So I’m to make pens that “work in zero gravity” – for our purposes, that means pens which can write 'upside down'. Ellen is to produce the inks. I'm dependent again on someone else, because if she fails to produce a suitable ink, then I’m stuffed too.
What's more, this challenge is not as easy as it first seems. A capillary action pen will work okay, but a ball-point pen is another matter, and it seems that the programme makers are expecting me to produce both types.
I decide to make a large version of each type that I can scale down if I have time. As the capillary pen is going to be the easier of the two to produce, I start on that. It’s surprising how difficult a challenge this is under Rough Science conditions.
It takes an age just to gather together the tools and materials that you think might be useful. Then you’re constantly revising your ideas in order to overcome some small design problem that you hadn’t foreseen.
Nevertheless, by the end of the day, I’ve managed to produce something that will do the trick – a “pen” that works by capillary action. It looks like, and more or less is, a large felt-tip marker. It’ll do for now. Tomorrow I need to tackle the more-demanding challenge of making a large ball-point pen.
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.
The capillary-action pen is easy enough to make on a smaller scale, and it works really well with inks made from food colourings. Let’s hope that Ellen manages to produce a natural ink that’s just as usable. I’ve every confidence in her, as she’s been beavering away at her ink challenge for two days now.
As for the smaller ball-point pen – well, that’s a bit more difficult. Just by chance, I notice there are some bicycle wheels in the workshop – presumably for use in Jonathan’s ‘Mars Rover’ challenge in Programme One.
Inside the hub of one of the wheels is a ball-race with some small (about three millimetre diameter) ball bearings that are just the right size for my smaller ball-point.
What’s more, one of the caps from a superglue container serves perfectly as a housing for one of these small ball bearings if I cut just the right amount off its pointed end.
By the end of the day I’ve four different pens, each of which works (in a way). What’s more, Ellen’s managed to manufacture some natural ink that fits the bill perfectly.
What seemed an easy challenge has turned out to be more demanding than I’d first imagined, but we got there in the end.