Dim and ON

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Model T Ford Forum: Forum 2010: Dim and ON
Top of pagePrevious messageNext messageBottom of page Link to this message  By Bernd Lorenzen on Saturday, May 29, 2010 - 03:53 am:

Hi everybody,

As we will visit the German TUEV with the 1922 Tourer we need to know, if the lights have to have a high beam and a low beam. The switch says "dim" and "on".
The headlights just work on "dim" on the switch.
Probably a somewhat weird question...

Thanks,
regards,
Bernd


Top of pagePrevious messageNext messageBottom of page Link to this message  By Adrian Whiteman on Saturday, May 29, 2010 - 05:40 am:

Not a silly question at all. I read up a few sources on this as I had the same question.

This is what I found - but I stand to be corrected by those with more expertise than me:

The headlamp bulbs have two filaments the same wattage. They are placed in different positions in the bulb so that when "On" the main filament is at the optimum position for reflection to give best light. When switched to "dim" the filament changes to the second one which is positioned so that it reflects the light more downwards than ahead.

So in both position "On" and "dim" you get the same brightness, just that the light is reflected more ahead in "On" and more downwards in "dim".

That being so, there is a bulb sold by suppliers that has a brighter wattage for "On" filament and a lower one for the "dim" filament, so there is a difference in brightness if this is used. I have installed these and actually can't see much difference! Some advise these bulbs give problems with wiring overheating. I have not experienced that so can't comment.

You do need to ensure that the lights are correctly aligned, as explained in the Ford Service Manual.

Cheers
Adrian


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Deichmann on Saturday, May 29, 2010 - 07:09 am:

To add a little to what Adrian just stated - the "On" position should light the filament which will sit in the focus point/hot spot of the parabol. That will in principle send all the reflected ligt beams out in a parallel cluster and hence long range.
The other filament is on when "Dim" is on. This is positioned a little back of and over the focal point/hot spot. That will disperse the beams a little and send them downwards. It should then not bother an approaching car.
You may also get bulbs, where the dim filament sits on a small shield/mirror, that will send all the light upwards in the reflector. As it is off focus it will send all the beams downwards. Modern H4 lamps have same principle and you MAY risk that TÜV insists of this kind of bulb. It is easy to distinguish the one from the other as the lower part of the headlight looks darker than the upper when using the shield type bulb.
I am sure, though, that the bulb without the shield gives the best light as the opening of which the light comes out is bigger than with the shield. With a T you do not have that much light after all, so you can use all you can get.
Just my 0,02 € advice
(€ since you are German - ha ha)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf on Saturday, May 29, 2010 - 07:30 am:

On a T, On is dim and Dim is dimmer.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank Harris on Saturday, May 29, 2010 - 10:04 am:

As a note of information, some old cars had a lever that moved the light bulb from the dash board while driving to focus it rather than to have two filiments. There was a moisture sealing problem and they found out that it was cheaper to run two wires and a double bulb rather than move the bulb with a lever mechanism.

Also on gas lamps there is a rack that can be used to move the burner fore and aft in order to focus the light beam for best performance and I suppose that is why early electric lights had a lever action bulb mover.

Just thought you might like to know that tid-bit of useless information.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert G. Hester Jr. on Saturday, May 29, 2010 - 10:14 am:

Bernd, you could install a Lucas light switch. I like the four position one that has OFF, DIM, FLICKER and SMOKE. Then again, perhaps not. :-) :-) Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bernd Lorenzen on Saturday, May 29, 2010 - 07:56 pm:

Thanks Adrian and Michael.
I understand how it supposed to work. The headlights on the Tourer are only working on "Dim" and nothing happens at the "On" position of the switch. I guess something is wrong with the wiring. And yes, the bulbs do have two filaments. At least these two are glowing pretty bright...
Frank, thanks for the historical background on "low and high beam technique".
Steve, fortunately we do not have a dimmer Dim than On ;-)

Regards,
Bernd


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Saturday, May 29, 2010 - 08:57 pm:

I have a pair of reflectors from probably the 1920s that use solenoids to move the bulbs for focus. They were on a 1922 Franklin I saw, among others.

I remember Reid Welch going on about the repro sockets that align the filaments vertically, rather than horizontally, a dumb thing.

These are my halogen setup.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erich Bruckner on Sunday, May 30, 2010 - 09:45 am:

I always thought the original ford bulbs used to have two filamints, one small, one larger, for a true difference in light output. Modern bulbs use two near equal filamints and work on the shifting focus principle described above. The problem comes that the T light socket is set so the filamint actually is malpositioned, having not been designed for this type bulb, such that the focus swithces from side to side, instead of up and down. That is what I have read. Anyone else ever heard that?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bernd Lorenzen on Sunday, May 30, 2010 - 07:25 pm:

Ricks,
nice pic of your speedster, looks a lot brighter than our lights plus you`ve got three ;-)
I suppose you could really go at night instead of crawling!?
Did you have to change the sockets for the halogen bulbs?
Erich,
do you mean the problem with repro sockets Ricks is refering to?
I have to admit that I simply cannot tell anymore if they are aligned horizontal or vertical on the Tourer because we changed a couple of bulbs, cleaned the sockets, took everything apart, etc. Finally we were lucky that they both worked at all and had about the same "brightness".

Thanks,
Bernd


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