"Steam 101"
For Instructions to operate a Weeden Steam Engine follow this link



How a Toy Steam Engine Works

toy steam engine parts
 There are two elements necessary for a steam engine to function, heat and water. The water is heated in a boiler, this may be either a horizontal or a vertical cylinder, as the water is heated to boiling steam is created, steam unlike water is compressible so the more steam produced the greater the pressure of the steam in the boiler. This pressure has to be regulated, otherwise the boiler may burst causing a large volume of steam to suddenly escape, possibly causing bodily harm, steam can cause severe burns.

Steam pressure is controlled by either letting it escape to do work by pushing a piston in an engine cylinder, or gently released by a safety valve which is designed to retain the working pressure required to run the engine.

The temperature of the heat applied to the boiler also regulates the amount of pressure created, there has to be a balance between the amount of steam created and the amount of steam used by the engine.

The steam produced has to have room to expand, so a boiler is only half filled with water to allow room for steam expansion.

Toy steam boilers are heated either with a flame type burner or an electrical element. Flame type burners use alcohol as a fuel and wick to produce the flame. On most Weeden burners the height of the wick determines the amount of heat produced.

Safety Valves

You will find four basic styles of safety valves, FIgure 1 is the most common, it has a spring loaded plunger and threads into the boiler. Figure 2 is an older style of the spring loaded plunger, you unscrew the top to fill the boiler. Make sure the plunger is free to move and there is spring pressure with these two styles. Figures 3 and 4 are weighted styles, the arm with the weight attached puts pressure on a plug to block steam from escaping, lift the arm up to fill boiler.

new sv
Figure 1
 old spring
Figure 2
 weight style
Figure 3
 disk sv
Figure 4

Burners

If unit is flame heated fill burner about half full with Wood alcohol, which is also known as Methanol, Methyl Hydrate or Methylated Spirits. Adjust wick height so tip of the flame just touches bottom of boiler. Keep an eye on the water level in the boiler, do not let it run dry. After a few runs you will have a good idea how much alcohol to add to the burner to get a maximum run time. Figure 5 is common for most upright models, however larger units may use double wick burners similar to figure 6. Figure 7 is typical of most horizontal boiler models.



single burner
Figure 5		 17 burner
Figure 6		 3 wick Figure 7


Alcohol vapors can communicate flame, so fire doesn't have to touch the liquid, it can ignite the vapor that comes from evaporating alcohol. Always be sure the flame is extinguished before refilling the burner, be aware that outside in daylight it is often difficult to see the burning flame.
With an electrically heated boiler it is simply a matter of plugging it in and waiting for the boiler to come up to pressure. With an electrically heated boiler there is a greater risk of boiling the boiler dry, it is very important to keep an eye on the water level.
A note of caution, the original electrical cords had two prongs with no ground, for safer operation they can be changed to a three prong configuration. Instructions here.

Boilers
weeden 17
 Fill the boiler so the water level is midway in the sight glass, once level reaches bottom of glass shut down and refill the boiler. Sight glass tubes and replacement units are available here.

Filling the boiler with hot water will allow a quicker start up and longer run time.