A 'proper' way to have a 24 cylinder liquid-cooled aero engine for the ww2?

GrauGeist said:

The DB610 had the individual crankshaft centerlines about as close together as you're going to get with coupled/paired engines, regardless of the configuration (positioning of the engines).

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Another factor to consider, is the size of the coupler and it's interior components needed to transfer power from the engines to the drive shaft.
In the attached photo of the DB610, you can see the size of the coupler housing in relation to the engines and it's size was relevant to the gear sets as well as drive disconnects for each engine.

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Great photo. Thank you for your thoughts. I don't know much about this engine, but is there any casting that connects the two V's other than the gear reduction drive? The concept I had was that the two crank centers would be farther apart.

I've been thinking about this thread again. Is there any apples-to-apples comparison of H, double-V, W, and X layouts with regards to frontal area? Same bore and stroke, poppet valves for all, etc.?

There were some drawings done in old text books and/or magazine articles back in the 30s. I just can't remember where at moment. Also the difference between 5cyclinder, 7 cylinder, 9 cylinder and 11 cylinder radials (yes I said text book )
constant was they were supposed to be for engines of the same power.
Vs were the best, H and X were roughly the same although the H was bit less,
As I recall the drawings were of the different engines superimposed on a 9 cylinder radial of the desired power? and percentage equivalents of frontal area
The liquid cooled engines didn't figure in the radiator.

Might have been in an old copy of Flying magazine or Airplane but they are off line now.

In discussions of the V 3420, one of the weight differences was having 2 cranks, which I think was 150 lbs.