Admiral Beez
Major
What about diesel radials? The tech in that field has changed a lot since the 1940s.
Large Radial Engines Were About As Good As Can Be?
- Thread starter kitplane01
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Shortround6
Major General
True but in the 1960s and 70s standard car engines were using cast iron crankshafts and cast iron rods. The high performance engines got forged crankshafts and forged rods. However non bearing surfaces may still have been left rough. Aircraft engine cranks were machined from forged billets. Aircraft cranks and rods were machined and polished all over.
Materials have gotten a lot better, heat treatment has gotten better (an often over looked manufacturing process) but let's remember that aircraft cranks and rods were routinely magnafluxed during inspection and it took quite awhile for even custom built hot rod engines to get that kind of treatment/care. Allison cranks after early 1942 were both shot peened and nitrided, how long did it take for those treatments to show up in car engines?
Radial engine build practices are seldom discussed in books but the V-12 parts in both the Allison and Merlin were pretty carefully matched for weight, please examine that as percentage of weight rather than an absolute limit in grams or ounces. Set of 2 pistons and rods for an Allison or Melrn are going to be way heavier than any car engine.
I can't imagine that the Radials were thrown together with any less care when you had over 1000 hp acting on one crankpin.
Post war (out of bounds for the original premise) R-2800C series commercial engines were good for 2400hp wet for take-off and weighed just under 2400lbs. about 2050-2100hp dry and max continuous of 1800hp at 6000-8500ft depending on exact engine.
As another note one of the post war R-2800s (the CB series?) used pistons with relocated wrist pins and longer connecting rods to reduce the side loads. This was discovered and used by hot rodders/high performance engine builders when?
I will say it again, improvements can be made, but high performance aircraft engines in and just after WW II were decades apart from car engine practices of the time.
It seems like the modern Ford 5 liter engines (and close) go about 411-430lbs dry weight? depends if the flywheel is counted or not? The aircraft engines have reduction gear assembly included in their dry weight and that could be around 200lbs?
AMCKen
Senior Airman
Don't forget that the rating method changed between 1971 and 1972. That meant an automatic drop of about 25% in the horsepower numbers, even if the actual usable power didn't change. Then they added leaner fuel mixtures and restrictive exhausts that wouldn't apply to aircraft engines.
davparlr
Senior Master Sergeant
Well, I'm not an engine man ala Shortround6 and others but I have a few comments
1. I think a tremendous amount of study was done during WWII in all sorts of science, eg, hydrodynamic wave theory was advanced to support amphibious landings. I am sure aviation piston engine performance studies were intense, not so much after the war.
2. As Shortround6 stated, the automobile engine operations is quite a bit of difference compared to aircraft engines and marine engines. Most automobile engines pull close to idle power/torque most of the times. My G70 runs at around 1700 rpm at 70 mph, whereas aircraft and marine engine constantly pulls lots of torque on normal operations. A corvette lemans race engine only pulls about 1.5 hp/sqin. whereas my 365 hp 3.3T generates 1.8 hp/sqin, and a 2.0T G70 generate 2.1 hp/sqin. Endurance at torque is an important requirement for aircraft and marine, not so much for automobiles.
3. So, while I do think improvements in various superchargers, material, synthetic oil (?), seals, maybe manufacturing process, etc. would improve performance of aircraft engines, I don't think by a lot.
4. Side comment, we went to the moon using slide rules.
1. I think a tremendous amount of study was done during WWII in all sorts of science, eg, hydrodynamic wave theory was advanced to support amphibious landings. I am sure aviation piston engine performance studies were intense, not so much after the war.
2. As Shortround6 stated, the automobile engine operations is quite a bit of difference compared to aircraft engines and marine engines. Most automobile engines pull close to idle power/torque most of the times. My G70 runs at around 1700 rpm at 70 mph, whereas aircraft and marine engine constantly pulls lots of torque on normal operations. A corvette lemans race engine only pulls about 1.5 hp/sqin. whereas my 365 hp 3.3T generates 1.8 hp/sqin, and a 2.0T G70 generate 2.1 hp/sqin. Endurance at torque is an important requirement for aircraft and marine, not so much for automobiles.
3. So, while I do think improvements in various superchargers, material, synthetic oil (?), seals, maybe manufacturing process, etc. would improve performance of aircraft engines, I don't think by a lot.
4. Side comment, we went to the moon using slide rules.
- Thread starter
- #25
kitplane01
Airman 1st Class
- 135
- Apr 23, 2020
Hard to imagine that ever being reliable enough for useful service.
Weirdest part .. water cooled radial.
