That’s cool! Do you use it? It’s neat to use razors from yesteryear, especially if you have a connection. I often wonder who used the razors I shave with, but I’ll never know with mine.
The closest I come to using a straight razor is a Rolls Razor. Basically it’s a segment of straight razor on a stick. (google it for more) They give great shaves as do straight razors.
(Relax folks, we’re just killing time waiting for the Q8. )
Not SRP; Damn Fine Shave, The Other Safety Too, The Shave Nook, and Shave my Face2.
I got going in the hobby because I was rebelling against the high price of cartridges, then found razors of yesteryear and while I haven’t saved any $ I enjoy shaving a lot more and get better shaves with better products. But someone who only wants to get a good shave can do that and save a lot of $ if they just don’t get into the hobby aspect. But AD is a communicable disease and it’s just as dangerous to get onto the shave forums as it is to be here.
I have to agree. I was a little surprised that this is going through but not the thicker shelf. I was a little surprised the weight savings was agreed as a good thing (other than just to play along with TF at this point, which is reasonable) Extra weight near the LED definitely absolutely will increase turbo time. It's more thermal mass, takes more heat to heat it up. A little extra heat conductance in what might not be a very constraining path anyway is less clear. I'm not worried about it either way but I think TF is giving us the board to be dimplomatic and get things agreed and done, and I think we're giving them the shelf for the same reason.
Yeah, it is pretty neat BrianK. I used it a bit in my younger years, but not now. I mostly use a double edge saftey razor that I got when I was a teen. It is a bit over 50 years old & still going strong. :+1:
I do look at the straight razor and think that if it could talk…. the stories it could tell.
And what you said about good shaves & saving $$ is absolutely true!
So is the part about AD being a “communicable disease”…
I had never heard of the Rolls Razor, it looks pretty cool also. :+1:
If they would have asked first, suggesting to change the thickness from 7 to 5 for the reasons give, I don't think we would have said yes. Now that it's been done, different situation. I do like the lighter weight though, but doubt the shelf made much difference. The M6 has more metal, but maybe not used the best way - a lot less finning, heavier tailcap:
Yeah, metal around the head, well turbo time should grow pretty much in proportion to weight there, and fins, even better. It takes twice as much heat to bring twice as much metal to the same temperature. Anyway, it's not much and it's fine, I think both issues sound like they're getting pretty small. Half of me wants to buy two, but it's not "the better half".
My basic rules (I think most modders/designers would agree with) with some cost consideration for passive cooling in flashlights:
limit the # of thermal junctions: metal to metal, threaded connections, use one piece construction, etc.
metal to metal junctions should be as close and large as possible (well clamped, smoothed surface flat contact, etc.)
where there are thermal junctions, increase their efficiency (solder, thermal grease/epoxy properly applied, etc.)
copper is best closest to the heat source, aluminum has it's advantages in shedding heat out (might not all agree here), maybe aluminum is just more practical for this than copper, for example
the more surface area exposed to the air in the outside shell, the better (more fins, more size, more...)
location, location, location - get the material mass and cooling fins closer to the source
active cooling would be great, but practical implementations abound
Take these rules and apply practical limitations and trade-offs of cost, portability, functionality, styling, etc.
You don't touch on is mass much though. Heat transport is one thing, but heat capacity is another. Mass doesn't impact sustainable output much except as it affects other the other things (thickness of thermal path etc), but it surely impacts turbo time. Aluminum can hold almost 1 Ws/(g*K) so at for 50K rise, 50g more mass will hold about 50s of heat at 50W. Copper by the way has a much lower heat capacity by mass, for better or worse though it makes up for it by weighing more.
True, just mention the location of the mass, not the amt of mass - need to update the list
I like the premise of the classic CPU heat sinks - copper inside at the chip, aluminum to the air.
Others know the details better, but I think/thought copper is great for pulling heat, aluminum can conduct it quicker. Measurements and specs from SinkPAD and tests done here on BLF show copper MCPCB's perform better, but not by any big margin, and pflexpro here has some really interesting test results for P60 configurations that has some general use applications.
