We at sea never got to see an engine as a whole like this and to see one under test is great. The dyno is obvious but not familiar with the counterweight system to, I assume, measure the force. I suppose they add weights on untill something balances as indicated by a pointer that the chap on the ground must be looking at, and then work out the force.
Great picture, must have been quite a sight.
I wonder how they dealt with the cooling.