# Figure-8 crossover junction Physics of

1. Nov 24, 2003

### Stephen Ngqwebo

Hi,
Does any one know about the figure of eight crossover junction.
I wanna make a model toy where a cylinder is moving around the track completing the figure of eight, similar to model trains. How does one drive this cylinder around and how does it cross over from the circle of the eight to the other? How are the machanicks of this junction?

2. Nov 24, 2003

### LURCH

I suppose the simplest way would be to make one section of track go underneath the other at the intersection, like a bridge. But that may not satisfy your needs, especially if you want a situation where there's a possibility for two of your cylinders to crash.

The next easiest solution I can think of is to simply make the track straight near the intersection. Rather than making your figure-eight look like two circles, you could make it look like an "X" with half-circles at the top and bottom to close off the free ends. This way, each time a cylinder approaches the intersection, it will tend to go straight, and that will take it through the intersection and on to the other half-circle of the track.