this half-seconds balance is a 3" diameter, 3/8"thick birch ring. it has small wooden pins around the perimeter. inside of each of these pins is a #8 setscrew - these can be screwed in and out to adjust the poise of the wheel (it has to be perfect).
for a "hairspring", i used a very small clockspring. i'm not sure what it came out of, but it measures 0.125" x 0.007" by 28". the inside end is epoxied to the balance shaft, and the outer end is fixed to the frame. there is a moveable anchor on a small lever - this slightly changes the effective length of the spring to regulate the period. just like a watch!
the escape is a double-roller swiss lever, designed with the help of Mark Headricks wonderful book.
this is my second balance-wheel wooden clock (my Falling Ball clock has a one-second wheel). It takes a lot of tinkering to get the inertia of the wheel correct for the desired period and a given spring, but it's actually quite easy.