We consider here the timing aspect of the equation.
Train timing has evolved over the years, and one of the biggest changes has been in the equipment available for measuring time. We consider, firstly, mechanical stop watches that were the only option for the first 150 years of timing trains. We explain the timing methods used and consider their advantages and disadvantages
We consider the current options in terms of digital stop watches; what features are available and their relevance for timing trains, and explain lap and split times. We suggest methods for operation for recording passing times.
Readers will appreciate that computers (either laptops or PDAs) are able to record times accurately, and will probably realise that computers can then be used to calculate speeds and analyse the data in a number of ways. We explain what hardware features are necessary to record times accurately, and the software that can be used to record times and calculate speeds.
Mechanical Stop Watches
It is perhaps only in the last twenty years that cheap and reliable digital stopwatches have been available. Until then, recorders used mechanical stopwatches which measured only to .2 sec and were relatively expensive. In those days, it was not unusual to use a wrist watch to record clock times at passing points and then calculate the elapsed time. A single mechanical stopwatch would be used to take readings at mileposts and calculate speeds from a ready reckoner. (Most mechanical stopwatches had only three modes: Start; stop and reset to Zero)
With increased speeds, it became advisable to take times at half-mile intervals in view of the difficulty of viewing the stop watch dial. It was not uncommon for recorders to add a second stop watch, and a "leap-frog" technique was adopted:
Whilst it was feasible to use digital stopwatches exactly as explained above, we would discourage this, as the arrival of new equipment, gives more timing opportunities.
First, potential buyers must consider how they want to use the equipment. There are numerous suppliers, and differing levels of complexity, but the following items should be considered:
Some watches display both lap and split times, whilst other only allow one or the other. Some watches store the most recent lap and split times.
Assuming that the user has a single digital stop watch which displays lap and split times, then he should start the watch on departure and take visual readings at each passing point. The lap button should be pressed when passing mileposts and the lap time noted. The RPS Train Timing Guide gives suggestions relating to the frequency of milepost observations. The ready reckoner can be used to ascertain speed. The lap button can also be used to record signal stops and restarts, and the lap reading will indicate the length of stop. The watch should be stopped at each station stop.
For watches without the split facility, the lap key should be used as above, but the lap time must be noted and the difference between the two most recent times manually calculated and the ready reckoner used to give the speed.
The advantage of this technique is that there is a continuous record of readings and any errors will be obvious from apparently incorrect speeds.
Readers familiar with computers will appreciate the timing applications that are available with existing software, and that data can be recorded and saved for subsequent download and review. Assuming that a degree of portability and reasonable battery-life is required, we will consider applications using PDAs.
Whilst most Pocket pc PDAs are supplied with a Pocket Excel spreadsheet, they are limited because the operating system currently only records times to the nearest second, which is not sufficiently accurate to calculate speeds from milepost observations.
However, there is a software application supplied by z4soft called Ptab which records to 1/100sec. The time is calculated by clock "ticks" from the computer and only operates when the computer is turned on, so it is important that the automatic power-off does not operate, otherwise elapsed times will be incorrect. As with other devices, it is important that the user can easily, accurately and firmly press the button to record the time. For each reading it is necessary for the operator to press the button to record the time, press again to move the next row, and again to display the macro for the next reading. The resulting spreadsheet calculates the elapsed time, the current speed and the milepost location of the reading. An example of a train going north from Stafford is shown below
It can be seen that on leaving the train, the recorder has a complete analysis of the journey. It is recommended that times at passing points are recorded manually from a stop watch. They could be recorded on a separate Ptab "sheet". However, switching between sheets could cause passing times to be missed.
Recent PC operating systems now record times to 1/100sec, so Excel spreadsheets similar to the one shown above can be used on laptops in trains.
If readers would like sample Ptab and Excel spreadsheets, please contact the editor (firstname.lastname@example.org)
We hope that this has given readers an appreciation of what equipment is required and available, but if you require further information, please contact appropriate members of the committee