Stuart06
Is there a power component attached to the crane chains,,,or is it just muscle power.
Hard to see in the photo, but, I'll wager some form of chain hoist was used
There's a sprocket with teeth to engage the lifting chain, this is turned via a second chain whic hoperates via some gears to give some mechanical advantage.
How much advantage is often not much. There's a ratchet that engages the lifting chain so that it does not slip back while hoisting.
That chain versions are better than the lever versions (modern version shown)
in that you can get a couple of guys on the chain if required.
The thing that really helps the guys in that photo is that the T34/76 had no turret basket (tough on those inside as you spin the turret for tripping) or they would have needed about twice as much lifing height.