Good post there, speedy.
These were the 'first generation' of chainsaws, back in the 1950s; they were 'two man' operation, as the engine had to be kept upright, due to the float type carburettor. Some models were built for sawmill use, with 3-phase electric motors, and bar lengths up to 8 feet, at least!
These petrol powered units most often had a gear drive to the chain drive sprocket, so as to allow the bar to be rotated to the horizontal plane, for falling cuts.
Tillotson's invention of the diaphragm carburettor in the 1950's was the game-changer for chainsaws; it made the one-man chainsaw a reality.
It did take a few years for really workable lightweight chainsaw models to be developed though, so the early 1960s was when the one-man saws really took off here.
