Conductive ability of metals

There are a plethora of metals and non metals on the periodic table with which to play about with when making a flash light. It dawned upon me earlier that conductive efficiency is paramount to longevity and perhaps in light intensity. Copper is widely accepted as the preferred metal for electrical conduction right? However there are various grades of copper. For example the sort used for water pipes and then the sort used for Hi-Fi applications, namely Oxygen Free Copper. So it comes to pass that using hi grade OFC should improve a flashlights operation right? With the relative size of the flashers (tiny) this shouldnt even be a costly upgrade either. Then there is the ultimate metal for conduction.....SILVER.

Now silver is widely available and for our purposes is again not all that expensive. Again a few flavours.....Silver plate on OFC. Sterling silver and pure silver. I would imagine pure silver to be rather soft though for flashlight contact surfaces. Then there is more, even the solder used can be upgraded to high content silver audio grade solder. I would imagine this to have an overall impact on the flashlight. But then again this is just a hypothesis by a newbie. Would like some input from the manufacturers on this one?

You're thinking too hard. The limiting factor is the metal to air/skin interface.

That's it.

Period.

turbodog said:

The limiting factor is the metal to air/skin interface.

That's it.

Period.

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So changing the internal copper parts to silver has no affect? Don't electrons flow differently in different mediums...etc?

The heat will flow through some metals better than others (the best being copper and silver as you mentioned), but really it's not all that important for the whole body of the flashlight. As mentioned above, the heat might be able to flow really well into the metal body of the flashlight, but then you still have to get rid of it. The transfer of heat is much harder from metal-> air than it is through the metal, so in the end this is what limits it.

Having a good chunk of copper or silver directly in contact with the led will help to pull the heat out of the led directly and prevent it overheating. After this it then depends what you want the light to do. If you want to sink lots of heat for a short run time, you just need a BIG lump of metal. All the heat from the led goes into heating up this metal, keeping the led cool enough. If you are looking for longer run times however you need somewhere to put that heat. Using a reasonably conductive metal to join the slug on the base o the led to the flashlight body is the best way to achieve this. Most of the heat is actually taken via your hand rather than the air (try this with a bright light - it will get much hotter if you leave it on a desk than if you hold it).

Basically you are right - using the best materials for heat conduction will help. You just probably wouldn't notice the difference, and neither would the led. You would also run into problems with structural integrity as you mentioned, as the best conductors are very weak. The cost is another factor - a small quantity of silver might not be all that expensive, but it's still many times more expensive than a piece of aluminium. And if you try and make a whole light out of it you'll really start to see the costs add up.

In other words, it just ain't worth it.

Chances are that holding the flashlight near or by the head and using your blood to transfer heat will more than offset any use of better metals.

"Oxygen free" copper in audio applications is a gimmick. None of the companies challenged on this or any other such devices have ever allowed a true double blind test to be done.
The article in a recent edition of MaximumPC shows that most people, even audiophiles have trouble descerning the difference between tracks played at different compression rates even on pieces they are very familar with.

Flashlights tend to be pretty small so don't need to move heat a great distance. But if you wanted the head where the high-powered LED is to be slender and the heat sinking down by the base, a heatpipe it the answer, since liquid can transfer heat far more efficiently than solids.

With all due respect my aforementioned post was in regards to the contact of the circuit and the battery. The efficiency to drive power from the battery to the LED. The heat issue is a different story I would think?

I consider myself an audiophile and, while I've never been involved in a true double blind test, I've heard comparisons between cables using very high end switches. But the results are often in conflict to what the companies would have you believe. AudioQuest is a big proponent of the solid strand construction (4 to 16 very heavy strands of solid OFC. Their cables always sound much more dull and lacking in higher frequencies than fine stranded cables such as Kimber or Nordost. I can hear these differences consistantly and I've heard them when the store was 'pushing' AudioQuest.

Keeping in mind, I'm not trying to convince anyone that $1,000 worth of cables will transform a $5,000 system as compared to the same system using $50 worth of cables. There is a difference, but it's not really extreme enough to justify the cost of the best cables.

I've done little comparison with silver plated cables and solid silver stranded cables, but again, they were from different manufacturers. Generally, the silver or silver plated cables tend to transmit even more high frequency information, often to the point of sounding somewhat harsh in many systems.

What does audio have to do with flashlights? Not much, other than probably several folks into high end flashlights would appreciate high end audio if presented in a neutral fashion. But there is a difference.

As an aside, my college education was in physics and physical chemistry though that certainly doesn't mean I have nearly the hands on experince with different materials that many of our custom light builders have... If I were to set out to design a fairly high end flashlight, I would likely build the head and heatsink out of copper, the body out of aluminum and there would be a little recessed area where the primary conductor would be stranded silver plated copper from the tailcap to the regulator. I'd hard chrome the light inside and out as a lighter finish, or I'd nickle place the inside of the light and HAIII the outside of it for the darker finish. And if I could get the company that used to offer it to open up to smaller channels again, I'd build one out of low carbon stainless steel and plate it in boron carbide... VERY cool looking finish.

Even electrically, it will only make a slight measurable (and I mean slight, in the order of a few mV) difference.

I've measured the resistance of a Mag 3D (aluminium body) from the tail cap to the - terminal of the switch. That includes 3 contact points (probe to tail, body to switch, probe to switch). I measured 0.014 ohms (14 milliohms). The vast majority of that resistance was the contact resistance, and not the resistance from the aluminium its self.

Even somehow, if using copper or silver magically made it 0, that's only a gain of 14 milliohms. You'd have to push 10A through that path before you'd really notice the difference.

