Diesel Locomotive Vs Electric Locomotive Lights

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Diesel Locomotive Vs Electric Locomotive Lights
Posted by alloboard on Friday, March 10, 2017 12:42 AM

     Why do electric locomotive have brighter whiter headlights and number boards than diesel locomotives? For instance the AEM and ALP44 electric locomotives had stronger headlight and numberboards than the F40PH diesel locomotives. The ALP46 electric locomotives high brighter lights than the newer ALP45DP locomotives.

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Posted by pajrr on Friday, March 10, 2017 3:40 PM

Some locomotives are switching to LED lighting. They can be much brighter than regular light bulbs in the same voltage range. It is probably just a matter of what bulb the builder or railroad decides to use. Go to any hardware or grocery store and look at regular household bulbs vs. LED bulbs. LEDs draw so much less wattage that they can be much brighter for any given wattage draw. If you see an Amtrak ACS-64 electric the LED headlights in those are unbelievably bright.

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Posted by alloboard on Friday, March 10, 2017 10:52 PM

I understand, but too many diesels use dimm bulbs which makes me ponder that it may be some practice that diesels use dimmer bulbs.

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Posted by NorthWest on Friday, March 10, 2017 11:15 PM

There shouldn't be. Most of the locomotives use the same bulbs in order to help keep common parts supplies.

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Posted by pajrr on Saturday, March 11, 2017 5:34 AM

Trains are required to dim their bulbs when parked on a siding or passing another train. I am assuming that every train you are seeing is not parked or meeting another train, but just letting you know that there are instances when bulbs are purposely dimmed at times.

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Posted by alloboard on Saturday, March 11, 2017 1:45 PM

Thanks for the info. I did not know that there are times when locomotives dimm their bulbs. You were right as I mentioned earlier, I meant when the diesels were on the move.

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Posted by RME on Saturday, March 11, 2017 2:12 PM

Many older diesels have inherently dimmer bulb technology.  In some cases they are running through a dropping resistor, which will yellow and dim the emitted light; LEDS, particularly pseudowhite with phosphors, emit a whiter light that can be perceived as brighter as well as providing more "lumens per watt."

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Posted by alloboard on Saturday, March 11, 2017 2:25 PM

I knew it! That's the problem! I think that the newer diesels are not interested in super bright white led bulb technology.

RME
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Posted by RME on Saturday, March 11, 2017 4:01 PM

alloboard
I think that the newer diesels are not interested in super bright white led bulb technology.

I think they are -- the GEs I observed yesterday use them -- annoyingly and I think a bit unsafely -- as rear-step lights.

There may be a current FRA restriction on using some forms of LED 'replacement' in place of current sealed-beam head and ditch lights; you can't 'dim' a typical LED so you have to bank-switch them to get the 'dimming' effect, and the individual devices are very sensitive to overvoltage and surge, so a "replacement" headlight bulb requires quite a bit of circuitry to do what a comparatively cheap filament in a glass envelope does fairly well, albeit more dimly and inefficiently.

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Posted by M636C on Saturday, March 11, 2017 4:38 PM

The lighting standards clearly only specify performance rather than technology, although the examples quoted indicate conventional filament bulbs.

The first cost of LED lamps is higher, possibly not as much as the supermarket prices for individual bulbs, but the longer life of LEDs must save on operating costs which might justify the higher first cost.

As I've indicated before all of the Pacific National Cv40-9i units were fitted with LED headlights (along with new FDL-16 engines and new cab electronics but no new external paint) so the cost wouldn't be noticed in the overhaul. These are mounted in the standard dual sealed beam casing, but whether they are bulb replacements isn't clear at least externally.

One of the four trains I photographed yesterday had these units leading and the very bright headlights make them very visible. I wonder whether in the absence of a parabolic reflector if the visibilty from the cab improves as much as the visibility of the train from the ground.

RME, what do you see as unsafe about LEDs as step lights?

Peter

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Posted by RME on Saturday, March 11, 2017 7:57 PM

M636C
The first cost of LED lamps is higher, possibly not as much as the supermarket prices for individual bulbs, but the longer life of LEDs must save on operating costs which might justify the higher first cost.

I'd have to wonder if 'railroad equivalent' LED replacements would be higher in percentage cost over 'domestic' equivalents due to the more restricted volume of 72v-compatible hardware for driver boards, connectors, etc.  Something I would note is that the cost savings for these lights aren't the same as the 'usual' amount touted in consumer lights, as the railroads aren't paying utility rates to run them, but the much longer unattended life would be very attractive both in terms of first cost and ongoing maintenance.

I wonder whether in the absence of a parabolic reflector if the visibility from the cab improves as much as the visibility of the train from the ground.

Looking strictly at the 'beam' characteristics of the emitted light, you can get better results from a number of small diodes each with its own little aspheric reflector and lens, especially 'off-axis' from the pattern of a typical reflector headlight or sealed beam.

There's a little more to it in that the emission spectrum of most 'pseudowhite' LEDs can be relatively peaky, so that the perceived brightness of the emitted light is very high, but the actual reflected spectrum that lets you actually see things is much less, and distorted as to visible color.  That's a reason why things illuminated by cell-phone screen 'white' light look so washed out and strange.  There are ways around this but they're only just starting to catch on.

RME, what do you see as unsafe about LEDs as step lights?

The step lights I'm familiar with are the ones on older EMDs and cars like the Comet Is, where the light has a directed 'hood' that keeps most of the emitted light down on the steps and just the lower corner of the step risers.  On the two GEs I saw, the light was larger, cushion-shaped, and shining straight out from its position in the middle top center of the second step riser, with a great deal of glare and only a small amount of 'spill' onto the step tread itself.  The light itself was that fake 'warm white' that doesn't show reflected color well.  I would not have wanted to gauge where the railings and step edges to climb aboard were with that light shining almost right in my eyes when standing on the ground ready to take the first step.

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Posted by alloboard on Saturday, March 11, 2017 8:59 PM

I just remembered now that the NJTrransit Riverline DMUs have bright led lights. The headlights could be just a tiny little bit whiter, but they are very bright.

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