Trapped Outside

by glyphobet
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  • White

    White nylon plastic with a matte finish and slight grainy feel.

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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.

Other versions:

Without the ball:

Solid, hollow inside:


Remember to give this model five stars if you like it!

© 2009, Matt Chisholm. All rights reserved.


IN: 0.973 w x 1.515 d x 1.417 h
CM: 2.472 w x 3.848 d x 3.6 h


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@erichschlaikjer: I heard back from Shapeways; they can't print moving parts in metal, that's why this can't be printed. Here's a version that has no moving parts:
April 6, 2011, 4:27 pm
Well, first I ordered it in basic plastic, but since that was way below the minimum spend I splashed out on Gold Plated Glossy, which at the time was quoted at $70.45. I thought it might go nicely with my glass klein bottle xmas ornaments.
April 1, 2011, 8:02 pm
@erichschlaikjer: Not sure what went wrong with your order. I've emailed Shapeways tech support to try to figure it out for you. Do you remember what specific metal material you ordered?
April 1, 2011, 6:16 pm
My order was canceled because they can't print the ball. Perhaps this was because I tried to print it in metal, but they didn't say.
April 1, 2011, 1:04 pm
Sounds like you received the old version. Could you post a picture of the model you got?
August 30, 2010, 7:54 am
Just a week ago or so, the end of July. Weird.
August 5, 2010, 2:23 pm
Interesting, I updated it to the version with the slit in February 2010. When did you order your model?
August 5, 2010, 2:38 am
Mine didn't have a slit along the surface, as described... but I think I like it better that way! Can still see the ball at the ends of its "tunnel"
August 4, 2010, 8:50 pm
Read more about the mathematics of Boy's Surface here: Construct a paper model here: See some nifty videos here:
July 19, 2009, 9:56 pm


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