I'm going to show my ignorance here but let me ask anyway. When a diesel has 2 sets of horns ( the Southern Rwy for example ) does just one set blow at a time? And if so, how does the engine select which one to blow in what direction?
CofG
"The Right Way"
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What types of diesel locomotives are your asking about? If you are looking at photos of old "F" type units, then yes, there was a horn facing rearward and one facing forward; thus one for forward movement and one for calling in the Flagman from the rear of the train. Early "GP" type units, being bi-directional, had hors facing in each direction of movement.
Hot Water, I'm talking about Southern Rwy highhood units ( GP35, GP38, etc. ). They had a set of horns on top of each end.
CofG
"The Right Way"
They probably had dual controls, and thus a set of horns facing "forward" no mater which direction they where operating.
When you say dual controls, do you you mean that there were to control stands ( one on each side of the cab )? If so were they both active at the same time or was there a switch of some sort to select which control stand you wanted to operate?
CofG
"The Right Way"
When you say dual controls, do you you mean that there were to control stands ( one on each side of the cab )?
yes
If so were they both active at the same time or was there a switch of some sort to select which control stand you wanted to operate?
yes, the handles of any control stand are pulled when the stand is not in use thus locking out the controls. I am sure hotwater will explain it better.
To be more specific, EMD had two "options":
1) Dual control stands = two complete control stands in the cab. Changing form one control stand to another, i.e. left or right, was no different from changing ends in a locomotive consist. Cut ou one control stand/brake valve and cut in the other control stand/brake valve.
) Duplex controls = one large control stand in the center of the cab. all the levers moved no mater which side you were controlling from. Ideal for switching locomotives.
. . . how does the engine select which one to blow in what direction?
CofG
"The Right Way"
On the Southern SD40-2's we swapped for them to try out our GP50's, there was one control stand in each cab. (They were set up for the long hood end to be the front.) There was a 5-bell Nathan horn at the front of the long hood, and another at the top of the short hood. On those units, the reverse lever selected which horn would be sounded by a solenoid. There was an electrical switch on the control stand, much like the sanding switch used on early second-generation EMD units, which was used by the Engineer to sound the horn.
On F7 units with one forward facing and one rearward facing single note "blaster" horns, there were two different setups. Some roads used two whistle cords, so that the Engineer pulled one to sound the horn in one direction only, or both if he so chose. The other setup was to have one whistle cord attached to both whistle valves. The spring-loaded whistle valves which actually sent air to the horns on F-units were mounted on the ceiling.
Tom
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