output stabilization

Hi Experts, Like to know, I got 12V 4500rpm DC motor, which I'm using as Generator by manually rotating it's shafts, & connected it's output to full-wave bridge rectifier & 1000microF capacitor at output, but I'm getting fluctuating output of 1V, kindly let me know what all other...

I bought a power supply adopter (old, used, made for some device) of 24v 4.5A (from 230vac mains). It is a fixed output psu. My intention is to make it a variable psu of 30v to <=5v (as low as possible, and continuously variable). Schematic (simplified) of its error-amp circuitry is attached...