Railway Preservation News

250P25 32V Locomotive Headlight Bulbs
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Author:  Bobk [ Sun Oct 18, 2015 9:54 pm ]
Post subject:  Re: 250P25 32V Locomotive Headlight Bulbs

Where is the problem?
I just ordered two dozen 32V 250W headlight bulbs through the AAMSCO web site...

are these the Chinese bulbs and if so are they now reliable?

Author:  Scott Kwiatkowski [ Mon Oct 19, 2015 4:54 am ]
Post subject:  Re: 250P25 32V Locomotive Headlight Bulbs

The bulbs are not Chinese, they are made in Mexico.

It is my understanding that the tooling that makes these bulbs in Mexico came from a factory right here in New Jersey, (the promise land)!

As far as reliability is concerned, LV 112 tested the first hand made Aamsco samples made in Mexico and they have been in the loco since early spring. The filament is a little different then the originals but the brilliancy is fine.

As far as the NOS glue thing is concerned. Now I am not a bulb manufacturer but Bob the owner of Aamsco is and has been in the biz for over 40 years. When I asked him about the NOS bulbs blowing out he mentioned the glue drying out......what the hell do I know...I do choo choos, he does bulbs.


Not in the dark, NJ
(copyright Howard P.)

Author:  robertmacdowell [ Wed Nov 11, 2015 3:45 pm ]
Post subject:  Re: 250P25 32V Locomotive Headlight Bulbs

What resistor values are you using in front of this bulb for 75v applications?

For what it's worth, on one engine I notice GE's OEM design calls for about 78 watts for the "dim" setting on a 250w bulb.

I've worked out the theoretical numbers, and done some field testing. Just wanted to hear some practical experience.

Author:  Pegasuspinto [ Wed Nov 11, 2015 6:31 pm ]
Post subject:  Re: 250P25 32V Locomotive Headlight Bulbs

Ohm's law isn't really theory, it's practical. Assuming we take the voltages and wattages at face value...
250 watt bulb at 32 volts pulls 7.8 amps
The new resistor will need to 'waste' 43 volts at 7.8 amps, meaning it will dissipate 335 watts.
The resistor will be 5.5 ohms. Normally you want to double the wattage of the resistor for best life, so you need a 5.5 ohm 670 watt resistor, mounted where it can properly shed 335 watts of heat.

Mouser has a suitable resistor in stock:http://www.mouser.com/ProductDetail/TE-Connectivity-CGS/TE1000B5R6J/?qs=sGAEpiMZZMtlubZbdhIBIPa2k8RrYDlhFfNo7hXCZj0%3d

To drop to a 'dim. 75 watts is a little harder to calculate because the resistance of the filament changes with the temperature, But switching a 3 to 3.2 ohm resistor into the circuit will get you pretty much in the right spot, looking at about 100 watts of resistor.

This would be suitable:[url]http://www.mouser.com/ProductDetail/ARCOL-Ohmite/HS100-3R-F/?qs=sGAEpiMZZMtlubZbdhIBIEidPY%252bx%2fLaaWO8L3JnAJBg%3d

Author:  David H. Hamley [ Thu Nov 12, 2015 8:59 am ]
Post subject:  Re: 250P25 32V Locomotive Headlight Bulbs

When calculating dropping resistors and other factors on "nominal 32V" systems, those with 16 cells of lead-acid battery, shouldn't you be using the voltage at which a normally adjusted and fully charged system operates?--such as 37.5V.

The 25 ton GE I service uses a 200W 30V sealed beam headlight and thus always has some resistance in the circuit that accounts for the difference between 30V and the 37.5V, with a further resistance to provide the dim setting. The GE schematic shows the two resistances as 1.13 ohms and 3.98 ohms respectively.

That schematic refers to the headlight bulbs as 200W 32V, but those in actual use are marked 30V.

Author:  Pegasuspinto [ Thu Nov 12, 2015 9:50 am ]
Post subject:  Re: 250P25 32V Locomotive Headlight Bulbs

The bulb in question is primarily used on steam locomotives, which have no battery. In any case, with the scarcity, expense, and that they may go through bouts of unavailability, it might be wise to run them at no higher then rated voltage.

Author:  filmteknik [ Thu Nov 12, 2015 1:55 pm ]
Post subject:  Re: 250P25 32V Locomotive Headlight Bulbs

Hopefully the new source will be fine, the problem is solved and this is moot. But here was my idea for something that could be done by a small entrepreneur using existing halogen bulbs (assuming there is one suitable). Thus they would not need to be concerned with filament forming, evacuation, argon, etc. just a little spot welding of lead extensions to put the filament where it needs to be. Bulb shown is an Osram HLX 100W / 12V. I imagine a higher wattage bulb would have a larger envelope. Maybe bigger leads and two to the shell would better to thwart vibration. A more elaborate solution would involve an actual socket for the bi-pin bulb. Think outside the box.

locobulb.jpg [ 22.73 KiB | Viewed 1026 times ]

Author:  Pegasuspinto [ Thu Nov 12, 2015 2:23 pm ]
Post subject:  Re: 250P25 32V Locomotive Headlight Bulbs

The problem is the voltage. 32vdc is a heritage voltage, used on old farms, old boats, old railroad equipment, and from what I can gather at least some cold war era AT&T generators.

However? http://www.bulbtown.com/Q300T3_CL_119mm_36V_300_WATT_119MM_T3_HALOGEN_R7S_p/j8236.htm

Disclaimer-this bulb might be very, very fragile. Might blow on the first track joint.

Author:  Dave [ Thu Nov 12, 2015 3:58 pm ]
Post subject:  Re: 250P25 32V Locomotive Headlight Bulbs

I have taken advantage of bad bearings in a dynamo and, along with adjusting the governor, made it put out 24 volts which allows for adaptively using off the shelf truck lamps and fixtures instead of 32 volt stuff, no resistor required except for dimming. I'm also working on the concept of using Peltier Junctions to keep batteries charged to power the lighting with heat wasted through the boiler shell or smokebox. I think LEDs would be particularly good in this adaptation....... and the steam saved by not running the dynamo is a bonus.

Author:  Pegasuspinto [ Thu Dec 31, 2015 6:17 pm ]
Post subject:  Re: 250P25 32V Locomotive Headlight Bulbs

These popped up on Ebay. Buyer beware!


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