Back Up Hose Question

We used to do it that way back before they had radios. You could usually do it without dumping the air, if you were careful. (Or, in my case, lucky)

In a word...no you should not do that.

When running, the brake valve in the locomotive is in the release position. In that position, it will attempt to maintain whatever brake pipe pressure is set on the regulating valve. If you opened the back up hose valve just a little, the locomotive brake valve will interpret that as a "leak" in the brake pipe and will supply more air to the brake pipe to maintain the pressure, countering your attempt to lower the brake pipe pressure.

If the locomotive brake valve is in the service zone (brakes already applied lightly) and you open the caboose valve, what happens then will depend on the type of brake valve in the locomotive. If the locomotive brake valve is set up for Pressure Maintaining, then the brake valve will behave exactly the same as it would in the release position. If it does NOT have pressure maintaining, then you WILL reduce the brake pipe pressure and apply the brakes more heavily.

I would not suggest you attempt this. It would be very easy to dump the air into emergency, even with only a slight move of your valve. That is because the locomotive brake valve is designed to lower the brake pipe pressure at a very smooth, controlled rate. A small but sudden drop in pressure, as might happen when you initially move your valve, could be interpereted by the loco brake valve as an emergency application, which would put the air into emergency...even though that is not what you intended.

 I should have elaborated that you would gradually open the back-up valve to get a decent blow to get an application. It wasn't hard to get the idea if you saw it done once or twice, but, of course, there was always a chance of dumping the air. That's how we used to stop freight trains from the hind end. (like if you had a hotbox or something)

Those graduated conductor's valves located inside the caboose body had a reputation for making unwanted emergency applications and everybody I worked with went out on the platform and used the back-up valve to bring the train to a stop without dumping the air.

I don't know what they do nowadays - everybody has a radio and nobody has a caboose.

RBDR

Sorry for not replying to you sooner. Thanks. I haven't seen such a thing done but just happened to think "could you do this if you had to" yesterday. Again, I stress I would not attempt such a thing. We use radios and hand signals. Radios of course when backing on the return trip with the fireman on the caboose with dump valve and whistle calling distances/clearance the engineer. Always be ready to use hand signals should the radios fail....

Another thing - I seem to recall reading a railroad in the midwest (Perhaps METRA in Chicago?) uses the backup hose, or a brake valve on the rear of the train, perhaps in the cab car, to stop when the engineer is in the engine and is backing into a station. Not 100% sure and I may be way off. 

When you pull the air from the back up hose, you might as well be slowly opening an angle cock, you are letting air escape directly from the brake pipe. That's why the pressure maintaining equipment on the engine will try to maintain, it thinks a leak has appeared.  The locomotive's automatic brake valve, does not directly reduce the brake pipe pressure. It reduces pressure in the equalizing reservoir, which in turn makes a controlled service reduction in brake pipe pressure.

You should avoid blowing that little whistle on the cab if the engineer has made a brake application to control the train. If the whistle on the cab is being blown, air escapes from the brake pipe and when released the pressure in the brake pipe increases and could cause the brakes to unintentionally release.

In the 60's when Santa Fe first started rebuilding the cabooses and installing chemical air flush toilets, they plumbed them into the brake pipe. They found out right away that would cause the brakes to start to apply, so they installed a small volume reservior with enough air to flush the toilet, and it re-charged through a small choke.

Hard to avoid that when you've got crossings.

I seem to recall years ago watching a train backing into a terminal, might have been Hoboken.  When it reached the proper stopping point, the person on the rear would deliberately dump the brakes with the backup hose.

Just thought that I would let you know so that when the tourists start getting beat up with slack action and the engineer wants to know what the heck is going on, you can tell them that you have been playing with the whistle.

When N&W first started laying welded rail, the unit trains had a "Tie Down" car in the middle where the rails were tied down to keep them from sliding. They needed an impact wrench to loosen the nuts holding the rails down, so, they used an impact wrench coupled into the trainline for a source of air. 

