Date: Thu, 19 Sep 1996 16:06:52 +0100 (BST)
From: D.J. Walker
Robert Smith writes:
> On the subject of halogen vs. tungsten headlamp bulbs, remember that
a watt
> is a watt, regardless of whether it's employed to excite halogen
ions or a
> tungsten wire.
Halogen lamps don't work by exciting halide ions. They use a single tungsten filament wire, just like a normal bulb, as I believe I wrote to this list, some time ago.
Basically, what causes a tungsten filament in a bulb to glow, is heat, what causes a tungsten filament in a bulb to _blow_, is excessive heat and melting of the metal, as a result of excessive resistance at some point in the wire. This is caused by:
A) a especially narrow bit in the wire...
\ | | /
______________ ___________
e ---> \___/ e---->
e----> ___ e--->
______________/ \___________
/ | | \
Narrow bit, heat
builds up because
the electricity
has
a hard time passing.
B) impurities which also restrict flow....
\ \ | | |
/ /
_______________________________
e-----> X @ . e_-_-_->
e-----> O / # e-_-_->
_______________________________
/ / | | |
\ \
Impurities,
"get in the way"
of the electrons.
Also, excessively thick bits of wire will be unusually cool, owing to the ease of flow at these points. This puts an extra strain on the rest of the wire, overheating it, and leading to a blow, eventually.
Any of these situations could be remedied, if some means of depositing extra tungsten metal around the hot bit of highly resistive metal, and removing it from around thicker, cooler bits, existed. This is what halogen bulbs do, they automatically regulate the resistance in their wire filaments. The inside of a "halogen" bulb is full of WF6, tungsten hexafluoride (fluorine is the "halogen" involved here). This is a gaseous compound which does not attack dry glass, unlike a lot of other fluorides. When heated, this compound will decompose into tungsten metal and fluorine gas. Are you starting to get the picture? In the areas around hot bits of high-resistance wire, the WF6 breaks down, depositing tungsten onto the hot wire, thickening it, and removing the high-resistivity in this area. Similarly, the fluorine gas will attack cold metal, to form new WF6, but can't attack the hot areas of metal, since the WF6 will immediately decompose again. So overly thick, cool bits of wire have their excessive tungsten stripped away, and will return to normal heat as the resistivity is restored. As a result a tungsten bulb is far less likely to blow, because it has this self-regulating function.
This has a number of advantages. Normal, non-halogen bulbs tend to have big beefy filaments in them which are robust enough to withstand over-heating at various points along their length. However, they need to be heated more to glow to the same extent, and all this excess heat they generate is radiated off as wasted energy. The _real_ Wattage of a non-halogen bulb is higher than that of a halogen bulb of the same light output, because they _waste_ a lot of Watts, as heat energy. The Wattage listed on a bulb is a measure of how many Watts it puts out as _visible_ light energy, not the total Wattage it puts out (the non-halogen bulb puts out a lot more energy, as _infrared_ light: if we had eyes whose sensitivity extended into the infrared region, halogen bulbs wouldn't be necessary, we'd be able to see the infrared light the normal bulb was putting out. In fact, we might not need lights at all, since we'd be able to see in the dark...).
So the advantages of halogen bulbs are, that they can use much thinner wires, are likely to last longer, and pull less energy from your wiring loom to produce the same amount of visible light. The main problem with halogen bulbs is that they need silca-glass envelopes. This is a type of glass which is especially resistant to being dissolved by fluorides. The WF6 in the bulb is never totally pure, you see, and neither is the tungsten wire. The continual process of vaporisation and deposition which occurs every time the bulb is turned on and off, will allow stray elements like hydrogen and oxygen to creep in, over time, whose fluorides are far more corrosive towards glass.
This is especially true of hydrogen. HF is among the few materials which will dissolve glass, turning it into gaseous SiF4. This is why you should never touch the silica-glass envelope of the bulb. not only does it stain _very_ easily (causing an enormous thumbprint to precede you everywhere you go, at night) but the moisture in your sweat will work its way through the pores in the glass (and yes glass really does have pores) into the interior of the bulb. The H2O reacts with the fluorine (F2) to produce HF and OF2 (yes, a halide of oxygen - even stable halides of xenon and krypton exist... fluorine really does like to react with things) The presence of the HF causes a self-sustaining reaction to occur (non chemists skip the equation below)
4HF + SiO2 (glass) --> SiF4(gas) + 2H2O
2F2 + H2O ---> OF2 + 2HF
4HS + SiO2... etc. See, it's as self-sustaining as the WF6/tungsten reaction.
