0-60: CLASS 700
Neville Hill gives a Class 700 the chance to showwhat it can do on third-rail power.
We have tried them on AC, now how about DC?
ACORRESPONDENT from the former Southern Region suggested that the most likely candidate for the third-rail fastest 0-60mph trophy could well prove to be a Thameslink eight-car Class 700 on the Swanley to Shortlands section. If you are in luck, you could even have a race away from Swanley with another unit from the SouthEastern stable.
It is not surprising that a start from Swanley looked impressive, as it is downhill at 1-in-100. In fact many of the gradients on this stretch of line would do credit to the Pennines! The eastbound start from Bromley South is 1-in-95 while Bickley is 1-in-100. St Mary Cray is precariously perched in the middle of a 1-100 gradient giving chance to average favourable and unfavourable conditions. Two round trips between Bickley and Swanley also gave the chance to time a 1-in-100 downhill start from the latter station westbound.
The train runningwas enviably consistent, with halfaminute late effectively counting as the maximum delay. In terms of driving, however, there was a wide variety of methods employed. One driver gave up accelerating at 60mph between Swanley and St Mary Cray, whereas another touched 84mph on the 2.68mile section.
One coasted over the westbound summit before Bickley, whereas another ran hard and braked hard.
The 12-car Class 700 we previously sampled under the wires on the Midland was credited with 0-60mph in 46sec. Despite the same power/weight ratio available on the eight-car variety, it was obvious that direct current third-rail was not going to match alternating current overhead supply but, even so, the results were slightly disappointing. The best downhill run managed to reach 60mph in just 57sec, but uphill the best example took 80sec, with a median 68.5sec rounded up to 69sec.
Looking at other third-rail units in our Rail Express league table, Class 465 managed 69sec, Class 707 70sec, Class 375 70sec and Class 507 73sec. This is a remarkable coincidence, implying a traction current supply issue that constrains the power available. The RE Factors, however, vary widely – which perhaps illustrates the ‘black art’ of third-rail power calculations.
The eight-car Class 700 has a potential 4291hp available, effectively untapped on third-rail, but if this is used for calculating the RE factor the figure produced is all but 30% lower than the overhead supply performance.