US Army Hyper Engine

[Shortround6]

A few things need to be put into context.

for instance "Continental Motors, Inc., Lycoming's main rival in the general aviation engine market"
is both true and very misleading to modern readers.
Both companies were building 200-285hp 7 or 9 cylinder radials for the general aviation market. Lycoming would not get into the low end flat four market until 1938.
Continental was doing rather well with A-40 engine (about 40hp) that is unrelated to later Continental flat fours. It would take WW II and the aftermath to knock out the other general aviation engine makers, Kinner, Jacobs, Franklin, and others leaving Continental and Lycoming to really dominate the market.

"From 1935 the engine design proceeded at a faster pace after a number of former Continental engineers, who had become unhappy with the working conditions there, joined Lycoming"

Continental was acting like a job shop for the Army, they built parts and ran single cylinder engine tests for the Army when the Army told them to. They were putting little or no money or effort into the engine unless the Army paid them to. And the Army was often late in paying. It was all piecemeal contracts. Army would pay(or contract for) a one cylinder test rig of certain features and want it run for a certain number of hours. If it broke Continental, who hadn't designed it, was responsible for fixing it and completing the test at Continental's expense. Progress, as can be imagined, was glacial.

For the Lycoming " In 1936, the single-cylinder development tests exceeded expectations, passing its 50-hour test requirement. The full-size engine was ready for testing in 1937, and was rated at 1,000 hp "
Continental would not build a 12 cylinder version of their engine until 1939 or 40.

 

[Zipper730]

A few things need to be put into context. . . . for instance "Continental Motors, Inc., Lycoming's main rival in the general aviation engine market" is both true and very misleading to modern readers.

So basically, they were competitors in making small engines, not big ones for military applications?

Continental was acting like a job shop for the Army, they built parts and ran single cylinder engine tests for the Army when the Army told them to. They were putting little or no money or effort into the engine unless the Army paid them to. And the Army was often late in paying.

I didn't know about the late payments: Was this absentmindedness or limited funding?

For the Lycoming "In 1936, the single-cylinder development tests exceeded expectations, passing its 50-hour test requirement. The full-size engine was ready for testing in 1937, and was rated at 1,000 hp"

I'm amazed they didn't just drop the Continental design or put it on back burner.

 

[wuzak]

I'm amazed they didn't just drop the Continental design or put it on back burner.

The Continental was the Army's baby. The Lycoming was not.

The Army had control over the Continental design, but not Lycoming's.

 

[Shortround6]

So basically, they were competitors in making small engines, not big ones for military applications?

Call it "medium" sized engines for 4-5 seat aircraft or for small multi engine airliners.

Both used 3 Lycoming radials. Lycoming would NOT get into the really small (under 100hp market) until about 1938.

I didn't know about the late payments: Was this absentmindedness or limited funding?

Limited funding, please remember that by the Spring of 1939 the army owed Allison over $900,000 for work already done.
It was this dribs and drabs of money for small increments of progress that dragged the the development out for so long.

I'm amazed they didn't just drop the Continental design or put it on back burner.

The Continental was the Army;s "baby". Their engineering dept had the most input into it's design and the most ego and career "points" tied up in it.
The Lycoming was 2nd string. The Allison wasn't even a "hyper" engine.

 

[Zipper730]

The Continental was the Army's baby. The Lycoming was not.

The only reason that the Lycoming's design wasn't designed by the US Army was because Continental apparently wasn't willing to design the engine to a specification that the US Army gave them, so they designed everything themselves, and had Continental build it.

Lycoming was building to a specification that they evidently worked out with the US Army, and that would, far as I know, give them control over it.

Limited funding, please remember that by the Spring of 1939 the army owed Allison over $900,000 for work already done.

Gotcha

 

[Shortround6]

No, Continental was building everything the Army told them to build. They just weren't willing to put any of their own money in the project.
The Army was doing the designing but had no manufacturing or machine shop facilities and in the early 30s a limited ability to test engines. So they contracted those parts of the program out. The Army also change the "specification" every few years in the early 30s. Making Continentals reluctance to put any of their own money into it even more understandable.