So, I hope it's obvious why it isn't true to say that...
> If a tungsten bulb and a halogen have the same watt rating, they'll
draw the
> same current and have a similar effect on the bike's electrical system.
The logic of your argument was good, Robert, but I felt I had to speak up, to clear up some of the confusion relating to excited "halogen ions", and also because I can't resist the chance to look like a really brainy bastard, on a medium in which you're very unlikely to get punched in the gob.
Apologies to those long-timers on this list who've read the above account before, and those who realise that my description of what occurs in a halogen bulb is somewhat of an over-simplification. if you want to come round and punch me, my current address is:
[ED: Removed as he's moved, no really]
Any bike thieves interested in breaking in, and stealing all my worldly goods, may like to know that "I swear do-on't have a gu-un" (but then, that's what Kurt Colbane said, isn't it ;-) and look what happened to him)!
Dan
Date: Thu, 19 Sep 1996 15:26:28 EDT
From: d matheson
Good ASCII man . . . ., but my bs filter requires me to ask . . . OK now, if the glass has pores, then how can high pressure arc lamps work without pumping all the gas out? Also, why can I specify bubble size and distribution on glass that I buy, huh? I can buy glass with no bubbles at all, and that's what's used to make bulbs. Rumour has it that the oil on your finger contains salt. This salt acts to de-vitrify the glass bulb, so that it loses the ability to withstand the internal pressure generated by the hot gas. The glass then puffs out.
I think you'll find that the wattage is a measure of the electrical input power. Lumens or lux would be the measure of the light output. The tungsten bulbs are more efficient at converting lectricity to visible light because they run hotter and have a higher colour temperature. Oh, and another thing, all regular glass is silica. Some forms are soda lime, fused silica (quartz glass), borosilicate, etc. For glass that will never give up, try synthetic sapphire.
Date: Fri, 20 Sep 1996 01:14:16 +0100 (BST)
From: D.J. Walker
> Good ASCII man . . . ., but my bs filter....
Is blocked, mate, you want to get it checked, or fit a bs pressure meter at some point in the line where the bs goes to your head, to ensure the supply is still getting through and lubricating your belief system...
> now, if the glass has pores, then how can high pressure arc lamps
work
> without pumping all the gas out?
Hydrogen is the smallest element of all, it can be absorbed by metals like palladium to a truly phenomenal extent (they purify hydrogen by putting a pressure of hydrogen on one side of a bit of palladium metal and a vacuum on the other side. The hydrogen is _the_only_material_in_existence_ that can diffuse through the metal and reach the other side: therefore, pure H2, the other side of the palladium screen).
The pores I'm talking about, are the kind of pores that'll let hydrogen, or more likely hydride ions through. A hydrided ion is a bare proton, a bare nucleus composed one of the two smallest stable particles that can possibly exist anywhere in this, and probably a good few other universes, other than the electron.
> Also, why can I specify bubble size and distribution on glass that
I buy,
> huh? I can buy glass with no bubbles at all, and that's what's used
to
> make bulbs.
Bubbles? Okay, you buy glass with bubbles in... that's not like pores mate... we're not talking about the kind of pores you can see with the naked eye (nor even with any kind of eye, attached to any kind of instrument).
> I think you'll find that the wattage is a measure of the electrical
input
> power.
Wattage is a measure of power. Power is the rate of doing work. Infrared light is light, just as surely as any other kind of light in the electromagnetic spectrum, from radio waves to gamma radiation. A electric light filament is a good example of a machine intended to produce light energy, i.e. light waves in the visible range, that our eyes can see; but which wastes a lot of its energy as heat-energy, which does nothing, but keep the headlamp shell a bit warmer than it would otherwise be. An electric bar fire is an very good example of a machine designed to produce invisible infrared energy, but which wastes a lot of energy by putting it out as visible light energy, which does bugger-all to keep us warm, but explains why it's impossible to miss an electric bar fire, even if its being used in a darkened room.