Updated list:
limit the # of thermal junctions: metal to metal, threaded connections, use one piece construction, etc.
metal to metal junctions should be as close and large as possible (well clamped, smoothed surface flat contact, etc.)
where there are thermal junctions, increase their efficiency (solder, thermal grease/epoxy properly applied, etc.)
copper is best closest to the heat source, aluminum has it's advantages in shedding heat out (might not all agree here), maybe aluminum is just more practical for this than copper, for example
the more surface area exposed to the air in the outside shell, the better (more fins, wider, spread it out)
bigger is better - I’m all about that mass, bout that mass, no treble
location, location, location - get the mass and cooling fins closer to the source
active cooling would be great, but practical implementations abound
The specific heat of aluminum is ~0.900J/(g K) and the density is 2.70g/cm^3. The specific heat of copper is ~0.385J/(g K) and the density is 8.96g/cm^3.
Let’s say a S2 triple spacer is 3.8cm^3 (because kiriba-ru lists his cu spacers as 34g). An Al spacer will weigh 10.26g and a Cu spacer will weigh 34g.
An S2 triple is say, 35W heat energy needing dissipation (35W = 35 J/s). The allowable Temp increase over ambient we define as 50*C.
Q=c*m*(T2-T1)
For Aluminum: (35J/s)(X)=(0.900J/gC)(10.26g)(50C) —> X=13.2s
For Copper: (35J/s)(X)=(0.385J/gC)(34)(50C) —> X=18.7s
So for a fixed _volume _of metal (which is basically the constraint we are facing), the Aluminum will heat up to our predefined “limit” temp in 13.2seconds, compared to 18.7s for copper. The copper will take 42% longer to heat up to the same temperature.
Copper is of course be three times heavier, so it is up to the user to subjectively decide if copper is worth the weight penalty. But objectively, copper is the better heatsink material without argument (I doubt anyone is arguing this).
Note that this calculation is purely regarding the heatsinking ability of the metal, which is not the same as it’s ability to dissipate that heat to the environment. As Flintrock points out, the heatsink calculation primarily (but not only) affects the light’s initial ability to maintain it’s output in Turbo before output starts dropping due to heat buildup.
The ability of the metal to then shed that heat to its surroundings (either in continuous use, or after the light has been turned off or reduced in power, it doesn’t matter) is a different calculation, where the thermal conductivity of the metal is the critical variable – and copper has a higher (better, in this case) thermal conductivity than aluminum. So for identical conditions/environments/geometries (i.e. apples-to-apples), copper will shed heat to its environment quicker as well, and thus perform better in this regard as well.
To add another factor involved in regard to what happens in a flashlight:
Copper is about the best heat conductor in existance, while aluminium, though twice as bad, is still very very good at it. The amount of heat that is conducted is also a function of cross section area the heat has to go through which is increasingly smaller while closing in on the heat source. That is why very close to the led (i.e. the solder pad) using copper has a large effect, while further away it becomes ever so irrelevant to use copper or aluminium.
There were many pages of interesting discussions on copper/ALU/stainless steel in the Kronos X5/6 topic.
Made me Google and anodised ALU is better in shedding heat then bare. I think even color plays a part but that is info from much longer ago when I liked doing crazy cooling in computers.
The heat “holding power” of aluminum, and mass, is easily demonstrated. And most folks do it frequently.
Put something in a hot oven to cook on a piece of aluminum foil. Take it out and one can immediately lift it by the loose ends of the foil. It had temperature but not enough heat stored to burn skin. Note that it’s foil and not an aluminum pan. Add mass in the form of a pan and all of a sudden it contains plenty of stored heat to burn.
Would it be more accurate to refer to the increasing temperature gradient as you near the LED, instead of cross sectional area? I think I understand what you are trying to say with the cross-section analogy, but the driving force is the temperature gradient (which as you say is lower, farther away from the LED), right?
OK, digging deeper into my memory (I don’t still practice thermodynamics regularly, this is stretching the bounds of my memory) and refreshing myself with some Wikipedia, Fourier’s law of heat conduction is proportional to both temperature gradient and cross sectional area. But I’m thinking that’s applicable to say, the LED heat pad vs the MCPCB base (very small area at the LED pad limits the heat flux at that point, larger area at the MCPCB allows for more conductance across that plane). Within a homogeneous material, I think the mechanism is thermal diffusivity, which is a function of thermal conductivity, density, and specific heat.
Actually, as I refresh more, thermal diffusivity appears to be the characteristic that I was kind of getting at with the above calculation using density. (nope, that would be volumetric heat capacity. ) Only precious metals have better thermal diffusivity than copper, Copper is moderately better than aluminum, and aluminum is significantly better than any other common material.
