The motor will rotate continuously, the tilt being done by a cam or pin that raises the rocker arm once a revolution. You don't say what height the 3.4 kg is raised to. My physics is 50 years old, so lets raise 3.4 kg through 1 cm = 3.3 n/m , do this every 2 seconds (30 RPM) = 1.5W, allow a lot for the resistance of the cam, call it a 5W motor! The real problem is that it has to be a "universal" motor fed via a "light dimmer" and a big gearbox reduction, say fro 2800 to 30, i..e. 90 :1. A sewing machine motor + gear box would be a good home brew solution.
Frank