The right size bulbs?

[jonathan]

I have 5 locos that need lights (removed the welder lights).  I experimented with my 80's version GP35 by installing two 12 volt GOW bulbs.  The lights work but they are so dim, you can only see the lights with the shell off and the engine running about 80%.  I'm not discouraged as this is my first attempt.  The fact that the bulbs light at all is good news so far.

So... what is the right size incandescent bulb to use?  Not ready to mess with LEDs, yet. Oh... I connected the 12 volt bulbs in series; one was to light the top headlight and number board the other was to light the front lens and marker lights.  I have seen 1.5V bulbs at the LHS, thought these were too small... perhaps not.

I'm saving my 2 GP40s (made in this decade), until I get this right.

Regards,

Jonathan

[pdlethbridge]

I use the 12-16v Grain of rice bulb. Its smaller than a grain of wheat but gives a nice glow. I have used it on all my locos. I use DCC, so I get a great glow even at slow speeds. If you are running using analog (DC) Then you would need a constant brightness and reversing circuit and 1.5 v bulbs.

[Jim Banner]

Try wiring your two lights in parallel.  In series, each gets only half the voltage, so even at full speed, they only get about 6 volts each.  In parallel, they will both get the full voltage.  They will operate a little hot at 12 volts, but unless you run your trains at full speed, they will never see the full 12 volts.

Two questions - are you using dc or DCC?  This affects lighting.
And what is a "welder light?"  I wasn't sure if that was a light that was too bright or one that flickered.

Jim

[jonathan]

Jim/PD,

I am DC. 

The "welder" or "arc welder" light is that light that sits in the middle of the cab in some Athearn engines.  Not very realistic looking... this is what I'm attempting to change.

I will try both running the 12 volt parallel and connecting 1.5 volt in series to see if I get the desired effect.

In normal operations I never run over 70%, usually 50% is top speed on my railroad.  So I don't mind getting bulbs on the small side.  Will save the reversing circuit for the newer models.  I should be more comfortable with these tiny wires by then.

Thanks a million!

S,

Jonathan

[jward]

you could try adding a resistor in series with the bulbs, once you have them wired in parallel.

you'd need to experiment to see which resistor value gives you the light output you desire.

the resistor serves two functions: it lowers the operating voltage of the bulb thus prolonging its life. it also dissapates some of the heat that the bulb would have put out. the resistor will also heat up some, but it will probably be in an area with better ventilation than the headlight.

[jonathan]

Well, after a little testing I got the best light and color result from connecting 3 3.5v GOW bulbs in series.  Just twisted them together and touched the ends to the rails, while turning up the power.   The best illumination seemed to be in the 50-60% power range, which is right around where I operate.  Granted they weren't soldered to a locomotive yet.

jward, thanks for the tips.  I intend to glue a little aluminum foil around the inside of the loco shell where I mount the bulbs.  Will this help prevent warping the shell (heat)?  I would gladly pick up a resistor from radio shack,  BUT I'm electrically ignorant.  What if the salesman is, too? It could happen...   So, what size resistor is appropriate? 

I don't want to make the bulbs so dim I can't see them.  Also, does polarity matter?  In other words should the resistor be first connected to the bulb stem (that bare metal piece that sticks out of the front of the frame), then bulbs.... or bulbs to the stem and resistor on the motor clip?   I'm so ignorant of this stuff, I don't even know if the question made sense.

I better go camping for a while, I feel a PD headache coming on.

Thanks,

Jonathan

[pdlethbridge]

 ACHE, ACHE, ACHE

[hotrainlover]

I replaced ALL my lights in Athearn engines with LED lights.  I used a 1000 watt resistor, and the lights worked on DC or DCC operations....

I bought a pack of 100 lights a t Walley World for 6 bucks...  That was a great find!!

[Jim Banner]

jonathan,
Some 15 ohm, 1/4 watt resistors would be useful.  Each one that you put in series with your string of three bulbs will drop the voltage by about 1 volt.  You might end up with more than one in the loop to get exactly what you want, but hey, they are cheap.

In a series circuit, it does not matter which comes first, last or in the middle.

I am pretty sure that hotrainlover meant that he used a 1000 ohm resistor.  Wattage is a measure of how much heat a resistor can dissipate, and is also related to physical size.  The last 1000 watt resistor I used was something like a foot long, 2 inches in diameter and water cooled. 

pd,
with all those headaches I am wondering if you are related to my wife.

Jim

[jward]

go with what jim recommends as far as resistors go. the 1000 ohm resistor mentioned by somebody else is suitable for leds which operate on low voltage of 1.5 to 2 volts.  the resistor you'd need for bulbs is much lower in value. as for concetions, if you are using the original athearn mounting, i'd trim the copper spring piece which contacts the pickup bar on the truck, and solder one end of the resistor to the stub of copper that's left. the other end should be soldered to the metal clip that runs from the truck to the top of the motor. be aware that the metal that athearn uses in their pickup clips doesn't solder well.

as for the foil, that may act as a good heat sink. at the very least, it will reflect more light and make the buld seem brighter.

radio shack salesmen usually know next to nothing about the parts they sell. they've cut way back on the parts they sell in recent years so that it is just a tiny part of their business now. their focus is on high end electronic gadgets, parts are there but not where the big money is.....the salesman are adept at finding catalogue numbers but can rarely answer technical questions anymore.

[jonathan]

OK, let's see...  no worries jward, I removed the brass clip for the light. I'm soldering right to the bare metal.  I'll be singing 15 ohm, 1/4 watt resistors all the way to radio shack (heaven forbid I should write anything down).

The last project for lighting is finding tiny clear jewels or beads for the marker lights.  I've drilled a 1/16" hole where the lights go.  That crafty stuff is usually measured in metric (1.5mm?).  Anyway I'll get that figured out soon enough.  Thanks, kind Sirs.

Regards,

Jonathan

[Jhanecker2]

Jonathon :  1.5 mm is about right since there are 25.4 mm in an inch. Looked at your album, nice work . That picture titled "White Castle" reminds me of a restaurant from the neighborhood I grew up in lincoln Park in Chicago. The building still exists on the southeast corner of Lincoln Avenue and Sheffield Avenue. Walthers must have used some sites in Chicago for some of their models or some of the buildings in Chicago must be fairly common all over.   John  II.

[DUCKY01]

I use Minitronics 1.7mm, 12volt bulbs in all my Athearn locomotives. I use
a small piece of brass tubing as an insert into the plastic shell, and the bulb
slides inside the tube to prevent heat damage to the shell. Since I have replaced all the original Athearn motors with a lower amperage can motor,
there is no need to install current limiting resistors in line with the bulb. I use the same bulbs in all my HO trolleys as well.

[hotrainlover]

Jim,
Yes you are right.  1000 watts is a WHOLE lot!!  Thanks for the correction.

[jward]

if you intend to light those class lights, why not try thin strands of fiber optics? you can run the strands to near your light bulbs, and have lit class lights. not sure which railroad you model, but on conrail they were usually lit red. a thin coat of paint on the end of the fiber optic strand should give you a red colour. with bulbs you can use red nail polish, but that will probably attack fiber optics.