It's not enough of a difference to make it worthwhile.

cratz2 said:

I consider myself an audiophile and, while I've never been involved in a true double blind test,

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If you can distinguish the difference in a true double blind test then you need to find a sponsor.
You would gain them $1,000,000.00 worth of free publicity and you would gain $1,000,000.00 cash.
These devices violate known laws of physics and as such qualify for Randi's little prize.

A search for audio on his site yield's among other articles this one which deals with $2500.00 power cables...

Mike Painter.....

Take most of what Randi says with a grain of salt, he's as much of a huckster as anyone else. He makes his living claiming to debunk myths and must appear to be an unbiased authority in order to do so. Unbiased he is not. Some of his conclusions are flat out wrong. Double blind testing doesn't work for everything. We're beginning to stray from the topic of this thread so I won't say much more, except that blind acceptance of Randi is no better than blind acceptance of anything else.

rosso said:

With all due respect my aforementioned post was in regards to the contact of the circuit and the battery. The efficiency to drive power from the battery to the LED. The heat issue is a different story I would think?

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Actually, the most thermally conductive metals are also the most electrically conductive metals, although I'm not sure if that's a fundamental relationship or an incidental one. Regardless, you can answer your own question if you look up a few numbers. You'll want to find the "specific resistance, ρ" of copper, aluminum, silver, etc. Specific resistance is measured in ohm*meter or ohm*inch or something like that, since ρ = Resistance*Area/Length. Think about what each of those terms mean.

If you want to spend the money for silver, don't make a silver flashlight body. Flashlight bodies have lots of area, so you'd reduce the resistance from almost zero to... 58% of almost zero. If I were you, I would measure the circuit resistance in my flashlight, ignoring the bulb and the battery, but not the contacts that they make to the light. If there's significant resistance, no doubt it's a result of small or dirty contacts. Clean the contacts, eliminate contacts, and think about how to increase the contact area. Don't believe the OFC bull**** (unless you can find data to back up the claims.)

I'm familiar with the offer, it was also offered by another gentleman, mostly known for car audio. It's simple enough though... find a high end audio store in your area (absolutely NOT a mass volume store) and tell them you would like to compare cables. I mean, you can't go in with such a closed-minded attitude that you KNOW you won't be able to hear the difference, but I've been into audio for a long time. And I've been a musician for a long time. I've met folks that claim that cables make ZERO difference and on the other end, I've met folks that claim that little pieces of rubber or metal placed on a speaker in a certain way will transform a system from barely listenable to nearly orgazmic.

As with most things, the truth lies somewhere in between the two extremes. If cables made zero difference, then the highest end speakers and electrical components would use unprocessed scrap aluminum as conductors... but NONE of them do. On the other hand, if your system consists of some mass produced, single driver, paper cone speakers you bought in 1973 and some crappy amp and source, then of course the best cables in the world aren't going to make a lick of difference. But to think that there is absolutely no difference between the worst cables and ones properly constructed out of quality materials and connectors won't make a difference in a $100,000+ high resolution system in a dedicated room... well... that's just plain silly.

But then, of course everyone won't be able to hear the difference. Some folks can't hear the difference between a stock stereo in a 1988 Buick Regal and a custom installed $3,000 stereo with properly aimed front stage drivers. Some folks can't hear the difference between between a fine violin made from proper wood and one made from plastic. And some folks can't even tell when one of the tweeters in their home speakers is completely blown and not working.

But I digress...

Bottom line is, the conductive difference between a common aluminum bodied flashlight and all silver connections hand soldered in a clean room is going to be VERY minimal. Far too minimal to justify the difference. But there are still people out there that will want the bettern connection and will pay for the bettern connection.

But to think that there is absolutely no difference between the worst cables and ones properly constructed out of quality materials and connectors won't make a difference in a $100,000+ high resolution system in a dedicated room... well... that's just plain silly.

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Yet no one is willing to spend the time to actually apply for the prize.
They make excuses, claim that it can't be done or just ignore the chance for a rather impressive amount of money.

This will be the last I say of it because we've gone arguably off topic (since we're applying it to audio rather than flashlights) but have you ever compared audio cables under ANY circunstances? Regardless of the measurable differences, would you not agree that there MUST be a difference between 97% copper, 99.999% copper, silver plate and pure silver?

For someone that has never compared them to say that no one can hear the difference between the crappiest copper cables and the highest quality copper or silver cables makes about as much sense as someone that has never seen a variety of Luxeon flashlights saying there's no difference between two TW0J stars. I mean, many folks claim to be able to tell the difference, but no doubt, someone, somewhere will claim that there can't possibly be a difference.

cratz2 said:

This will be the last I say of it because we've gone arguably off topic (since we're applying it to audio rather than flashlights) but have you ever compared audio cables under ANY circunstances? Regardless of the measurable differences, would you not agree that there MUST be a difference between 97% copper, 99.999% copper, silver plate and pure silver?

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The difference in the two wires is the difference between the two percentages and would affect the resistance of the wires to some small degree.
The difference in the ability to transmit an analog electrical signal after it has passed through the crimps and soldier and resistance into a magnet has never been demonstrated in any valid scientific testing.
It's easy to do.
It has not been done.
30

International Annealed Copper Standard (IACS%)
I believe these are the values which best describe the differences in specific conductivity of metals. The IACS is based on the electrical conductivity rating of various metals whether inert or alloy. All metals are compared to the conductivity rating of Copper (100%) in the scale. Silver being more conductive, however, not practical enough a substance to use as a basis for a conductivity curve origin.

turbodog said:

You're thinking too hard. The limiting factor is the metal to air/skin interface.

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Yes. Heat transfer behaves very similarly to electrical resistances in series. To improve the overall rate, it's most productive to attack the largest resistance. For the smallest resistance, even huge percentage improvements will have little overall effect on the total resistance.