The Infinite Hyperboloid Marble Track, Spinning Pen Holder

####The Infinite Hyperboloid Marble Track, Spinning Pen Holder

*The marbles on the hyperboloid go round and round, all through the tracks! *

This design is a synthesis of three previous projects, involving the hyperboloid, marble rings, and linkage bars. It is of multiple uses -- a bottomless hyperboloid holder, a revolving holder with a bottom, or an infinite marble track.

Seeing kids try to put marbles into the hyperboloid pencil holder in a previous project, I decided to add two donut structures at both ends to create an infinite hyperboloid marble track. To connect the terminal parts to the body, I referred to the snap-in design used earlier.

Marbles of a diameter between 10mm and 16mm can be used. You may need a LOT of marbles to fill the tracks. Of course, there is no need to fill the tracks. Try experimenting with ¼ or 1/3 (about 30 to 50) and see how it works.

####Alternatively,
If we use only one cap, we get a revolving pencil or pen holders, holding pens of a diameter between 10 mm and 16 mm.

####Warning
Once the end parts are snapped in, it is really HARD to remove, which may be a good thing! A looser version is provided in case it is desired. Have fun and do be SAFE!

####See Also
1. Hyperboloid Pencil Holder/Cable Organizer: https://www.thingiverse.com/thing:3757579

1. Marble Rings: https://www.thingiverse.com/thing:3159072 & https://www.thingiverse.com/thing:3160114

2. Snappy Linkage Bars: https://www.thingiverse.com/thing:2822460