The motor should be at the top of the belt so it pulls the belt and not drags the belt like you have but also like to say an amazing build and effort well done mate just turn the motor around and you will have it nailed, I work on conveyor belts and screens for a living and that's where the motors are always located up the top rather then the bottom and i one day asked the fitter why isn't the motor down the bottom and said to me that pulling is easier the dragging, all the best mate hope this works better for you
Working on mine now....parts printed...waiting on motors and variable switch....any stl for the convayer belt? I'll post pics when done....thanks so much for the trommel files....they are awsome!!