Re: What's that noise?

[matthew@mail.usyd.edu.au (Matthew Geier)]

In article <7hfguv$4ro$1@lios.apana.org.au>,
C. Dewick <craigd@lios.apana.org.au> wrote:
>In <373AF121.2E4A8EE5@ozemail.com.au> David Johnson <trainman@ozemail.com.au> writes:
>
>>More voltage, but more specifically more current.  Some high current DC CBs have
>>a blast of air to blow the arc out an arc chute which also makes noise.
>
>Which is what made the old red single-deck sets here in Sydney so much fun,
>because the main CB's were *huge*, and sat under the middle of the floor of
>the motor cars with the arc chutes facing out to the sides. 
>
>When they tripped (such as when the driver shut off suddenly during a heavy
>powering manouvure), you'd see a huge flash and an arc (much like a Jacob's
>ladder, but controlled) writhe out of the body of the CB via the arc chute
>as the air blast blows out the ionising path to break it quicker


 This was particularly exciting if set tripped while trying to depart a
station during the peak hour. Hords of people right up near the platform
edge would witness a huge flash, bang and the smell ozone come from under
the car.
 More than one 'scared witless' passenger then ran to a station assistant
and asked that the train be stopped and that the emergency services should
be called to tend to the explosion.