CALCULATING SCALE SPEED

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Updated July 2017


Much has been written over many years in various magazines about the subject of speed. Sometimes it has involved many complicated formulae which if you wanted to be to the instant would send you scurrying for a calculator every time you cared to accelerate. Like many of us, my main measure used to be what looked to be visually correct imagining a "scale man walking alongside the train" among the other techniques that we modellers use.

I was starting to get frustrated by formulas and guess work until I saw an article or letter in a magazine which stated "... in HO, the scale speed of an engine is equivalent to the number of inches that are travelled in 5 seconds".

My own layout is a 4x8 with a section of straight track at the front 38 inches long. So if that distance was travelled in 5 seconds then it was travelling at 38mph, slightly less was 35mph and slightly more was 40 mph. Checking this out on a calculator, I found this to be very accurate. About half the distance travelled was 20 mph, 6-8 inches less than the section was 30 mph. As this suited the speed of my freight trains which I mostly run, this worked out quite well for a while.

About 6 months after happily working with this system, I realised that with an HO boxcar being 51/2 to 7 inches long that I could check speeds in the yard by lining it up passing a signal, pole, tree or other marker. By counting 5 seconds I could be travelling between 5 and 7 smph, or multiples such as 10 or 15 smph. You will be surprised at how accurate you can become at counting 5 seconds. You can use this on other portions of the layout where you may not be able to read a digital readout boxcar anyway, even if you could afford to buy one or you are able to make one.

After some time again, I saw an O scale exhibition layout which as part of its detail showed a recently "re-laid" section complete with survey pegs which bought back a lot of memories. As a child I would often ride the front of railcars on a section of line that had been recently duplicated with pegs adorning the centre of the track at even intervals. I would try to count them as the train accelerated and then decelerated between stops. Once used for track alignment, the survey pegs  are usually left to rot so they are evident for quite some years depending on the extremes of weather.

I do not recall having seen survey pegs in North America but I did find a colour photo on Page 175 of "America`s Colourful Railroads" by Don Ball showing a Santa Fe passenger train negotiating a section of track with pegs clearly showing. Anyway I have now applied them to my own layout over a space of 80 inches using spikes, clipping off the heads and painting most of them white except every fourth one which is yellow (for Start, 20,40,60 & 80) The detail is small enough not to be outstanding (in fact most people do not notice them at all) and the odd speeds can be worked out as a portion of the 5 inch space.




You can see one of the white spikes clearly here standing proud of the sleeper. This is one of the intermediate spikes representing the 5, 10 or 15 mph markers.

Every 4th spike is painted yellow for the 5 10 15 and 20 mph markers and the detail is fine enough not to have a problem being spotted




Without going into the mathematics involved, the spike method of distance marking can be used for all scales. For the 5 mph graduations the spacing is 5 inches in HO, 5.75 inches in OO, 2.75 inches in N, in O it would be 9.2 inches, 1 Scale (for any 1n31/2 modellers assuming your equipment is 1:32) is 13.8 inches and G scale for those of you in LGB at 1:22.5 is a whopping 19.6 inches.

If, as I do, you live in a metric country and you wish to work in metric (which for model railroading purposes only, I do not) then it is easy to use a multiple of 5 kilometres per hour using the survey peg method. The spacing of the pegs would be 80mm in HO, 91mm in OO, 43.5mm in N, 145mm in US O scale (1:48) or 160mm in 1:43.5 scale, 217mm in 1 scale and G scale is 308.6mm. Obviously you may need more pegs as the speed factor is higher i.e. as 50mph is approximately 80kph you will need 16 pegs by comparison to 10 and as European and Japanese passenger trains in particular are usually operated faster in the prototype,  a longer section would be required. I would not try to count a factor of less than 5 seconds as your accuracy may suffer.

If you do this, particularly in N scale, you may be surprised just how fast you have been operating your trains. This is because of the relative distance you are away from trains in scale yards/metres from where the action is and the further away you are, the slower the train appears.

One of the spinoffs of all this is that when I am observing prototype operations. When the train is moving slowly and I know a car is 50ft long then I can count 5 seconds and work out how fast it is travelling to within a couple of mph,(1 car =7.. 2 cars = 14 mph etc). Thus I have a reference on which to base my operations on the prototype more realistically... and that is just part of the game in this great hobby of ours!