I have been searching for information about the brightness of the headlight bulbs used on steamer during the 1930s to 50s. Still, I only can find some advertisements of headlight manufacturers that sold locomotive headlight with a “250,000 candlepower” light bulb inside. Take PRR as an example, I have seen a lot of pics showing K4s, M1s, Js only had a tiny light bulb which looks like a 40 watts incandescent bulb inside a pre-war model headlights with a larger reflector, post-war engines like the S2 turbine, Q2, K4s with headlight above the smokebox only had a much smaller headlight without light reflector inside, only painted white inside. I would like to know if there was any regulation about the headlight brightness of the States’ railroads? Did railroads in the 40s use light bulbs below 100 watts to cut costs? Thank you very much! [Y]
Many (most?) steam locomotives had a 32V DC electrical system. Not sure how that originated or how it was chosen.
The steam turbine-driven dynamos on those engines can put out a lot of power, and are perfectly capable of powering bulbs which appear just as bright as those on modern diesels.
But speaking of PRR headlights, their GG1 electrics in particular were known for having headlights that were never bright enough, from a crew’s point of view at least.
Just speaking of personal experience, for what it’s worth, thirty-plus years ago we went for a ride on the steam-powered Morris County Central, a now-defunct tourist line that operated out of Newfoundland NJ. [:'(]
Anyway, it was a night-time ride called “The Moonlight Special.” As the locomotive ( A 1907 Baldwin product if I remember correctly) made it’s dramatic approach to the station someone said over the stations loudspeaker “Do NOT look directly at the locomotives headlight! It’s as bright as the sun!”
Whether or not it was original equipment or not I don’t know, but that announcer wasn’t kidding!
That was a fun ride, by the way!
Thank you very much! It seems that difference railroads had difference standard in the past. Milwaukee Road Hiawatha installed additional mar lights on their Class A and F7 Hudson in late 40s, almost at the same time period, PRR also added an small auxillary headlight on some of their K4s and all(?) of their T1s (but their GG1, PA and centipede etc still only had the original single headlight) NYC’s Niagara had the headlight conversion (from single headlight to duel beam) in Nov, 1948, I wonder what was the reason behind these changes. [I]
Much more to this.
Mars/Gyralites, etc. in that era had little to do with brighter headlighting; I have seen rotating sweep lights that spotlighted a much larger section of view but such an effect would be largely wasted on steam with long boilers or other impediment to forward visibility. Many of the red Mars-type lights were to show stoppage or UDE on multiple-track routes rather than grade-crossing safety.
As I recall, the Pyle dual-beam lights used postwar on NYC power were primarily intended to keep a light burning if one bulb went out. A number of early E units featured a rosette of sealed-beam units in the hole of a reflector light; this gave about as bright a light as a non-arc light could produce from such a location.
Many GG1s were given dual sealed-beam conversions (not protruding as the Pyle conversions for steam headlight casings were) and very late, so were a number of B&O engines. I have documentation of at least one PRR T1 with vertical sealed-beam conversion (in 1948) and to me this really improves the look of the ‘second-generation’ production front end.
There is still some research going on as to what the T1 ‘auxiliary’ light does. It does not oscillate, and it is not colored, so the supposition that it is a ‘fog’ light closer to the track in poor visibility may be correct.
I mentioned the Morris County Central a bit earlier, care to see a bit of it?
First is a mid-sixties commercial…
https://www.youtube.com/watch?v=MkWzvVItgss
And a railfan home movie shot in 1974.
https://www.youtube.com/watch?v=V6Ac4aXRY9A
It was a fun ride!
Time flies, but memories last forever![8D]
[quote user=“Overmod”]
Much more to this.
Mars/Gyralites, etc. in that era had little to do with brighter headlighting; I have seen rotating sweep lights that spotlighted a much larger section of view but such an effect would be largely wasted on steam with long boilers or other impediment to forward visibility. Many of the red Mars-type lights were to show stoppage or UDE on multiple-track routes rather than grade-crossing safety.
As I recall, the Pyle dual-beam lights used postwar on NYC power were primarily intended to keep a light burning if one bulb went out. A number of early E units featured a rosette of sealed-beam units in the hole of a reflector light; this gave about as bright a light as a non-arc light could produce from such a location.
