view of the siphon at the front left corner of the water tank next to the pilot fuel strainer

All Stanley cars included a steam powered water siphon for the purpose of filling the car's water tank.  At the very beginning of the 20th century horse watering troughs were plentiful and it was easy to pull alongside and simply siphon full the car's water tank from the trough.  As the automobile became the preferred mode of personal transportation over the horse and buggy the number of horse troughs began to dwindle.  Stanley owners then had the option of using a hose to fill their car's water tank or finding a suitable stream or pond from which to siphon water for the car.

Filling the water tank on a Stanley condensing steam car is easily accomplished with a hose by adding the water through the cap of the condenser (radiator).  However, when the cars were built there were still homes that did not have the luxury of water provided from pumps.  As an alternative to filling the water tank from a hose, Stanley retained the tried and tested method of using a steam siphon.



The Stanley siphon works along the same principals as the injectors found on steam locomotives for forcing water into the boiler against the boiler's pressure.  The photo at the right is of an early Stanley siphon designed for use with a hose.  One end of the siphon (bottom of the photo) is threaded so that the siphon may be permanently attached to a 3/4" piece of pipe going to the water tank.  The supply hose is slipped over the ringed barb (right in the photo) while the other end of the hose is placed in a water source (this end of the hose had a screen assembly to prevent the sucking up of debris).  Steam is applied to a fitting that protrudes through the center of the siphon to the end where the siphon connects to the 3/4" pipe (you can see the 1/4" tubing from the steam supply centered in the 3/4" pipe threaded end of the siphon).

Operation of the steam siphon relies on the condensing of the steam back into water and the resulting vacuum that is created.  When the steam siphon valve is opened a small amount to admit steam to the siphon the steam rushes down the 3/4" pipe and into the water tank (a generous 1-1/2" diameter vent pipe is provided with the water tank to prevent it from becoming pressurized by the steam).  As the steam rushes down the pipe it pulls air along with it setting up a vacuum in the pipe which draws makeup air from the hose.  The drawing of air from the hose creates a vacuum in the hose and water is drawn into the hose.  Water is slowly pulled into the hose as the siphon is primed.

Once the hose has been filled with water and the water reaches the siphon, the water quickly condenses the steam and a vacuum is formed in the space once occupied by the steam.  The water quickly fills the space once occupied by the steam and since the steam was moving at a high velocity due to it being released from the end of the steam supply tube, the water takes on the moving kinetic energy of the steam and quickly travels down the 3/4" pipe into the tank.  At this point there is a definite pitch change in the operation of the siphon signaling that the siphon has been primed and the steam valve can be opened further to admit a greater quantity of steam.  This increased quantity of steam is not only moving faster but the added volume of steam that can be condensed by the cooling action of the water allows for very rapid filling of the water supply tank.  If the steam valve is opened too much the water can not condense the steam fast enough and the siphon will stop functioning and actually blow water back down the supply hose.

How easily a steam siphon will pick up its prime depends on the length of hose being used and how great the vertical distance or "lift" is from the intake end of the hose to the siphon.  Generally the steam siphon will easily pick up is prime on a 25' length of rubber hose that is sitting in a water supply no more than 10' below the level of the car.  Often, if the lift is of great distance the use of a check valve on the suction end of the hose along with prefilling the hose with water will allow the siphon to pick up its prime easily.

When placing the supply hose in the source of water it must be placed in such a way that mud, sediment, stones, and other debris are not drawn into the water tank (often placing the end in a small coffee can so that the coffee can serves as a suction receptacle works well).  The water drawn in by the steam siphon must be clean and clear.  If muddy water is put in the supply tank the pumps will transfer it to the boiler where the generation of steam will leave the mud behind to foul the boiler and shorten it's life.  Additionally grit in the water will damage the seats of the pump check valves along with quickly plugging up the water tank filter and water system strainers.