Inverted aero engines

[Kevin Johnson]

...
I read that one bank had a CR of 7.5 and the other 7.3, I wonder what that was for?

https://ww2aircraft.net/forum/threads/d ... st-1053920

[hoodeng]

Rolls Royce were of the opinion rearward facing exhaust stubs were a boost for aircraft speed and opted to boost the engine via crank driven centrifugal superchargers, the last versions for the V1640 being two speed two stage units controlled by barometric pressure.
The Allison V1710 on the other hand went down the path of using the exhaust to power a turbocharger and gain additional boost that way , this system was self regulating in a way for boost as the reduction in atmospheric pressure as altitude gained reduced pressure on the turbine outlet allowing for higher turbine speed.They even had a crack at turbo compounding the 1710 close to the wars end.

Cheers.

[Kevin Johnson]

...
For radial engines, it's usually "plugs off" for the bottom cylinders before attempting the start, otherwise the whole thing may hyrdolock and bend a rod.

Yes, you are correct:

https://haa-uk.aero/document/engine-hydraulic-locking/

[Truckedup]

Rolls Royce were of the opinion rearward facing exhaust stubs were a boost for aircraft speed and opted to boost the engine via crank driven centrifugal superchargers, the last versions for the V1640 being two speed two stage units controlled by barometric pressure.
The Allison V1710 on the other hand went down the path of using the exhaust to power a turbocharger and gain additional boost that way , this system was self regulating in a way for boost as the reduction in atmospheric pressure as altitude gained reduced pressure on the turbine outlet allowing for higher turbine speed.They even had a crack at turbo compounding the 1710 close to the wars end.

Cheers.

It was not Allison's choice to use turbo supercharging, the US military was dictating requirements for engine and airframe manufacturers. The Allison was a great engine but the turbo models suffered from boost control problem...Mostly over boosting and detonation.A pilot in the heat of combat didn't have time to fiddle with sensitive boost controls.The problems with the turbo Allisons in the p-38 caused the US to replace many with the new P51..All US four engine bombers had radial engines with dual stage supercharging, mechanical blower and turbo..Boost control was not a problem for bomber engines running at a steady speed and controlled by a co pilot or flight engineer. I don't believe any other Allied or Axis planes use turbo charging other than a few limited situations.

[mk e]

Kind of unrelated but a good story. My great uncle who just died a couple years ago at 110 once told me about airplane engine superchargers. There was a huge push to make more hp in the bombers so they could fly higher and faster with more bombs and guns and armor....supercharging at ever increasing boost was the solution.

Designing new superchargers and getting them to fit the plane takes time ....spinning the existing supercharger faster doesn't so that's what they did. Out in the field they found the impeller couldn't really handle the rpm reliably...many were fine but any flaw and the impeller would explode and often kill the copilot. The pilot was fine because the engine deflected the explosion due to the supercharger mounting location, but they were losing copilots. They couldn't turn the boost down, and couldn't find a way to fix the impeller, at least not quickly.....so right side engines got at 1/2" thick blast shield over the supercharger so when they exploded the copilot would live.

War is about what can be done TODAY and preferably done with what you already have which leads to things that look confusing 80 years later once the people involved are gone and the explanation lost.

[Ron E]

110?! Wow. Your uncle had quite a run.

[mekilljoydammit]

Rolls Royce were of the opinion rearward facing exhaust stubs were a boost for aircraft speed and opted to boost the engine via crank driven centrifugal superchargers, the last versions for the V1640 being two speed two stage units controlled by barometric pressure.
The Allison V1710 on the other hand went down the path of using the exhaust to power a turbocharger and gain additional boost that way , this system was self regulating in a way for boost as the reduction in atmospheric pressure as altitude gained reduced pressure on the turbine outlet allowing for higher turbine speed.They even had a crack at turbo compounding the 1710 close to the wars end.

Cheers.

