Haha, the two holes right above each other make this a lot trickier...
Well for something like this, legos, k'nex, whatever building toys you can get your
hand on, will help a lot with creating stuff. You could use wood and the like, but
legos and k'nex really help with the trial/error aspect of something like this. K'nex
has many roller coaster track pieces that could be used to carry the ball easily
with some modifications. In fact, I think they have tracks actually designed for balls
as well, though they are for bigger balls...Anyway, onward to some of my ideas.
So some simple machines that can be easily implements... (These are pretty obvious,
so you probably already figured stuff like this out). You are pretty much guaranteed to
need an incline somewhere in your machine, being used as a ramp.You could easily use
a falling mass connected to a pully to directly lift a platform with the marble. Once it
reaches a certain height, the platform would hit a stopper on the very edge such that
it tilts forward (sorry about the bad descriptions). Something like this is fairly common,
so you could try something like the apparatus in this image.
http://http://scioly.org/wiki/images/1/1c/SC-springtype.gif
So essentially, a green spring is held down as a mass falls downward. As it falls, the
spring is stretched. Once the mass has reached the ground, the mechanism holding
down the spring is released, while a mechanism locks the spring on the other end.
As the spring restores itself, a pulls a string that drags a platform forward, pushing
the marble along. I have no idea how effective this would be - the stronger the spring,
the faster the marble will move. But then you would need a heavier mass to deal with
the larger restoring force. Also, construction would be tricky :P.
I don't have an image for this one, so it'll be harder to understand. Anyway, a marble
could roll down a ramp into a...spoon like extension? The extension would be attached
to an threaded axle. The velocity of the marble would cause the spoon-like extension
to begin spinning in a circle. Similar to a wing-nut, it would slowly rotate downward, like
a wing-nut would on a threaded rod. At the bottom, it would hit another ramp, upon
which the marble would roll out. Hope that makes sense!
Anyway, that's all I can think of now...I hope I helped! :)
Edit: Realized I didn't even overview a simple system. Something pretty simple would
be a launching mechanism (Spring or falling mass) connected to a lifting mechanism
(another falling mass or an incline). From there, you can just have it roll right back
to the exit hole. Once you have that, you can stick in all sorts of other stuff.