The Army decided on the cylinder bore and stroke, (and changed it at least once and maybe twice) the Army decided on the type of construction (separate cylinder), the army decided on the number of valves per cylinder and so on.

 

[wuzak]

No, Continental was building everything the Army told them to build. They just weren't willing to put any of their own money in the project.
The Army was doing the designing but had no manufacturing or machine shop facilities and in the early 30s a limited ability to test engines. So they contracted those parts of the program out. The Army also change the "specification" every few years in the early 30s. Making Continentals reluctance to put any of their own money into it even more understandable.

The Army decided on the cylinder bore and stroke, (and changed it at least once and maybe twice) the Army decided on the type of construction (separate cylinder), the army decided on the number of valves per cylinder and so on.

The Army decided on a flat 12, before changing their mind and going for an inverted V-12.

 

[Zipper730]

No, Continental was building everything the Army told them to build. They just weren't willing to put any of their own money in the project.

So, the Army considered it theirs because it was designed exactly as they told them to?

Was the Lycoming O-1230 designed this way because of the USAAC's request for a flat engine? Or did they prefer a flat engine? I'm just curious based on the time-table, and I'm not sure when they were told to make a flat engine.

The Army was doing the designing but had no manufacturing or machine shop facilities and in the early 30s a limited ability to test engines. So they contracted those parts of the program out. The Army also change the "specification" every few years in the early 30s. Making Continentals reluctance to put any of their own money into it even more understandable.

I could imagine that

The Army decided on the cylinder bore and stroke, (and changed it at least once and maybe twice) the Army decided on the type of construction (separate cylinder), the army decided on the number of valves per cylinder and so on.

And the reason they designed each cylinder individually was because they didn't think the other way would work?

 

[wuzak]

Was the Lycoming O-1230 designed this way because of the USAAC's request for a flat engine? Or did they prefer a flat engine? I'm just curious based on the time-table, and I'm not sure when they were told to make a flat engine.

The Army/Airframe manufacturers were after a flat engine.

And the reason they designed each cylinder individually was because they didn't think the other way would work?

It's because that was the hyper cylinder arrangement.

 

[Zipper730]

The Army/Airframe manufacturers were after a flat engine.

Wait, there were actual contractors which wanted this? I thought it was just the USAAC. I'm curious which manufacturers (if I had to guess, Northrop/Douglas -- Northrop loved flying wings, and Douglas had owned Northrop for some period, and Martin -- the XB-16).

It's because that was the hyper cylinder arrangement.

So the engine was entirely built around a very specific cylinder design?

 

[Shortround6]

Wait, there were actual contractors which wanted this? I thought it was just the USAAC. I'm curious which manufacturers (if I had to guess, Northrop/Douglas -- Northrop loved flying wings, and Douglas had owned Northrop for some period, and Martin -- the XB-16).

There is a little bit of the chicken and the egg thing going on, If the army wants buried engines do the airframe makers tell them no? Or do they make what the army seems to want?
There were all kinds of theories as to what efficient aircraft should look like in the 30s. including

So the engine was entirely built around a very specific cylinder design?

Yes.

