Lego Polar SundialSunday, July 25th, 2010
Polar sundials, like equatorial dials, have the gnomon and face tilted to accomodate for the lattitude where they are to be used. These kinds of dials are especially adaptable to construction from Lego bricks because they use parallel lines to mark that hours rather than the angled lines used on a more traditional horizontal dial.
The polar dial pictured is constructed mostly of 1×4 bricks and plates, mounted on an old-style 2×4 hinge so it is easily adjusted to the local latitude. It is set up by putting the hinge at an angle equal to the colatitude so the face is parallel to the Earth’s axis and pointing the upper side to the pole.
The time is read by the shadow of the upper edge of the gnomon (called a style in this form). In this model, the hour lines are marked where the differently shaded bricks meet. Noon is at the center, with the morning hours read on the left side and the afternoon hours on the right (when used in the Northern Hemisphere). Most polar dials are constructed to be used between 6 AM and 6 PM, but the long shadows cast at these hours would make for a rather wide model, so I shortened the face to read between 7 AM and 5 PM.
Here is the dial casting a morning shadow, reading about 7:30 AM: