0 to 60! Just how nimble are today’s locos and units, and what’s the quickest off the mark?
After roving Coastway backwaters with Southern Region diesel units last month, our performance expert John Heaton FCILT returns to the Brighton main line to tangle with third rail power delivery.
WE are back on third rail 750v DC power supply following a couple of trips in search of the threatened Class 313s (see September issue). This month’s trip involved a 12-car Class 700/1 dual voltage Siemens ‘Desiro City’ packed with a massive 6439hp capability to move just 400.6tonnes tare. Whether the installations could feed these hungry monsters is a different question.
Post-pandemic pleasure-seeking passenger numbers rose steeply as we headed towards Brighton, adding about 20tonnes to the set’s plated weight by the time we reached the coast. There are many 1-in-264 rising gradients from station stops on this route, so the southbound departure from Burgess Hill, used for the Class 377 article (see July issue), becomes the most suitable for assessing 0-60mph against the slightly adverse 1-in-1378.
In similar fine conditions with a dry rail our serpentine Class 700/1 took 0.90miles and 83.38sec to reach 60mph compared to 0.85miles and 81.75sec for the 8-car Class 377 combination with a nominal horsepower of 4024. Both trains are shown in the table. In terms of raw power/gross weight ratio, the Class 700/1 packed 15.3hp/tonne compared to 11.9 for the Class 377s.
Driving techniques can easily explain the minimal differences in the time taken to reach 60mph and, of course, the 8-car Class 377 was only 20% lighter than the 12-car Class 700/1 even though it comprised 33% fewer vehicles.
The pattern was repeated on the
1-in-264 starts, with the Class 377s managing 0-60mph in 0.98miles and 90sec compared to 1mile and 95.22sec for the Class 700/1. On the same gradient from Hayward’s Heath, but with fewer trains around to draw power, the Class 700/1’s performance rallied, the respective figures being 0.87miles
and 85.96sec for the Class 377s, and 0.9miles and 85.19sec for the ’700/1’. Overall, Class 700/1 operating in 25kV AC mode, with over 40% better RE factor and ‘time to 60mph’, makes for a more representative image of the class than ‘south of the river’ on third rail.