This is a model of Boy's Surface, a one-sided surface with no edges and no pinch points.
In the cutaway images you can see a small ball. It can roll in three directions but is trapped in the space cut out by the single-sided surface.
The ball is visible through a single cut that winds around the surface.
Note: The ball is red for clarity in the screenshots only. The entire model will be the same color when printed.
Without the ball: http://www.shapeways.com/model/237518/trapped_outside__track_.html
Solid, hollow inside: http://www.shapeways.com/model/233704/trapped_outside__solid_with_hole_.html
Remember to give this model five stars if you like it!
© 2009, Matt Chisholm. All rights reserved.