Scale Speeds

[NECRfan]

I was lousy at math in school, and now it's coming back to haunt me.  How do I measure the scale speed of an N scale locomotive?  I want to restrict my speeds to 15 mph.

[tomikawaTT]

Scale speed = prototype speed / scale reduction.

For modeling purposes use feet per second rather than miles per hour.  88 ft/sec = 60 mph

15mph = 22 ft/sec

Dividing 22 by 160 yields 0.1375 ft/sec, which is just over 2 feet in 15 seconds.  It will take you four minutes to run a 33 foot N-scale mile.

Chuck (Modeling Central Japan in September, 1964 - in twice-N, 1:80 scale, aka HOj)

[wjstix]

An easy way to do it is measure out a scale mile on your layout - I like to use freight cars on the track creating a train say three real feet long. Just push it along and put a marker down every three feet. That way you don't have to get into using pi and such to calculate curves. Then as noted, it will take four minutes for a train going 15 MPH to cover the mile, two minutes at 30 MPH, one minute at 60.

[gregc]

sometimes its more convenient to work with units that you can see in front of you.   the following shows how to express full-scale speed in mph in n-scale units of seconds per foot.  

for example, at 15 mph it takes 7+ seconds to travel 1 foot.

    fps    = mph * 5280 ft / 3600 sec     feet per second
    sc-fps = fps / 160                    n-scale feet per second
    sc-spf = 1 / fps                      n-scale seconds per foot

       MPH       FPS    SC-FPS    SC-SPF
        10      14.7       0.1      10.9
        15      22.0       0.1       7.3
        20      29.3       0.2       5.5
        25      36.7       0.2       4.4
        30      44.0       0.3       3.6
        35      51.3       0.3       3.1
        40      58.7       0.4       2.7
        45      66.0       0.4       2.4