Model Railroad System
2.2.2
Overall User Manaual
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This program is based on the information posted by Mark U. on the Yahoo XTrkCad list at the URL http://groups.yahoo.com/group/XTrkCad/message/4983 and the information supplied by rtroop on the TrainBoard forum in post no. 9 at the URL http://www.trainboard.com/grapevine/showthread.php?t=114497. This is a standalone program that incorporates the formulas presented in Mark U's spreadsheet and explained in rtroop's message. The formulas are as follows:
Where:
The main GUI screen of the LocoPull program is shown below. The GUI is broken down into sections:
The scale selection simply select the scale and is used to compute the degree of curvature.
This section of the GUI gathers information about the locomotives pulling the train. It is assumed that all of the locomotives have the same tractive effort, that is they are the same weight and have the same adhesion factor. This would generally be the case if the locomotives were the make and model. Three inputs are gathered in this section: the number of locomotives, the weight of each locomotive, and the adhesion factor of the locomotives. Two intermediate outputs are displayed here: the tractive effort of each locomotive and the net tractive effort of all of the locomotives together.
This section gathers two inputs and displays one intermediate result. The two inputs are the average weight of the cars and the average rolling resistance factor. The intermediate result is the average car rolling resistance.
This is simply the net tractive effort divided by the average car rolling resistance. The floor of the result is displayed as a whole number (since pulling a fraction of a car is not meaningful).
One input is gathered and three intermediate results are displayed. The input is the percent of grade and the intermediate results displayed are the added rolling resistance at grade of each car, the net rolling resistance per car, and the added rolling resistance of each locomotive at grade.
This section gathers two inputs and displays one intermediate result. The added inputs are the curve radius and the rolling resistance per degree of curvature and the intermediate result is the degree of curvature.
This is just the tractive effort less the tractive effort needed to pull the locomotives themselves divided by the combined rolling resistance of the average car: base rolling resistance plus the added rolling resistance due to grade, plus the added rolling resistance due to the curvature. The floor of the result is displayed as a whole number (since pulling a fraction of a car is not meaningful).