JoeyBones I found this schematic online just for interest sake : http://www.uoguelph.ca/~antoon/circ/ps-lm317.html
ralley Joey, Not sure if you were joking on that one. The uF is short for micro Farad. Farad being the measure of capacitance and micro the prefix meaning 10−6 (one millionth). The scheme you linked too is a bit more complicated as it uses a pot to adjust the output voltage, could be fun to simulate a dying battery though. Rob.
JoeyBones Thanks for explanation Rob. I'm sure my brother explained that too me a while back, but I forgot. About the PSu my buddy uses, he bought it from MANTEC. It is center positive, so you just have swap the cables around to change the polarity. I'm not sure if they do a center negative version.