I did not have a DCS system till around two years, though I had collected about 20 PS2 and 3 locos, I used to set my TMCC loco top speeds based on one mile in O scale is 110' which is 5.75 laps on a circle of O-72 track so if a prototype had a top speed of 75mph it would take 48 seconds to make 5.75 laps on my O-72 test track. One thing I found was all of my locos would stay on the track when running on a circle of O-72 at 100 scale mph.  Not that I normally run that fast.  I usually limit my passenger trains to 65mph and freight to 40mph. Another thing I noticed was that traction tires that were not glued on would not stay on long at 100 mph scale. I am reposting a scale speed chart as a jpeg that I posted earlier as a DOC. file as someone complained they could not open it.  Hope it helps you determing how fast your driving.          j103_7419


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RailRide posted:

I used a different table that breaks down speeds according to the number of inches traveled in a specific time period. For O scale, the number of inches traveled in 2.5 seconds is the scale MPH.


That is only a very rough estimate  and would depend on your ability to look at a stop watch and the loco at the same time for 2.5 seconds and accurately mark the point you start your measurement and where you end.  You end up off by almost 10% if you use 2.5 seconds 2.72727 (2.7) would be closer.    I hate to do arithmetic on a key board but here goes.   one mile = 5280' X 12" = 63360" in one mile  divided by 3600 seconds per hour  63360"/3600 = 17.6" per second is one MPH life size, divide that by 48 for O scale  17.6" / 48 = .366666" per second is one MPH in 1/48th  O scale.  .366666" X 2.5 = .9166  is short it should equal one.   Try 2.72727 X .366666" = .99999 that would be less than 1/10 of one percent off.  That's if your able to measure an accurate 2.72727 seconds and at the same time, accurately measure the distance the train traveled. Counting 1001,1002, 1003 would probably allow you to watch the train and mentally mark the start point and end. Still, it would be easy to be off by 10% in both your time and your distance traveled for a 20% cumulative error. You might as well guess,  2.5 or 2.7 seconds is just too short a time for any kind of accuracy.     Timing the length of time to travel a known distance is MUCH easier.  BTW, about the table in my post, I made it so that I could easily set the top speed of my locos accurately within one or two scale mph in TMCC. It's off less than one percent at each speed.       j

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.




I measured my around the room layout at .7miles.  I have an Ipad and use a stopwatch App and then, knowing the distance and time, use a Time-Speed-Distance App to see how fast my BPRC equipped engines/trains are going.

I also use the DecibelX App to see how much noise my layout makes.


4+ years and STILL Having A Blast Running BPRC

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