Cold Steam Engine
The October 1949 issue of Model Railroader magazine contains an article entitled "Cold Steam Engines", about a very unusual live steam, or rather, cold steam locomotive. The system described was developed by Emil Vollenweider of Sacramento, California.
The photos below show an O scale locomotive modified to operate off the CO2 gas emitted by melting dry ice. The ice is placed in a sealed reservoir in the tender. A pipe leads to the locomotive where a valve controls the flow of pressurized gas to the cylinders. The valve is controlled by an electric motorized mechanism, connected to the two-rail track. The output from the valve flows into a small equalizing tank hidden inside the boiler, and then to the left and right cylinders.
This schematic plan shows the path of the cold gas. The gas vaporizes from the solid dry ice in the tender. It passes through a pipe to the throttle valve in the cab and equalizing tank in the boiler into the cylinders. For simplicity, the steam chest and exhaust piping are not shown. From "Model Railroader", October 1949.