"Terry Harper" wrote in message

"TheOneKEA" wrote in message
om...
I live in Richmond and take the District Line into Central London
about once a week. Sometimes I change trains at Turnham Green to go
to Ealing Broadway. When I am at Turnham Green, I have noticed that
the tracks make strange noises when either a Piccadilly or a District
train is approaching. No matter how fast the incoming train is
traveling, the tracks twang, rattle and vibrate like huge springs are
being snapped back and forth. Once the train has passed by, the sound
continues until the train is well away from the platform.

I have not heard this anywhere else on the Underground except at
Turnham Green and some of the stations east of it (the tracks at
Earls Court and Victoria make the sound, but it's much more faint
than at Turnham Green). Does anyone have a clue as to what I'm
hearing?

We get the same effect at Hassocks on the Brighton line. It is
vibration of the conductor rail. You can tell because it starts when
the conductor rail switches into the centre as the train nears the
station, and stops when it switches back to the outside beyond the
station.

But at Turnham Green it starts well before the outside conductor rail
switches position. Of course, with a fourth rail system, the centre
conductor rail stays in the same place through stations, so maybe that's why
it starts early and stays singing longer on LU. Presumably the conductor
rails are much less rigidly mounted than the running rails?