by whowhatwhere, published
Very cool idea (not mine it was posted as a competition idea by Everythingmechanical http://blog.makezine.com/archive/2010/04/makerbot_giveaway.html)
Seemed easy enough to make a simple one so here it is.
2 part inner tube 2 part outer tube and a tumbler (you need 5 to complete assembly)
I've included the SKP file for those interested.
I'm still very new to 3d modeling and sketchup (learned a lot this past couple of weeks tho) so my images are still pretty ordinary.
If I get the chance I'll come back and do an exploded image to show assembly a little bit more clearly.
I assumed that glue could be used to attach the end caps to the inner and outer tubes but it would not take much to put in a small hold and use a screw (allowing the tumblers to be changed if wanted ( or taken apart of the combination is forgotten)
obvious improvements would be to alter the tumbler design so the actual value for each tumbler could be changed, etc.
I can see a few ways this might be done but none I'm terribly happy with right now.
Plate 5 v1.1
This is a modified tumbler with many pick groves to make it harder to use machine tolerance issues to determine the combination.
Plate 5 v1.2
This is a modified tumbler in 2 parts enabling the tumbler to be "re-configured" to change the values.
This design has not been tested.
Print out 1 each of plates 1 to 4 and 5 of place 5.
Plates 1 and 2 assemble to make the inner tube (see the image supplied)
Plates 3 and 5 assemble to make the outer tube but only glue the end cap in place after the tumblers (plate 5) have been put in place (and tested with the inner tube.
Mark the faces of the tumblers as desired.