1930-1945: alternative engines for military purposes (5 Viewers)

[swampyankee]

Their 'small' V12s were compact and reliable engines, but there the benefits really stop. Something that is V6 sibling of a 30-35L V12* would've gotten them compactness and reliability, too, but also lower price and time to make the engines and gearboxes, easier maintenance in the field, and will require the shorter engine bay.

* Germans were thinking about the heavy tanks much before they gotten into that in reality, that a big V12 should be powering.



The French were designing and making heavy tanks in the 1920s and 30s. Them opting for V12s for these tanks, with en eye for V8 and/or V6 versions for the smaller tanks might've been both economicaly and military prudent.
Also - their heavy tanks were big and boxy. A good radial engine would not be too much for the hull to house these.


An inline 6 would've been an ideal engine if the tank has the 'Merkava' layout - engine sits besides the driver, front sprocket driving the tracks. While not common on tanks of the day, it was not unheard of - Vickers light tanks had that, so did a lot of Soviet light tanks, and so did the Elefant (but with the electric 'transmission'). Frees a hefty % of the hull length and volume, and the tank can be repurposed into a SP chassis in an elegant fashion.

Another way of making the engine+transmission bay a good deal shorter was to have the engine being installed in the transversal position. That 'trick' was done on the T-43 tank, making the tank much roomier. An inline 6 installed in such a fashion would've netted even greater benefits vs. the longitudinal installation.

Every configuration has its issues, and packaging is a worse problem for AFV than small weight increases.

Looking at 1930s technology levels, I think some options are unlikely, like Hyperbar engines or extreme levels of supercharging, as in MTU's modern tank engines.

Some possibilities:
Two stroke spark ignition engines. These would require direct fuel injection to be reasonably efficient, and that technology was bleading edge. Obviously, crankcase scavenging is out. Roots blower or stepped piston would be easiest, but a Lysholm compressor would likely be better. Schneurle porting would likely be best, as uniflow designs require valve gear, opposed piston, or split-single configuration. The last has been used in cars and motorcycles, that is small engines with up to about 4 cylinders. OP spark engines were uncommon but not unknown.

 

[tomo pauk]

Two stroke spark ignition engines. These would require direct fuel injection to be reasonably efficient, and that technology was bleading edge. Obviously, crankcase scavenging is out. Roots blower or stepped piston would be easiest, but a Lysholm compressor would likely be better. Schneurle porting would likely be best, as uniflow designs require valve gear, opposed piston, or split-single configuration. The last has been used in cars and motorcycles, that is small engines with up to about 4 cylinders. OP spark engines were uncommon but not unknown.

Not too bad idea for an aircraft engine, too...