Classicly

The Rubicon ran three or four hours on a charge, depending on the work load. Normally, three or four daily trips were made to the roundhouse, to exchange a “tired” engine for a freshly-charged one. Eighteen-inch pistons enabled the engines to move their own weight with just a few pounds of steam, so it was rare for them to be stranded away from their “lifeline.” The storage tank was insulated with a two-inch layer of magnesia. It was fitted with baffles to keep the water from sloshing back and forth as the engine started and stopped.