Indicated Power and Indicator Diagrams

Indicated Power and Indicator Diagrams

The word “indicated” comes from the use of “Indicator Diagrams” that before the electronic era were mechanically plotted to indicate the variation in steam pressure inside a cylinder against the piston position as it sweeps through the piston over the length of its stroke.  Separate diagrams for both ends of the cylinder were usually being […]

Drawbar Power and Equivalent Drawbar Power

Drawbar Power The power output at the drawbar of a locomotive, the drawbar being the coupling between the locomotive and the train that it is hauling. Drawbar power used to be measured by attaching a “dynamometer car” between the locomotive and its train.  A dynamometer car incorporates a number of measuring devices including a calibrated spring for […]

Tractive Effort

Tractive Effort “Tractive effort” (TE) is the force applied by a locomotive for moving itself and a train. Tractive effort or tractive force is measured in kilo-Newtons (kN) or pounds force (lbf) where 1 kN = 228.4 lbf. As with “power”, there are different methods of measuring tractive effort: Drawbar tractive effort – the force […]

Power-to-Weight Ratio

Power-to-Weight Ratio The Power-to-Weight ratio of a car is a measure of its ability to accelerate. A steam locomotive’s ability to accelerate is governed by its the ratio of its “power : total train weight” ratio and by its adhesive weight and adhesion coefficient (ignoring resistance factors). The Power-to-Weight ratio of a steam locomotives is […]

Locomotive Power

Locomotive Power Power is defined as “the rate of doing work”. Common units of power in the metric system are Watts (W), kilowatts (kW), Megawatts (MW) and Gigawatts (GW), where 1 Watt = 1 Joule per second = 1 Newton-metre per second. Alternative units of measurement are calories per second and kilo-calories per hour (1 […]