Many GG1s were given dual sealed-beam conversions (not protruding as the Pyle conversions
The T1 picture I have (at a coaling tower in Indiana) is indeed double sealed-beam, with the bulbs vertical (as in the GG1s that were converted). It is possible (I have not yet found any drawings for the T1 conversion) that the mounting is the same basic or perhaps even detail design. It appears to be the same idea of putting the two bulb mounts in a plate and installing this in the opening for the reflector mount.
I had very little experience with PRR reflector headlights EXCEPT to note that when the ones in E7s on the Bay Head line were on ‘bright’ and you were directly in line with the beam they were dazzlingly bright, about as bright as the sun to a 4-year-old watching from a car going across a grade crossing. I in fact thought (by comparison with the sealed-beam lights on some of the RS units going through Tenafly on the Northern Railroad) that this had to be one of those fancy 7-bulb high-speed lights, until the locomotive motored past, in Tuscan glory … with relatively dim headlight appearance to the side.
As with many laser applications, too much ‘beam visibility’ to the sides just shows that light’s being wasted from the main purpose of illuminating the parts of the ROW the engine crew immediately needs to see. These lights did have reflectors, and some care was taken to design them so that the brightest part of the filament in the bulb was at the geometric focus of the parabolic mirror.
On the other hand, of course there was a dimming function (or meets would have been dazzling just as an opposing crew would need reasonable detail vision to check the following train for problems). I do not know whether this was done with resistors or simply by controlling the turbogenerator, but there are people here who will definitively know. As you can readily imagine there is little use for the headlight as a road-illuminating device during the daytime, and particularly if regulated via turbogenerator speed (and hence steam mass flo
Think PRR E7s had brighter headlights than other E7s? Anyone got an E7 manual showing available choices?
Not at all, really! Just noting that the ones I saw were single-bulb reflector lights, and EXTREMELY bright in the line of the beam.
All the seven-light arrangements I’ve seen were on older units (I think nothing more recent than an E6) and I don’t know if these were ‘factory’ options or special order components. The history of ‘optical warning’ of high-speed trains is an interesting subject (some details are covered in Kratville’s book on the UP Streamliners) as at least some of the idea was to provide very bright beams either projected in front of trains or vertically into the sky like rotating premiere searchlights to signal motorists that Something Significant Was Approaching. Since this was a prominent component of the later rationale for adoption of ditch lights, it may merit more attention than it has historically received.
One very probable reason for disuse of the seven-bulb headlight would be the FRA requirement that all bulbs be working ‘as installed’ on inspection. Those familiar with the Southern Pacific’s foray into safety lighting in the '60s will remember how that ended, with openings plated off … and safety not at all enhanced.
You can’t judge how bright a headlight is during the day, cloudy or not. I drive along a rail line (actually two mainlines running parallel) going to and from work every day. During daylight hours, you can hardly tell the headlights are on. At night, they’re incredibly bright.
It’s kinda like big league ballparks that shoot off fireworks when the home team hits a homerun. It’s not very impressive during day games, much more visable at night.
Note too that headlights have more than one brightness setting, so can be on, off or dimmed by the engineer.
Remember - most railroad rule books require headlights to be in the dim position
Thank you very much for your very detailed response! I really apprecicate it and I mostly agree with you guys. I did try to find pics or evdiences of steam locomotives headlight at night from 30s to 50s, but I can only found some touched up photos which probably used for promotional proposes. Anyway the answer is more clearer for me now after reading you guys first hand experiences or professional knowledges about lightings. To sum up, headlights of steam engines in the past was like a flashlight we use nowadays, it shoot a beam a long distance but does not necessarily light up all of the area close to the flashlight thus when people looks directly to it, it is as bright as the Sun, but it looks dimmer when people looks at it from the side. Assumes a headlight which had a light reflector installed, used a 100 watt (about 1000 lumens) incandescent bulb inside, I believe it was still bright enough during extreme weather at brightest mode, I have seen how a 1000 lumens flashing can do on youtube, its actually very bright.
(Pic 1: A PRR K4s headlight shooting lights beam at night. Source: online archive of Railroad Museum of Pennsylvania)
Headlight bulbs were brighter than that. Considerably brighter. Modern ‘standard’ voltage is 74, but some older systems that ‘charged’ at 72V nominal only provided 64V nominal battery voltage to devices such as lighting. Steam turbogeneration was (as I recall) generally in about the 32V peak range. Bulbs however are rated in watts (for a given nominal voltage) in indicating the I2R power dissipation and hence the candlepower/‘lumen’ output of the incandescence.
