Mikulin AM-38 construction

Pasoleati

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Seems that finding construction details is very difficult on this engine. For example, what kind of cylinder liner/block construction did it have?
 
Its a bit like a cross between a V-1710 and a Merlin. Wet liners, with 2-piece block and crank-axis split crankcase. The heads
are very similar to the V-1710 in terms of valve angle and coolant system layout. In many respects, very modern
and well designed in my view.
1606935451204.png
 
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Thanks! How are the liners attached? If I remember correctly, the carburettors are between the inlet and the supercharger outlet?
 
Thanks! How are the liners attached? If I remember correctly, the carburettors are between the inlet and the supercharger outlet?
Photos a bit blurry, but it appears the liners are installed in almost exactly the same was as the 2-piece block Merlin (i.e. "sandwich" top hat) -
but, with a bit of the Allison design thrown in too as it extends UP into the chamber walls a bit like the V1710.
 
I wonder what improvements were made on the AM-42 over the AM-38? Net sources indicate the AM-42 had a very low compression ratio of 5.5:1...
 
I wonder what improvements were made on the AM-42 over the AM-38? Net sources indicate the AM-42 had a very low compression ratio of 5.5:1...
AM-42 had significatly increased boost and revolution. You can see in this table АМ-34-42 data.png
 
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I wonder what improvements were made on the AM-42 over the AM-38? Net sources indicate the AM-42 had a very low compression ratio of 5.5:1...

Better late than never, I guess :)
AM-42 featured a stronger/heavier construction where needed (mostyl crankshaft and crankcase), an improved lubrication system, while the crakshaft was with counterweights. Thus it was possible to increase RPM to 2500. Lower compression ratio allowed for increase of boost. Put together (higher RPM + higher boost), the engine was capable for extra 300 HP vs. AM-38F. However, it took a lot of time for the AM-42 to became service-worthy, Russian-language Wikipedia notes that it took about 18 months of testing and modifications for the engine to pass the 100-hour test.
(we can note that VK-107 engine, that was to power the late-war Yak fighters, was limited to 25 hr in service when introduced)
 

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