It was not Allison's choice to use turbo supercharging, the US military was dictating requirements for engine and airframe manufacturers. The Allison was a great engine but the turbo models suffered from boost control problem...Mostly over boosting and detonation.A pilot in the heat of combat didn't have time to fiddle with sensitive boost controls.The problems with the turbo Allisons in the p-38 caused the US to replace many with the new P51..All US four engine bombers had radial engines with dual stage supercharging, mechanical blower and turbo..Boost control was not a problem for bomber engines running at a steady speed and controlled by a co pilot or flight engineer. I don't believe any other Allied or Axis planes use turbo charging other than a few limited situations.

I note the P-47 was also turbo plus supercharged like the 4-engine bombers.

[Truckedup]

I note the P-47 was also turbo plus supercharged like the 4-engine bombers.

Yes and it's R28000 didn't have the over boost issues like the Allisons in the P38... Part of that is the radials ran less boost, maybe half that of liquid cooled engines. Arguably, the P&W R2800 was the best piston engine of the war.
The P-38 also had mechanical and turbo supercharging..

[peejay]

The think the exhaust valves were forced open during the time when the plane was standing with the models that had exhaust ports in the V.

Due to superior engineering, the axis planes were better than allied planes, in all respects bar one: production numbers.

That's not what I'd read about the Me109. It's been a while, but from what I remember Allied pilots bitching about when they got to sample them, the controls got really heavy at higher speeds, they had a variable prop but it was manually adjusted so you had to keep your head in the cockpit so to speak, and they had a laughably small range. Under an hour of flight time. (The low range did mesh well with the doctrine of shooting down Allied bombers over German soil for civilian morale reasons. Not a good way to win a war though)

The Zero was a fine plane in the 1930s. Unfortunately for Japan, they didn't really move past that.

In both cases, a concentrated effort on destroying manufacturing infrastructure helped stifle innovation. Lack of available resources, especially oil, did the rest.

I don’t think there was a better plane on the allied side than Messerschmidt ME-262. That plane obsoleted all propeller fighters.

Once the Americans (including head of technical staff at Boeing) saw the German research materials on airplanes in 1945, including the experimental data from a supersonic wind tunnel and the equations explaining the data, they telegraphed home “Stop the design!” That’s how B-47 Stratojet become to exist.

The German wing design of B-47 survived to B-52. B-52 might end up being in service until 2050.

Americans perfected the radar and radar targeting system, the proximity fuse, and the atomic bomb, so I’m just talking about planes here, not overall technological superiority. Those three technologies really moved the needle on the Pacific.

I'm not discrediting any of that. After all, the US did "paperclip" a whole lot of German engineers during and after the war.


The aircraft as actually produced, however, were lacking. In no small part thanks to a concentrated effort in destroying them on the ground or in the factories before they had a chance to be produced. Allied pilots gained a large respect for the Luftwaffe's pilots for their skill in combat DESPITE the sh** they had to fly into battle.

[hoodeng]

The picture is of what a pilot or flight engineer could observe at the exhaust ejectors on a V1710 .

During the war RAF pilots were encouraged to " Reduce the revs and boost the boost and you will have enough petrol to get home to roost" i believe this instruction was also given to pilots with P&W powered aircraft.

Cheers.

[peejay]

The picture is of what a pilot or flight engineer could observe at the exhaust ejectors on a V1710 .

During the war RAF pilots were encouraged to " Reduce the revs and boost the boost and you will have enough petrol to get home to roost" i believe this instruction was also given to pilots with P&W powered aircraft.

Cheers.

Supposedly, Charles Lindbergh inspired this... he flew combat missions and people thought he was sandbagging because he'd always come back to base with a lot more fuel than everyone else. It's because he was running lower RPM and more pressure, this resulted in better fuel economy.

Notice that the modern trend is to smaller engines that need boost practically to maintain speed? This is not an accident.

[Krooser]

It didn't matter what type of advanced aircraft were created by the Axis....Prolonged war with the 1940's USA was futile do to seemingly unlimited resources and production with little fear of attack of our factories. By 1945 there were 1000 plane raids made up of US and UK bombers protected by several thousand fighter planes. 3 million gallons of high octane gasoline for such a raid transported from the USA to Europe by a 1000's of US built ships...And the course the atomic bomb and the B29 to deliver it ,and the original target was Germany...
The logistics of managing such a campaign are mind boggling...

