Re: Train Accident in Blue Mountains

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

In article <384E35B3.32401A9F@zeta.org.au>,
Don Allitt  <nahgfa@zeta.org.au> wrote:
>Well then what about when the emergency brakes come on there is an automatic dumping
>of sand in front of the wheels or even reverese thrust thru the electric motors.
>Don.

 Sand maybe, trying to reverse the motors would almost certainly 'pull the power',
however keeping the electric brakes active at the same time might help, but it might
also cause the wheels to lock and make the problem worse.

 There is a technique of braking electric motors called 'plugging' which basicly shorts
the motor out while it is in 'generator' mode, very effective, but it does heat the motors
at lot.
 Loftus tram museum have a japanese tram that hooks its two motors to one another back to
front so both motors in 'gen' mode fight one another. It was nearly as effective as the
trams air brakes!.

 Note high speed trains do have additional braking options - magnetic track brakes and
eddy current brakes, which if applied at speed on a TGV or ICE can result in track damage
they grab so well. I understand that a TGV has to run back to the depot at low speed after
a full emergency brake application for replacment of stressed brake and bogie parts!

 Fitting magnetic track brakes (as used on the trams) to the the EMU fleet may be even more
effective at averting collisions that train stops, as the drivers then stand a chance of
stopping the trains in sighting distance.