Now, pulling off the rails was a tedious job when you got to the end of a rail and wanted to stop with the end of a rail very close to the next rail to be pulled off. This required a deft touch with the air brake and power to accomplish and not have an issue with slack. This usually wasn't a problem as long as you were on level or going uphill. But, if going downhill and you stopped to connect the two rails, the guy on the tie down car used that air wrench sucking air out of the trainline. When he stopped, the trainline pressure would go back up, releasing the air brakes and causing a dangerous situation with a slack run-in.

Just be careful out there!!!

Are you really relying on that little air whistle to signal for crossings?? I don't think that's what it's for.

The Valley RR in Essex, CT does the very same thing.  I've been a passenger many times in the caboose while they have been using that air whistle when the engine is pushing through crossings.

Does the air whistle even meet the FRA minimum decibel requirement?

I'm glad you mentioned this, Jim.

A lot of folks don't realize that that after the train air brakes have been applied, the brakes will release if the brake pipe pressure increases by only 1 to 1.5 pounds! The system is set up to function this way in order to facilitate a quick release of the train brakes when used in normal service.

Using a back up hose or a caboose whistle is not normal service. Using the whistle depletes air out of the brake pipe, but the locomotive feed valve will try to maintain the same pressure against this big "leak" by admitting air into the brake pipe. When that "leak" suddenly stops (when you stop blowing the whistle) there can be a little pressure spike in the brake pipe before the brake valve can react to the fact that the "leak" stopped. In that brief moment, that pressure spike can easily reach a couple of pounds! It will propagate through the brake pipe and release the brakes! As you pointed out Jim, in certain situations that can be a very dangerous situation!

The shorter the train, the greater the chance of this happening. On a long freight train of 50 cars or more, the pressure inertia in that long brake pipe makes this a very unlikely scenario. However, on the typical short trains run on the scenic roads, this could easily happen.

The Webmaster brings up a good point. A small rise in brake pipe pressure will cause a serial action from one valve to another and completely release the brakes on standing train. Example. The train has stopped and the engine is cutting off to pick up at the elevator. The Engineer is drawing the brake pipe down preparing to cut off. As I've had happen hundreds of times, the brakeman won't wait, just reaches in and turns the angle cock, and gives you a "go ahead". The short version of the rule (forget the hand brakes part for a minute) says the Brakeman must wait until the Engineer blows the whistle signal indicating the exhaust has stopped blowing, and THEN he can close the angle cock. The reason for this is, when the engineer's brake valve is still exhausting, that means brake pipe air is still travelling towards the brake valve, and has not stabilized. When the angle cock is quickly snapped shut, the air flowing toward the brake valve bounces back causing a brief pressure spike against the nearest control valve. That valve thinks the brake pipe is being recharged, and starts a serial release through the train by porting emergency air into the brake pipe to help restore pressure. Each valve, one right after the other, does the same thing, and next thing you know, your train rolled off while you were doing your pickup. I saw that very same thing happen on the Santa Fe when I was working, half a dozen times at least. Not on any train I was on, but a few times on my old territory, or on the system somewhere. When cutting off, I would hit the ETD trigger at the same time I cut off, to guarantee the rear portion went into emergency, just in case somebody decided to "bottle the air", which believe it or not, in 2010, a few would still try and do if it was cold out. That was just asking for trouble, and unemployment.

I've wondered about that too. Back in the day the peep whistle (and a trainman's lamp at night) were legal and we used to shove all over the place with them. I don't know if it has been changed.

I'm glad Big Jim brought up about over using the whistle, it could cause problems...

If you want a whistle or horn of the rear of the train fed by the brake pipe, there should be a whistle reservoir.  The whistle reservoir should be feed through a C-1 charging check valve with a 1/32" diameter choke in it.  All the air for the whistle will come from the whistle reservoir.  You can make the reservoir as large as you want, it will just take longer to recharge it when the whistle is used.  This reservoir will have no impact on the train's brakes if the brake pipe does not already have excessive leakage.  This is the same arrangement that was used for the caboose toilet.