Hi Ernie,
They are still doing the investigation, and it may be some time before the official cause is determined, but preliminary reports indicate operator error, or sight glass malfunction. The sight glass is a water filled glass tube that gives a direct reading of the water level in the boiler. The water level MUST be higher than the top of the firebox when it is under steam. On old steam train engines, they had fusible metal plugs in the top of the firebox. That way if the heat got too intense in the firebox, the plugs would melt and steam would blow into the firebox putting out the fire (in theory). I don't know whether steam tractors have this same system or not. I doubt if they were as strictly regulated as the train engines were at the time. I've seen many of these tractors left totally unattended, with a full head of steam at steam tractor shows through the years. I always tend to walk away from them when I would see that. I've been interested in trains for years and I understand the dynamics of steam propulsion and it's dangers, and I've developed a very heathy respect for these old monsters. Even the little ones running 70-80 lbs. pressure can make a horrific explosion if not properly operated. The bigger ones can have 150 lbs or more operating pressure. Some of the late steam train engines had over 225 lbs pressure, but there were many more safeties build into them by the late 40's. Steam tractors were pretty well obsolete by the late 20's, so they never had all the latest safety equipment.
