The helium question was addressed a few years ago by a British unicyclist, and it’s still one of my favorite postings. He presented a complex mathematical formula that showed how to measure the benefit of helium gas over air in a unicycle tire. His summa
ry: though there was reduction in weight, it was minimal. The net effect would be equal to riding without socks.
What volume of air do you think would be in the average Gazz 24" x 3"?
Or more to the point (and saving me a lot of thaught and time :)), how
much lighter would a unicycle be that’s fitted with a Gazz filled with
helium? Is helium the lightest available gas?
What if you made a uni that had some sort of really light gas in the
tyre, frame, cranks, and seat?
Helium is a very interesting substance. It is the first in a series of Noble Gases, also known as monatomic gases.
The molecular weight is a little more than 4, meaning one mole of gas has a mass of about 4 grams. A mole occupies around 22.4 liters at STP.
Helium is the most volatile liquid known, boiling at 4.215K. For example, the melting point of molecular hydrogen is 13.96K at it’s triple point at 54mm pressure.
But molecular hydrogen (H2) has a molecular weight of only 2, about half of helium. If the goal is weight reduction, hydrogen would do best.