[chickenman]

I made a crank from a 1" cold rolled rod welded to a 3/4" bolt with head cut off offset to one side mounted in 2 1" pillow block bearings

then mounted the pitman arm in the sketch to crank and to bolt welded to angle welded under screen frame

a v belt pully on shaft and engine or motor and your in business

the chain and bungee cord are to stabalize pitman arm
an eye will have to be kept on bungee, you may want to have a spare handy