Redneck engineering

I built an overhead trolley crane over my "to be" Granite (http://tanbrown.org) shop. I used 5 inch "H" beams (2) and (http://maplered.com) have a free roling trolley on one beam, and (http://maplered.com) a motorized trolley on the other. My problem is the motorized trolley puts the other one in a bind, so it does not move as intended. I realize NOW that the force should have been in the middle of the parallel beams, but does anyone know of an alternative to making it operated without doing so? Any advise for this redneck engineer would be greatly appreciated. thanks steve