In the example photo of the C&NW locomotive, the upper centered light and the classification lights all seem to be outfitted with Fresnel lenses.
Here's a photo of a similar one:
Wikipedia has an article on the subject of Fresnel ( pronounced in these United States as " fruh-nell"--accent on the later syllable) lenses.
Generally, they are used to generate a very tight beam--think lighthouse. In this case, I expect that was also what was planned.
Ed
I am thinking the type of lense is the giveaway to the answer sought in this thread.
Notice in the picture that user GMPULLMAN (CNW loco) posted above. The lense on the aux light matches the class lights. The headlight is a standard lense. Gut feeling tells me that finding out why the lense is rippled (like the marker lights on the CNW loco) and not a flat pane of glass would elude to the answer of its existance.
However, note on the T1 (also posted above by GMPULLMAN), the lense matches that of a flat pane headlight. Two distinct differences in lense make between the two locos (speculation: the reasons of use must be different). On the T1 however, judging by its low mounted position and similar lense type as the headlight, I would summize this provided light closer to the front of the loco and closer to the ground. Giving the train crew a better lit area just infront of the loco. In the area the headlight cant light up. Kind of like illuminating a blind spot.
To me, im thinking the aux light on the CNW seems to be a signaling light, or indicator light of some kind rather than a high beam projective light to see by.
Interesting indeed!
PS heres a front on view of a T1 with low light.
http://www.angelfire.com/film/prrpics/t15513a.JPG
An interesting addendum to this thread, Shorpy just posted a photo of a C&NW H class 4-8-4 with an auxiliary light above the headlight.
Again, counter to the reasoning for it being a fog light. Perhaps, when the locomotive is moving in service areas this lamp would be used since the beam spread would make for better illumination in the immediate area rather than the spot-focused beam of the headlight? Also so as not to blind anyone working in the area.
http://www.shorpy.com/node/18905?size=_original#caption
Interesting... Ed
NYC's L-3 and L-4 Mohawks had small lights installed in their air pump shields when they were fitted with elephant ears. The location matched the location of the fog lights on the T1's. Were these the NYC's equivalent of the same thing?
Tom
Notice the brackets to each side of the lamp housing. Even on the T1 you will notice the cutouts in the grille. The lamps housing would move side to side in a sweeping motion. They are a PRR Lines West developement for grade crossing warnings. Sort of like a Gyrolight but instead of an oval movement it was only side to side. Mars lights had a figure 8 patern. The sweeping lights were fitted to passenger locos that were assigned to the high speed race track. When speeds went from 60mph to sometimes 80+ mph grade crossing accidents became common and close calls were an every day, every run occurance.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
I found this description of fog lights:
"fog lamps provide a wide, bar-shaped beam of light with a sharp cutoff at the top, and are generally aimed and mounted low."
I think the point is to not have the headlight reflected back into the eyes of the engineer by the fog. I note that most of the lights in the photos above have the light mounted up pretty high. Which makes me question the idea that they are fog lights. The light on the T1 might qualify, however.
Just so everyone can see what the OP is referring to...
[edit] Sorry, I missed the photo link that he provided! But I found two other photos of K4s with the aux. light and the 5479 above makes at least four K4s that had the light installed.
A first, looking at the photo I thought the light could be an illusion...but after a search in Pennsy Power I there is a photo that shows a bright lamp just above the keystone and below the headlight, but on a mainline passenger train. I have no clue to it's purpose.
Mark H
Modeling in HO...Reading and Conrail together in an alternate history.
While the K4, T1 and Niagara didn't spend much time in yards, they did pass through them. According to contemporory Rule 17 (Josserand, Rights of Trains) the headlight was to be dimmed when passing through yards or passenger stations. It was probably easier to provide a separate lamp than to reduce the voltage to the main headlight.
Chuck (Modeling Central Japan in September, 1964)
Ask a PRR museum site. There are PRR discussion groups if you do a Google search for them. At least you can post a result which should be accurate. Generally in a forum, opinions are often seen. I only posted a link I found.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Hi, Alvie
I had posed a similar question years ago here inquiring about the Pyle twin sealed beam headlights on all the S-1 Niagaras and many of the Hudsons and Mohawks that had been equipped with them in later years. Never did get a decent answer. Most posters at the time thought I was asking about classification lights which was not the case.
In MANY of the NYC photos I have seen these auxiliary lamps are lit along with the two headlight lamps... I never found any reference to these in employee timetables or rulebooks, either.
Many, but not all, of the PRRs T1s had auxiliary lights in the front air compressor screen as seen above. I have also viewed photos of some of the K4s with the lights you mention, too. I am still in the dark about these .
I cannot imagine them being "yard" lights as, the T1 especially, didn't spend much time in yards (as compared to, say I1s, J1s and M1s) from what I know the T1 spent a great deal of time between Chicago and Crestline.
Maybe your inquiry will bring a fresh look at these auxiliary lights and someone can shed some light on the subject.
Take care, Ed
Look at the below link. Seems to be a "yard" light from a Google search.
http://www.webcircle.com/users/cobrandt/200005.txt
Hi all, I'd been looking at photos of K4s and I'm wondering, can anyone tell me more about this light under the main headlight on postwar Pennsy K4s? http://www.northeast.railfan.net/images/prr3880s.jpg this modification appears to be rare as I've seen very few in photos and videos of K4s.
TIA
Alvie