I don’t know why this hasn’t occurred to me before since I have been acquiring EMD F-units, both F-3s and F-7s, from a variety of manufacturers for decades. All of them have one rooftop horn facing forward and the other backward. Since they all have this feature, I assume it is based on the prototypes. My question is why would one of the horns would face backwards?
That’s the Doppler Shift horn, a half tone lower that sounds back towards you at that grade crossing the locomotive you were watching just crossed.
Well, might seem obvious but one was for moving forward and one for backing up.
F_horn_NYC by Edmund, on Flickr
F3_manual by Edmund, on Flickr
Then there’s the situation where some roads were still using flagmen. They would have to be called back to the caboose when the train was cleared to move. The rear-facing horn could be used to “throw” the sound toward the rear of the train.
Santa-Fe_FT-cab by Edmund, on Flickr
Some engines were equipped with a dual-volume whistle valve for yard or road use. Two lanyards so the engineer could choose the louder “mainline” horn or less air volume for close-in yard work.
Nathan_Valve by Edmund, on Flickr
Many roads had operating conditions or preferences of the mechanical department or state laws that affected the choices and options of air horn use over the years. Lots of variables out there.
Good Luck, Ed
That’s not what Doppler Shift means or how it works.
Also, while a number of railroads used single-chime horns like this on early diesels, not all did.
What you see on most diesels today (and on some other railroads even back then) are 3- or 5-note horns, and you’ll notice that usually the horn bells are arranged in a 2/1 or 3/2 forward/backward arrangement. The whole horn blows the same chord all the time, and sound is directed in all directions.
Plus, some railroads that bought diesels with single chime ‘blat’ airhorns in the 1940’s-50’s later changed them out for multi-chime horns. I know Missabe Road’s SD-9s (not F’s, but same generation) came with single chime horns, which (after experimenting with Hancock air whistles) the railroad came to replace with 5-chime horns.
Note too that for a long time all model railroad manufacturers just put the one-forward/one-backward single chime horns on all the F-unit models they made, regardless of whether that was correct for that prototype engine and railroad. In recent years, some manufacturers try to make sure their models have the correct ‘prototype specific’ details…but not all manufacturers do that, or only do it on their higher-end more expensive models.
THIS time, I think he did it on purpose and knowingly.
Ed
Prior to about 1950, all locomotive air horns were “singles”. And there were a good many of those, at the time.
The guy who thought it would be good to have multiple bells was Robert Swanson, whose work led to Nathan.
Here’s a link to (I’m surprised) the Wikipedia article on locomotive air horns:
https://en.wikipedia.org/wiki/Train_horn
So, back when Varney and Globe were first producing their F’s, they pretty much nailed the air horns.
Ed
I am sure. Here goes the Mike-Merry-Go-Round.
[+o(]
Step 1) Post something you know is incorrect.
Step 2) Wait for the right answer.
Step 3) Say your answer was correct even though it was not.
Step 4) Enjoy the argument.
Step 5) Go back and edit your original response.
Step 6) Explain how you are never wrong.
I am glad Ed (G M Pullman) gave the OP the correct and informative answer.
-Kevin
Yes, I know.
On a model locomotive the Doppler shift would not be noticeable anyway, speeds are too low and speed of sound doesn’t scale…
I’m pretty sure humour is not prohibited by forum rules.
I have heard this before.
Were cabooses ever equipped with a signalling device to send a signal back to the locomotive?
-Kevin
Yes. Before radios became common, the Santa Fe used wig-wags to communicate from the caboose to the locomotive.
JW
Yes they had a whistle, typically on the rear platform next to the brake valve.
The sound-equipped Athearn Genesis cabooses have horns/whistle.
Ed
BPRR 1002 by Todd Dillon, on Flickr
Many, but not all, NYC wood cabooses had distinctive hi-lo whistles permanently mounted to the cupola:
NYC_caboose_cupola by Edmund, on Flickr
Depending on service assignments. Probably most road cabooses did not have permanent roof-top whistles. I’ve seen examples of Leslie A-125 horns mounted up there, too.
The “peanut” whistles found on the end platforms would not sound loud enough to ever reach the cab of a locomotive but “might” get the attention of an automobile driver at a crossing during a backup move. Those whistles were usually combined with an emergency brale valve so the air could be dumped. These were also attached to “pigtails” that could be connected to the rear air hose.
NYC_wood-caboose by Edmund, on Flickr
[addendum]
I’ve witnessed times when one of the rear-end crew, when it was time to signal the engineer they had everything in place to proceed, would make a brake pipe reduction using the brake valve in the caboose (not the emergency valves) this would alert the engineer, by watching his BP pressure gauge, that he could then proceed.
Cheers, Ed
Looking at photos of EMD FT Unit 103 which was built originally as a drawbar connected ABBA unit the one large horn faces “forwards” on each A Unit. There appears to be a smaller horn also facing forwards. Later photos showing preserved 103 as an AB Unit (customers abandoned the four unit drawbar connection very early on) show the more usual two horns on the A Unit, one facing each way.
F3 were equipped with the two horns, one facing each way.
FM Trainmasters and similar came with two horns, one facing each way.
Perhaps the two horn system reflects the fact that these diesels could be run just as effectively in reverse direction. In the case of cab diesels this would be any AA combination would logically have a horn facing forwards at each end. Any AB unit or single RS unit would benefit from two horns, one facing each way. Modern cab diesels seem to have forward facing horns only.
On the Jersey Central in the early 1960s, the big six-motor RSD Alcos had two horns. The rear-facing one (the engine being set up to operate long-hood-forward) blew a lower note and was used to distinctively communicate with the caboose or to call in flagmen.
I think the ‘Doppler shift horn’ was a joke; the idea would be to make railfans think the train was going faster than it was.
If it was indeed a joke, it would be helpful if you used an emoji to convey that - e.g. [:o)], [;)], [swg], or [(-D]. Otherwise, you run the risk of making folks [|(] because your intended meaning was not understood properly [:S].
Tom
Actually FT 103 were two A-B sets. The A-B sets were connected by drawbar, but the B units had regular couplers at the other end. They were sometimes split up for testing. For example, Great Northern used one A-B sets on runs between Mpls-St.Paul and Duluth-Superior.
BTW that’s why FTs had the odd unbalanced look, the trucks at the ends where the drawbar was located were very close to the ends of the body; the trucks at the other end were set back on the A and B unit creating an overhang to allow for couplers.
http://research.nprha.org/Diesel%20Diagrams/EMD%20FT%205400A-5410D.jpg
Later F units - both A and B - had the trucks set equal distance from the ends on both ends, so could have couplers at both ends.
This guy’s horn wasn’t for signaling back to the locomotive. It was installed around 2007. That caboose is used in the multi mile backup move between East Butler and ARMCO/AK Steel/Cleveland Cliffs. They use it to honk at grade crossings.