About this 3D model

An ancient astronomical instrument used in navigation - More complex ones also had mathematical functions.I'm interested in making precision devices with my makerbot and this seemed like a good place to start - This is version 1, if it prints OK then I will progress with other versions with more features (such as a circular slide rule)I'm posting the sketchup files in case anyone would like to modify, or improve the design (I'm new to 3d modeling so it's pretty crude)