Warbird Information Exchange

I have been trying to find out for months why the germans always installed their V-12 engines inverted. I have a few ideas, but none of them really make sense. The spanish 109 has a merlin right side up, so thrust lines and room for the guns don't add up. On the Fw-190 D9 series, the engine is on the fuselage centerline, so what difference would it make, other than lowering the center of mass to change cg on the fuselage??? Also the Me-110 and JU-88 have inverted V's so cockpit visibility is also out. If it was a better way to install them inverted why didn't the Brittish or the Americans ever install one inverted?? Does anyone have a definate answer?? Thanks!!

First, they were all installed correctly, right side up. The engine was designed as an "inverted" engine. The installation is conventional.


From Wikipedia "Certain types of V engine have been built as inverted engines, most commonly for aircraft. Advantages include better visibility in a single-engined airplane, and lower centre of gravity. Examples include World War II German engines produced by Daimler-Benz and Jumo."

There really is no real way to determine what actually set the manufacturer in motion regarding inverted engines without a really detailed look at the processes they had at their disposal for manufacturing. The DB was no better or worse configuration wise than the Merlin, and the difference is truly cosmetic when it comes to configuration. The upright 12 has no advantage over an inverted one based on physical limitations, it s simply different. The early DB's had roller bearings on the connecting rods, perhaps as Herschel Green stated in his book, for the simple reason that they did not trust their plain bearings quality of manufacture.

The only engines that had "poor" or somewhat difficult configurations were probably from Napier....or Bristol.

They didn't really install them inverted, they installed an inverted engine. There is a difference. The engine was designed from the outset to be that way up.

With a single engined fighter, it improves visibility over the nose, and probably helps a bit with a twin too. I gather the prop-hub cannon doesn't work with a "right way up" engine but I've never thought about why, unless there wouldn't be anywhere to mount it.

It was considered in early thoughts for the Merlin but the UK aircraft designers didn't like the idea. There's a photograph around of a full-scale mock-up of an inverted Merlin. A party of visiting Germans saw it and it's been suggested that's why the German engines were inverted. Personally, I think German engineers of that era were more than capable of coming up with it on their own.

Edit: must type quicker.

In the 109 the cannon is between the pilot's feet. With a higher thrust line the butt of the cannon would be in the middle of the instrument panel. I believe that Messerschmitt also liked the inverted triangle fuselage shape because with a low winged aircraft it had a natural filleting effect. As has been mentioned, visibility is improved with a narrower cowling, but I wonder what was lost with the large gun blisters on the upper cowl and the huge side air intake on the later 109 models.

If you look at some of the prewar designs, everything from the aircooled Argus in the Storch to some 1930s diesels, the Germans seemed to have an affinity for inverted vee designs. With a dry sump engine design there really is no disadvantage to an inverted engine. Ranger built a number of inverted engines including an aircooled V-12, the V770.


http://www.airvictorymuseum.org/html/ra ... 70-11.html

Cannon location is better without all the fussy intake pipes in the way (as was the later M.G. installations) look at the cannon installation on the P-39/63, where the cannon barrel went out thru a hole in the reduction gearbox for the prop, also could have been Willys stab at fashionable styling since about every other airplane built in that time frame had twin verticals as they must have been 'the style' OR...'das ist der vay ve vants it dood' from the RLM.

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The cannon went right thru the center of the engine. Positioned at the top of the inverted "V", below the crank case and above the intake manifold and out the nose case.

In photo 3, the square flat plate with 4 bolts (just below starter/generator) is where the cannon went thru.

A drawback to the nose cannon was the supercharger had to be mounted on the side of the engine, rather than the back as is more common.

We all know the German penchant for refining rather than starting anew...remember Mercedes auto ads but a decade ago? They were quite proud of the fact that it took an expert to tell one year from another. They despise the Detroit mentality of "fresh design every 3 years". Well before the Germans were using cannon and aluminum airframes, they were using inverted design. There are thousands of reasons for mounting the engine heads up or down. Likely a very important reason engine designs are the way they are is the groundwork that was laid years before. The DB600 series dates back to biplane applications. But it was a sound design that showed promise from further refinement....carburetors were discarded for injection, various blowers allowed higher altitude performance etc. They had a few good designs that demonstrated their potential and they simply refined the design.
Many of the systems can be dealt with....induction pipes in the way of a cannon? Well, look at that Ranger pic....the exhaust is in the vee and the induction is outboard. That design would be real easy to turbo with all the exhaust in the center and aligned. So too, could a, say DB600, have the induction moved out board as it is OHC there is no issue with pushrods and such...simply reverse the head. The oil scavenge of an inverted vee can get a bit complex with possibly 4 points requiring scavenge...but that too can be overcome.
The bottom line is....many of the paths designs took were continuations of earlier groundwork. This is especially true in nations that lacked resources in desparate times...it would be much easier to wring every bit of performance out of a design than to redesign, retool, and requalify anew.

I've always wondered if there were ever any problems with oil pooling in the combustion chamber when the engine was not running, leading to damage on start-up. Is this not the reason why radials are "pulled through" before start-up?

Anyways, I'm sure there is an easy answer but like I said, I've always wondered.

Also, isn't the DB601/605 supercharger run at a higher, almost-turbo-like speed than regular superchargers? Although, of course, it is shaft, not exhaust, driven.

cheers

greg v.

Yes, I've seen stills and video of the engines being pulled through before startup.



What is a "regular supercharger"? The T-6 has a 10:1 supercharger ratio so at 2,000 RPM the supercharger is turning 20,000 RPM. There is also a version of the R-1340 with a 12:1 supercharger ratio.

Great post, Wheels up, but:

Really? I think you are making a big thesis on a wobbly foundation there. The Detroit mentality seemed to be to keep the working bits (engine, suspension, fuel system etc) well past their sell by date in mutton dressed as lamb with cars that only acquired different bling each year. Of course taking undefined period car design to 1930s aircraft design's a stretch too.

There are numerous clichés about German engineering, but for industrial quality and performance they've never legged behind other leading industrial nations, and have often been ahead. Why, and what the different 'norms' might've had to do with that, I don't know, but I don't think they've ever 'just' kept an old concept going well past the sell by date. I'd suggest that was a British industry problem, but I've just been hit by a Union Jack wearing Teddy. They've not been shafted by Japanese cars or (less so) aircraft designs, unlike, say, Britain, the US and Australia.

As to The Inspector's "Willys stab at fashionable styling" - I don't buy that - ruthless form follows function would be a good summary of his attitude.

However, aircraft designers have to use the engine available, and engine designers need aircraft designers and ministries to tell them what is going to be needed in five years - a tough call in the 30s and 40s. If you broaden your type lists to include say Russian, Italian and French configurations, engines and design principles, it's a lot more varied.

Just a few thoughts!

_________________
James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

I got it, its so they could fly upside down, then the engine is right side up.

BDK

sorry, by "regular" supercharger I was loosely referring to those installed on contemporary liquid-cooled V-12's, so in this case I guess that would be the Merlin, Griffon & Allison.

I couldn't find any online figures for the supercharger speed of the DB601/605, but as I stated earlier I was under the impression that this speed was allegedly higher than that of other contemporary (i.e. not German made) V-12's. I could guess that this may be partially based on the distinct exhaust note of the 601/605.

At any rate, is this some old wive's tale B.S. myth, or does it have some basis in reality?

Again, just curious.

cheers

greg v.