Parametric oscillation holds the key to working Bessler's wheel.

Second clue.

A swing has its centre of gravity below the pivot, unlike a perfectly balanced wheel whose centre of gravity lies at its axle or pivot.

With a child standing on the swing's seat,  the centre of gravity is lower and is closer the seat.  If the child bends his legs he lowers the centre of gravity even more and if he straightens them he raises it again.  If he rocks the swing a little he can make it move back and forth a greater distance by timing the straightening and bending of his legs

But the swing moves to and fro whereas we seek a solution in which the swing moves only in one direction, around and around the pivot. There is a sport known as ‘Kiiking’ in the native language of Estonia where it is practised as a national sport.  In kiiking the ropes are rigid steel bars, enabling the swinger to build up his swings until he passes over the top of the pivot - his feet are of course attached to the seat.

Yes, I know, another elementary clue, and yet a vital ingredient in making Bessler's wheel work.

JC