Instructables
Picture of Bicycle Trailer Hitch
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Bike hitches are difficult to make - I usually just screw in an eye hook into the frame where I would normally attach a rear rack.  If you have a rack attached or just want something stronger, here are some photos of how I took a motorized chain tensioner, disassembled it and made it into a bike hitch.
Supplies needed: stalwarth eye hook and chain tensioner.
caitlinsdad3 years ago
Doesn't this cause problems when you want to turn left? The trailer bar would rub against the wheel or you risk torquing out that rear tube. Maybe attach it to the seat post instead?
Looking at the picture, turning right might cause the trailer bar to touch the wheel.  

However, if the tube had a some curve to it the trailer bar would clear the wheel in all but the tightest of turns.  A shape somewhere between a ? (question mark shape) and a 7 (shape of a seven) would do the trick.

I would use a hitch pin for the vertical bolt so the trailer could be removed without tools.  Use some old inner tube scraps to protect the frame in case you're not just attaching this to a rust bucket bike.  Also, a safety strap of nylon or thin cable that loops through the frame to a mini carabiner is a practical and easy safety step.
No, the first person was correct. Turning left would cause the issue. The front of the bike is to the right of the screen. If you are sitting on the bike (generally how people give directions) when the bike turns left the bar would come in contact with the bicycle tire.

I don't see how you could even thing turning right would cause the main issue. You must be looking at it wrong, be confused between right and left, or just failing to pay attention to detail.

Whatever the case, the first person's comment is the correct one.
It depends upon the angle of the trailer attachment, TBH. EG: http://www.instructables.com/id/Welded-bike-trailer/