A Watt is a Joule used, per second. if you're using X amount of Joules, per second, in a lamp bulb, that's how many joules it's using: how much energy you're using. However, it can be used to produce visible light, to show you your way home, or heat, which is no good to anybody, 'coz you can't see it. Our eyes aren't sensitive to heat radiation (infrared radiation). Our _skin_ is, that's why we feel the warmth from an electric bar fire, when we sit beside it. But we can't see with our skin, can we. At least, us Europeans can't. What genetic mutations may have occurred, in the land of the atom bomb, I have no idea ;-)! So the amount of energy used by a non-halogen bulb is equal (it's _Wattage_ is equal: the amount of energy used over a given amount of time, is the same), but it's output of visible light (the stuff you can see, and which is useful to you), is lower. A lot of Watts are being wasted as non-visible light. You can't see it, it's drawn out of your wiring loom and effectively gets wasted in creating a microscopic temperature rise in whatever it's pointed at. Your headlamp is acting like a miniature, and very inefficient, electric bar heater.
I'm quite prepared to believe that some of you don't want to fit halogen bulbs, like some of you don't want electronic ignition, but I'm a fluorine, and noble gas chemist (albeit an unemployed one). You're reading stuff written by a bloke who _knows_ what xenon difluoride smells like, has had HF burns on his skin, and is sitting within twenty feet of a big can of fluorine gas, several FEP tubes full of tungsten hexafluoride, a great quantity of HF and a variety of other exotic compounds. Your bs filter was blocked before you met me, I assure you.
Dan
Date: Fri, 20 Sep 1996 02:08:12 -0400
From: Mike Taglieri
>Just one thing puzzles me. How is light output, visible or otherwise,
>measured in watts? As units of power (work done over time, at its
simplest
>expression) how do watts relate to luminous intensity?
>
>Please *enlighten* us.
As far as I know light is not REALLY measured in watts, at least in the professions where light must be measured accurately. The problem is that light is an ephemeral radiation rather than a thing you can pack into a measuring cup, so people began to quantify it by comparison, using the light produced by "standard" candles. In the English system, one "foot-candle" is the light equivalent of a standard candle at one foot, a "foot-lambert" is a footcandle reflected off a 100% reflective surface [which, in fact, exists only in theory], and a "candle-per-square-foot is a footlambert divided by pi. More recently, it's gotten worse [or perhaps better if you're into this stuff] because instead of plain old candles science uses the "candela", which is defined as 1/60 of the light per square cm produced by a black body heated to the temperature of molten platinum, 2046 degrees Kelvin.
Everything crystal clear now? This is partly why Ansel Adams, the photographer whose "Zone System" taught sensitometry to an entire generation, used shutter speeds and lens openings rather than the official mumbo-jumbo measurements because he discovered, in a memorable understatement, that the "variety of standard units confuses the uninitiated." [The Negative, Morgan & Morgan 1968 at 1].
I suspect that they started using watts for popular comparisons of light measurement for the same reason -- the official units are incomprehensible.
Also for many years incandescent lights were the only thing people had in their homes, and so they all got roughly the same amount of light with a watt of power, so it became easy to compare the amount of light you'd get with the amount of watts the light consumed. When consumer fluorescent lights came along, it made sense to say they gave you 100 watts of light on only 20 watts [or whatever it is], and nowadays you'll even see a Coleman lantern that burns gasoline being advertised as producing "100 watts" worth of light and everyone understands what they mean. (Of course, maybe one person in 1000 could tell you what a watt IS, but anyone can tell you that he wants a 60 watt bulb for the hall closet and gets a headache unless he has a 100 to read by. . . .)
Now, halogen bulbs come along, which as Commando Dan neatly explains, are a more efficient kind of incandescent bulb that squeeze more light out of a watt, but not enormously more, like a fluorescent, so it's probably not worth it for advertisers to boast you get 112 watts of light out of 100 watts, but just to say they burn brighter and last longer, and they do. I've explained in the past that I use only a 20 watt halogen pilot light on my Commando in the daytime. I haven't the faintest idea how many lumens it puts out, but it's easily bright enough to keep me from getting a headlight-violation ticket, and I wouldn't dream of trying that trick with the original.