- Thread starter
- #26
kitplane01
Airman 1st Class
- 135
- Apr 23, 2020
I was under the impression that 1 pound per horsepower was about as good a gasoline engines got, especially without electronics. That's about the R-1830 and the R2800C you describe.
Any clue if the R2800C was more fuel efficient, or required less maintenance, etc???
Shortround6
Major General
The war time "C"s had better finning than the "b"s and could make the same power with 10% less cooling airflow for less drag, OR make more power and still stay cool.
Another difference between the big radials and modern liquid cooled car engines, You have to get enough airflow through the cooling fins (anything over 3/16ths of inch 4.75mm away from the fins doesn't do any cooling), If you are going to make high power for more than few seconds you have to be able to keep the engine from overheating.
some of the shrouds/baffles have been removed. Maybe with modern materials and machining processes you can make deeper fins and fins closer together?
They knew how to make power, the problem was keeping the engine from wrecking itself. Remember, 2400hp for 5 minutes, not 15 seconds.
FAA (commercial ratings)
https://rgl.faa.gov/Regulatory_and_...0f9435e20432008525676a006759e7/$FILE/5E-8.pdf
Another difference between the big radials and modern liquid cooled car engines, You have to get enough airflow through the cooling fins (anything over 3/16ths of inch 4.75mm away from the fins doesn't do any cooling), If you are going to make high power for more than few seconds you have to be able to keep the engine from overheating.
some of the shrouds/baffles have been removed. Maybe with modern materials and machining processes you can make deeper fins and fins closer together?
They knew how to make power, the problem was keeping the engine from wrecking itself. Remember, 2400hp for 5 minutes, not 15 seconds.
FAA (commercial ratings)
https://rgl.faa.gov/Regulatory_and_...0f9435e20432008525676a006759e7/$FILE/5E-8.pdf
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wuzak
Captain
The Merlin 66 was rated at 2,000hp from 1,650 cubic inches, the Packard Merlin V-1650-9 was rated at 2,200hp with ADI and the Merlin RM.17SM was rated at 2,200hp without ADI and cleared for flight at 2,400hp.
EDIT: With ADI, 3,150rpm, extra TEL in the fuel and +36psi boost the RM.17SM managed 2,600hp.
swampyankee
Chief Master Sergeant
- 4,030
- Jun 25, 2013
Salmson made quite a few liquid-cooled radials between the wars. So did, on a much larger scale, Nordberg. The Soviet M-503 diesel (42 cylinders) was also liquid-cooled. Liquid-cooled aircraft radials (neither the Nordberg diesels nor the Zvezda M-503 are aircraft engines by any stretch of the imagination!) are uncommon because there's comparably less benefit for liquid-cooling a radial than an in-line.
chris mcmillin
Airman
The OP asks were air cooled radials about as good as they could've been, I say yes with qualifier.
After the war the P&W and Wright companies evolved their best most useful engines to airline/commercial abilities. This was a big step in power, operating envelope, and reliability.
In my career I operated the R-2600, R-1830 and R-985. We ran them all on 100/130 until it no longer was available, then 100LL.
2600 ran pretty long, about 1000 hours before overhaul usually indicated by reduction of indicated operating oil pressure and/or torque measured by 30"hg turning a certain rpm.
1830 was a great engine that would kill itself by losing a cylinder by dropping a valve or something and bending a rod necessitating a bottom end teardown. The Engine With The Glass Rods.
985 ran forever, max continuous was same as take off power, 1600 hour TBO for commercial ops, were running great when they pulled them off.
Okay, now in commercial and airline ops for big stuff my dad flew the Howard Super Ventura and pressurized Howard 500 with CB-17 R-2800 engines. They took off using 115/145 gas with ADI, 2500 hp, then cruised at altitude (25,000 in the 500) at 65% power and the engines ate the reduction gearbox bearing races at 200 hours.
On TWA dad flew the Connie with EA1 R-3350 engines, 115/145 gas, no ADI, reduced power flat rated take offs, 33% rated power cruise flight and they were pulled at 1000 hours for overhaul. His recollection was PRT fires were the usual reason for shutdown in flight and didnt damage the engine itself. At 33% power the L-1049G cruised at 270 kts true so that Connie was pretty slick.
Anyway, the engines were the top of their game, carefully overhauled they still perform the same, race power means nothing in normal ops with innocents onboard so these are real world numbers.
Interestingly, the engine Lyle Shelton set the 3Km speed record in 1989 was a hybrid 3350 with 5 years of operation when it failed in Reno 1992 due to bad avgas sold to the competitors.
