Recreational & Family - Pulling a sled?

I pulled my son around in the sled behind my mountain bike today. It worked out great except I couldn't turn right without getting the rope caught up in my rear tire and having it pulled up and making a mess of things. Does anyone else pull a sled (or anything tied on with a rope) behind a bicycle? How do you attach the rope to the bike?

I'm thinking about making something that i put on the back of the bike and tie the rope onto. Maybe I'll try to use part of an old trailer - or maybe part of a rack. I haven't thought about it too much yet but thought maybe someone else has already done this.

I'll post pictures of whatever I come up with.

We live across the street from a school, and when my kids (in their 20s now) were small, I used to pull them around the five-acre lawn on a sled or saucer. They loved it, but it wore my butt out in a hurry.
I just tied the rope to the seatpost and lived with the occasional snarl. Off the top of my head, one posssible solution that occurs to me (haven't tried it and not sure it would work) would be to get a piece of conduit long enough to go from the rear axle, around the back of the tire and back to the other side of the axle, with a little left over. Flatten the ends, drill holes for the axle and mount it as a yoke sticking out the back. Tie the rope to that and haul away.

My Grandpa used to pull our sled with his bike. It had a sturdy back rack, where the cable (it wasn't a rope, either a steel cable coated with plastic or an electrical stranded wire/cable - i never asked him) was tied. Since it was a cable and not a rope it had some stiffness to it, preventing it from getting into the wheel on the turns.

Perhaps a set-up like this?
http://homepage.mac.com/juanwilson/islandbreath/2009Year/2009-02/090208trailer4.jpg
If you already have a rack the other parts could be easily sourced from a hardware store. Of course when the rope slacks it could still get snagged but I bet it would work a lot better than having it tied to the seat post. In this picture it looks like the parts clamping the bracket in place are from a kickstand.

I came up with a solution today that actually worked pretty well. I put a loop in the rope around the seatpost and string it thru a rear rack. Then behind the rack I used an brake cable housing to hold the rope up a little bit more to keep it off the tire. I took some pictures because I thought it would be easier to just see.

1. Here you can see I had an old rack with no real good way to attach the front of it. I wrapped some old tube around my seatpost and pulled some zipties tight on there. It works (for now at least)!

http://static.zooomr.com/images/8713383_234861c96a.jpg (http://www.zooomr.com/photos/kidpurple/8713383/)

2. Now I string the rope down and up thru the rack, this is just to keep the rope centered back there.

http://static.zooomr.com/images/8713387_16cedcc497.jpg (http://www.zooomr.com/photos/kidpurple/8713387/)

3. Some slack still might end up with the tire catching the rope - so I added this brake cable housing and put a little loop in the rope so it hangs there. On tight corners it can slip out of there - but it never was a problem. This step might not have even been necessary.

http://static.zooomr.com/images/8713390_90db24576e.jpg (http://www.zooomr.com/photos/kidpurple/8713390/)

4. To keep the brake cable housing in place I wrapped some duct tape around one end and strung it thru back here where I would have attached a fender.

http://static.zooomr.com/images/8713393_d5ef0a2a39.jpg (http://www.zooomr.com/photos/kidpurple/8713393/)