The British engineer Harry Ricardo was one of the foremost experts on internal combustion engines right after WW I and in 1927 he published a paper stating the conventional poppet valve engines had fundamental problems and would never exceed 1500hp among other things. He turned out to be wrong about this for a number of reasons that didn't exist when he wrote the paper.
He claimed that the poppet valve had reached it's peak of development and such engines were limited in specific output as in power per cubic in of displacement. For some reason this was like waving a red flag in front of a bull to the US Army engineers and in 1930 they started a series of experiments at Wright field to prove this wrong. They were very fortunate to have S.D. Heron in their employment at the time. and a one cylinder test rig soon exceeded the limit/s claimed by Ricardo. The Army then decided to go for an engine that would develop one HP per cubic in. The engine would keep the the same 4 5/8s bore as the test engine but would shorten the stroke to 5 in from 7in to allow increased RPM. Each cylinder was 84 cu in and the total engine was 1008 cu in. The individual cylinders were decided on for several reasons, not the least of which the Army deciding to the run the engine at 300 degrees F on pure (or nearly) Ethylene glycol coolant so they could use smaller radiators. The Army does not enter into an agreement with Continental until 1932. By 1934 things are not moving as well as hoped and the army instructs Continental to use a bigger cylinder ( 5.5in bore for 118 cu in per cylinder). The army engine guys want an V-12, the army airframe guys are insisting that all future engines will be buried in the wings. The Airframe guys win the argument. By 1938 a complete engine has been built and passes a 50 hour development test in 1939. The Allison passed a 150 hour test at the same power level in 1937 and the Merlin had had passed the British type test at 1030hp in 1936. By this time fighter wings were way too thin to take an opposed engine and even bomber wings were looking iffy. The Army engine guys decide that perhaps they should go back to an upright V. The Army airframe guys decide (Based on a Visit to Germany by Charles Lindbergh) that inverted Vs are the way to go and in 1939 Continental is told to stop with the O-1430 and build an IV-1430. Which is way too late.

 

[wuzak]

Another defining characteristic of the "hyper cylinder" was 2 valves in a hemispherical chamber.

 

[Zipper730]

There is a little bit of the chicken and the egg thing going on, If the army wants buried engines do the airframe makers tell them no? Or do they make what the army seems to want?

There's also the possibility that they get ideas from what the USAAC is developing.

There were all kinds of theories as to what efficient aircraft should look like in the 30s. including
View attachment 541016

The Burnelli aircraft. What was the opinion of them at the time?

Yes.

This whole thing was an experiment right? Why didn't they work with NACA to design the cylinder; then distribute the literature to the rest of the engine manufacturers? I figure that this would improve the knowledge base in the United States engine industry.

The British engineer Harry Ricardo was one of the foremost experts on internal combustion engines right after WW I and in 1927 he published a paper stating the conventional poppet valve engines had fundamental problems and would never exceed 1500hp among other things. He turned out to be wrong about this for a number of reasons that didn't exist when he wrote the paper.

Sodium cooled poppet valves, high octane gas, and higher degree of supercharging?

He claimed that the poppet valve had reached it's peak of development and such engines were limited in specific output as in power per cubic in of displacement. For some reason this was like waving a red flag in front of a bull to the US Army engineers and in 1930 they started a series of experiments at Wright field to prove this wrong. They were very fortunate to have S.D. Heron in their employment at the time. and a one cylinder test rig soon exceeded the limit/s claimed by Ricardo.

Ironically, they proved right there, that the premise that Ricardo made was wrong.

The Army does not enter into an agreement with Continental until 1932.

Wait, two years went by between when they produced a workable cylinder and radiator, and when they contracted the contractor?

By this time fighter wings were way too thin to take an opposed engine and even bomber wings were looking iffy.

Most fighter aircraft had single-engines, and that was already an odd idea unless you had a pusher-prop. I'm not sure what the general idea was on pusher props, and if they realized that you'd be rendering bail-outs impossible.

Another defining characteristic of the "hyper cylinder" was 2 valves in a hemispherical chamber.

Wait, I thought three or four valves worked better?

 

[wuzak]

This whole thing was an experiment right? Why didn't they work with NACA to design the cylinder; then distribute the literature to the rest of the engine manufacturers? I figure that this would improve the knowledge base in the United States engine industry.

Because NACA (National Advisory Committee for Aeronautics) were aerodynamicists, not engine designers.

Sam Heron worked for the Engineering Division of US Army Materiel Command. He designed and developed the hyper cylinder. I'm not sure how widely the information was distributed, but it did not apply to the air-cooled engines of Wright* and Pratt & Whitney and was too late, probably, to influence the Allison V-1710, which had began development in 1928/1929.

Ironically, they proved right there, that the premise that Ricardo made was wrong.

