Windward performance makes a wing wheel for the Sparrowhawk that uses
two skate wheels. It's really neat and has a natural spring arc made
out of carbon fiber and fiberglass with two skate wheels on the
bottom. It pivots 360 deg for which every way you drag the
sailplane. Yes the wing is only 42 lbs so it might not scale up to
full weighted sailplanes. Sorry I have no photos but I thought it
might be an interesting idea out there for those entrepreneurs. It
does not fold but stores well as it is small. Just an idea that you
don't have to use a bike tire like every one else.
JOhn