I found an old Nordic Track ski machine for $40. Pulled the flywheel, the bearings, the clutches, and drag adjustment belt. Cobbled up this.

Above is the footrest which is adjustable.

Above is the flywheel and clutches mounted in a 18mm Baltic birch frame. I need to design a better alignment frame for the pulleys.

Above: the "legs" are these rockers. They are too unstabile for me to control at this point. I will need to make a shoe that fits over them to adjust the amount of rocker.

Above is another view of the flywheel in it's frame.

The drag on the flywheel can be adjusted up to "11".