S/C, the USAAF will ask for a turbocharged version, while the 1st versions can feature a 1-stage S/C and still be useful.

 

[wuzak]

Perhaps the Pratt & Whitney R-2600?

P&W changed to the R-2800 when they learned that Wright was making an R-2600.

 

[Shortround6]

The design should be nothing complicated, but a type of engine the even non-specialized factories can make en masse.

High powered aircraft engines and non-specialized factories are sort of mutually exclusive, especially when you throw in the can make en masse requirement.

We read all the time about Ford and Chevrolet and Studebaker and even Packard making airplane engines, what is seldom mentioned is that they didn't make them (or most of them) in their old car factories. They made them in newly built and newly equipped factories which were pretty much shuttered when production stopped and the companies went back to building cars. Special machine tools were designed and built that greatly increase production, soma of rather large size that were near useless for making small parts in small batches.
One such machine is described on page 54 of the report here: http://www.enginehistory.org/References/WWIIEngProduction.pdf

Two large machines took up 956 sq ft (88 sq meters) of factory area and required 17.4 man hours (a misprint) per 3 shift day. Using conventional machinery would have required 5 radial drills, 1 radial tapper, and 1 vertical mill with a rotary table, This collection of machinery would have required an additional 278 sq ft of space and required an additional 121.6 man hour per 3 shift day.

You can't make V-12 airplane engines on machines that built V-8 or straight 6 car engines, at least some parts like crankshafts, the machinery isn't big enough. Same with trying to build radials. An easily built airplane engine is going to be suitable for trainers.
Fairchild PT-19 trainer.

powered by a Ranger L-440 engine.

An air cooled 6 cylinder 441 cu in (7.2 liter) engine that could make 175hp on 65 octane fuel but weighed 376lbs.

Even Continental didn't try to make complete high powered aircraft engines in their exiting plant and they had been making GA engines for years. They built a new plant several miles away when the Army decided to try to put the IV-1430 into production, when the engine didn't work Continental built P & W R-1340s ( over 5000 of them) before shifting over the Merlin V-1650-7s near the end of the war (797).

The car makers were called upon to provide their mass production know how and management skills. Not to try to make very large, high powered engines on the machinery that turned out 3-5 liter cast iron cheap car engines.

 

[Kevin J]

Yes, tough luck to convince the P&W to make what Wright designs, and vice-versa, but lets give it a shot.
How should look an engine that, in different version of a basic design, is slated to power majority of US 1-st line combat aircraft for the upcoming ww2? The design job will start some time in 1935, so the 1st engines can be flying in 1939, and start powering the aircraft by late 1940. The design should be nothing complicated, but a type of engine the even non-specialized factories can make en masse. It is not about the most powerful engine either, not about the cheapest one, but the engine that is the best blend between power, size, weight and reliability. The plausible/feasible growth in power is also a factor.
Certainly, the USN will ask for a 2-stage S/C, the USAAF will ask for a turbocharged version, while the 1st versions can feature a 1-stage S/C and still be useful.

You've been drinking tap water? It has fluoride in it. Or perhaps you're a closet commie?

 

[tomo pauk]

High powered aircraft engines and non-specialized factories are sort of mutually exclusive, especially when you throw in the can make en masse requirement.
...
The car makers were called upon to provide their mass production know how and management skills. Not to try to make very large, high powered engines on the machinery that turned out 3-5 liter cast iron cheap car engines.

Yes, you have the point.

Perhaps the Pratt & Whitney R-2600?

P&W changed to the R-2800 when they learned that Wright was making an R-2600.

Several types might fit the bill, each with their benefits and shortcomings:
- a big V12 (2000-2200 cu in?); advantage might be that it can offer best streamlining, disadvantage is that US engine companies don't have experience in big V12s, be it in design, troubleshooting or manufacturing
- a not too big, nor too small 14 cyl radial - talk a short-stroke version of R-2600, or a BMW 801 with out the tight cowling and fan, or the over-bored R-2180, or something like the ASh-82. Call it R-2500? Advantages might be that US companies know radials, and it should be cheaper than a 18 cyl solution.
- an 18-cyl sibling to the R-1830, lets call it 'R-2350' (about 10% bigger than Homare). It should be turning better RPM than a 14 cyl engine, but it will be more expensive. The 18-cyl sibling to the R-2000 = 'R-2570'?

