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Re: What is Known So Far
Author: d
Date: 09-19-2013 - 09:51
>locomotive independent brakes are a "straight air" system that loses effectiveness as main reservoir air pressure declines.
Technically speaking, this is not correct, although they do lose effectiveness as MR pressure declines below the set point of the relay valve (which in some cases is about 1/2 that of the MR).
>nor inadvertent operation of locomotive air brakes by fire department responders - just bleed off of the locomotive independent brake system that was primarily holding the oil train from rolling off of that hill above Lac-Megantic.
If, as many have speculated, there was only locomotive running and cut-in (as the controlling unit), and the fire dep't shut it down, then in a very real sense the fire department did release the independent, inadvertently.
>the five unit locomotive consist caused 30 axles of operative air brakes to dwindle down to 5 axles with handbrakes
The preliminary report says "unknown number of handbrakes on the train", by which they probably mean "engines and cars". So, if you are going to say this, then you must know how many brakes the engineer actually tied and the design of brake lever systems on each locomotive and each car in the train.
On 2-axle locomotive trucks with one brake cylinder per truck side, usually the case with composition shoes, the handbrake applies the brakes on two axles. When there are two brake cylinders, typical with cast iron shoes, it's usually only one axle. On three axle trucks it can vary between one and three axles depending on how the brake cylinder and lever system is arranged.
On any freight car with truck-mounted brake cylinders, it's either one or two axles. For any car with foundation brake rigging (body-mounted brake cylinder), it's all axles on the car.
So if you do know how many hand brakes the engineer actually set, and the lever systems they were connected to, get ahold of the Canadians chop-chop.
Regardless of all this, I do happen to agree with you that deliberation by somebody wasn't a factor, except for carelessness/sloppiness by the RR in it's operating practices and procedures.
Technically speaking, this is not correct, although they do lose effectiveness as MR pressure declines below the set point of the relay valve (which in some cases is about 1/2 that of the MR).
>nor inadvertent operation of locomotive air brakes by fire department responders - just bleed off of the locomotive independent brake system that was primarily holding the oil train from rolling off of that hill above Lac-Megantic.
If, as many have speculated, there was only locomotive running and cut-in (as the controlling unit), and the fire dep't shut it down, then in a very real sense the fire department did release the independent, inadvertently.
>the five unit locomotive consist caused 30 axles of operative air brakes to dwindle down to 5 axles with handbrakes
The preliminary report says "unknown number of handbrakes on the train", by which they probably mean "engines and cars". So, if you are going to say this, then you must know how many brakes the engineer actually tied and the design of brake lever systems on each locomotive and each car in the train.
On 2-axle locomotive trucks with one brake cylinder per truck side, usually the case with composition shoes, the handbrake applies the brakes on two axles. When there are two brake cylinders, typical with cast iron shoes, it's usually only one axle. On three axle trucks it can vary between one and three axles depending on how the brake cylinder and lever system is arranged.
On any freight car with truck-mounted brake cylinders, it's either one or two axles. For any car with foundation brake rigging (body-mounted brake cylinder), it's all axles on the car.
So if you do know how many hand brakes the engineer actually set, and the lever systems they were connected to, get ahold of the Canadians chop-chop.
Regardless of all this, I do happen to agree with you that deliberation by somebody wasn't a factor, except for carelessness/sloppiness by the RR in it's operating practices and procedures.
