Correct. Note that the 3rd axle wheel sets also have thinner flanges than the others.
I think this will answer your question. The inside cylinder drives a crank axle on No. 2 position, while the mini-crankaxle can be seen on the 3rd...
Don't forget that the 3rd coupled axle is also a cranked one (taking the place of an eccentric) to drive the inside Walschaerts/Heusinger valve...
Not forgetting that it has provided jobs for quite a few people.
Cab view of an LNER 6-cylinder engined Sentinel railcar. Note the 3-mm hot water injector at bottom left. [ATTACH]
Dents? Honourable battle scars.
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