Re: Retainers-How did they work?


soolinehistory <destorzek@...>
 

--- In STMFC@..., "Jack Burgess" <jack@...> wrote:

Bill...check out:

http://www.railway-technical.com/brake2.shtml

and scroll down to retainers. I'll let others comment on the details you ask
about.
A couple comments in addition to Mr. Krug's text:

IIRC, in our era retainers only had two positions... ON and OFF.

There was a danger beyond making multiple brake applications on a long grade (otherwise known as "pissing away your air"). Brake cylinders leak. As long as the brakes are applied via a reduction of the train pipe pressure, the car reservoirs are not being recharged. So, as long as the brakes are applied, the cylinders leak, and are replenished from the reservoirs, until the reservoirs are empty, and then guess what? No air :(

The solution in the days before dynamic brakes, was to "cycle" the air: taking an application, holding it for so many minuets, then releasing it and allowing the reservoirs to recharge for so many minutes. It's during this recharge period that the cars with retainers set are expected to keep train speed in check.

The special instructions of the employee timetable would dictate how many cars, or what percentage of cars, needed retainers set. The train would stop, and the two brakemen would start, one from each end, and set the required number. In our era, the retainer valves were mounted up near the roof, so they were easier to set by walking the car tops. I suspect that where there were a lot of low cars interspersed with the house cars, that whole blocks got skipped, and retainers were set on whichever cars were most convenient... after all, the slack is going to be bunched by the retainers on the head end anyway.

The cars with retainers set never had their brakes released, so those wheels got HOT... there are more than enough stories of trains coming down hills with rings of fire around the wheels. This is a recipe for developing thermal cracks in cast iron wheels, so most roads limited the amount of time retainers could be set, and required a mandatory wheel cooling period. During the cooling period at the bottom of the grade, the brakemen again walked the train to "turn down" all the retainers, and inspect the wheels and brakes.

This was by no means a high speed operation.

Dennis

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