Recently I read where someone had some problems with building log cars from wood & finding them way under weight. I built several of my own with absolutely no problems. I started out with 3/8" wide steel flat stock about 1/8" thick. This went the full length of the car. I wrapped this with thin pieces of wood to look as if the whole thing was a beam. These things tracked very well. Most of my items are packed away right now but I will try to find these & post some pics.I also have milled out a groove in the bottom logs & placed soft lead weights in the groove.If the later is your choice make sure your weight is evenly distributed on each side log so the car dosen't lean.