nickaix posted:Here is a question about a detail I have not yet seen addressed. In the Calgary Herald article linked above, their "source" says this:
Retainers — devices meant to ensure the train’s brakes don’t lose pressure — would have been activated by the original crew and should have held, said the source.Whatever are these? Something to keep the brakes from releasing while the train line is being pumped back up? Or what?
You are pretty much correct. Retaining valves (Retainers) are devices which allow the ability to control the air in an individual railcar's brake cylinder. It may allow the air in the cylinder, which is applying the brakes shoes to the wheel, to exhaust from the brake cylinder completely (normal position) or be manually set to hold a predetermined amount of air (10 -20 p.s.i. depending on setting) in each cylinder after the Automatic Brake Valve handle in the controlling locomotive has been moved to the release position. When their use is desired, they must be manually set and released on each piece of equipment. This allows for a variable percentage of cars to "retain" their air brake application. Used mostly in heavy grade territory to assist in controlling speed downgrade or hold cars in place while air brakes are being recharged. With the advances and refinement of dynamic braking, their use has waned.
And while I'm here, let me say that I much appreciate the contributions from real railroaders here. It's a blessing to have access to so much expertise.
