Inverted aero engines

[plovett]

I don't think radial or inverted engines needed the plugs taken out to evacuate oil prior to start? Just turn them over a few times to pump the oil into the exhaust and then make lots of smoke when it starts up?

[ptuomov]

Maybe the biggest disadvantage the Germans had in aircraft engine design was the lack of high octane gas. I'm making up numbers, but they had something in the range of 87 to 100 octane. The Americans had up to 150 octane. This allowed much higher manifold pressures. Again making up numbers, but maybe over 70" on 150 octane and a little over 40" on 90 something octane.

The Germans compensated by using larger displacements (P&W R2800 not withstanding), and using chemical charge cooling, like N2O and water/methanol mixtures. But the allies could add those to their already higher boosted engines, too.

The fuel octane is probably the biggest factor, in my opinion.

Since jet engines could use very low octane fuel, that was a game changer for them.

paulie

That’s another excellent point. Comparing the obsolete, dead-end design of B-36 that required 150 octane gas and had continuous engine problems (336 spark plugs and propellers) to B-47 stratojet makes it clear. Although during my the war, the Germans didn’t have enough jets for it to make much of a difference, andbwith piston aircraft the available fuel makes a huge difference.

[plovett]

I'm not sure about the 90 degree rotation on German blowers. Maybe to simplify and shorten intake ducting to blower? It doesn't look like it shortens the engine length. Since frontal area is so critical on fast machines maybe they are trying use the area at the top(small) part of the Vee?

JMO,

paulie

[plovett]

Maybe the biggest disadvantage the Germans had in aircraft engine design was the lack of high octane gas. I'm making up numbers, but they had something in the range of 87 to 100 octane. The Americans had up to 150 octane. This allowed much higher manifold pressures. Again making up numbers, but maybe over 70" on 150 octane and a little over 40" on 90 something octane.

The Germans compensated by using larger displacements (P&W R2800 not withstanding), and using chemical charge cooling, like N2O and water/methanol mixtures. But the allies could add those to their already higher boosted engines, too.

The fuel octane is probably the biggest factor, in my opinion.

Since jet engines could use very low octane fuel, that was a game changer for them.

paulie

That’s another excellent point. Comparing the obsolete, dead-end design of B-36 that required 150 octane gas and had continuous engine problems (336 spark plugs and propellers) to B-47 stratojet makes it clear. Although during my the war, the Germans didn’t have enough jets for it to make much of a difference, andbwith piston aircraft the available fuel makes a huge difference.

Yeah, imagine two engine builders on here building blown engines for the same use, with roughly the same design restrictions. One can only use 87 octane pump gas and the other guy can use the absolute best race gas. That's the basic situation the Germans were faced with.

JMO,

paulie

[Truckedup]

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...

[ptuomov]

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.

[Circlotron]

I don't think radial or inverted engines needed the plugs taken out to evacuate oil prior to start? Just turn them over a few times to pump the oil into the exhaust and then make lots of smoke when it starts up?

That's if the plug can still manage to fire after being covered in oil.

[Truckedup]

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....

[Kevin Johnson]

I don't think radial or inverted engines needed the plugs taken out to evacuate oil prior to start? Just turn them over a few times to pump the oil into the exhaust and then make lots of smoke when it starts up?

That's if the plug can still manage to fire after being covered in oil.

Start up of BF 109:
https://www.youtube.com/watch?v=XFry3BCf0_Y

Ask these people (owners of the above plane): https://www.facebook.com/flyingheritage/

If you read the start up procedures in the manual there is no special procedure listed for draining out oil from the plug hole. Under the fault diagnosis chart, though, they do list the symptom of deep red flames in the exhaust meaning that oil is present and that means the scavenge pump might need to be replaced.

[ptuomov]

I don't think radial or inverted engines needed the plugs taken out to evacuate oil prior to start? Just turn them over a few times to pump the oil into the exhaust and then make lots of smoke when it starts up?

That's if the plug can still manage to fire after being covered in oil.

Start up of BF 109:
https://www.youtube.com/watch?v=XFry3BCf0_Y

Ask these people (owners of the above plane): https://www.facebook.com/flyingheritage/

If you read the start up procedures in the manual there is no special procedure listed for draining out oil from the plug hole. Under the fault diagnosis chart, though, they do list the symptom of deep red flames in the exhaust meaning that oil is present and that means the scavenge pump might need to be replaced.

I think it was the Russian inverted V planes that had a procedure to force open the exhaust valves after shut-down such that excess oil would drain into the exhaust manifold? I don't recall what the German plane shutdown procedure says.

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.

[Grp5L]

Maybe the biggest disadvantage the Germans had in aircraft engine design was the lack of high octane gas. I'm making up numbers, but they had something in the range of 87 to 100 octane. The Americans had up to 150 octane. This allowed much higher manifold pressures. Again making up numbers, but maybe over 70" on 150 octane and a little over 40" on 90 something octane.

The Germans compensated by using larger displacements (P&W R2800 not withstanding), and using chemical charge cooling, like N2O and water/methanol mixtures. But the allies could add those to their already higher boosted engines, too.

The fuel octane is probably the biggest factor, in my opinion.

Since jet engines could use very low octane fuel, that was a game changer for them.

paulie

The Germans did have C3 fuels, some of the engines are marked up as using it. It's the equivalent of 150 Avgas.
I read that one bank had a CR of 7.5 and the other 7.3, I wonder what that was for?

[plovett]

Maybe the biggest disadvantage the Germans had in aircraft engine design was the lack of high octane gas. I'm making up numbers, but they had something in the range of 87 to 100 octane. The Americans had up to 150 octane. This allowed much higher manifold pressures. Again making up numbers, but maybe over 70" on 150 octane and a little over 40" on 90 something octane.

The Germans compensated by using larger displacements (P&W R2800 not withstanding), and using chemical charge cooling, like N2O and water/methanol mixtures. But the allies could add those to their already higher boosted engines, too.

The fuel octane is probably the biggest factor, in my opinion.

Since jet engines could use very low octane fuel, that was a game changer for them.

paulie

The Germans did have C3 fuels, some of the engines are marked up as using it. It's the equivalent of 150 Avgas.
I read that one bank had a CR of 7.5 and the other 7.3, I wonder what that was for?

No way, dude. Not in any significant quantity anyway....or not until the very end.

[mk e]

A guy I know designed a plane and planned to build it soon retirement. For space and weight reasons ( i think he said) the design called for an inverted engine but he was unsure about setting an engine up this way so step 1 was to build and test the engine. He went with BBC and it ran fine upside down. The rest of the plane fall victim to the great recession but last I knew he still had the engine an test stand.

My bad...it was a 406 SBC, oil pickups on both ends of both valve covers.

[gruntguru]

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.

[emsvitil]

Just how efficient are the short exhaust stakes anyway?