I took one of these 3 wheel things and mounted a hitch ball in the middle of
it and put the ball into the tongue of my ACME eze-tow dolly when I want to
slide the dolly up under the rear of the MH when in a park.
Makes it very easy to move the dolly, BUT, it doesn't work very well in
gravel or dirt because the small wheels dig in, works fine on pavement.
So I have another idea, take a swivel with a small (maybe 8") pneumatic
tire and mount or weld a ball on that.
Now on the ACME dolly, there is a hole about 1/2" dia. on the top of the
hitch where the ball fits into, says it is so you can tell when the ball is all
the way into the dolly socket. Now if I weld a short pin that is just smaller
than the 1/2" hole, right on top of the ball, it will stick through the hole
and prevent the ball from moving around in the socket.
Thus keeping the swivel tire assembly always verticle in the socket
and letting the swivel turn in any direction.