As just stated , leverage can play a key role. The length of the bars and where the joint is connected on the tilter matters as well. If the bar is connected at the very base of the tray it will be a lot harder to push than if the bar was towards the top.
Check out these threads for more detailed info:
Tilter Physics
Optimizing Speed of Tilter with P-Loop
Tilter Simulation for Torque Calculation