Current PAR56 sealed-beam lights, per FRA (see 49 CFR 229.125) are 350W and produce 6200 nominal lumens initially (the light output degrades somewhat over the 500-hour nominal life of the lamp). Multiply this by two for the headlight, then add two for the ditch lights. It is common to see a SI equivalent, usually 200,000 candelas, used for the bulb’s nominal light output.
Of course when the light is on ‘dim’ the light output is much lower…
The ‘standard’ GE headlight bulb for steam applications was as I recall the 250P25 32V. (The size code represents 25 eights of an inch diameter, and P is a round envelope shape.) Initial output is 4650 lumens with nominal 500 hour life.
Incidentally, that second picture is not of T1 5500, it is the ‘replica’ prow that has been constructed for the T1 Trust.
6200 lumens would be the bulb’s total light output – 200000 candela refers to the light intensity within the beam, lumens per steradian or some such thing.
Thank you for correcting me Overmod, I can’t believe I forgot the number of the T1 building by T1 Trust is 5550 not 5500! [I]Speaking of T1s, I remember in the book “Black Gold - Black Diamonds: The Pennsylvania Railroad & Dieselization” by Eric Hirsimake, one of the problem T1 6110,6111 had were the sockets vibreated loose caused headlight bulbs failed.
By the way, a 4650 lumens headlight with light reflector inside it must be very dazzling! One of the reason I am interested in this topic because I always think that Steam locomotive running at night with its headlight turned on is a very cool thing. I remember when I was a kid, I always draw steam engine on a sketchbook (even though I hadn’t seen a steam engine in person until I grew up), adding headlights, paint the light beam in yellow on my fantacy steam engine was one of the funniest thing for me. Thank you very much for providing the light bulb model, with more keywords and details, I can’t dig deeper on this topic. [tup] [I]
Thanks! I just watched a video demonstrate how powerful is a 6200 lumens flashlight on youtube, thats “crazy bright”!
I found this articles in Popular Mechanics July, 1938. The whole magazine has been uploaded to Google books [:)]
700,000 candlepower is equal to 8.7 million lumens!! I can’t believe it’s true!
Be difficult to work through all the necessarily-empirical measurements to determine what the “700,000 candlepower” represented. I would have to wonder if the mathematical conversions involved have given a result in line with those for modern sealed-beam lighting even though they are within an order of magnitude and use much better optics and focus adjustment.
The bulb of course does not translate its rated 250W entirely into visible light, and there is no discussion of the frequencies of visible radiation that ‘count’ as the output of the bulb – whether they are included in the 1/683 factor of conversion. Likewise the radius from the filament/focus where the cross-section of the headlight beam is computed is significant, as some very large percentage of the emitted light energy is represented there (and would have to be extrapolated across a full steradian at that radius for candela, nominally within spitting distance of candlepower). Note that this radius is, or ought to be, where the beam reaches the appropriate range above track level – as with the generations of earlier large-reflector headlights, the reflector is aimed somewhat down rather than parallel to the direction of travel. (You can see the effect almost overemphasized in many early etchings or artworks showing locomotives, where the beam is aimed much closer to the locomotive almost like a cone intersecting the track; it seems pretty clear in the cut accompanying the PM article.)
I do not think just applying the 12.57 factor from cp to lumens is going to give a meaningful result here.
I don’t know what appropriate conversion might need to be made for a PAR56 to give effective beam intensity in candela; erikem can backstop all these thoughts and calculations reasonably effectively.
Thank you very much for sharing your professional insight here Overmod! I tend to believe that it was 200,000 to 250,000 candlepower, a figure used in an advertisement of Pyle National in 1940s, I didn’t save the pic from the internet though. I believe your analyze on this topic that directly converting candlepower to lumens by using the 12.57 factor cannot get us a meaningful result. I am an amateur railway enthusiast, in this case I can only take a wild guess. I bet the lighting effect of old train headlight was like a 4000 to 6000 lumens flashlight we use nowadays on brightest mode, with a much larger diameter and light reflector inside, it might be even brighter [I]
Btw, I found a clip of headlight reflector test in the PRR movie “Clear Track Ahead!” (1946), please check it out if your are interested in this topic (time stamp is 24m39s)