It wasn’t even close once the US started a full industrial mobilization of the economy for the war. Not only did the US build 1.25 million tons of shipping capacity per month but also configured it such that in 1943 convoys were equipped with escorts that had sonar, radar, and a small air wing.

To get an idea of the massive shipping done by US ship convoys... The Nazi U boats sunk at least 1000 us cargo ships.Yet at the worst, it was about 7 percent of the total shipping...Meaning 93% got to their destination....That was considered acceptable by WW2 standards...The US lost something like 70,000 aircraft to accidents and combat..More than any other combatant other than the Soviets..The US just built more airplanes...After the Normandy invasion in 1944, the US supply lines stretched up to 300 miles , 10,000 GMC 2-1/2 ton trucks literally bumper to bumper and covered by an aluminum overcast of 1000's of P47 fighters....

My Dad was an armed guard aboard the cargo ships headed to Murmansk Russia early 1942 iirc. He told me on his first trip he was given a .45 and an M1 to defend against the U boats. Later 5" deck guns were mounted on cargo ships but, due to a lack of gun barrels, the gun mounts held wooden " telephone poles" rather than barrels.

He was told to point them at the U boats.... early German subs needed to surface to fire torpedoes as I recall.

[peejay]

It wasn’t even close once the US started a full industrial mobilization of the economy for the war. Not only did the US build 1.25 million tons of shipping capacity per month but also configured it such that in 1943 convoys were equipped with escorts that had sonar, radar, and a small air wing.

To get an idea of the massive shipping done by US ship convoys... The Nazi U boats sunk at least 1000 us cargo ships.Yet at the worst, it was about 7 percent of the total shipping...Meaning 93% got to their destination....That was considered acceptable by WW2 standards...The US lost something like 70,000 aircraft to accidents and combat..More than any other combatant other than the Soviets..The US just built more airplanes...After the Normandy invasion in 1944, the US supply lines stretched up to 300 miles , 10,000 GMC 2-1/2 ton trucks literally bumper to bumper and covered by an aluminum overcast of 1000's of P47 fighters....

My Dad was an armed guard aboard the cargo ships headed to Murmansk Russia early 1942 iirc. He told me on his first trip he was given a .45 and an M1 to defend against the U boats. Later 5" deck guns were mounted on cargo ships but, due to a lack of gun barrels, the gun mounts held wooden " telephone poles" rather than barrels.

He was told to point them at the U boats.... early German subs needed to surface to fire torpedoes as I recall.

Scary shit!

I understand that most Liberty ships were lost not to German torpedoes but to poor metallurgy. The cheap steel we built them with would go brittle in the North Atlantic and ships would just split in half and sink. The ones that survived would have feet-wide splits in them, and no doubt a full complement of browned uniforms!

When you can put enough industrial might into them that you can go from laying the keel to launching a loaded ship in four days, some amount of losses are acceptable. As for the people... well... war is hell

[ptuomov]

I don’t think there was a better plane on the allied side than Messerschmidt ME-262. That plane obsoleted all propeller fighters.

Certainly a much higher performance aircraft but needed a lot more development to be any threat to the outcome of WW2 even had it been available in large numbers. Biggest issue was maintenance intervals and service life of the jet engines.

I agree that it wasn’t the end of jet development, but it did have a 4:1 aerial combat kill ratio while fighting against vastly superior numbers. The allied air forces had to destroy those planes on the ground.

Of course no single weapons system had any potential to change the outcome of the war, after the US joined.

[rfoll]

A word here about productivity. I heard a story about the German tanks. Marvels of engineering, but difficult to produce in quantity. The Russians statistics were that a tank an average of 11 minutes in combat, so rather than use complicated roller bearing assemblies in the wheels, they made due with bushings and the like.