H4 halogen bulbs in dual mode

[hypoid53]

Driving my Spitfire in the evening twilight last night, my new Halogen headlight conversion proved to be a vast improvement on the original sealed beam units. I have them relayed with uprated wiring, and it was a relevation to flash the main beams whilst dipped to reveal a much better overall beam pattern.
It would be a simple matter to have the dip relay come on when in main beam BUT would the bulb life suffer at twice the heat loading, and would the headlight unit cope with the heat ?
Anyone got long-term experience with H4 bulb life if used in this way?

[Stuart Wilson]

The lamp pod on my rally car has both filaments powered at the same time, never had an issue.

[hypoid53]

Iain and Stewart, thanks for your input. I have a drawer full of 1N4001 diodes so will use a trio of these to to control the dip relay as suggested. I do not generally use the car at night so maybe bulb longevity is not an issue..... but it is reassuring to know my lights are fit for purpose. 🙂

[TedTaylor]

If wired to run permanently be aware that you may exceed the maximum legal headlight power rating for the public road.

As mentioned, if you do this do check that the earth return cable is capable of carrying the power.  Short bursts (as in flashing ) would be OK but continuous there would be a great danger of overheating the cable.

MUT

[esxefi]

^^ I thought that the max wattage allowed was for cars after a certain year as the bulbs have to be 'e' marked.

I think the modern lights,HID and others that are used these days seem way brighter than the older stuff but they use LESS power.

our fiat 500 has dip and main on at the same time when you flip to main beam.

[GT6 M]

TBH, I cant see the point
reason, when my heedleets are on full beam, and I pull the flash
then there vv little extra light going along way ahead.

its only the dipped beam bit light,n the OE dipped beam area up,

And Ted right, as I found out,the earths on the Triumphs are v v thin in ordinary  set up,  Plus all thee,s years there be corrosion and broken starnds, leading to even hotter wire temps and less light
use some serious earth wire

{My own lamps as uprated, worked ok, but got less powerfull as time went on, due to the earth wires getting too hot,
they were black, corroded with heat when took oot
plus wrapped in insulation in the loom did nae help }

Ye be much better off gett,n better light either fit,n  biga bulbs to the MB side
or getting some spots / driving lamps

One for the Boffins,
If a car was so soooo fast, that it went faster than light speed,
would its headlights be useless, as the light maynot even get oot the bulb!!!
(think)(think)

M

[esxefi]

ha.

no they would still work as the car AND the headlight are both travelling at the same speed to start with

you try it and tell me i'm wrong

[Hogie]

Hmmmm!!  
                main AND dip at the same time. They do different things - the dip would add very little value to the overall effect. OK the rally boys may think different
BUT they are often driving in vastly different conditions.
The gearbox has quite few gears - why not use 3rd and 4th at the same time - it doesn't work.

Whatever halogens you have fitted I'm sure there are better ones - Osram 'Nightbreakers' have a very good name.

As for the speed of light - there are more important issues ;!! what is the speed of DARK?

Roger

[hypoid53]

Quoted Text

Whatever halogens you have fitted I'm sure there are better ones - Osram 'Nightbreakers' have a very good name.

They are Nightbreakers in Lucas halogen headlight units. I found that the main beam on my Spitfire does not illuminate the immediate area in front of the car and the dip fills this in nicely. I live in rural Devon with badgers and deer major collision threats in our dark and deep lanes.  

[Jonny-Jimbo]

I learned from our lighting department at work that an important part of how the light falls on the road is the filament design in the bulb itself. Not all bulbs sold after market meet the legal requirment for beam pattern.

The engineer showed us using a VW Golf headlight, how without changing the position of the light, the bulb itself makes a huge difference to the light pattern. All Ring lights meet this requirement - not all after market ones do.

[RobPearce]

I once had a Dolly Sprint that somebody had rewired to use both filaments at once. By the time I got it, all the affected bulbs had burnt out their earth terminal and two had melted the earth wire in the loom. I wouldn't recommend it.

[RobPearce]

Quoted from GT6 M

One for the Boffins,
If a car was so soooo fast, that it went faster than light speed,
would its headlights be useless, as the light maynot even get oot the bulb!!!

Meaningless question. Relativity tells us that nothing can travel faster than light - the nearer you get to light speed the slower time goes for you, so even if you keep accelerating you only approach, never exceed.

Also, the speed of light (in vacuo) is constant and fixed for any observer, which means that the light leaving the headlights of a car travelling at 80% of light speed will be travelling exactly at light speed both in absolute terms and relative to the car! Or at least, both the driver and the pedestrian will see the light travelling at the same speed relative to themselves. Yes, really.