Pentrex (sp?) has a video on air brakes, when they have their specials you
can get this tape for free (BOGOF). Otherwise I think they are $9.99 +
shipping. I do not know if they are still available, but I enjoyed the tape
[ everybody else who watched it fell asleep ! ] I assume it was a training
movie people would have to sit through.
Rich
-----Original Message-----
From: John Knopp [SMTP:jdknopp@g...]
Sent: Thursday, August 24, 2000 4:33 PM
To: BRHSlist@egroups.com
Subject: Re: [BRHSlist] please, more on air brakes
At 01:10 PM 8/24/2000 -0500, John S. wrote:
>Regarding further specifics of air brake dynamics I speak for
myself, and
>I suspect a great many others, when I say that while I have a basic
>general knowledge of how a train's pressurized air line keeps the
brakes
>on individual cars released, and how angle cocks are used to retain
that
>pressure when cuts of cars are set out, past that I am a little bit
fuzzy.
>For example, how and why retainers are utilized in practice has
never been
>adequately explained to me.
I should probably wait for the professional Rails to answer but
since I'm
at home and have a few minutes you'll have to wade through my
explanation!
It may be necessary for an engineer to set and release the brakes
several
times on a steep grade but when the brakes are released the train
begins to
accelerate, obviously. If the engineer tries to quickly reset the
brakes
he gets less braking than before because the air reservoirs have not
had a
chance to recharge. It can take forever and a day to recharge the
air on a
long freight train (probably seems longer when one is charging down
a
mountain, I'm guessing!) so someone came up with the idea of
"retaining"
some of the air in the brake cylinder after the train brake is
released,
thereby keeping the brakes applied while still allowing the
reservoir to
recharge. The retainer was born....
Retainers are manually operated - a crew member must walk the train
and
manually set them. They have four positions AFAIK - direct release,
slow
release, low-pressure hold and high-pressure hold. Usually only a
percentage of cars are set to retain - it's up to the engineer to
decide
how he wants them set.
As far as your other questions - I'd better sit back and learn
something
from the pros....
John Knopp
jdknopp@g...
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