Hi Kiwi and welcome to The Gauge. Will this help you? http://www.trainweb.org/nrmrc/pubs/speed.html Loren

If it's HO: measure the distance in inches that your train travels in 5 seconds. This is the same as the scale speed in MPH (about 1% error). If it's N, THEN you have to go back to school:mrgreen::mrgreen:

HO Speed Yes indeed its HO thought we were smart while at a EXPO when someone asked us what was the REAL SPEED, we omitted we had no idea of hand, so hence here or somewhere looking around, then we decided to do a test ourselves as follows 10 fingars span = 9 inches x 10 = 90 inches, taking 12.14 seconds, not sure where to go from here inches into miles x seconds into hrs, now looking for the calculator 90 / 63360(inches in mile) = 0.00142045e x 60 x 60 = 3600(seconds per hr), on my calculator this reads 5.11362, ??? mph or s there mre to add, like 1.87 scale I AM NOW REALLY CONFUSED THANKS 4 ur reply

So I am nearly right with my sums then or so far away it dont matter, sorry to say can not afford one of them for now

9" in 12.14 s = 3.71 " in 5 s (9*5/12.14) or 3.71 scalemph (estimated by the 5 second rule) or 3.67 scalemph (true value) How close did you measure the 12.14 seconds?:mrgreen::mrgreen: BTW, I don't see the 12.14 seconds in your calculation. And yes, you can multiply the true speed by 87.1 to get the scale speed. The distance is scaled, but the time is always constant.

Again, with your second hand or stop watch, measure the distance (in inches) traveled in 5 seconds (easy way). If you travel 36" in 5 sec, you are going 36 scale mph (small error). The true value is 36 X 87.1 / 88 or 35.63. This error (1.02%) might be less than you can really measure with your second hand!! :mrgreen::mrgreen: