The most accurate way to determine the scale speed of your model train is to run it at fixed throttle or speed over a closed loop. First, measure or calculate the distance (in feet or inches) around the loop. Then, measure the time (in seconds) required to complete the loop. For O gauge/O scale 1:48, the scale speed (miles per hour) will be:
SMPH = ((distance around loop - feet) / (measured time - seconds)) X 48 X 3600 / 5280
which is equal to:
SMPH = 32.727 X (distance around loop - feet) / (measured time - seconds)
If you measure the loop distance in inches, the equation becomes:
SMPH = ((distance around loop - inch) / (measured time - seconds)) X 4 X 3600 / 5280
which is equal to:
SMPH = 2.727 X (distance around loop - inches) / (measured time - seconds)
If you insist on higher accuracy, run the train ten times around the loop, measure the time and don't forget to multiply the loop distance by ten before using these equations.
MELGAR
