A young fella needed a sulky for the back of this
walk-behind zero-turn mower.  This is my junk metal
contraption that should work pretty good for him.
One-inch steel round inside one-inch pipe for the
swivel points, with grease fittings.  Wheels are
cheap, ball-bearing units but should be okay
for this application.
sulky1 is overall picture of entire machine
sulky2 is starting point of rear mount
sulky3 is the "tongue" mount to keep operator behind handles
sulky4 is the rough framework
sulky5 and sulky6 is the final result.