Reply to "Magnetic Track Debris Pickup"

I have not built mine yet but that is why GRJ has the magnet separated by the bottom of the car from the track.  On my test the magnet sat on the bottom of one of the old postwar plastic gondolas with plastic trucks.   the magnet  does exert some attractive pressure on the car toward the rail.  trick is to be sure you can pick up the metal but not bog down on the rails.  There was at least one thread several months ago where forumites shared designs on these cars but for some reason my searches do not find it.