Scale Speeds
With 1 scale kilometre being somewhere around 52 metres, the scale mile rolls by at around 82 metres.
If your line runs alongside the garden fence, and the fence comprises 6'0" panels, then eight seconds to get from one fencepost to the next is a scale ten m.p.h.
D = Measured Distance (Metres)
T = Time to travel D (Seconds)
Scale MPH = (3600 / T) / (84.7 / D)
The following article was submitted to the egroup in December 2000.
Most model trains are driven much too fast. Get to the end of the line too soon, or once around the circuit too fast, and your railway will seem even smaller than it really is. Slow is realistic. Slow is prototypical. Small i.c. locos often had three speed gearboxes, equating to 5 m.p.h., 10 m.p.h. and 15 m.p.h. A report in the 'The Locomotive' for 1924 on the testing of a new railcar by Drewry comments that the engineers expressed themselves 'well satisfied' with a top speed of 18 m.p.h. The speed limit under the Light Railways Act was just 25mph. (remember the scene in the Titfield Thunderbolt, when the enthusiasts were warned not to go too fast...?).
So how slow is slow? Speed is a combination of time and distance, usually expressed as miles per hour. A mile is 1760 yards. Divide by 19 and you find that a scale mile is just 92.6 yards. I measured my line and it came to 59 yards end to end, which at 0.6 is just over half a mile. But what about scale time? Well, No. Our locos are 1:19 scale, admittedly, but they use real fire and real water to make real steam at real pressures, often at about 40 p.s.i. Similarly, time is real. There are 3600 seconds in an hour. Take a real speed of 10 m.p.h. Divide 3600 seconds by 10 and you will see it takes 360 seconds to cover each (real) mile at this speed. If it takes 360 seconds to cover a scale mile of 92.6 yards, divide 360 by 92.6, round it up to whole seconds, and you will see it takes four seconds to cover each yard at 10 m.p.h. for a model at 1:19 scale.

Keeping it very simple for those of us who don't like maths, if your line runs alongside the garden fence, and the fence comprises 6'0" panels, then eight seconds to get from one fencepost to the next is a scale ten m.p.h. On my Ashton Forest Lt Rly., a loco taking four minutes to go from end to end is doing about 10 m.p.h. Less than two minutes and it's going much too fast, and the driver can expect to be on the carpet in front of the Fat Controller.
John Angell
8 December 2000