In short, I suspect that we measure light in watts because it's become natural to do so, even though it's logically wrong. Somewhere on the packaging of a light bulb, you'll probably find the actual lumens it puts out [in tiny, tiny type], and if you find that useful to you, feel free to compare them.
Mike Taglieri
Raul -- '72 Commando Interstate
Date: Sat, 7 Sep 1996 12:07:21 -0400
From: Mike Taglieri
>Can anyone solve a simple wiring problem for me?
>
>My Mk11 Commando master switch no longer has any 1,2,3,4 indent on
>the back, so I'm at a loss as to how to wire it. Suggestions gratefully
>received.
On my '72 [and, according to Clymer, all models later than '71] the #1 terminal is always hot and is a direct line to the battery. In the engine-on position, it's hot to #2 only. In the parking light position, it's hot to #3 only. In the engine-and-lights, it's hot to #2,3, & 4. Therefore, you can figure out your switch with a test light or ohm meter and a little detective work.
One other suggestion on this subject: I once pushed my bike 2 miles mostly uphill because the engine died, only to find that one of those damn spade terminals had NEARLY come off after I bumped it changed the air filter, then vibrated off in the middle of the ride. Soon after that, I soldered the wires to the terminals, permanently encased the whole back of the switch in electrical tape, and installed a 4-prong snap-apart connector (salvaged from a Honda) higher up in the wiring so I could remove and replace the ignition switch without ever having to #@&% around with these wires again. Try to get a waterproof connector, or put it high enough into the harness so it doesn't have to be waterproof.
Mike Taglieri
Raul -- '72 Commando Interstate
Date: Thu, 19 Sep 1996 21:06:29 -0400
From: Mike Taglieri
>Replaced with gen-yoo-wine Lucas. Perfect function ever since.
>
>Now ignition switches, *those* are a very different story. Damn things
don't
>last more'n 30,000 miles. Pry 'em apart, clean lube and fiddle, get
another
>5-10,000. But is it worth it?
It's possible to rebuild a Lucas ignition switch to better-than-new, although it's tedious. The trick is to give the contacts a greater resemblance to a Japanese ignition switch. If you take apart an old Honda switch, for example, you'll see that a wiper contact moves back and forth over several brass contacts mounted in a sheet of fiberglass/resin material (whatever it's called -- I'm calling it "fiberboard" here). The contacts are mounted so they're dead flat with the surface of the fiberboard, which is very smooth, so the wiper contact can move from contact to contact with no jolts and very little friction.
Contrast this to the Lucas design: you'll see a similar array of contacts except that they're crudely formed and pressed into the fiberboard, sticking up like nail heads that weren't hammered in all the way. Then a second piece of fiberboard with holes in it is laid [not glued] on top of the first one, so when you turn the key, the wiper contact falls down into each hole, gets dragged up across the [not so smooth] surface of the contact, then down the other side and up out of the hole toward the next one, resulting in a lot of slop, which gets progressively worse since the fiberboard with the holes can move around against the one with the contacts until they're not even concentric to the holes anymore. In short, the Honda switch was built to last and the Lucas one to sell . . . cheap.
But you can make the Lucas contact-plate like the Honda one: clean both pieces of fiberboard thoroughly and epoxy them together, making sure to fill the holes completely with epoxy. Then sand the surface down on a piece of sandpaper on glass until the contacts are dead flat against the surface of the fiberboard and there are no voids anywhere, finishing with fine sandpaper so the contacts are shiny. Now the wiper can slide easily over the contacts, prolonging their smooth surface and its own life. Then, as Tom said, pack them with grease.
Finally, there is a sort of dam halfway between the keyhole and the contacts to keep the water from getting in. Being Lucas, it's made of cardboard, or at least it was on mine, so coat it with silicone or epoxy to give it at least a chance to stay in one piece.
* * *
Finally, even if you have no intention of doing this rather tricky ignition switch job, buy a junker Honda switch from a bike breaker someday just for kicks -- ignition, directionals, kill switch, I don't care -- and take it apart on the bench side-by-side with the Lucas equivalent. Try it with a lamp unit too, like a back up light or a turn indicator.
Your eyes will be opened and you shall see the truth. . . as long as you're fortunate enough not to have a Lucas lamp fixture over your workbench. . . .
Mike Taglieri
Raul -- '72 Commando Interstate