Use Of MU Hoses

[Ron Marquardt]

While we're on the su[not allowed]ect of MUing BL2's, I thought  I would address another question I am often asked.  What are all the hoses on the ends of the locomotives for?

Well, there are two under the coupler, but except when the locomotive is used in passenger service the smaller of the two is often not there.  The larger one, the top one, is the brake pipe hose.  This hose carries the engineer's brake valve signals through the locomotives and train, and is used to charge, apply, and release the brakes on the train.  It is
the same hose that is coupled between the cars throughout the train.

The smaller hose is a signal hose used in passenger service, and the conductor could operate a valve in the cars to signal the engineer for various things such as reminding him of slow orders, asking for more heat or less heat on the train, or maybe advising him of problems such as brake sticking, etc.  Remember, these were used in the days before
radios and walkee-talkee's.

The five hoses on the pilot, beginning at the coupler and working out, are the main reservoir supply pipe, the application and release hose, the actuating hose, and the forward and reverse sander hoses.  They are usually found on both sides, but only one side need be coupled.

The main reservoir supply pipe connects all the main reservoirs on the locomotive units together so they can act like one big air reservoir.

The application and release hose permits the engineer to apply and release the independent (locomotive) brakes uniformly on all the units in the consist.

The actuating hose is used keep locomotive brakes released during an air brake application with the train air brakes.  This is desirable to control slack action when working power during a brake application.  The engineer operates this feature by depressing the handle on the independent (locomotive) brake valve.

The last two hoses are the forward and rear sanding hoses, to make sure the sanders are operated uniformly on all the units in the consist.  Newer locomotives did not have these hoses because sanding is now done electrically, and controlled through the electrical jumper cables.  / Ron

PS, in the picture of the #501, the crooked pipe directly below the coupler is the steam connection that provides heat to the passenger cars when that unit is coupled to the train.  Locomotives without steam generators are not equipped with this pipe.

[Chuck Stewart]

Thanks, Ron...great info.  What exactly did the conductor's communication signal sound like in a steam and diesel loco cab...whistles, bells, hisses...? 
Maybe someday you can educate us/me on MUing diesel control.  EMD used electrical and Baldwin air(?).  What exactly was being controlled...a throttle on the engine or governor, etc.?
And what about MUing units with different gear ratios.  One guy told me it was ok but it sounds like bad news to me.

[Mark Johnson]

Ok, one more dumb question from somebody known for connecting things incorrectly - were the MU hoses & cables keyed in any way to prevent one from hooking the wrong things together? (Obviously, you wouldn't get an air line crossed with an electrical connector, but two different air lines are another story).

Thanks!

Mark J
Columbia MO

[Ron Marquardt]

Well, there were air tests performed to make sure everything was coupled correctly, but you just coupled opposite hoses together so there was little chance for error.  They weren't keyed or marked as far as I know, but everyone who worked out there was well qualified for the jobs they worked.  / Ron

[Ron Marquardt]

Chuck, in response to your question it was a little air operated whistling sound in the cab of the engine.  As far as the electrical MU (standard 26 pin jumper cable) is concerned, they "trainlined" the throttle, reverse, sanders, sometimes the front and rear headlights, probably the generator field switches, transition if it was manual, and no doubt some other mechanical department electrical functions that I don't know anything about.  The control systems had to be designed to MU with each other.  On the Monon our EMD's wouldn't MU with FM's or Alcos, but the later GE's would MU with Alcos.  Gear ratios weren't considered when MUing locomotives.  Each unit did as it was designed to do, and even though some of them may not have been operating at 100% efficiency at some speeds, they still did well together.

I remember the air brake equipment on the RS2's had to be modified before they could be used between two C628's.  I don't know if there was anything electrical that was modified at that time or not.

When you see photographs of mixed consists of Monon locomotives, don't jump to the wrong conclusions.  We could MU the air hoses, or set up the engines dead in tow, without using the trailing units for power, and they might look like they were all being used for power when they were actually being deadheaded somewhere.  / Ron

[Chuck Stewart]

Thanks, Ron!