Wait, two years went by between when they produced a workable cylinder and radiator, and when they contracted the contractor?

Harry Ricardo published his paper in 1927 and the USAAC began their experiments in 1930. So, no two years did not go by between the USAAC developing a working cylinder and letting a contract to Continental.

No irony involved.

Wait, I thought three or four valves worked better?

Considering that Heron started working with a Liberty engine, which had 2 valves per cylinder, he was probably constrained from doing anything else.

 

[Shortround6]

Heron had worked on the Wright J5 before working on the hyper-cylinder. He also (as I mention in the other thread) was a principle in the design of the R.A.F. 8 14 cylinder two row radial in 1916 that was developed post war into the AS Jaguar and 1/2 a Jaguar (one row) was an AS Lynx that saw about 6000 made for trainers between the wars.

 

[Zipper730]

Because NACA (National Advisory Committee for Aeronautics) were aerodynamicists, not engine designers.

I thought they did some research with engines...

Sam Heron worked for the Engineering Division of US Army Materiel Command. He designed and developed the hyper cylinder. I'm not sure how widely the information was distributed, but it did not apply to the air-cooled engines of Wright and Pratt & Whitney and was too late, probably, to influence the Allison V-1710, which had began development in 1928/1929.

Wait a second, didn't Pratt & Whitney and Wright have some inline engines?

As for the X-1800/H-2240/H-2600, and H-3130/3730, I'm not sure when those designs started, but the 3130/3730 seemed to come before the X-1800/2240/2600 from what I recall (which is odd, I'd figure the biggest would come last).

Harry Ricardo published his paper in 1927 and the USAAC began their experiments in 1930. So, no two years did not go by between the USAAC developing a working cylinder and letting a contract to Continental.

How much time would have been shaved off the design if they simply continued with a V-cylinder?

 

[wuzak]

I thought they did some research with engines...

Possibly, but I am unsure that they did.

They certainly tested engine and propeller installations to compare drag.

Wait a second, didn't Pratt & Whitney and Wright have some inline engines?

Well, yes.

The Pratt & Whitney X-1800 was inspired by the Napier Sabre. The X-1800 and XH-2600 are the same engine, and it came first.

The Wright R-2160 had similar cylinders to the "hyper" cylinder, in that they were 2 valves per cylinder OHC, but they were smaller and based on their air cooled cylinder.

How much time would have been shaved off the design if they simply continued with a V-cylinder?

Since Continental did not build a full flat 12, instead starting with the IV-1430 in 1938, I'd suggest no time would have been saved.

For the time before they built the IV-1430, Continental were testing the cylinder, which could work in a flat or vee engine.

 

[Jugman]

There was two 3130 projects. The first one was originally an air cooled "x" for the Navy that was converted to liquid cooling early in its development. This project started about the same time as the Double Wasp. It was abandoned shortly after the H-2600 project was started in favor of a scaled up H-2600.

NACA did plenty of work on engines. Muchof it related to fuels, spark plugs, cooling, etc.

 

[Zipper730]

Possibly, but I am unsure that they did.

That's a surprise

Well, yes.

The Pratt & Whitney X-1800 was inspired by the Napier Sabre. The X-1800 and XH-2600 are the same engine, and it came first.

Why didn't that design get built? Was there something wrong with it, or it just wasn't ready in time?

The Wright R-2160 had similar cylinders to the "hyper" cylinder, in that they were 2 valves per cylinder OHC, but they were smaller and based on their air cooled cylinder.

That I never knew, but it does seem to indicate that the literature was spread throughout the contractors to some extent...

Since Continental did not build a full flat 12, instead starting with the IV-1430 in 1938, I'd suggest no time would have been saved.

Wouldn't the USAAC have had to avoid re-drawing everything? I figure that would have saved some time -- not sure how much, but...

For the time before they built the IV-1430, Continental were testing the cylinder, which could work in a flat or vee engine.

Didn't know that...

 

[swampyankee]

Why didn't the X-2600 get built?

A little project called the Double Wasp. Hard to argue with the decision.