steam automatic mounted to the firewall on the left side of the boiler compartment

Stanley steam cars operate at steam pressures between 500 and 600 pounds per square inch depending on the setting of the steam automatic.  This maximum pressure is determined by the setting of the steam automatic.  As the pressure reaches the set point of the steam automatic the fuel flow to the main burner is closed off.  When the steam pressure drops below the set point of the steam automatic fuel is allowed to flow to the main burner.

The steam automatic has a pressure sensing diaphragm at its upper end which is piped to the top of the boiler.  At the bottom of the steam automatic is a valve which controls the flow of fuel to the burner.

HOW THE STEAM AUTOMATIC CONTROLS STEAM PRESSURE

If you review the flow of fuel from the pressure tanks to the burner you will observe that burner fuel (kerosene) flows first through the low water automatic, then through the burner firing valve (located on the dash), and finally to the steam automatic before it can reach the burner.  This arrangement allows for the low water automatic to insure no burner fuel can get to the burner regardless of the setting of the burner firing valve.  The steam automatic placed last in the fuel plumbing also insures that if the firing up valve is opened while the boiler is at pressure, that fuel from the pilot tank will not be fed to the burner which could cause the steam pressure to rise even though the steam automatic wasn't calling for the burner to be firing.

At the top of the steam automatic is a beryllium-copper disk or diaphragm (435).  This diaphragm is clamped between the two halves of the shell of the steam automatic (431 & 432).  The underside of the disk rests against a washer (441) which helps to keep the heavy spring (443) centered while steam at boiler pressure is admitted to the top side of the disk.  An adjusting screw (434) and washer (440) allows for the spring tension against the disk to be set such that the diaphragm doesn't start moving and compressing the spring until the steam pressure reaches 500 pounds.

Also connected to the washer (441) at the top of the spring is a push rod (444) which transfers the position of the diaphragm to the valve stem (445).  At the lower end of the push rod is a packing gland (438) and packing nut (439) which keeps the kerosene that surrounds the lower part of the valve assembly from leaking out as the valve operates.

The valve body (447) contains the valve seat (448) and valve ball (445B) along with the valve stem (445).  Kerosene (gasoline for the early model Stanleys that used gasoline for both the pilot and burner) from the main burner pressure tanks is admitted through the valve seat (448) portion of the valve and when the valve is open passes out through one of two ports in the valve body (447)

When the steam pressure reaches 500 pounds the diaphragm (435) overcomes the spring force against it and it moves slightly to compress the spring (443).  As this motion happens a valve push rod (444) moves to apply pressure to the valve stem(445).  At the end of the valve stem the small ball bearing which acts as the valve (445B) is pressed against the valve seat (448) by the valve stem.  This action cuts off the supply of fuel flowing though the valve seat (448) portion of the steam automatic.  As long as the ball bearing is pressed into the valve seat fuel flow is stopped.

When the steam pressure drops the spring force overcomes the steam pressure acting on the disk and the diaphragm moves such that the valve stem releases the pressure on the ball bearing and thus fuel can pass though the valve on its way from the main burner pressure tanks to the main burner.

The Cruban Machine & Tool Works manufactured various steam car aftermarket parts and even a custom steam car.  Click on the link below to review an advertising card describing the features of the Cruban Empire Steam Automatic.

~ Cruban Empire Steam Automatic ~