Headlamp Bulbs

[Grim]

P.S I always do avoid touching the glass, but I've never quite understood how grease on your fingers can blow a light bulb, does any one else know?

Basic stuff:

 

It's because the envelope is made from silica, and not glass because the glass would soften at the temperatures that envelope is required to run at in a halogen.

At these temperatures, grease and general crap from your hands corrodes the envelope, causing it to overheat.

 

More stuff (only read here if you're really bored):

 

The limiting factor of the efficiency of the light output of the blub (brightness per watt) is the temperature of the filament (hotter = more light per watt). At too high a filament temperature, evaporation of tungsten from the filament is high (eg when you put a lamp on at too high a voltage and it causes the envelope to go 'silvery').

To stop this condensation of tungsten onto the envelope, a halogen element is added (in other words chlorine), and the evaporating tungsten reacts with the chlorine, forming WCl3 (tungsten chloride), which condenses on the filament and releases the chlorine back into the envelope. The tungsten redeposits at the thinnest sections which are the hottest preferentially.

The envelope has to run at a much higher temperature to stop the condensation of WCl3 onto the envelope, which would defeat the object, as the tungsten would not be able to return to the filament.

 

If the envelope did corrode, it would absorb more of the heat from the bulb, and the balance between evaporation and condensation would be upset, causing a localised evaporation and failure of the filment.

[Guest STEVE OXON]

blimey! must have been bored.

steve

[Guest timswait]

  its an old wives tale

or it would give you warnings on the pack

It does give warnings on the pack!!

[Guest Battery Bill]

Grim

Zzzzzzzzzzzzzzzzzzzzzzzz

[Guest Battery Bill]

Tim

It does give warnings on the pack!!

 

Nice answer that will shut him up

[Guest rizla]

load of goldilox

[Guest TerryBarry]

Manufacturer's Information

 

Tungsten halogen lamps are similar to incandescent lamps but instead of just being filled with inert gas they also have small quantities of halogens (bromine, chlorine and iodine) or their compounds added to the filler gas and use quartz instead of glass for the lamp capsule. Benefits of tungsten halogen lamps include:-

 

A slightly higher colour temperature than ordinary tungsten incandescent lamps, giving a bright, white light, ideal for shop display lighting.

Physically much smaller than equivalent tungsten incandescent lamps.

Longer rated life – typically 2000 to 5000 hours or more.

 

One disadvantage of tungsten halogen lamps is that the quartz envelope is much more sensitive to contamination than ordinary glass bulbs. The quartz capsule must not be touched with bare hands since contamination can lead to overheating and severely reduced life. Some designs get around this by encapsulating the lamp inside a glass envelope.

[Guest chris brown]

Nice one Terry that told him ( and he was an AA man at one time - always did think they were useless)

[Guest rizla]

still a load of rubbish,ive yet to see one fail due to being touched,we have taxis that run round here with no glass on their headlamps,and the light still works,you cant get more contaminated than that

 

9 years as a senior aa technition trainer to be more acurate chris

[Mitch]

"technition trainer"

 

You have done it now Riz, open the flood gates.

 

And can we now decide, the touching the bulbs with bare hands cause's hot spots, leading to premature failure,

 

Now someone lock this thread!!!!!!!!!!

 

Mitch

[Guest Battery Bill]

Andrew

9 years as a senior aa technition trainer to be more acurate chris

 

Why did you not build your own car then ?

[Guest rizla]

:gdit: too busy working,no garage and changing 5 million headlamp bulbs on recall cause i farted on them :angry:

[Guest Battery Bill]

Temper Temper

[Guest docter fox]

I think you touched a nerve

 

so in conclusion, which are the brightest bulbs?

[Les Welsher]

so in conclusion, which are the brightest bulbs?

 

The ones that haven't blown because you touched them

 

Les