Good evening,

I am doing some maintenance work on a 1925 Baldwin steam locomotive, and as part of winter maintenance am completing a complete rewiring of the electrical system. The previous wiring job I am finding is both incomplete and questionable, and I am having trouble finding light bulbs, resistors, and information on the electrical system.

The locomotive is equipped with a Sunbeam Turbogenerator, as well as two Sunbeam Headlights. I am unsure of the model, as the tag is missing, but I believe it is a 32v 500w turbogenerator.

The light bulb currently in the headlight is a 34v 250w bulb labeled "Made in EC". The locomotive is missing the resistor and fuse box, as the wiring was only partially completed, so currently will only operate on high. The switch is a Ralco three position switch, with a bottom twist switch for the cab light.

I am looking for any sources and guidance on the following:
- Headlight bulbs
- Number board/headlight compartment bulbs
- Cab bulbs
- Resistors
- Fuses
- Wire sizes
- Period accurate wiring and hardware
- Electrical wiring diagrams

Any of the above would be appreciated. If anyone has pictures or diagrams of how their engines are setup that would be appreciated as well.

Thank you in advance,

Matt

For old railroad equipment, appropriate wire (stranded copper, rubber insulation with woven cloth covering) is now hard to find (most modern wire is insulated with plastic).

Apparently the only place where such wire is still specified and used is in telephone central offices. Southwire Corp. (https://www.southwire.com/) manufactures Telcoflex wire for that market.

At WRM, we have used Telcoflex in several restorations with good results. We purchased our supply from Cobra Wire & Cable (http://www.cobrawire.com).

see file for dimming resistor info and wiring diagram

I believe AAMSCO can still supply headlight bulbs.

https://www.aamsco.com/light-bulbs/railway/

Those images have been compressed quite heavily. While useful information, including resistance values, may be read in the second image, the wiring diagram image conveys little usable information. A higher-quality, less-compressed set of images would be helpful.

Bob, Thanks for the heads up on the poor quality of the PDFs. I was unable to edit the original post for some reason. I have posted better quality images below (I hope!).
Resistor info

Wiring diagram

If I understand correctly, that bulb won't need a resistor for 'dimming' in the typical voltage-reduction sense. There should be three contacts in the socket, two corresponding to the 'regular' and 'dim' positions, and one for common return (as in a domestic three-way switch). Examine the switch: it will either have two positions supplying 32V or two positions to a common ground.

See how the center conductor is a 'center tap' for the filament? High will energize the length of the filament, dim will energize half of it (probably with the other half taking up some glow by conduction) AT THE SAME VOLTAGE... and the current should look after itself.

I'd naively expect the center-tapped wattage to be around 125W, 32V, P = EI, P = I^R to get the tapped-filament resistance if you need it. I doubt you need a ballast or power resistor in that circuit unless you need overspeed control should the filament suddenly fail under load...

Typical 'three'way' bulbs have two distinct filaments, one from each contact, and the switch goes 1, 2, 1+@ in rotation to connect them. The pictured design probably stresses the center of the filament, especially in jolting or vibration, and I expect that if the filament fails it will 'fall off' the intermediate contact rather than keeping a 'low' reserve -- this leads me to wonder whether screwing the bulb in to leave the 'hook' in the contact facing up gives you the best chance of keeping low if you have a break.

Last I knew, as of several months ago, AAMSCO had stopped production of the 250 W locomotive headlight bulb and has no plans to resume making them. We have not been able to find another supplier so far. Diesel locomotive PAR sealed beam lamps in the correct voltage and wattage are available but they require modification to the headlight case and don't look right.

What's your need on this?
Does it have to be absolutely original in all respects to be right...
Or, does it just need to work?

If you just need it to work, put a modern diesel locomotive 32V 250W sealed beam bulb in it... Easier to get and will probably give you better light....

This is for use on an operating steam locomotive. Use in the dark is currently limited, but we are preparing for expanded operations which may include more nighttime operations. At the moment is more for visual appearance and having a white light on the leading end.

I did notice what you pointed out above and was curious as to if that was a possible function. The only thing there I do not see is where a third wire would attach to the outlet? I will have a chance this weekend to look at the outlet better but from the picture attached I do not see anywhere the third wire would go.

If the above is the case, are the two inputs able to utilize the one common return without back feeding the input not in use?

The idea of leaving the "hook" facing up is an interesting thought, and emphasizes the need to find a source for replacement bulbs.

Does that bulb actually have two contacts on the bottom?

I don't think it does. A threaded base isn't conducive to contacts on a bulb aligning with contacts in the socket. It's not feasible. A bayonet mount (like older brake/tail light bulbs).. I could see that, but not threaded E26's.

I suggest that the center post inside the bulb is to steady the filament, since it's a rough service bulb. Don't want that filament to break during use while white hot. Look in the glass envelope the filament leaders are anchored in... you can just about see the two outside leads going down to the base.. .there's nothing beneath the center post.

Surely the headlight switch contains the resistance for dimming.

Since the incandescent light bulb ban is taking effect this year, the manufacture if incandescent bulbs has been stopped. You will not find an incandescent bulb except from old stock and collectors. Once factories stop producing incandescent bulbs even Amsco won't be able to have them made. Unless there is some underground operation in some third world country but the quality would be questionable.

Here’s another possibility for a supplier: Multipower International. They say they can still get parts and even locomotives from China. While they don’t specifically list bulbs, it seems likely they can get them.

http://www.multipowerinternational.com/index.html

Is this the same socket and bulb base as on a 3-way household lamp? The come in both standard and larger Mogul sizes.