From: ahk@chinet.com

John Albert  wrote:

>I downloaded the pdf format of the Lac Megantic report.

>It goes on for around 191 pages (in pdf format), but most of
>it is irrelevant as to answering the question, "why did the
>train move?"

>That answer can be found on page 23, in Table 1, "Locomotive
>event recorder information".

>Evidently, the engineman made a grave mistake in leaving his train the
>way he did. This mistake may not have been an intentional, but if he had
>done ONE MORE THING [re-apply the automatic brakes] -- even though the
>number of hand brakes was insufficient to hold the train -- the train
>would not have moved within the time frame it did, even though there was
>no longer  enough (or any) locomotive air pressure to keep the locomotive
>independent brakes applied. . . .

Thanks for the explanation. Given the completely worn brake shoes on
several of the locomotives (hand brake application applies just 2 of 12
brake shoes), I take it leaving automatic brakes applied would have left
all 12 shoes applied on each locomotive, partly making up for some of
the bad brake shoes that would worn beyond usefulness.

I read the whole report yesterday, except for the pages on the fire itself.

Several questions on what you wrote:

I take it that the automatic brake application and the independent brake
application are controlled separately. Are there two separate brake
handles?

The report went through the actions of the Quick Release Brake (QRB) valve
on the GE locotives, 3 of the 5 locomotives in the engine consist. To
engage the hand brake, the air must be dumped, which is what the QRB valve
does. A brake chain connects the hand brake wheel to the QRB valve; one
of the QRB valve because of temporary maintenance performed had to be
released manually, but the engineer didn't know to do this. I take it this
dumps the air in the automatic brake cylinder without dumping the air
in the independent brake cylinder, right? Does this mean that the independent
brake was still applied in the GE locomotive with the faulty QRB valve,
at least until the air pressure dropped in the independent brake cylider?

I take it the other two locomotives don't have QRB valves. Cars themselves
wouldn't have QRB valves, right? In these situations, is the air still
dumped in the cylinder that maintains automatic brakes in order to apply
the hand brake?

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