Inverted V-12

[V1670]

Question for the engine gurus out there: What are/were the advantages/disadvantages of an inverted V-12 design, specifically the Daimler-Benz DB-607? Seems like (as far as this rookie knows) the Germans were the only ones who went with this configuration while the Allies went with a standard design. Seems like it would be simpler for the propeller drive, but more complex for the lubrication system. Inquiring mind would like some feed-back. Thanks

[ArmyMP]

Re: Inverted V-12

Off the cuff and not an engine guy here. One driving factor was to mount the 30mm cannon center line with the airframe. No space in the wing for that size. It was originally designed to run inverted and worked very well. Being fuel injected had a bit to do with it as well. As far as the bombers engines were concerned in the He-111 and a few others, there was no reason to change it. The Japanese also had a license built Db (made by Kawasaki and others) in the Tony line of fighters sans cannon. The Jumo served the same purpose well for the 190 D series as well as Ta-152 variants and in some bombers. Those guys pretty much had the whole engine thing figured out from the get go. But allas...Merlins and Griffons found there way in as the Kestrel had been in the first 109.

[W J Pearce]

Re: Inverted V-12

Hello V1650,

I probably have a few things that are incorrect, but you will get the idea.

I think you mean the DB 601, 603, and 605 engines. Those were the main DB engines during WWII. The DB 607 was a diesel based on the DB 603.

The advantage of the inverted V (IV) is that the narrowest part of the V is a top, giving the pilot better visibility over the sides of the engine when compared to an upright V, which has the widest part at top. A 20 mm or 30 mm cannon did fire through the propeller hub, but Hispano-Suiza / Klimov and others did the same thing with an upright V-12. On a direct drive engine, the inverted configuration put the propeller higher on the aircraft, but that was of little consideration for the geared engines of WWII.

The IV does have a more complicated oil system with sumps being added inside the valve covers. The real disadvantage of the IV is oil accumulation in the cylinders/intake after the engine has been sitting. This is the same issue that radials have, except an IV has the issue with all if its cylinders.

Obviously, the issues of an IV engine were not too severe because DB stuck with that configuration, as did Junkers and Argus. But the Germans were not the only ones who used IVs, they just had the most prolific use. I think all the Japanese IV engines were based on German engines. This is also true with some Italian IV engines. However, the Isotta Fraschini Delta and Reggiane Re 100 series engines were independent designs (the Reggianes were inverted Ws).

Britain had the de Havilland Gypsy Twelve (King), but I cannot recall any other IV engines. Rolls-Royce had considered an IV when they started designing the PV-12, but ultimately went with an upright V. The PV-12 became the Merlin. The US had the Continental XI-1430, Chrysler XI-2220, the Ranger V-770, and some other lesser-known IV engines (Packard built inverted Liberty V-12s in the 1920s).

Some of the IV engines listed above were late to the party and were not develop beyond the test phase. It was not that they were bad, they were just redundant or obsolete by the time they were to go into production.

There is a rumor/myth that a German delegation from DB visited the Rolls-Royce factory in the early 1930s and saw drawings of the inverted PV-12 engine. And so the rumor goes, the DB 600 engine was laid out the same way. I think this has been proven to not fit the developmental timeline of the DB engine, but I cannot recall for certain.