making a 12v 20 amp power supply using a center tapped transformer

I found an older unregulated 12 power supply on craiglist and I want to add voltage regulation to dial down the no load voltage(22 volts per leg after being rectified and filtered). Here is the example:
After breadboarding, it doesn't seem to provide any voltage regulation and I can't adjust the voltage using the 10k pot. Have I misinterpreted the purpose of the circuit? Is there a better way to do this?

Firstly that circuit is delivering pulses of current to a battery, its making no attempt to
regulate a voltage (the battery itself does that). It varies the delivery of the pulses
dependent on the battery voltage. It won't do anything useful without a battery as load.

That said there are also many ways this circuit could go wrong, you need to first
check everything carefully. Without an oscilloscope its going to be much harder to
track down issues.