 

[Kevin J]

Yes, you have the point.



Several types might fit the bill, each with their benefits and shortcomings:
- a big V12 (2000-2200 cu in?); advantage might be that it can offer best streamlining, disadvantage is that US engine companies don't have experience in big V12s, be it in design, troubleshooting or manufacturing
- a not too big, nor too small 14 cyl radial - talk a short-stroke version of R-2600, or a BMW 801 with out the tight cowling and fan, or the over-bored R-2180, or something like the ASh-82. Call it R-2500? Advantages might be that US companies know radials, and it should be cheaper than a 18 cyl solution.
- an 18-cyl sibling to the R-1830, lets call it 'R-2350' (about 10% bigger than Homare). It should be turning better RPM than a 14 cyl engine, but it will be more expensive. The 18-cyl sibling to the R-2000 = 'R-2570'?

Nice ideas, but with P&W do you end up with the unreliability issues that the Homare had too. Maybe with Wright you end up with a decent power plant for the P-40, after all if the Russians can do it then the Americans should be able to do it too, and earlier perhaps. Just imagine such a plane kicking Japanese arse in PNG and at Guadalcanal. ANZ wouldn't have needed their Boomerangs, Kittyhawks, Spitfires and Corsairs. Maybe the Aussies would be licence producing them.

 

[tomo pauk]

Nice ideas, but with P&W do you end up with the unreliability issues that the Homare had too.

I have no intention to have the CR of 7:1, let alone of 8:1 and then feed the engine with 87 oct fuel. Nor I have a major wish to push the engine to 3000 rpm.

Maybe with Wright you end up with a decent power plant for the P-40, after all if the Russians can do it then the Americans should be able to do it too, and earlier perhaps. Just imagine such a plane kicking Japanese arse in PNG and at Guadalcanal. ANZ wouldn't have needed their Boomerangs, Kittyhawks, Spitfires and Corsairs. Maybe the Aussies would be licence producing them.

Americans are certainly in a better starting position than Shvetsov team.

 

[Shortround6]

- a not too big, nor too small 14 cyl radial - talk a short-stroke version of R-2600, or a BMW 801 with out the tight cowling and fan, or the over-bored R-2180, or something like the ASh-82. Call it R-2500? Advantages might be that US companies know radials, and it should be cheaper than a 18 cyl solution.
- an 18-cyl sibling to the R-1830, lets call it 'R-2350' (about 10% bigger than Homare). It should be turning better RPM than a 14 cyl engine, but it will be more expensive. The 18-cyl sibling to the R-2000 = 'R-2570'?

You suggest starting in 1935 but the fuel of the day was 87 octane, which rather puts a limit on the amount of power you can get out of engine (actually the basic cylinder) of a certain size unless you go nuts with the rpm. See Napier Dagger and Sabre
In 1935 Wright knows 9 cylinder single row radials. They are starting work on the R-2600,.
In 1935-36 Pratt knows 9 cylinder single row radials and they have been burned by the big 9 cylinder R-1860. Yes they are working on the R-1830 and R-1535 but those are about 900-1000hp and 750hp engine respectively. Your 18 cylinder R-1830 R-2350 might only be good for around 1150hp. Adding four cylinders increases the displacement by 28% which may not have been enough to make the project worth while, they could get a 19% increase in displacement with the R-2180 with next to no change in parts count and only a bit more machine time on the parts. They do know that 100 octane is coming, they just don't know when. If you want big power you are going to need a big engine. They need to look 4-5 years down the road, not one -two years.
On April 21st 1937 initial specifications for the R-2800 were released. Estimated weight was 2100lbs and power on 100 octane gas was estimated at 1650hp/2500rpm for take-off and max continuous was 1300hp/2300rpm at 10,000ft.
If your proposed engines cannot match or exceed 1500-1600hp in the planning stage they are probably of little interest. The R-2180 was originally a 1200hp engine on 87 octane fuel.
The later R-2000 managed to beat this, in part because it ran at 2700rpm (early versions) instead of 2500rpm.
However the development and improvement in cooling fins should not be overlooked in the increases in power of newer engines compared to older ones.

