The hub pilot wheels use one nut to hold both wheels on. Budd wheels have an outer nut to hold the outside wheel on and the inner stud nut to hold the inside nut on. The Budds also had right hand and left hand threads. The stud nuts will have an L stamped into the end.
Definition(s) Flammable Gas. Substance that exists exclusively in the gaseous state at normal atmospheric pressure and temperature and is capable of igniting and burning when mixed with air (oxygen) in the proper proportion and subjected to a source of ignition.
Not all gases are flammable. eg carbon dioxide, nitrogen or helium. Flammable gases are those which react easily with oxygen in the air to cause combustion... such as hydrogen, methane or propane etc. Even flammable liquids are flammable only because they give off a flammable gas at temperatures below. Gasoline evaporates at room temperature into a mixture of flammable gases which are far more flammable than the liquid itself.