I have a "Swan" trailer (from Germany) and "Swan" towout gear.

The wing wheel is the typical cuff around the wing and bicycle wheel.

A bit ingenious is the "suspension" they built into the setup. The
two vertical square tube aluminum forks that connect the cuff to the
wheel axle do not connect directly to the axle, but to an offset from
the axle that allows some pivoting movement. I think I have some
digital photos somewhere and if anyone is interested, I might be able
to dig them up and e-mail them. No, I don't have ready access to the
wing wheel itself at the moment.

The Swan wing wheel cuff fits over the wing at the very end of the
wing. It is a hinged cuff made of aluminum and padded with felt. All
frame members are made from aluminum. The wheel is a spoked steel rim
bicycle wheel. I don't know the diameter, but it may be 20"
Maybe... I've used it only a few times and it worked well. I've only
seen it work from the mirror of my car and not from walking behind my
car to see if it's twisting and popping the wing. I'm sure a
castoring wheel would work much better for most setups.

Ray Lovinggood
Carrboro, North Carolina, USA