 

[tomo pauk]

You suggest starting in 1935 but the fuel of the day was 87 octane, which rather puts a limit on the amount of power you can get out of engine (actually the basic cylinder) of a certain size unless you go nuts with the rpm. See Napier Dagger and Sabre
In 1935 Wright knows 9 cylinder single row radials. They are starting work on the R-2600,.
In 1935-36 Pratt knows 9 cylinder single row radials and they have been burned by the big 9 cylinder R-1860. Yes they are working on the R-1830 and R-1535 but those are about 900-1000hp and 750hp engine respectively. Your 18 cylinder R-1830 R-2350 might only be good for around 1150hp. Adding four cylinders increases the displacement by 28% which may not have been enough to make the project worth while, they could get a 19% increase in displacement with the R-2180 with next to no change in parts count and only a bit more machine time on the parts. They do know that 100 octane is coming, they just don't know when. If you want big power you are going to need a big engine. They need to look 4-5 years down the road, not one -two years.
On April 21st 1937 initial specifications for the R-2800 were released. Estimated weight was 2100lbs and power on 100 octane gas was estimated at 1650hp/2500rpm for take-off and max continuous was 1300hp/2300rpm at 10,000ft.
If your proposed engines cannot match or exceed 1500-1600hp in the planning stage they are probably of little interest. The R-2180 was originally a 1200hp engine on 87 octane fuel.

I do favor a 14 cyl engine.
What kind of power and weight should the early 'R-2500' display, with diameter of 51-52in and weight of ~1800 lbs dry on 87 oct, and on 100 oct? Ability to match M-82 and BMW 801C (disregarding the turbo and 2-stage S/Ced options for the moment)?

The later R-2000 managed to beat this, in part because it ran at 2700rpm (early versions) instead of 2500rpm.
However the development and improvement in cooling fins should not be overlooked in the increases in power of newer engines compared to older ones.

Agreed all the way.

 

[Shortround6]

I do favor a 14 cyl engine.
What kind of power and weight should the early 'R-2500' display, with diameter of 51-52in and weight of ~1800 lbs dry on 87 oct, and on 100 oct? Ability to match M-82 and BMW 801C (disregarding the turbo and 2-stage S/Ced options for the moment)?

I would look at the Wright R-2600 but you are mixing up the timelines here. Just a few years can make a large difference in the capabilities of an engine.

The R-2600 went into service in the Boeing 314 clipper in the summer/fall of 1938. The first version was rated at 1550hp for take-off and 1200hp max continuous but later versions in the Clipper were soon rated at 1600hp for take-off and 1350 Max Con. fuel needed is a subject of question, Wright spec sheets say 91/96 or 90, 95. FAA says 95 octane.
https://rgl.faa.gov/Regulatory_and_...c9d0fb71db90d8525670e0065d195/$FILE/TC176.pdf

 

[tomo pauk]

Thank you.
We could probably look at 1500-1550 HP on early 'R-2500' engines down low and 2400 rpm, and perhaps 1200-1300 HP at 2400 rpm and 13000-14000 ft (just don't install a too small impeller)? The short stroke should be more conductive to increase of rpm, so by 1941 we might be looking at 2600 rpm for 5 min limit (that is in-between the M-82 and BMW 801C)?
This should be also the time for the advent of 2-stage and turbocharged versions as production engines' versions/installations.

