What is a single wheel trailer?

A single wheel trailer is a trailer that has only one wheel supporting it.
A trailer is usually defined as having one or two axles and having two wheels per axle. These conventional trailers attach to the vehicle towing them, at one point, the trailer hitch and ball. Single wheel trailers have only one wheel. The trailer attaches to the tow vehicle using a special hitch, which attaches at two points to the vehicle, not just one.

Trailer tracking

On a conventional trailer, when the tow vehicle turns, the trailer follows at a reduced radius. This is because the pivot point between the tow vehicle and the trailer is the hitch and ball. Think of a semi truck making a right turn in front of you. The truck (tow vehicle) must go very wide around a turn because the rear most wheels of the trailer follow at a much reduced turn radius. If the tow vehicle doesn't go wide enough around the turn, it will collide with what ever is at the inside of the turn (i.e. curb, stop sign, pedestrian, your car etc.). Thus the signs on the back of most semis "This vehicle makes wide right turns."

Single wheel trailers, on the other hand, are the opposite. They turn wider than the tow vehicle. How is this possible? A large castor wheel. Think of the front wheel of a shopping cart at the grocery store. These front wheels are capable of spinning all the way around. This same concept is the way the wheel on a single wheel trailer steers. It has the capability to rotate all the way around. The wheel must perform this way because unlike the conventional two wheeled trailer, that pivots at the hitch and ball, the single wheel trailer pivots at the wheel itself.

Hitches