Essentially, there are two problems I have to overcome
to get a ‘zero-gravity’ ball-point pen to
work. I have to find a suitable “ball”,
and something it can sit in such that it’s held
firmly in place while being free to ‘roll’.
Then there’s the question of how to deliver just
the right amount of ink to the ball in order for it
to write evenly and continuously…and upside down!
A spring-loaded marble inside a piece of copper tubing
containing some ink, with an inflated balloon providing
the pressure to force the ink onto the marble seems
to work – provided the ink is sufficiently viscous.
All the designs I've tried for these pens are far from
ideal, but at least the two I end up with are functioning
pens that will write 'upside down'. Tomorrow, I’ll
aim to scale down both the capillary-action and ball-point
designs and try to get them to work more effectively.