Steam Locomotive Designer

Try designing your own steam locomotive. True steam locomotive design is an art (getting a locomotive that is not too slippery, one that will fit through clearances, having the correct horsepower for the terrain and loads it will have to pull, etc.). However, that doesn't prevent us from having some fun with a few of the important parameters that are used in steam locomotive design.

This Web page will allow you to specify the parameters that are used to determine Tractive Effort. As each parameter is changed, the resulting tractive effort and number of required axles will be computed and displayed.

Live Steam Modelers: While the sliders will not let you specify values in your ranges, you can still enter any value in the text fields. Remember to press the "Enter" key after changing a value.

[Java Steam Locomotive Designer Applet] Make sure Java is enabled on your browser.

NOTE: Press the <return> key after entering any text.

The computed tractive effort is based upon a coefficient (0.85). This coefficient is the combination of Mean Effective Pressure and a friction term. The friction term is set to '1.0' when roller bearings are specified. I have found that the specifications of many steam locomotives which had roller bearings still used the equations based on the friction term used for friction bearing locomotives. The axle loading is based upon a Factor of Adhesion of 4.0.

Below are few examples of existing steam locomotive designs. Try entering one of these or one of your own.

Big Boy:
Boiler Pressure: 300 psi
Driver Diameter: 68 in
Cylinder Diameter: 23.75 in
Piston Stroke: 32 in
4 cylinders Tractive Effort: 135,375 lbs 		Nickel Plate Berkshire:
Boiler Pressure: 245 psi
Driver Diameter: 69 in
Cylinder Diameter: 25 in
Piston Stroke: 34 in 2 cylinders Tractive Effort: 64,135 lbs 		NYC J3a Hudson:
Boiler Pressure: 275 psi
Driver Diameter: 79 in
Cylinder Diameter: 22.5 in
Piston Stroke: 29 in 2 cylinders Tractive Effort: 43,440 lbs
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