 

[Shortround6]

Unfortunately Wright is not a really good indicator as their 1600hp and 1700 hp engines changed radically. Like changing the crankcase from Aluminium to steel and using a new crankshaft? I have no idea what they did with cylinders and heads but I do know that the R-1820G100 was also radically different than the R-1820G200. All for another 100rpm and 100hp.
Cooling fin area went up a tremendous amount. From about 1930-32 with the first R-1820s to the R-1820G200 cooling fin area more than tripled. from the Early engines to the G100 the fin area went from about 1000 sq in per cylinder to about 2800 sq in per cylinder and for the G200 the fin area went to 3510sq in per cylinder.
This is part of what makes evaluating air cooled engines so difficult. You can't just pour high octane fuel in the tank, adjust the boost settings and go. While higher octane will certainly allow for higher power it may not do it for 5 minutes (or less) until the engine overheats and even the higher octane fuel detonates in the hotter engine.
The 1300-1350hp R-1820s changed the cooling fins radically again, as did the 1900hp R-2600s.

 

[tomo pauk]

Yes, the changes in technology and materials will still happen.
The 2-stage S/Ced engines should be providing perhaps 85% of what 2-stage R-2800s were making? Talk around 1300-1400 HP at 20-22.5 kft ( 'A' series vs 'B' series), or about 1450-1550 HP at 16-18 kft? Granted, the 'ALT P-40' will probably have the 1-speed S/C version, with about 1300-1400 HP at 13000-15000 ft (again depending on how far we are going into 1940s).
The turboed 'R-2500' solves the Johnson's dilemma , and we know what the 'Thunderocket' will have in the nose (unless it makes the Lockheed's design under license).

 

[Shortround6]

Again you have timing and you have cooling problems with air cooled engines,

It is easy for us now to sit back and scoff at the idea that air cooled engines would not properly cool at high altitudes when using turbos. This idea was firmly entrenched in AAC thinking in the 30s. However look at the increase in cylinder fin area I described in the previous post, The B-17 switched to the engines with the 3514 sq in of fins per cylinder in either the B model or the C. Cooling at high altitudes was no longer the big problem ( but still a problem) that it had been even in 1938-39.
It just took new designs of cylinder heads and cylinder barrels with new methods of manufacture to do it.
Yes you could apply these lessons to other engines but saying you are going to plan on these improvements in 1935-37 when you are doing you initial design for the small displacement radial is pushing things.

Shvetsov had built two different 2835 (?) cu in 14 cylinder radials using M-62/63 cylinders before shortening the stroke to make the M-82.
You are working backwards, as in such and such an engine worked in 1941-42, how do we go back in time and get it to work in 1936-39. Or how do I take the 1942 engine and make a plausible argument that development could have started in 1935 vs some other historical larger engine.
The Historical larger engines were that large due to limits on BMEP from the available fuels, the limits on RPM due to limits on materials ( bearings and lubrication+ strength/fatigue life of the metals) and limits on cooling, fin pitch and depth with current manufacturing techniques.

 

[tomo pauk]

Again you have timing and you have cooling problems with air cooled engines,

It is easy for us now to sit back and scoff at the idea that air cooled engines would not properly cool at high altitudes when using turbos. This idea was firmly entrenched in AAC thinking in the 30s. However look at the increase in cylinder fin area I described in the previous post, The B-17 switched to the engines with the 3514 sq in of fins per cylinder in either the B model or the C. Cooling at high altitudes was no longer the big problem ( but still a problem) that it had been even in 1938-39.
It just took new designs of cylinder heads and cylinder barrels with new methods of manufacture to do it.
Yes you could apply these lessons to other engines but saying you are going to plan on these improvements in 1935-37 when you are doing you initial design for the small displacement radial is pushing things.

Someone have had enough of confidence in a turboed radial engine when the (X)P-43 was ordered.
There was a lot of altitude records where the radial engines were used, granted not in a turboed form, but some of them used 2-stages of supercharging, like the Bristol 138. Actually, all of the altitude records in 1930s were attained by aircraft powered by radial engines.

Shvetsov had built two different 2835 (?) cu in 14 cylinder radials using M-62/63 cylinders before shortening the stroke to make the M-82.
You are working backwards, as in such and such an engine worked in 1941-42, how do we go back in time and get it to work in 1936-39. Or how do I take the 1942 engine and make a plausible argument that development could have started in 1935 vs some other historical larger engine.
The Historical larger engines were that large due to limits on BMEP from the available fuels, the limits on RPM due to limits on materials ( bearings and lubrication+ strength/fatigue life of the metals) and limits on cooling, fin pitch and depth with current manufacturing techniques.

Sounds like I've suggested that Americans adopt a jet engine. Shortening the stroke was nothing new by early 1930s.

 

[Shortround6]

Someone have had enough of confidence in a turboed radial engine when the (X)P-43 was ordered.
There was a lot of altitude records where the radial engines were used, granted not in a turboed form, but some of them used 2-stages of supercharging, like the Bristol 138. Actually, all of the altitude records in 1930s were attained by aircraft powered by radial engines.

Difference was the turbo was supposed to make sea level power at 20-25,000ft. Air at 25,000ft is about 45% the weight per cu ft as it is at sea level so it has 45% of the cooling power for the volume of airflow, Yes it is colder which helps somewhat.

and again, engine designs were not static. The YP-43s ordered in March of 1939 and delivered in Sept 1940 (2nd month of the BoB) used -35 engines with a 5.25 supercharger gear. Engine was good for 1200hp at up to 20,000ft.
The first production P-43s, ordered in late 1940, got -47 engines with 7.15 supercharger gears and were good for 1200hp at 25,000ft Both of these engines used 100 octane fuel. first delivery may of 1941. The -49 engine used in the later P-43s was good for the same power ratings on 91 octane fuel (?) and deliveries started in Sept 1941.

I don't know what the actual differences were in the engines or engine installations. The -49 did use a different carburetor than the -47 but I have no idea what the effect was.

The record setting aircraft were making nowhere near the power at altitude that they were at sea level or at the FTH of the engines, so the thermal load was nowhere near as great.
On the Bristol 138 they may not have even clutched in the auxiliary supercharger until the plane was at very high altitudes 35,000ft ? engine was rated at 500hp not 700-800hp of it's low altitude contemporaries.

Sounds like I've suggested that Americans adopt a jet engine. Shortening the stroke was nothing new by early 1930s.

Shorten the stroke was nothing new. But shortening the stroke to increase rpm to make up for the reduced displacement is a very fine act.

 

[tomo pauk]

Difference was the turbo was supposed to make sea level power at 20-25,000ft. Air at 25,000ft is about 45% the weight per cu ft as it is at sea level so it has 45% of the cooling power for the volume of airflow, Yes it is colder which helps somewhat.

Again - I'm not asking anything extra for the newly fanged radial. The sea level power to be had at 20-25 kft is fine to me.

and again, engine designs were not static. The YP-43s ordered in March of 1939 and delivered in Sept 1940 (2nd month of the BoB) used -35 engines with a 5.25 supercharger gear. Engine was good for 1200hp at up to 20,000ft.
The first production P-43s, ordered in late 1940, got -47 engines with 7.15 supercharger gears and were good for 1200hp at 25,000ft Both of these engines used 100 octane fuel. first delivery may of 1941. The -49 engine used in the later P-43s was good for the same power ratings on 91 octane fuel (?) and deliveries started in Sept 1941.
I don't know what the actual differences were in the engines or engine installations. The -49 did use a different carburetor than the -47 but I have no idea what the effect was.

Thank you.

The record setting aircraft were making nowhere near the power at altitude that they were at sea level or at the FTH of the engines, so the thermal load was nowhere near as great.
On the Bristol 138 they may not have even clutched in the auxiliary supercharger until the plane was at very high altitudes 35,000ft ? engine was rated at 500hp not 700-800hp of it's low altitude contemporaries.

I'm okay with the 2-stage S/Ced version produces at hi altitudes (22-23 kft) about 70% of the low-level power.

Shorten the stroke was nothing new. But shortening the stroke to increase rpm to make up for the reduced displacement is a very fine act.

Actually, my 1st reason is to have the frontal area being not too big, and to shave some weight (that might be a tall order). Engine of 51in diameter will have the frontal area of 2043 sq in, the one of 55 in diameter = 2376 sq in of my math is correct. Or, about 15% more for the larger engine.
Shortening the stroke while increasing the rpm was done by Bristol (Mercury vs. Pegasus), the rpm went up by 150, the power was down by ~5% for the Mercury.