Train Timing Page 1 - Make Your Journey More Interesting
Some enthusiasts talk about the locomotive giving a good thrash, but it is really performing to the best of its ability, or is it making a lot of noise but not enough power to keep time? Typically, a diesel locomotive can be expected to produce around 75 to 80% of its rated output to move the train, the remainder being lost in internal resistances, etc. The position with electric traction is more complicated, since there is usually a continuous rating, which can be used for long periods without overheating, but this power can be exceeded safely for short periods where necessary.
The best way to tell if the locomotive or unit is performing well is to time your journey and then calculcate how much power is necessary to maintain the observed speed at key locations on the journey.
All you need to start is a stopwatch. Many digital watches include a stopwatch facility. If the watch has a bleeper, it is preferable to disable it by opening the back of the watch and carefully snipping the electrical connections to and from the bleeper. This avoids disturbing your fellow passengers with irritating noise, and also increases the battery life.
Next, use the stopwatch to record the times taken from the start of your journey to pass intermediate locations, and to arrive at the next stopping station. The locations can be a matter for personal choice, provided you use the same location on every trip, so that you can compare successive journeys. Also record the speed at each location (see below).
Some people time at every ¼ milepost, but many mileposts become hidden by vegetation in summer. Other people use station buildings, signal boxes, or bridges near to the sites of closed stations as their timing points. The position of some of these locations relative to the mileposts can be found in various publications - for example, the excellent Quail track plans. Note that the railways still use miles and chains for measurements - presumably it would be too expensive to replace every milepost by metric posts. There are 80 chains per mile, so that one chain equals 22 yards, i.e. slightly longer than a Mark 1 or 2 coach, but shorter than Mark 3 stock.
Speeds in mph can be calculated as follows:
Speed = (900 / Time in seconds per ¼ mile)
or Speed = (1800 / Time in seconds per ½ mile).
For example, 9.0 secs per ¼ mile or 18.0 secs per ½ mile corresponds to 100 mph.
You can use a spreadsheet to calculate and print a table relating speed to time taken per ¼ or ½ mile. Using ½ mile intervals is preferable if possible, since this reduces errors if one milepost has been misplaced. See Timing Page 3 for an example of a time/speed conversion chart.
Alternatively, you can use a portable GPS (Global Positioning Satellite) receiver. Many of these give a direct reading of speed, by calculating your position (latitude / longitude) from the radio signals broadcast by a network of space satellites, and how much that position changes from second to second. The disadvantage of GPS is that you can lose the radio signal due to tunnels, high cuttings and buildings, and if your train is moving quickly, it may take a while for the GPS to re-establish your position and speed. In addition, GPS does not work in some rolling stock, including Voyagers & Pendolinos, due to reduction in the radio signal by the materials used in construction of these vehicles. One advantage of GPS is that you can use it when mileposts are not visible, e.g. at night, or when trees and other vegetation are growing like weeds.
Then, you put everything together into a performance log, something like those on Train timing Page 2.
It helps to know about gradients and speed limits, so that you know where and why the train might slow down or accelerate. Gradient Profiles of many British lines appear in a book originally published by Railway Magazine, and later republished by Ian Allan. Other profiles appear in books of line histories. Beware, however, that there is some uncertainty about the accuracy of some of these gradient profiles.
There are published techniques for calculating power outputs, for which you will need to know about the resistance to motion (friction, etc.) of the coaches, etc. Using a spreadsheet makes these calculations fairly simple - but I have omitted the calculations here, since some enthusiasts simply wish to record the fastest journey time made by different classes of locomotive or multiple unit.
Permanent and temporary speed limit signs are erected at the lineside, and permanent limits are shown in Sectional Appendices - if you don't work for the railway, then copies of older issues may sometimes be purchased at railwayana stalls and shops, etc.
If you want to know more about train timing, I suggest you contact the
Railway Performance Society, or view their website at:
Also recommended is Andy Flowers's train timing site at:
http://www.girdlers.demon.co.uk
Please note - for professional rail staff, the term "train timing" has a different meaning - it is the process of preparing the running times for regular and special train services.