Re: Seattle Car 272

["David Bennetts" <davibenn@pcug.org.au>]

"David McLoughlin" <davemclNOSPAM@iprolink.co.nz> wrote in message
news:39939AFA.57C0@iprolink.co.nz...
> Len and Elizabeth Newstrum wrote:
> >
> > Our local TV just gave an update on this.  It seems that the driver and
> > mechanic had clean drug and alcohol tests.  The driver got a
> > low-pressure (pneumatic?  hydraulic?)
>
> air brakes, from a compressor.
>
> > warning light and turned it off.
>
> >
> > Do any of you that have a lot of knowledge on these vehicles know enough
> > about their characteristics to comment on their brake systems?
>
>
> Well in Melbourne, Australia, where they came from, they had air brakes
> fed by a compressor as well as hand brakes for emergency stopping when
> the air failed (which was rare). They had Ferrodo compound brake shoes
> which gripped the wheels to slow and stop them and in a rushed stop the
> driver could dump sand on the track by a foot pedal to increase the
> grip.
>
> Have the hand brakes been removed from these cars in Seattle? The ones
> in Melbourne still have them.
>
> David McLoughlin
> Auckland New Zealand

I'm pretty sure the hand brake wheels were still in place when I saw the
cars in 1997, so if that's the case they still should be connected,
otherwise I don't know how you'd park them on a slope with power off, the
air would bleed off eventually so they'd run away, as indeed some trams did
in Sydney.  I was told about one running away from Chatswood Station years
ago, the driver and conductor ran after it and caught it around Archer
Street.

In an emergency trams fitted with resistance control can be stopped by
pulling back the reverser key to reverse position, then turning controller
handle to the first or second series notch, when tram has stopped secure it
with the parking brake.  If this procedure fails to operate because the
circuit breaker has opened cutting off the power, or if there is otherwise
no power to the controller (supply failure or pole off line etc), it is
necessary to turn the controller handle to full parallel; this cause the
motors to act as generators and they will oppose each other (two motor
trams) and in pairs (4 motor trams).  This action will not completely stop
the tram but reduce its speed to about 4 mph, it then has to be finally
stopped and secured on the handbrake.

The above actions should only be used in emergency because it can damage the
equipment.

Regards

David Bennetts
Canberra