'33 Headlight question

[Barry Wolk]

The '33 Continental is the first car I've owned from that era and I'm slightly confused about the headlights.

The service manual shows the original headlights were 21/21 candlepower lamps. The original owner installed 32/50 cp lamps and burned up the switch and some wiring. I've installed a hidden relay that shunts power to the headlamps around the light switch and everything works great.

My problem is that I don't understand how the lights are supposed to work. I assume that low beam is 21cp and high beam would be both elements burning at 42 cp. However, the way the foot pedal switch seems to work is that you get one filament or the other, but not both.

Why would you have a 21/21 cp bulb if the output was the same on high and low beam?

Also, where can I get the 3/16" cork gaskets for the headlight seal?

[West Peterson]

Tognottis has 1/8th. Give 'em a call and see if they have anything thicker. One of the restoration guys on the forum may have a better answer.

Tognotti's Auto / Truck / Import World

[Curti]

I cannot speak to the 21/21 CP bulb which make no sence to me. The era dimmer switches that I am familiar with are one or the other not both. In reference to the gasket, go to the local hobbyshop and get some model airplane fuel line, it works great.

[Barry Wolk]

I cannot speak to the 21/21 CP bulb which make no sence to me. The era dimmer switches that I am familiar with are one or the other not both. In reference to the gasket, go to the local hobbyshop and get some model airplane fuel line, it works great.

The fuel line is a great solution, thanks.

I think I may have figured out the 21/21 question. It seems that it's not the brightness of the filament, but it's position within the lamp. The two filaments are back to back, effectively blocking some light from half the reflector. The upper filament would be for low beam as its light bounces off the upper part of the reflector, aiming the light down and the lower filament bouncing the light upward, thus the "high beam".

[Friartuck]

Barry,

You have figured it our correctly. It's not the insensity of the filiment, but is location within the parabolic geometery that makes it a Low & High Beam. The upper filiment is low beam. If the head light bucket has an adjusting screw in the back, that also moves the filiment within the parabolic to focus the beam.

A 50 CP bulb should not have fried the switch contacts, but support your use of a shunting relay.

Chris

[Barry Wolk]

Are the quartz retrofits any better? Anyone have luck with those?

[ply33]

The fuel line is a great solution, thanks.

I think I may have figured out the 21/21 question. It seems that it's not the brightness of the filament, but it's position within the lamp. The two filaments are back to back, effectively blocking some light from half the reflector. The upper filament would be for low beam as its light bounces off the upper part of the reflector, aiming the light down and the lower filament bouncing the light upward, thus the "high beam".

The high beam filament should be located at the focus point of the parabolic reflector while the low beam will be off center.

Your original 21 cp filaments were rated to draw 2.63 amps. Assuming that your dash lights are on a separate switch, then your current load for your head light switch, assuming a typical car of the era with a single 3 cp tail light, would be 2.63+2.63+0.75 amps or 6 amps. I'd guess that the factory put in maybe a 100% safety factor and put in a switch rated at between 10 and 12 amps.

Now you install 50cp bulbs which draw 5.72 amps and have a load of 5.72+5.72+0.75= 12 amps. So you are at the limit of what the switch was designed for new. But you have nearly 80 years of corrosion in there. Even if you have only 0.1 ohm resistance (unmeasurable with a typical low end volt-ohm meter) you'd be dissipating 14 or 15 watts inside the switch. I'm not surprised you had a problem.

For some miscellaneous light bulb specifications see Plymouth First Decade: Light Bulbs

For what I did on my headlights see How good can those antique car headlights be?

[Barry Wolk]

That was very helpful.

Would't my low beams be more effective if I installed the bulbs 180° from their normal operating position? Since 99% of my driving tends to be low-beam, shouldn't I take advantage of the 50 cp output?

[ply33]

If you've:

1. Upgraded the generator to handle the higher load.

2. Upgraded or repaired the wiring to handle the increased current

3. Installed a relay to keep from damaging the headlight switch

4. etc.

So that running 50cp (approximately 36 watt) incandescent headlight bulbs is safe and reliable from an electrical point of view. Then I'd swap out those #1188 bulbs with some 35w/35w quartz-halogen bulbs from a place like Classic and Vintage bulbs to give you something like 70cp on both upper and lower beams.

For myself, the number of modifications to the electrical system needed to do that on my 1933 Plymouth exceeded my personal threshold for acceptable deviation from stock. So I am using 25w/25w quartz-halogen bulbs that draw about the same power as a #1000 (32cp/32cp) bulb but give about the same light as a 50cp/50cp bulb would (if one were available) so that I can keep my original generator, light switch, etc.

By the way, quartz-halogen bulbs may be more sensitive to voltage variations than incandescent bulbs and may burn out easier if the voltage goes a little high. I haven't had a problem but I have heard of others who have. On the other hand, I've buried a voltage regulator inside my original generator so that I don't have to futz with the poor regulation inherent in the old third brush generators. So maybe that is the reason I've not had a problem.

[Barry Wolk]

A previous owner had replaced the circuit breaker with a voltage regulator and added a third brush. Since I'm showing it as a survivor, I'll leave that modification.

The 35/35 quartz seem like a good idea.

[Seldenguy]

Barry --Looks like your lighting problem is solved. I can say how I solved the easy part of your request. I use round cotton cording in place of cork gaskets in my lamps. Can be purchased in many diameters to suit your needs.--Bob

[Barry Wolk]

In reference to the gasket, go to the local hobbyshop and get some model airplane fuel line, it works great.

It sure did.