Inverted aero engines

[Grp5L]

During WW2 German bombers and fighters were fitted with Jumo and Daimler-Benz inverted V12 engines, but the question is; why an upside down engine?
Out of interest they also has 3 and 4 valves per cylinder respectively, direct injection, stellite valve seats and sodium filled valves. Nothing's new is it...

Daimler Benz.jpg

[strokersix]

"hood" clearance I'll bet.

[tt 383]

I think I remember reading a pilots line of sight increased and frontal area being not only reduced but mass was more centered helping flight dynamics.

[lefty o]

i would imagine it was mostly done for packaging purposes. have to make one fit, and be somewhat aerodynamic.

[Scotty]

An old guy who used leyland p76 alloy v8 engines to do crop dusting told me they ran them upside down for additional prop to ground clearance. Made sense to me, he also showed me gearboxs they made up which had the advantage of raising the prop when the engine is mounted right way up.
They modifed the oil system to scavange out of the tappet covers, still ran the stock oil pump just re diverted the oil pickup as such.
They used an aircraft type of carburettor which works anyway up down ect
He did tell me he had fallen out of the sky a couple of times as well ,obviously he got away with it to tell the tales.

[Tuner]

https://en.wikipedia.org/wiki/Ranger_Engines



https://en.wikipedia.org/wiki/Ranger_L-440



https://en.wikipedia.org/wiki/Ranger_V-770

The Ranger 6 cyl. was turned upside down and used in race cars, cylinder head at the top. http://www.ewarbirds.org/automotive/1939bigcar.shtml
I recall one raced locally in about 1950 that left a trail of smoke behind it all the time. I was told it was because run upside-down from the way there were intended to be run the oil got in through the valve guides and something about their design made it difficult or near impossible to use a stem seal. The stem seals we are familiar with today didn't exist in those days.

[lefty o]

prop clearance does make sense. heck thats how the F-4 got its big gull wing, to keeps its prop out of the dirt.

[hoodeng]

One benefit of inverted engines was that it allowed for lower mounted machine guns grouped in the pilots line of sight ,so there was no need for a convergence zone required by wing mount guns, this allowed making wings thinner and lighter, also the landing gear was incorporated into the fuselage so adding another benefit to wing weight and design,the aim was to keep as much weight centered in the fuselage, the German Bf109 had this system .
But as the war dictated more fire power the guns migrated into the wings on this plane.Although other aircraft were developed throughout the war with central mounted machine guns firing in the pilots line of sight.
The Daimler DB600 that was initially installed in these planes had an interesting big end bearing arrangement there was a roller bearing that ran on the crank journal then a sleeve over that then rods running in another row of roller bearings for each rod.The layout of this engine did not change throughout the war although its capacity and performance increased considerably.It was considered a perfect engine from its outset.

Cheers.

[kimosabi]

Another key element on the upside down DB engines were the centerpiece of the ME109. A cannon mounting between the cylinder banks firing through the propeller hub. Pilots that had experienced both Spits and ME109's remarked how silent the 109 was compared to the Spits. Exhaust much lower exits.

[Circlotron]

I recall one raced locally in about 1950 that left a trail of smoke behind it all the time. I was told it was because run upside-down from the way there were intended to be run the oil got in through the valve guides and something about their design made it difficult or near impossible to use a stem seal. The stem seals we are familiar with today didn't exist in those days.

Aero engines are more likely to run continuously with low manifold vacuum or even positive pressure. This would discourage oil being drawn down through the inlet valve guide. In a car, manifold vacuum is often present, and what might have been good enough for a plane is no good for a car.

[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.

[Frankshaft]

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.

Would you have to raise the floor and lower the roof when porting?

[mk e]

Would you have to raise the floor and lower the roof when porting?

I'm pretty sure you just do what you always do, then flip the engine over, connect the breather to the oil pan and return pump to the valve covers...I'm pretty sure it was a dump setup with a pickup or 2 in each cover.

I remember him telling me he was worried about oil in the pistons and oil consumption but was very pleasantly surprised when it run fine. It was port fuel injected.

[plovett]

I think a higher thrust line is generally desired in propeller driven aircraft. An inverted engine allows you to do that without using gears to move the propeller up. It's good for simplicity and ground clearance. I think it is generally desirable to have the thrust line above the center of gravity for stability reasons, too.

JMO,

paulie

[Frankshaft]

Would you have to raise the floor and lower the roof when porting?

I'm pretty sure you just do what you always do, then flip the engine over, connect the breather to the oil pan and return pump to the valve covers...I'm pretty sure it was a dump setup with a pickup or 2 in each cover.

I remember him telling me he was worried about oil in the pistons and oil consumption but was very pleasantly surprised when it run fine. It was port fuel injected.

I was just trying to be comedic.