Last time I posted about using a table from Meyer to determine the steam port area. This can also be done from an equation: fractional steam port area = speed of piston in feet per minute X 0.1/600.
To demonstrate this, I updated the steam port worksheet to run the above equation:
Although the DLR runs at about 10mph, I decided to calculate at 15mph to give the engine a bit more headroom. At 15mph the required steam port area is 4.583 sq. in. I’ve chose a 7.5″x0.625″ steam port which equals to an area of 4.213 sq. in. (with semi-circular ends). The 7.5″ length was determined from Meyer’s suggestion that the length of the port be no less than 3/4 X cylinder diameter, so the rest is figuring out the width, which is actually a quadratic equation due to the semi-circular ends.
At 10mph the actual port area is 3.056 sq. in.
So for the chosen steam port size of 7.5″x0.625″ should be able to work for at least 10mph. Let’s see what the exact optimum speed for this sized port will be:
