There have been a couple posts recently about how to calculate a spreader constant. One of these posts was by justbad7. He contacted me by email to see if I could help him with his problem and I don't have any experience with an air flow-spinner only here. He has an air flow bed that has two floor chains. The two chains allow for half width spreading. Each chain has a separate drive motor and encoder. This is being controlled with a Raven 661 that I think has an external switch that is a three position switch, Left Off, a center position and Right Off. I am assuming the center position is both ON. One of the encoders has a damaged harness. I told him I doubt it will work correctly until that is repaired or replaced. How does the 661 control these seemingly two separate systems? I can understand how it might work when only one side is running but when both are running does it just read one encoder and then assumes the other side is identical? Does an air flow bed have an adjustable gate like a dry spreader or is the opening fixed? Thanks for any help.