Saw something really cool on the Interstate last night.
A van pulling a trailer passed me and pulled in front. He was going...ehh, let's say he was doing the <i>practical</i> speed limit
In my headlights, I noted that the trailer <b>had only one wheel mounted in the middle of the floor!</b>
Whoa! This merits some investigation. I went out into the other lane and drew alongside him, even with his bumper, and took a look at the workings. What looked like a couple stabilizers jutting from the underside of the two leading edges of the trailer were actually, on further study, <i>hitches</i> and the trailer was riding on a big, 14" industrial strength caster. The trailer itself was a 4x4x4' cube painted red and mounted with very functional lights. I don't remember seeing a trailer jack but I would imagine there was one.
I didn't get a better look because I was too circumspect to blink him over to the shoulder for an on-the-spot interview. I would imagine the pitch forces on the hitches would be about the same as any trailer but the roll and yaw are probably hellish. I followed him about thirty miles before I had to get off and I didn't see any fishtailing; he did skate back and forth in the lane a little but that may or may not just be his style of driving.
Basically, he created a literal 5th wheel trailer for, I'm guessing, around $150 in materials (and probably a lot less than that if one is signed up with Freecycle). It didn't fishtail and moved <i>with</i> the vehicle. I'd have to see how a rig like this would handle parking and city traffic before making a final assessment.