I saw a cut of new GTW coil cars the other day, and noticed that the retainer handles were painted white, and stood out from the rest of the car. It got me thinking about the use of retainers. I know they were used to a greater extent in past years (moreso in steam days), but are they still used at all today? For some reason, it just never occured to me that new cars were still built with a retainer valve. I know they’re needed for really steep grades (i think Saluda was the last/one of the last mainline uses of retainers), but with mainlines generally not being all that steep, are there any lines, main or other, that still use retainers on a regular basis?
As far as I know, retainers are part of the required air brake equipment on interchange rolling stock. Are they used? Sure; a lot of steep grades will have a timetable/special instruction entry for setting up a required number of retainers before desending the grade. With really good extended range D/B gear, this has become less of an issue. The DM&IR has set up retainers before desending ‘Proctor Hill’ to the Duluth ore docks; and I think they still use their special straight air valve so the engineer can setup the retainers from the engine. If there are not enough D/B ‘axles’ for the trailing tonnage, most railroads will require a stop and set up of retainers before desending a grade.
They might not be able to fully release the air, but there is no way to “set retainers” from the engine. Retainers are a manual valve that has to be turned on individual cars. Once set it cause the brakes on that car to not fully release a brake application, even if the train line releases, that is the pressure goes up in the train line. What retainers do is keep the brakes on AND let the brake system fully recharge.
Without retainers, the only way to recharge the brake systems is to release the brakes.
Engineers on the DM&IR can indeed control the retainers from the locomotive cab. There are 2 air lines on each locomotive and ore car. One is the normal ‘fat’ train line. The other is a special ‘straight’ air line that controls pistons on the ore car retainers. The enginer can set up the retainers and release them while in motion. All of the ‘Mini-Quad’ taconite service ore cars have this feature. The advantage is the the engineer can set up the retainers in the entire train, and ‘cycle’ the main train line while decending ‘Proctor Hill’ enroute to the ore docks in Duluth. Look at the following link and you can se the dual air lines on the cars:
Note that both air lines are ‘high’(a Missabe ‘feature’). The engines/cabooses have two sets of main train lines: One low for normal freight cars, and a high set for the ore cars. The reason for the ‘high’ setup is due to the very tight clearances between the wheels on ore cars. The ‘Mini-Quad’ sets are drawbared in 4 car sets with no ‘glad hands’ between the cars. This reduces air leaks in the frigid Minnesota winters, and allows the running of full tonnage taconite trains.
Somewhat limited - It is also used on the ex USS ore railroads in South America(Orinoco Mining). The system is known as the ‘Orinoco Retainer System’. Sort of predates the new ‘electronic’ air brake systems being tested currently. All done with air & mechanical action. IIRC, some rock/quarry operations use this as well .