You can purchase very smooth sheaves and bearings from Fenner Drives (http://www.fennerdrives.com/, Make sure you also get the correct spacers, as 17mm shaft is hard to work with). You can build a simple cablecam rig without any machining, using off the shelf parts. The specific design is up to you, but I suggest calling fenner for your sheaves, as they're smooth, high speed and high load, and synthetic, so they're quieter on cable. While it's more expensive, I also suggest using a synthetic 12 strand rope like Tech 12 (http://www.samsonrope.com/), as it will be quieter and have less vibration than steal cable.
-Jason
