My son and I were V-Stromming between Alpine and Marathon, running along side a train hauling strange (to us) flat cars. These cars had a structure on one end that had a large belt or truss suspended between two uprights. It looked like something you'd put under a horse to take strain off its legs. In Marathon we saw many more on a siding.
Anybody know what these cars are used for? Unfortunately we didn't think to use our phones to take a picture