The Darryl Greenamyer Bearcat in the Udvar Hazy Museum at Dulles has the same hybrid model number R-2800 engine it ran for the 1969 3Km record and flew to 2 additional wins and three placings at race power and then flew from SoCal to VA.
They were and are pretty good pieces of equipment.
Chris...
After the war the P&W and Wright companies evolved their best most useful engines to airline/commercial abilities. This was a big step in power, operating envelope, and reliability.
In my career I operated the R-2600, R-1830 and R-985. We ran them all on 100/130 until it no longer was available, then 100LL.
2600 ran pretty long, about 1000 hours before overhaul usually indicated by reduction of indicated operating oil pressure and/or torque measured by 30"hg turning a certain rpm.
1830 was a great engine that would kill itself by losing a cylinder by dropping a valve or something and bending a rod necessitating a bottom end teardown. The Engine With The Glass Rods.
985 ran forever, max continuous was same as take off power, 1600 hour TBO for commercial ops, were running great when they pulled them off.
Okay, now in commercial and airline ops for big stuff my dad flew the Howard Super Ventura and pressurized Howard 500 with CB-17 R-2800 engines. They took off using 115/145 gas with ADI, 2500 hp, then cruised at altitude (25,000 in the 500) at 65% power and the engines ate the reduction gearbox bearing races at 200 hours.
On TWA dad flew the Connie with EA1 R-3350 engines, 115/145 gas, no ADI, reduced power flat rated take offs, 33% rated power cruise flight and they were pulled at 1000 hours for overhaul. His recollection was PRT fires were the usual reason for shutdown in flight and didnt damage the engine itself. At 33% power the L-1049G cruised at 270 kts true so that Connie was pretty slick.
Anyway, the engines were the top of their game, carefully overhauled they still perform the same, race power means nothing in normal ops with innocents onboard so these are real world numbers.
Interestingly, the engine Lyle Shelton set the 3Km speed record in 1989 was a hybrid 3350 with 5 years of operation when it failed in Reno 1992 due to bad avgas sold to the competitors.
The Darryl Greenamyer Bearcat in the Udvar Hazy Museum at Dulles has the same hybrid model number R-2800 engine it ran for the 1969 3Km record and flew to 2 additional wins and three placings at race power and then flew from SoCal to VA.
They were and are pretty good pieces of equipment.
Chris...
wuzak
Captain
Pratt & Whitney developed the R-2060 "Yellow Jacket" liquid cooled radial in the early 1930s, before cancelling it to concentrate on air-cooled radials.
Wright developed the liquid cooled R-2360 Tornado, with 7 banks of 6 cylinders.
The BMW 803 was a liquid cooled 28 cylinder engine.
Wright developed the liquid cooled R-2360 Tornado, with 7 banks of 6 cylinders.
The BMW 803 was a liquid cooled 28 cylinder engine.
wuzak
Captain
The Jumo 222 may also be considered a 6 bank radial engine.
- Thread starter
- #33
kitplane01
Airman 1st Class
- 135
- Apr 23, 2020
What did they weigh if you include radiators and coolant and such?
I had no idea one could get 2,400/2,600 horepower from a Merlin. Don't tell the Spitfires-rule-the-world crowd.
- Thread starter
- #34
kitplane01
Airman 1st Class
- 135
- Apr 23, 2020
That's an argument that there were impressive, not that they were the best they can be. In fact, PRT fires and glass rods sound lake areas of possible improvement.
wuzak
Captain
About 2,000lb.
I had no idea one could get 2,400/2,600 horepower from a Merlin. Don't tell the Spitfires-rule-the-world crowd.
2,600hp was a test bench number, 2,400hp was cleared for use in flight testing, but it did not pass the type test at that rating.
The RM.17SM did not go into production and did not receive a mark number, though it was under test in 1944.
Probably ok on reliability, servicing time probably an issue it just has more of everything., there was a guy who posted here whose dad worked on it. The Napier Sabre and RR Eagle had 24 water cooled cylinders.
Builder 2010
Staff Sergeant
You can get 10,000 hp out of a automotive style V8 engine with mechanical supercharging and injection. It's the kind of engine that top fuel dragsters are using. All that said, the engine runs about 2 minutes total time, the race takes a little more than 3 seconds plus the startup and tire heating period. By the end of the 3 seconds, the spark plug tips burn off and the engine is running on compression ignition. Furthermore, it's not uncommon for one or more cylinders to be dead, with pistons possibly burned through. In other words, you can get fabulous amounts of power out of an engine that is only to live for a couple of minutes. Between races the entire upper end of these engines are rebuilt.
Peter Gunn
Master Sergeant
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