During the fabled and ill thought out BTC Modernisation plan in 50s, when diesels & electric locomotives we’re built because they weren’t steam powered regardless of if they actually worked, a need was raised to introduce new electric locomotives for the Kent mainlines. Like a few other Modernisation locos the order was conceived with little foresight into the future of the rail market – class 14s I’m looking at you, a train designed for a purpose that simply was beginning to not exist – and the same could be said of the future class 71s, built for traffic that within 20 years would all but dry up.
In 1958 the order was placed. Doncaster chimed and rang to the sound of locomotive builders nailing together the then classified HA type. All 24, E5000 to E5023, (E5000 later became E5024 – the first to the last) we’re dispatched to Hither Green with all haste to start operations.
The mechanical design of the HA had already been proven in the class 70s, the three bizarre southern beasts who’s size was only diminished by they’re torque. The basis of the class 70 was a flywheel booster. The flywheel was installed because DC electric locomotives have a limited length at which power can be taken from the 3rd rail, and gapping is common (gapping – when a train gets stuck in an area where there isn’t any 3rd such as a Junction or an entrance to a large station) The flywheel booster would be fed from the DC traction instead of the traction motors directly and then the flywheel would spin ensuring the generator continued to turn so the traction motors had a continued supply of power. That meant that on reaching a natural break in the juice rail the flywheel would still spin resulting in a constant continuation of DC supply, for a limited time, sort of like a delay of power to the traction motors. Class 73’s weren’t fitted with this and that’s why it’s like firework night in the cab when an ‘ED’ goes over a gap.
The other issues that the 70s originally tried to overcome and the 71s we’re to continue the mantel was that of 3rd rail in yards. As you can imagine a shunter walking around a yard with a 3rd rail isn’t going to be good for his continued health. The 3rd rail is an extremely dangerous think to have around somewhere that requires a workforce to be on foot walking around. To overcome this problem, the SR decided to fit its yards with a 650v DC overhead tram style wire. As a 70 or 71 came into a yard on its 3rd Rail it would pop up its diamond pantograph and power would be drawn from that instead, resulting in no third rail in yards, and a safer workplace for the shunters, all very simply but effective stuff – however it wasn’t to last, because a new idea was on the horizon that of the Electro Diesel – more on that one later.
The 71s when they turned up on the Southeastern we’re pushing 2,700 Bhp, in a Bo-Bo. The proven Swiss electrical gear they found themselves with was reliable and simple to maintain. It looked like the Southern had done well out of the Modernisation plan as other regions we’re quickly discovering that they hadn’t done quite so well. North of London re engine programmes we’re being talked of with locos barely past they’re fifth birthday, for the BTC it was nice to have a success down south.
The 71s we’re put to work on all the prestigious stuff, turns such as the golden arrow and Night Ferry we’re soon seen with a glistening HA strapped to the front. It’s torque and horsepower ready to power coastward with open abandon.
As TOPS hit the network and HAs had became the class 71s, passenger work was dying off. The Golden Arrow had finished and the night ferry wasn’t long off. Another problem arose, that of engineering works. The HAs needed the juice, and engineering work meant that juice was turned off. Planners at HQ often had to find huge spiralling routes to get 71s home and on duty. And the 71 had a nemesis now, the class 73s, they’d proven themselves a capable locomotive, not as powerful but they had an ace card up they’re sleeve – a small diesel engine. Class 73s could reach locations the 71s only dreamt of. The more 73s we’re rostered on trains the more the writing was on the wall for the 71s. In 1967/68 it became apparent that the Electro Diesels concept was the way forward, the yard’s centenary had fallen into disrepair and it was being taken down. Some pantographs we’re removed from the 71s as they we’re now deemed redundant. But someone had an idea, if work was drying up for the HAs and they we’re to be scrapped why not turn them into Electro Diesels, they’re power on the juice was awesome, heavy freight trains and newspaper trains we’re easy for the 2,700bhp locos, but it’s lack of power off the juice was signing it’s death warrant. Ten locomotives we’re selected to be converted to HBs or later class 74s. As we’ll soon read that idea was fraught with possibilities and hope, but in 1977 the remaining class 71s, most in perfect working order, we’re withdrawn and cut up, because quite simply work didn’t exist. The hope of more HAs being converted to HBs had gone up, like a HB’s Paxman engine, in smoke.
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