A technical question - About the Independent Brake.
I understand the operation of the train brake - I can even explain it to people.
And I understand the independent brake - for the locomotive(s) only.
What I’m hazy on is the relationship of the two - specifically where it comes to “bailing off” the independent.
I’m still about two steps from the right hand seat, and the accompanying issues of train handling, so this will just provide me with a better understanding of the system. The knowledge will eventually come in handy, though.
Say I do a reduction on the trainline, then bail off the independent. Do I do so by pushing down the independent brake lever (or sideways on a desktop) then releasing it, or do I have to hold the lever down? If it’s a push and release thing, when do I get the engine brakes “back?”
You bail it off with the independent lever in the release position. You can get the brakes back merely by applying the independent brake. Of course, if you released them, you won’t want to.
On some locomotives there is a tendency for the air pressure to ‘creep’ back into the brake cylinder after the independent has been bailed off. This problem was more frequent back when a locomotive consist might have multiple types of brake systems MU’d together (such as a 24RL, 6BL, 26L, 6BLC, along with varieties of MU2A valves). When you had combinations of these brake valves, problems with MU’ing were sometimes rather perplexing.
There are two ways to address this tendency. One way is by repeatedly bailing off the independent every 30 seconds or so during the time the automatic is set; the other (illegal and unsafe) way is to use the cap of a fusee and wedge it in the independent brake assembly such that the independent is forced into the ‘bail-off’ position. The second method is ill-advised however, because sometimes the block can get stuck which would make it difficult to quickly set the engine brake if one should have the need.
I believe I have a handle on it now (pun not intended, but allowed to let stand…) The primary engine I see is an ALCO RS3 - and old timer. Of course, the “protection power” is a 1939 SW1…
I kind of thought that’s how things worked, especially after watching engineers in action, but wanted to make sure…
So, will an engineer normally use both brake handles to stop/slow the train? I had made a gross assumption that independant brakes were used when there was no consist behind the engine, and that you would depend on train brakes if you had something behind you. Or, is it a matter of how much stopping power you need for a given event?[?][?]
The idea is that because the locomotive brakes set up first, and then the brakes begin to set from the first car backward down the train, if you leave the brakes on the locomotive set, because it set up first, the weight of the train will push it, breaking the friction between the wheels and the rail, causing it to lock the wheels and slid, making flat spots.
They use the weight of the train instead to pull the locomotive down to a stop, keeping the loco brakes bailed off till the last few seconds.
I think it is called stretch braking also, meant to keep the slack out, or the train stretched out.
I am not an engineer, so I will leave the rest of the answer to them, as they are better qualified to answer it.
Stretch braking definition: maintaining locomotive motive power while making a reduction on ther automatic brake valve while at the same time keeping the locomotive brakes off by holding the independent in the “bail-off” position.
JSGreen: your assumption is correct; the independent is used to apply locomotive brakes when there is no train behind the locomotives. Using the automatic will set and release the locomotive brakes without the use of the independent, it just takes longer for them to apply or release.
If the engineer is using stretch braking, then he should not use the independent; if the engineer needs additional braking effort, he just applies the automatic harder. If he is using the dynamics to control train speed, it is very dangerous to use air on top of dynamics unless you are on a fairly steep (>.75%) downgrade; in that situation, you can usually get away with making a ‘running release’ of the air if you only took a “first-service” reduction on top of full dynamics, or in ideal conditions perhaps maybe a 10# reduction. Any greater reduction of air usually requires bringing the train to a stop and waiting for the brakes to kick off before proceedin
Ed - Thanks! I’m impressed - a “command performance!”
Our profile is far from flat - there are grades approaching (or surpassing) 1%. I like to point out the “Camel’s Hump” to riders on the return part of our trip - it looks amazingly like the scene in Polar Express when the train is about to crest a hill and go on a very steep downhill ride.
That said, there are times when I will see the engineer do a trainline reduction, but bail off the independent. I can only assume at this point that the the object there is to keep the slack out of the locomotive/consist coupling.
